[PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[Christophe Leroy]

PPC64/IA64/PARISC have function descriptors. LKDTM doesn't work
on those three architectures because LKDTM messes up function
descriptors with functions.

This series does some cleanup in the three architectures and
refactors function descriptors so that it can then easily use it
in a generic way in LKDTM.

Patch 8 is not absolutely necessary but it is a good trivial cleanup.

Changes in v2:
- Addressed received comments
- Moved dereference_[kernel]_function_descriptor() out of line
- Added patches to remove func_descr_t and func_desc_t in powerpc
- Using func_desc_t instead of funct_descr_t
- Renamed HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to HAVE_FUNCTION_DESCRIPTORS
- Added a new lkdtm test to check protection of function descriptors

Christophe Leroy (13):
  powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h
  powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'
  powerpc: Remove func_descr_t
  powerpc: Prepare func_desc_t for refactorisation
  ia64: Rename 'ip' to 'addr' in 'struct fdesc'
  asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs
  asm-generic: Define 'func_desc_t' to commonly describe function
    descriptors
  asm-generic: Refactor dereference_[kernel]_function_descriptor()
  lkdtm: Force do_nothing() out of line
  lkdtm: Really write into kernel text in WRITE_KERN
  lkdtm: Fix lkdtm_EXEC_RODATA()
  lkdtm: Fix execute_[user]_location()
  lkdtm: Add a test for function descriptors protection

 arch/ia64/include/asm/elf.h              |  2 +-
 arch/ia64/include/asm/sections.h         | 25 ++-------
 arch/ia64/kernel/module.c                |  6 +--
 arch/parisc/include/asm/sections.h       | 17 +++---
 arch/parisc/kernel/process.c             | 21 --------
 arch/powerpc/include/asm/code-patching.h |  2 +-
 arch/powerpc/include/asm/elf.h           |  6 +++
 arch/powerpc/include/asm/sections.h      | 30 ++---------
 arch/powerpc/include/asm/types.h         |  6 ---
 arch/powerpc/include/uapi/asm/elf.h      |  8 ---
 arch/powerpc/kernel/module_64.c          | 38 +++++--------
 arch/powerpc/kernel/signal_64.c          |  8 +--
 drivers/misc/lkdtm/core.c                |  1 +
 drivers/misc/lkdtm/lkdtm.h               |  1 +
 drivers/misc/lkdtm/perms.c               | 68 ++++++++++++++++++++----
 include/asm-generic/sections.h           | 13 ++++-
 include/linux/kallsyms.h                 |  2 +-
 kernel/extable.c                         | 23 +++++++-
 18 files changed, 138 insertions(+), 139 deletions(-)

-- 
2.31.1

[PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[Christophe Leroy]

PPC64/IA64/PARISC have function descriptors. LKDTM doesn't work
on those three architectures because LKDTM messes up function
descriptors with functions.

This series does some cleanup in the three architectures and
refactors function descriptors so that it can then easily use it
in a generic way in LKDTM.

Patch 8 is not absolutely necessary but it is a good trivial cleanup.

Changes in v2:
- Addressed received comments
- Moved dereference_[kernel]_function_descriptor() out of line
- Added patches to remove func_descr_t and func_desc_t in powerpc
- Using func_desc_t instead of funct_descr_t
- Renamed HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to HAVE_FUNCTION_DESCRIPTORS
- Added a new lkdtm test to check protection of function descriptors

Christophe Leroy (13):
  powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h
  powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'
  powerpc: Remove func_descr_t
  powerpc: Prepare func_desc_t for refactorisation
  ia64: Rename 'ip' to 'addr' in 'struct fdesc'
  asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs
  asm-generic: Define 'func_desc_t' to commonly describe function
    descriptors
  asm-generic: Refactor dereference_[kernel]_function_descriptor()
  lkdtm: Force do_nothing() out of line
  lkdtm: Really write into kernel text in WRITE_KERN
  lkdtm: Fix lkdtm_EXEC_RODATA()
  lkdtm: Fix execute_[user]_location()
  lkdtm: Add a test for function descriptors protection

 arch/ia64/include/asm/elf.h              |  2 +-
 arch/ia64/include/asm/sections.h         | 25 ++-------
 arch/ia64/kernel/module.c                |  6 +--
 arch/parisc/include/asm/sections.h       | 17 +++---
 arch/parisc/kernel/process.c             | 21 --------
 arch/powerpc/include/asm/code-patching.h |  2 +-
 arch/powerpc/include/asm/elf.h           |  6 +++
 arch/powerpc/include/asm/sections.h      | 30 ++---------
 arch/powerpc/include/asm/types.h         |  6 ---
 arch/powerpc/include/uapi/asm/elf.h      |  8 ---
 arch/powerpc/kernel/module_64.c          | 38 +++++--------
 arch/powerpc/kernel/signal_64.c          |  8 +--
 drivers/misc/lkdtm/core.c                |  1 +
 drivers/misc/lkdtm/lkdtm.h               |  1 +
 drivers/misc/lkdtm/perms.c               | 68 ++++++++++++++++++++----
 include/asm-generic/sections.h           | 13 ++++-
 include/linux/kallsyms.h                 |  2 +-
 kernel/extable.c                         | 23 +++++++-
 18 files changed, 138 insertions(+), 139 deletions(-)

-- 
2.31.1

[PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[Christophe Leroy]

PPC64/IA64/PARISC have function descriptors. LKDTM doesn't work
on those three architectures because LKDTM messes up function
descriptors with functions.

This series does some cleanup in the three architectures and
refactors function descriptors so that it can then easily use it
in a generic way in LKDTM.

Patch 8 is not absolutely necessary but it is a good trivial cleanup.

Changes in v2:
- Addressed received comments
- Moved dereference_[kernel]_function_descriptor() out of line
- Added patches to remove func_descr_t and func_desc_t in powerpc
- Using func_desc_t instead of funct_descr_t
- Renamed HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to HAVE_FUNCTION_DESCRIPTORS
- Added a new lkdtm test to check protection of function descriptors

Christophe Leroy (13):
  powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h
  powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'
  powerpc: Remove func_descr_t
  powerpc: Prepare func_desc_t for refactorisation
  ia64: Rename 'ip' to 'addr' in 'struct fdesc'
  asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs
  asm-generic: Define 'func_desc_t' to commonly describe function
    descriptors
  asm-generic: Refactor dereference_[kernel]_function_descriptor()
  lkdtm: Force do_nothing() out of line
  lkdtm: Really write into kernel text in WRITE_KERN
  lkdtm: Fix lkdtm_EXEC_RODATA()
  lkdtm: Fix execute_[user]_location()
  lkdtm: Add a test for function descriptors protection

 arch/ia64/include/asm/elf.h              |  2 +-
 arch/ia64/include/asm/sections.h         | 25 ++-------
 arch/ia64/kernel/module.c                |  6 +--
 arch/parisc/include/asm/sections.h       | 17 +++---
 arch/parisc/kernel/process.c             | 21 --------
 arch/powerpc/include/asm/code-patching.h |  2 +-
 arch/powerpc/include/asm/elf.h           |  6 +++
 arch/powerpc/include/asm/sections.h      | 30 ++---------
 arch/powerpc/include/asm/types.h         |  6 ---
 arch/powerpc/include/uapi/asm/elf.h      |  8 ---
 arch/powerpc/kernel/module_64.c          | 38 +++++--------
 arch/powerpc/kernel/signal_64.c          |  8 +--
 drivers/misc/lkdtm/core.c                |  1 +
 drivers/misc/lkdtm/lkdtm.h               |  1 +
 drivers/misc/lkdtm/perms.c               | 68 ++++++++++++++++++++----
 include/asm-generic/sections.h           | 13 ++++-
 include/linux/kallsyms.h                 |  2 +-
 kernel/extable.c                         | 23 +++++++-
 18 files changed, 138 insertions(+), 139 deletions(-)

-- 
2.31.1

[PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Christophe Leroy]

'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h

It was initially in module_64.c and commit 2d291e902791 ("Fix compile
failure with non modular builds") moved it into asm/elf.h

But it was by mistake added outside of __KERNEL__ section,
therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
arch/powerpc/include/asm") moved it to uapi/asm/elf.h

Move it back into asm/elf.h, this brings it back in line with
IA64 and PARISC architectures.

Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 6 ++++++
 arch/powerpc/include/uapi/asm/elf.h | 8 --------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index b8425e3cfd81..a4406714c060 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -176,4 +176,10 @@ do {									\
 /* Relocate the kernel image to @final_address */
 void relocate(unsigned long final_address);
 
+/* There's actually a third entry here, but it's unused */
+struct ppc64_opd_entry {
+	unsigned long funcaddr;
+	unsigned long r2;
+};
+
 #endif /* _ASM_POWERPC_ELF_H */
diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
index 860c59291bfc..308857123a08 100644
--- a/arch/powerpc/include/uapi/asm/elf.h
+++ b/arch/powerpc/include/uapi/asm/elf.h
@@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
 /* Keep this the last entry.  */
 #define R_PPC64_NUM		253
 
-/* There's actually a third entry here, but it's unused */
-struct ppc64_opd_entry
-{
-	unsigned long funcaddr;
-	unsigned long r2;
-};
-
-
 #endif /* _UAPI_ASM_POWERPC_ELF_H */
-- 
2.31.1

[PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Christophe Leroy]

'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h

It was initially in module_64.c and commit 2d291e902791 ("Fix compile
failure with non modular builds") moved it into asm/elf.h

But it was by mistake added outside of __KERNEL__ section,
therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
arch/powerpc/include/asm") moved it to uapi/asm/elf.h

Move it back into asm/elf.h, this brings it back in line with
IA64 and PARISC architectures.

Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 6 ++++++
 arch/powerpc/include/uapi/asm/elf.h | 8 --------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index b8425e3cfd81..a4406714c060 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -176,4 +176,10 @@ do {									\
 /* Relocate the kernel image to @final_address */
 void relocate(unsigned long final_address);
 
+/* There's actually a third entry here, but it's unused */
+struct ppc64_opd_entry {
+	unsigned long funcaddr;
+	unsigned long r2;
+};
+
 #endif /* _ASM_POWERPC_ELF_H */
diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
index 860c59291bfc..308857123a08 100644
--- a/arch/powerpc/include/uapi/asm/elf.h
+++ b/arch/powerpc/include/uapi/asm/elf.h
@@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
 /* Keep this the last entry.  */
 #define R_PPC64_NUM		253
 
-/* There's actually a third entry here, but it's unused */
-struct ppc64_opd_entry
-{
-	unsigned long funcaddr;
-	unsigned long r2;
-};
-
-
 #endif /* _UAPI_ASM_POWERPC_ELF_H */
-- 
2.31.1

[PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Christophe Leroy]

'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h

It was initially in module_64.c and commit 2d291e902791 ("Fix compile
failure with non modular builds") moved it into asm/elf.h

But it was by mistake added outside of __KERNEL__ section,
therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
arch/powerpc/include/asm") moved it to uapi/asm/elf.h

Move it back into asm/elf.h, this brings it back in line with
IA64 and PARISC architectures.

Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 6 ++++++
 arch/powerpc/include/uapi/asm/elf.h | 8 --------
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index b8425e3cfd81..a4406714c060 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -176,4 +176,10 @@ do {									\
 /* Relocate the kernel image to @final_address */
 void relocate(unsigned long final_address);
 
+/* There's actually a third entry here, but it's unused */
+struct ppc64_opd_entry {
+	unsigned long funcaddr;
+	unsigned long r2;
+};
+
 #endif /* _ASM_POWERPC_ELF_H */
diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
index 860c59291bfc..308857123a08 100644
--- a/arch/powerpc/include/uapi/asm/elf.h
+++ b/arch/powerpc/include/uapi/asm/elf.h
@@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
 /* Keep this the last entry.  */
 #define R_PPC64_NUM		253
 
-/* There's actually a third entry here, but it's unused */
-struct ppc64_opd_entry
-{
-	unsigned long funcaddr;
-	unsigned long r2;
-};
-
-
 #endif /* _UAPI_ASM_POWERPC_ELF_H */
-- 
2.31.1

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Daniel Axtens]

Hi Christophe,

> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
>
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
>
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h

As Michael said on v1, I'm a little nervous about moving it out of uAPI
after so long, although I do take the points of Arnd and Kees that we're
not breaking compiled binaries, nor should people be using this struct
to begin with...

I've cc:ed the linux-api@ list.

Kind regards,
Daniel

> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
>
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};
> +
>  #endif /* _ASM_POWERPC_ELF_H */
> diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
> index 860c59291bfc..308857123a08 100644
> --- a/arch/powerpc/include/uapi/asm/elf.h
> +++ b/arch/powerpc/include/uapi/asm/elf.h
> @@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
>  /* Keep this the last entry.  */
>  #define R_PPC64_NUM		253
>  
> -/* There's actually a third entry here, but it's unused */
> -struct ppc64_opd_entry
> -{
> -	unsigned long funcaddr;
> -	unsigned long r2;
> -};
> -
> -
>  #endif /* _UAPI_ASM_POWERPC_ELF_H */
> -- 
> 2.31.1

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Daniel Axtens]

Hi Christophe,

> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
>
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
>
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h

As Michael said on v1, I'm a little nervous about moving it out of uAPI
after so long, although I do take the points of Arnd and Kees that we're
not breaking compiled binaries, nor should people be using this struct
to begin with...

I've cc:ed the linux-api@ list.

Kind regards,
Daniel

> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
>
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};
> +
>  #endif /* _ASM_POWERPC_ELF_H */
> diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
> index 860c59291bfc..308857123a08 100644
> --- a/arch/powerpc/include/uapi/asm/elf.h
> +++ b/arch/powerpc/include/uapi/asm/elf.h
> @@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
>  /* Keep this the last entry.  */
>  #define R_PPC64_NUM		253
>  
> -/* There's actually a third entry here, but it's unused */
> -struct ppc64_opd_entry
> -{
> -	unsigned long funcaddr;
> -	unsigned long r2;
> -};
> -
> -
>  #endif /* _UAPI_ASM_POWERPC_ELF_H */
> -- 
> 2.31.1

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Daniel Axtens]

Hi Christophe,

> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
>
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
>
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h

As Michael said on v1, I'm a little nervous about moving it out of uAPI
after so long, although I do take the points of Arnd and Kees that we're
not breaking compiled binaries, nor should people be using this struct
to begin with...

I've cc:ed the linux-api@ list.

Kind regards,
Daniel

> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
>
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};
> +
>  #endif /* _ASM_POWERPC_ELF_H */
> diff --git a/arch/powerpc/include/uapi/asm/elf.h b/arch/powerpc/include/uapi/asm/elf.h
> index 860c59291bfc..308857123a08 100644
> --- a/arch/powerpc/include/uapi/asm/elf.h
> +++ b/arch/powerpc/include/uapi/asm/elf.h
> @@ -289,12 +289,4 @@ typedef elf_fpreg_t elf_vsrreghalf_t32[ELF_NVSRHALFREG];
>  /* Keep this the last entry.  */
>  #define R_PPC64_NUM		253
>  
> -/* There's actually a third entry here, but it's unused */
> -struct ppc64_opd_entry
> -{
> -	unsigned long funcaddr;
> -	unsigned long r2;
> -};
> -
> -
>  #endif /* _UAPI_ASM_POWERPC_ELF_H */
> -- 
> 2.31.1

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
> 
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
> 
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h
> 
> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
> 
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

I wonder if we should add that third entry, just for completeness. And 
'r2' isn't a good name should probably be toc. And should it be packed? 
At any rate that's not for your series, a cleanup I might think about
for later.

Thanks,
Nick

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
> 
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
> 
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h
> 
> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
> 
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

I wonder if we should add that third entry, just for completeness. And 
'r2' isn't a good name should probably be toc. And should it be packed? 
At any rate that's not for your series, a cleanup I might think about
for later.

Thanks,
Nick

Re: [PATCH v2 01/13] powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> 'struct ppc64_opd_entry' doesn't belong to uapi/asm/elf.h
> 
> It was initially in module_64.c and commit 2d291e902791 ("Fix compile
> failure with non modular builds") moved it into asm/elf.h
> 
> But it was by mistake added outside of __KERNEL__ section,
> therefore commit c3617f72036c ("UAPI: (Scripted) Disintegrate
> arch/powerpc/include/asm") moved it to uapi/asm/elf.h
> 
> Move it back into asm/elf.h, this brings it back in line with
> IA64 and PARISC architectures.
> 
> Fixes: 2d291e902791 ("Fix compile failure with non modular builds")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 6 ++++++
>  arch/powerpc/include/uapi/asm/elf.h | 8 --------
>  2 files changed, 6 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index b8425e3cfd81..a4406714c060 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -176,4 +176,10 @@ do {									\
>  /* Relocate the kernel image to @final_address */
>  void relocate(unsigned long final_address);
>  
> +/* There's actually a third entry here, but it's unused */
> +struct ppc64_opd_entry {
> +	unsigned long funcaddr;
> +	unsigned long r2;
> +};

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

I wonder if we should add that third entry, just for completeness. And 
'r2' isn't a good name should probably be toc. And should it be packed? 
At any rate that's not for your series, a cleanup I might think about
for later.

Thanks,
Nick

[PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 2 +-
 arch/powerpc/include/asm/sections.h | 2 +-
 arch/powerpc/kernel/module_64.c     | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index a4406714c060..bb0f278f9ed4 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
 
 /* There's actually a third entry here, but it's unused */
 struct ppc64_opd_entry {
-	unsigned long funcaddr;
+	unsigned long addr;
 	unsigned long r2;
 };
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 6e4af4492a14..32e7035863ac 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct ppc64_opd_entry *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 6baa676e7cb6..82908c9be627 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
 }
 static unsigned long func_addr(unsigned long addr)
 {
-	return func_desc(addr).funcaddr;
+	return func_desc(addr).addr;
 }
 static unsigned long stub_func_addr(func_desc_t func)
 {
-	return func.funcaddr;
+	return func.addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 				    const Elf64_Shdr *sechdrs)
 {
-	/* One extra reloc so it's always 0-funcaddr terminated */
+	/* One extra reloc so it's always 0-addr terminated */
 	unsigned long relocs = 1;
 	unsigned i;
 
-- 
2.31.1

[PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 2 +-
 arch/powerpc/include/asm/sections.h | 2 +-
 arch/powerpc/kernel/module_64.c     | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index a4406714c060..bb0f278f9ed4 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
 
 /* There's actually a third entry here, but it's unused */
 struct ppc64_opd_entry {
-	unsigned long funcaddr;
+	unsigned long addr;
 	unsigned long r2;
 };
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 6e4af4492a14..32e7035863ac 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct ppc64_opd_entry *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 6baa676e7cb6..82908c9be627 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
 }
 static unsigned long func_addr(unsigned long addr)
 {
-	return func_desc(addr).funcaddr;
+	return func_desc(addr).addr;
 }
 static unsigned long stub_func_addr(func_desc_t func)
 {
-	return func.funcaddr;
+	return func.addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 				    const Elf64_Shdr *sechdrs)
 {
-	/* One extra reloc so it's always 0-funcaddr terminated */
+	/* One extra reloc so it's always 0-addr terminated */
 	unsigned long relocs = 1;
 	unsigned i;
 
-- 
2.31.1

[PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/elf.h      | 2 +-
 arch/powerpc/include/asm/sections.h | 2 +-
 arch/powerpc/kernel/module_64.c     | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index a4406714c060..bb0f278f9ed4 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
 
 /* There's actually a third entry here, but it's unused */
 struct ppc64_opd_entry {
-	unsigned long funcaddr;
+	unsigned long addr;
 	unsigned long r2;
 };
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 6e4af4492a14..32e7035863ac 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct ppc64_opd_entry *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 6baa676e7cb6..82908c9be627 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
 }
 static unsigned long func_addr(unsigned long addr)
 {
-	return func_desc(addr).funcaddr;
+	return func_desc(addr).addr;
 }
 static unsigned long stub_func_addr(func_desc_t func)
 {
-	return func.funcaddr;
+	return func.addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
 static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 				    const Elf64_Shdr *sechdrs)
 {
-	/* One extra reloc so it's always 0-funcaddr terminated */
+	/* One extra reloc so it's always 0-addr terminated */
 	unsigned long relocs = 1;
 	unsigned i;
 
-- 
2.31.1

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> There are three architectures with function descriptors, try to
> have common names for the address they contain in order to
> refactor some functions into generic functions later.
>
> powerpc has 'funcaddr'
> ia64 has 'ip'
> parisc has 'addr'
>
> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

I would have picked 'funcaddr', but at least 'addr' is better than 'ip'!
And I agree that consistency, and then making things generic is worthwhile.

I grepped the latest powerpc/next for uses of 'funcaddr'. There were 5,
your patch changes all 5.

The series passes build tests and this patch has no checkpatch or other
style concerns.

On that basis:
Reviewed-by: Daniel Axtens <dja@axtens.net>

Kind regards,
Daniel

> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 2 +-
>  arch/powerpc/include/asm/sections.h | 2 +-
>  arch/powerpc/kernel/module_64.c     | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index a4406714c060..bb0f278f9ed4 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>  
>  /* There's actually a third entry here, but it's unused */
>  struct ppc64_opd_entry {
> -	unsigned long funcaddr;
> +	unsigned long addr;
>  	unsigned long r2;
>  };
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 6e4af4492a14..32e7035863ac 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>  	struct ppc64_opd_entry *desc = ptr;
>  	void *p;
>  
> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>  		ptr = p;
>  	return ptr;
>  }
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 6baa676e7cb6..82908c9be627 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>  }
>  static unsigned long func_addr(unsigned long addr)
>  {
> -	return func_desc(addr).funcaddr;
> +	return func_desc(addr).addr;
>  }
>  static unsigned long stub_func_addr(func_desc_t func)
>  {
> -	return func.funcaddr;
> +	return func.addr;
>  }
>  static unsigned int local_entry_offset(const Elf64_Sym *sym)
>  {
> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>  static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>  				    const Elf64_Shdr *sechdrs)
>  {
> -	/* One extra reloc so it's always 0-funcaddr terminated */
> +	/* One extra reloc so it's always 0-addr terminated */
>  	unsigned long relocs = 1;
>  	unsigned i;
>  
> -- 
> 2.31.1

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> There are three architectures with function descriptors, try to
> have common names for the address they contain in order to
> refactor some functions into generic functions later.
>
> powerpc has 'funcaddr'
> ia64 has 'ip'
> parisc has 'addr'
>
> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

I would have picked 'funcaddr', but at least 'addr' is better than 'ip'!
And I agree that consistency, and then making things generic is worthwhile.

I grepped the latest powerpc/next for uses of 'funcaddr'. There were 5,
your patch changes all 5.

The series passes build tests and this patch has no checkpatch or other
style concerns.

On that basis:
Reviewed-by: Daniel Axtens <dja@axtens.net>

Kind regards,
Daniel

> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 2 +-
>  arch/powerpc/include/asm/sections.h | 2 +-
>  arch/powerpc/kernel/module_64.c     | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index a4406714c060..bb0f278f9ed4 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>  
>  /* There's actually a third entry here, but it's unused */
>  struct ppc64_opd_entry {
> -	unsigned long funcaddr;
> +	unsigned long addr;
>  	unsigned long r2;
>  };
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 6e4af4492a14..32e7035863ac 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>  	struct ppc64_opd_entry *desc = ptr;
>  	void *p;
>  
> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>  		ptr = p;
>  	return ptr;
>  }
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 6baa676e7cb6..82908c9be627 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>  }
>  static unsigned long func_addr(unsigned long addr)
>  {
> -	return func_desc(addr).funcaddr;
> +	return func_desc(addr).addr;
>  }
>  static unsigned long stub_func_addr(func_desc_t func)
>  {
> -	return func.funcaddr;
> +	return func.addr;
>  }
>  static unsigned int local_entry_offset(const Elf64_Sym *sym)
>  {
> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>  static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>  				    const Elf64_Shdr *sechdrs)
>  {
> -	/* One extra reloc so it's always 0-funcaddr terminated */
> +	/* One extra reloc so it's always 0-addr terminated */
>  	unsigned long relocs = 1;
>  	unsigned i;
>  
> -- 
> 2.31.1

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Christophe Leroy]

Le 14/10/2021 à 23:45, Daniel Axtens a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 
>> There are three architectures with function descriptors, try to
>> have common names for the address they contain in order to
>> refactor some functions into generic functions later.
>>
>> powerpc has 'funcaddr'
>> ia64 has 'ip'
>> parisc has 'addr'
>>
>> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.
> 
> I would have picked 'funcaddr', but at least 'addr' is better than 'ip'!
> And I agree that consistency, and then making things generic is worthwhile.

It's a function descriptor, there is only one address field, I don't 
think there is any ambiguïty here, and I prefer modifying the least 
impacted architectures.

Changing addr to funcaddr in PARISC would result in the following 
changes, on an architecture I know nothing about. It's more changes than 
we have on powerpc.

  arch/parisc/include/asm/elf.h |  4 ++--
  arch/parisc/kernel/kexec.c    |  2 +-
  arch/parisc/kernel/module.c   | 12 ++++++------
  arch/parisc/kernel/process.c  |  2 +-
  arch/parisc/kernel/signal.c   |  4 ++--
  5 files changed, 12 insertions(+), 12 deletions(-)



> 
> I grepped the latest powerpc/next for uses of 'funcaddr'. There were 5,
> your patch changes all 5.
> 
> The series passes build tests and this patch has no checkpatch or other
> style concerns.
> 
> On that basis:
> Reviewed-by: Daniel Axtens <dja@axtens.net>
> 
> Kind regards,
> Daniel
> 
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/powerpc/include/asm/elf.h      | 2 +-
>>   arch/powerpc/include/asm/sections.h | 2 +-
>>   arch/powerpc/kernel/module_64.c     | 6 +++---
>>   3 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
>> index a4406714c060..bb0f278f9ed4 100644
>> --- a/arch/powerpc/include/asm/elf.h
>> +++ b/arch/powerpc/include/asm/elf.h
>> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>>   
>>   /* There's actually a third entry here, but it's unused */
>>   struct ppc64_opd_entry {
>> -	unsigned long funcaddr;
>> +	unsigned long addr;
>>   	unsigned long r2;
>>   };
>>   
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 6e4af4492a14..32e7035863ac 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>>   	struct ppc64_opd_entry *desc = ptr;
>>   	void *p;
>>   
>> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
>> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>>   		ptr = p;
>>   	return ptr;
>>   }
>> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
>> index 6baa676e7cb6..82908c9be627 100644
>> --- a/arch/powerpc/kernel/module_64.c
>> +++ b/arch/powerpc/kernel/module_64.c
>> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>>   }
>>   static unsigned long func_addr(unsigned long addr)
>>   {
>> -	return func_desc(addr).funcaddr;
>> +	return func_desc(addr).addr;
>>   }
>>   static unsigned long stub_func_addr(func_desc_t func)
>>   {
>> -	return func.funcaddr;
>> +	return func.addr;
>>   }
>>   static unsigned int local_entry_offset(const Elf64_Sym *sym)
>>   {
>> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>>   static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>>   				    const Elf64_Shdr *sechdrs)
>>   {
>> -	/* One extra reloc so it's always 0-funcaddr terminated */
>> +	/* One extra reloc so it's always 0-addr terminated */
>>   	unsigned long relocs = 1;
>>   	unsigned i;
>>   
>> -- 
>> 2.31.1

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Christophe Leroy]

Le 14/10/2021 à 23:45, Daniel Axtens a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 
>> There are three architectures with function descriptors, try to
>> have common names for the address they contain in order to
>> refactor some functions into generic functions later.
>>
>> powerpc has 'funcaddr'
>> ia64 has 'ip'
>> parisc has 'addr'
>>
>> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.
> 
> I would have picked 'funcaddr', but at least 'addr' is better than 'ip'!
> And I agree that consistency, and then making things generic is worthwhile.

It's a function descriptor, there is only one address field, I don't 
think there is any ambiguïty here, and I prefer modifying the least 
impacted architectures.

Changing addr to funcaddr in PARISC would result in the following 
changes, on an architecture I know nothing about. It's more changes than 
we have on powerpc.

  arch/parisc/include/asm/elf.h |  4 ++--
  arch/parisc/kernel/kexec.c    |  2 +-
  arch/parisc/kernel/module.c   | 12 ++++++------
  arch/parisc/kernel/process.c  |  2 +-
  arch/parisc/kernel/signal.c   |  4 ++--
  5 files changed, 12 insertions(+), 12 deletions(-)



> 
> I grepped the latest powerpc/next for uses of 'funcaddr'. There were 5,
> your patch changes all 5.
> 
> The series passes build tests and this patch has no checkpatch or other
> style concerns.
> 
> On that basis:
> Reviewed-by: Daniel Axtens <dja@axtens.net>
> 
> Kind regards,
> Daniel
> 
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/powerpc/include/asm/elf.h      | 2 +-
>>   arch/powerpc/include/asm/sections.h | 2 +-
>>   arch/powerpc/kernel/module_64.c     | 6 +++---
>>   3 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
>> index a4406714c060..bb0f278f9ed4 100644
>> --- a/arch/powerpc/include/asm/elf.h
>> +++ b/arch/powerpc/include/asm/elf.h
>> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>>   
>>   /* There's actually a third entry here, but it's unused */
>>   struct ppc64_opd_entry {
>> -	unsigned long funcaddr;
>> +	unsigned long addr;
>>   	unsigned long r2;
>>   };
>>   
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 6e4af4492a14..32e7035863ac 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>>   	struct ppc64_opd_entry *desc = ptr;
>>   	void *p;
>>   
>> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
>> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>>   		ptr = p;
>>   	return ptr;
>>   }
>> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
>> index 6baa676e7cb6..82908c9be627 100644
>> --- a/arch/powerpc/kernel/module_64.c
>> +++ b/arch/powerpc/kernel/module_64.c
>> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>>   }
>>   static unsigned long func_addr(unsigned long addr)
>>   {
>> -	return func_desc(addr).funcaddr;
>> +	return func_desc(addr).addr;
>>   }
>>   static unsigned long stub_func_addr(func_desc_t func)
>>   {
>> -	return func.funcaddr;
>> +	return func.addr;
>>   }
>>   static unsigned int local_entry_offset(const Elf64_Sym *sym)
>>   {
>> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>>   static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>>   				    const Elf64_Shdr *sechdrs)
>>   {
>> -	/* One extra reloc so it's always 0-funcaddr terminated */
>> +	/* One extra reloc so it's always 0-addr terminated */
>>   	unsigned long relocs = 1;
>>   	unsigned i;
>>   
>> -- 
>> 2.31.1

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> There are three architectures with function descriptors, try to
> have common names for the address they contain in order to
> refactor some functions into generic functions later.
> 
> powerpc has 'funcaddr'
> ia64 has 'ip'
> parisc has 'addr'
> 
> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

It is the "address of the entry point of the function" according to 
powerpc ELF spec, so addr seems fine.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 2 +-
>  arch/powerpc/include/asm/sections.h | 2 +-
>  arch/powerpc/kernel/module_64.c     | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index a4406714c060..bb0f278f9ed4 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>  
>  /* There's actually a third entry here, but it's unused */
>  struct ppc64_opd_entry {
> -	unsigned long funcaddr;
> +	unsigned long addr;
>  	unsigned long r2;
>  };
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 6e4af4492a14..32e7035863ac 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>  	struct ppc64_opd_entry *desc = ptr;
>  	void *p;
>  
> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>  		ptr = p;
>  	return ptr;
>  }
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 6baa676e7cb6..82908c9be627 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>  }
>  static unsigned long func_addr(unsigned long addr)
>  {
> -	return func_desc(addr).funcaddr;
> +	return func_desc(addr).addr;
>  }
>  static unsigned long stub_func_addr(func_desc_t func)
>  {
> -	return func.funcaddr;
> +	return func.addr;
>  }
>  static unsigned int local_entry_offset(const Elf64_Sym *sym)
>  {
> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>  static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>  				    const Elf64_Shdr *sechdrs)
>  {
> -	/* One extra reloc so it's always 0-funcaddr terminated */
> +	/* One extra reloc so it's always 0-addr terminated */
>  	unsigned long relocs = 1;
>  	unsigned i;
>  
> -- 
> 2.31.1
> 
> 
> 

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> There are three architectures with function descriptors, try to
> have common names for the address they contain in order to
> refactor some functions into generic functions later.
> 
> powerpc has 'funcaddr'
> ia64 has 'ip'
> parisc has 'addr'
> 
> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

It is the "address of the entry point of the function" according to 
powerpc ELF spec, so addr seems fine.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 2 +-
>  arch/powerpc/include/asm/sections.h | 2 +-
>  arch/powerpc/kernel/module_64.c     | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index a4406714c060..bb0f278f9ed4 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>  
>  /* There's actually a third entry here, but it's unused */
>  struct ppc64_opd_entry {
> -	unsigned long funcaddr;
> +	unsigned long addr;
>  	unsigned long r2;
>  };
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 6e4af4492a14..32e7035863ac 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>  	struct ppc64_opd_entry *desc = ptr;
>  	void *p;
>  
> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>  		ptr = p;
>  	return ptr;
>  }
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 6baa676e7cb6..82908c9be627 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>  }
>  static unsigned long func_addr(unsigned long addr)
>  {
> -	return func_desc(addr).funcaddr;
> +	return func_desc(addr).addr;
>  }
>  static unsigned long stub_func_addr(func_desc_t func)
>  {
> -	return func.funcaddr;
> +	return func.addr;
>  }
>  static unsigned int local_entry_offset(const Elf64_Sym *sym)
>  {
> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>  static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>  				    const Elf64_Shdr *sechdrs)
>  {
> -	/* One extra reloc so it's always 0-funcaddr terminated */
> +	/* One extra reloc so it's always 0-addr terminated */
>  	unsigned long relocs = 1;
>  	unsigned i;
>  
> -- 
> 2.31.1
> 
> 
> 

Re: [PATCH v2 02/13] powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> There are three architectures with function descriptors, try to
> have common names for the address they contain in order to
> refactor some functions into generic functions later.
> 
> powerpc has 'funcaddr'
> ia64 has 'ip'
> parisc has 'addr'
> 
> Vote for 'addr' and update 'struct ppc64_opd_entry' accordingly.

It is the "address of the entry point of the function" according to 
powerpc ELF spec, so addr seems fine.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/elf.h      | 2 +-
>  arch/powerpc/include/asm/sections.h | 2 +-
>  arch/powerpc/kernel/module_64.c     | 6 +++---
>  3 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
> index a4406714c060..bb0f278f9ed4 100644
> --- a/arch/powerpc/include/asm/elf.h
> +++ b/arch/powerpc/include/asm/elf.h
> @@ -178,7 +178,7 @@ void relocate(unsigned long final_address);
>  
>  /* There's actually a third entry here, but it's unused */
>  struct ppc64_opd_entry {
> -	unsigned long funcaddr;
> +	unsigned long addr;
>  	unsigned long r2;
>  };
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 6e4af4492a14..32e7035863ac 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -77,7 +77,7 @@ static inline void *dereference_function_descriptor(void *ptr)
>  	struct ppc64_opd_entry *desc = ptr;
>  	void *p;
>  
> -	if (!get_kernel_nofault(p, (void *)&desc->funcaddr))
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
>  		ptr = p;
>  	return ptr;
>  }
> diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
> index 6baa676e7cb6..82908c9be627 100644
> --- a/arch/powerpc/kernel/module_64.c
> +++ b/arch/powerpc/kernel/module_64.c
> @@ -72,11 +72,11 @@ static func_desc_t func_desc(unsigned long addr)
>  }
>  static unsigned long func_addr(unsigned long addr)
>  {
> -	return func_desc(addr).funcaddr;
> +	return func_desc(addr).addr;
>  }
>  static unsigned long stub_func_addr(func_desc_t func)
>  {
> -	return func.funcaddr;
> +	return func.addr;
>  }
>  static unsigned int local_entry_offset(const Elf64_Sym *sym)
>  {
> @@ -187,7 +187,7 @@ static int relacmp(const void *_x, const void *_y)
>  static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
>  				    const Elf64_Shdr *sechdrs)
>  {
> -	/* One extra reloc so it's always 0-funcaddr terminated */
> +	/* One extra reloc so it's always 0-addr terminated */
>  	unsigned long relocs = 1;
>  	unsigned i;
>  
> -- 
> 2.31.1
> 
> 
> 

[PATCH v2 03/13] powerpc: Remove func_descr_t

[Christophe Leroy]

'func_descr_t' is redundant with 'struct ppc64_opd_entry'

Remove it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/code-patching.h | 2 +-
 arch/powerpc/include/asm/types.h         | 6 ------
 arch/powerpc/kernel/signal_64.c          | 8 ++++----
 3 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 4ba834599c4d..f3445188d319 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
 	 * function's descriptor. The first entry in the descriptor is the
 	 * address of the function text.
 	 */
-	return ((func_descr_t *)func)->entry;
+	return ((struct ppc64_opd_entry *)func)->addr;
 #else
 	return (unsigned long)func;
 #endif
diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
index f1630c553efe..97da77bc48c9 100644
--- a/arch/powerpc/include/asm/types.h
+++ b/arch/powerpc/include/asm/types.h
@@ -23,12 +23,6 @@
 
 typedef __vector128 vector128;
 
-typedef struct {
-	unsigned long entry;
-	unsigned long toc;
-	unsigned long env;
-} func_descr_t;
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_TYPES_H */
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..63ddbe7b108c 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 		 * descriptor is the entry address of signal and the second
 		 * entry is the TOC value we need to use.
 		 */
-		func_descr_t __user *funct_desc_ptr =
-			(func_descr_t __user *) ksig->ka.sa.sa_handler;
+		struct ppc64_opd_entry __user *funct_desc_ptr =
+			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
 
-		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
-		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
+		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);
 	}
 
 	/* enter the signal handler in native-endian mode */
-- 
2.31.1

[PATCH v2 03/13] powerpc: Remove func_descr_t

[Christophe Leroy]

'func_descr_t' is redundant with 'struct ppc64_opd_entry'

Remove it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/code-patching.h | 2 +-
 arch/powerpc/include/asm/types.h         | 6 ------
 arch/powerpc/kernel/signal_64.c          | 8 ++++----
 3 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 4ba834599c4d..f3445188d319 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
 	 * function's descriptor. The first entry in the descriptor is the
 	 * address of the function text.
 	 */
-	return ((func_descr_t *)func)->entry;
+	return ((struct ppc64_opd_entry *)func)->addr;
 #else
 	return (unsigned long)func;
 #endif
diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
index f1630c553efe..97da77bc48c9 100644
--- a/arch/powerpc/include/asm/types.h
+++ b/arch/powerpc/include/asm/types.h
@@ -23,12 +23,6 @@
 
 typedef __vector128 vector128;
 
-typedef struct {
-	unsigned long entry;
-	unsigned long toc;
-	unsigned long env;
-} func_descr_t;
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_TYPES_H */
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..63ddbe7b108c 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 		 * descriptor is the entry address of signal and the second
 		 * entry is the TOC value we need to use.
 		 */
-		func_descr_t __user *funct_desc_ptr -			(func_descr_t __user *) ksig->ka.sa.sa_handler;
+		struct ppc64_opd_entry __user *funct_desc_ptr +			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
 
-		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
-		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
+		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);
 	}
 
 	/* enter the signal handler in native-endian mode */
-- 
2.31.1

[PATCH v2 03/13] powerpc: Remove func_descr_t

[Christophe Leroy]

'func_descr_t' is redundant with 'struct ppc64_opd_entry'

Remove it.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/include/asm/code-patching.h | 2 +-
 arch/powerpc/include/asm/types.h         | 6 ------
 arch/powerpc/kernel/signal_64.c          | 8 ++++----
 3 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 4ba834599c4d..f3445188d319 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
 	 * function's descriptor. The first entry in the descriptor is the
 	 * address of the function text.
 	 */
-	return ((func_descr_t *)func)->entry;
+	return ((struct ppc64_opd_entry *)func)->addr;
 #else
 	return (unsigned long)func;
 #endif
diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
index f1630c553efe..97da77bc48c9 100644
--- a/arch/powerpc/include/asm/types.h
+++ b/arch/powerpc/include/asm/types.h
@@ -23,12 +23,6 @@
 
 typedef __vector128 vector128;
 
-typedef struct {
-	unsigned long entry;
-	unsigned long toc;
-	unsigned long env;
-} func_descr_t;
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_POWERPC_TYPES_H */
diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index 1831bba0582e..63ddbe7b108c 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
 		 * descriptor is the entry address of signal and the second
 		 * entry is the TOC value we need to use.
 		 */
-		func_descr_t __user *funct_desc_ptr =
-			(func_descr_t __user *) ksig->ka.sa.sa_handler;
+		struct ppc64_opd_entry __user *funct_desc_ptr =
+			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
 
-		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
-		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
+		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);
 	}
 
 	/* enter the signal handler in native-endian mode */
-- 
2.31.1

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'

So, if I understand the overall direction of the series, you're
consolidating powerpc around one single type for function descriptors,
and then you're creating a generic typedef so that generic code can
always do ((func_desc_t)x)->addr to get the address of a function out of
a function descriptor regardless of arch. (And regardless of whether the
arch uses function descriptors or not.)

So:

 - why pick ppc64_opd_entry over func_descr_t?

 - Why not make our struct just called func_desc_t - why have a
   ppc64_opd_entry type or a func_descr_t typedef?

 - Should this patch wait until after you've made the generic
   func_desc_t change and move directly to that new interface? (rather
   than move from func_descr_t -> ppc64_opd_entry -> ...) Or is there a
   particular reason arch specific code should use an arch-specific
   struct or named type?

> Remove it.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/code-patching.h | 2 +-
>  arch/powerpc/include/asm/types.h         | 6 ------
>  arch/powerpc/kernel/signal_64.c          | 8 ++++----
>  3 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
> index 4ba834599c4d..f3445188d319 100644
> --- a/arch/powerpc/include/asm/code-patching.h
> +++ b/arch/powerpc/include/asm/code-patching.h
> @@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
>  	 * function's descriptor. The first entry in the descriptor is the
>  	 * address of the function text.
>  	 */
> -	return ((func_descr_t *)func)->entry;
> +	return ((struct ppc64_opd_entry *)func)->addr;
>  #else
>  	return (unsigned long)func;
>  #endif
> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
> index f1630c553efe..97da77bc48c9 100644
> --- a/arch/powerpc/include/asm/types.h
> +++ b/arch/powerpc/include/asm/types.h
> @@ -23,12 +23,6 @@
>  
>  typedef __vector128 vector128;
>  
> -typedef struct {
> -	unsigned long entry;
> -	unsigned long toc;
> -	unsigned long env;
> -} func_descr_t;

I was a little concerned about going from a 3-element struct to a
2-element struct (as ppc64_opd_entry doesn't have an element for env) -
but we don't seem to take the sizeof this anywhere, nor do we use env
anywhere, nor do we do funky macro stuff with it in the signal handling
code that might implictly use the 3rd element, so I guess this will
work. Still, func_descr_t seems to describe the underlying ABI better
than ppc64_opd_entry...

>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_POWERPC_TYPES_H */
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index 1831bba0582e..63ddbe7b108c 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>  		 * descriptor is the entry address of signal and the second
>  		 * entry is the TOC value we need to use.
>  		 */
> -		func_descr_t __user *funct_desc_ptr =
> -			(func_descr_t __user *) ksig->ka.sa.sa_handler;
> +		struct ppc64_opd_entry __user *funct_desc_ptr =
> +			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
>  
> -		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
> -		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
> +		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
> +		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);

Likewise, r2 seems like a worse name than toc. I guess we could clean
that up another time though.

Kind regards,
Daniel

>  	}
>  
>  	/* enter the signal handler in native-endian mode */
> -- 
> 2.31.1

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'

So, if I understand the overall direction of the series, you're
consolidating powerpc around one single type for function descriptors,
and then you're creating a generic typedef so that generic code can
always do ((func_desc_t)x)->addr to get the address of a function out of
a function descriptor regardless of arch. (And regardless of whether the
arch uses function descriptors or not.)

So:

 - why pick ppc64_opd_entry over func_descr_t?

 - Why not make our struct just called func_desc_t - why have a
   ppc64_opd_entry type or a func_descr_t typedef?

 - Should this patch wait until after you've made the generic
   func_desc_t change and move directly to that new interface? (rather
   than move from func_descr_t -> ppc64_opd_entry -> ...) Or is there a
   particular reason arch specific code should use an arch-specific
   struct or named type?

> Remove it.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/include/asm/code-patching.h | 2 +-
>  arch/powerpc/include/asm/types.h         | 6 ------
>  arch/powerpc/kernel/signal_64.c          | 8 ++++----
>  3 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
> index 4ba834599c4d..f3445188d319 100644
> --- a/arch/powerpc/include/asm/code-patching.h
> +++ b/arch/powerpc/include/asm/code-patching.h
> @@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
>  	 * function's descriptor. The first entry in the descriptor is the
>  	 * address of the function text.
>  	 */
> -	return ((func_descr_t *)func)->entry;
> +	return ((struct ppc64_opd_entry *)func)->addr;
>  #else
>  	return (unsigned long)func;
>  #endif
> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
> index f1630c553efe..97da77bc48c9 100644
> --- a/arch/powerpc/include/asm/types.h
> +++ b/arch/powerpc/include/asm/types.h
> @@ -23,12 +23,6 @@
>  
>  typedef __vector128 vector128;
>  
> -typedef struct {
> -	unsigned long entry;
> -	unsigned long toc;
> -	unsigned long env;
> -} func_descr_t;

I was a little concerned about going from a 3-element struct to a
2-element struct (as ppc64_opd_entry doesn't have an element for env) -
but we don't seem to take the sizeof this anywhere, nor do we use env
anywhere, nor do we do funky macro stuff with it in the signal handling
code that might implictly use the 3rd element, so I guess this will
work. Still, func_descr_t seems to describe the underlying ABI better
than ppc64_opd_entry...

>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_POWERPC_TYPES_H */
> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
> index 1831bba0582e..63ddbe7b108c 100644
> --- a/arch/powerpc/kernel/signal_64.c
> +++ b/arch/powerpc/kernel/signal_64.c
> @@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>  		 * descriptor is the entry address of signal and the second
>  		 * entry is the TOC value we need to use.
>  		 */
> -		func_descr_t __user *funct_desc_ptr > -			(func_descr_t __user *) ksig->ka.sa.sa_handler;
> +		struct ppc64_opd_entry __user *funct_desc_ptr > +			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
>  
> -		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
> -		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
> +		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
> +		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);

Likewise, r2 seems like a worse name than toc. I guess we could clean
that up another time though.

Kind regards,
Daniel

>  	}
>  
>  	/* enter the signal handler in native-endian mode */
> -- 
> 2.31.1

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Christophe Leroy]

Le 15/10/2021 à 00:17, Daniel Axtens a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 
>> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'
> 
> So, if I understand the overall direction of the series, you're
> consolidating powerpc around one single type for function descriptors,
> and then you're creating a generic typedef so that generic code can
> always do ((func_desc_t)x)->addr to get the address of a function out of
> a function descriptor regardless of arch. (And regardless of whether the
> arch uses function descriptors or not.)

An architecture not using function descriptors won't do much with 
((func_desc_t *)x)->addr. This is just done to allow building stuff 
regardless.

I prefer something like

	if (have_function_descriptors())
		addr = (func_desc_t *)ptr)->addr;
	else
		addr = ptr;

over

	#ifdef HAVE_FUNCTION_DESCRIPTORS
		addr = (func_desc_t *)ptr)->addr;
	#else
		addr = ptr;
	#endif

> 
> So:
> 
>   - why pick ppc64_opd_entry over func_descr_t?

Good question. At the begining it was because it was in UAPI headers, 
and also because it was the one used in our 
dereference_function_descriptor().

But at the end maybe that's not the more logical choice. I need to look 
a bit more.

> 
>   - Why not make our struct just called func_desc_t - why have a
>     ppc64_opd_entry type or a func_descr_t typedef?

Well ... you usually don't flag a struct name with _t, _t will most of 
the time refer to a typedef.

If I want to avoid typedef (I know they are deprecated in kernel coding 
stype), it means the name of the struct must be changed in every 
architecture and it becomes tricky and it adds more churn in them, which 
is what I want to avoid.

At the end we risk to end-up with a messy set of #ifdefs.

Maybe this can be done as a second step, but I would like to minimise 
impact in this series and focus on fixing lkdtm.


> 
>   - Should this patch wait until after you've made the generic
>     func_desc_t change and move directly to that new interface? (rather
>     than move from func_descr_t -> ppc64_opd_entry -> ...) Or is there a
>     particular reason arch specific code should use an arch-specific
>     struct or named type?

As mentioned in kernel coding style, typedefs reduce readability, see 
https://www.kernel.org/doc/html/latest/process/coding-style.html#typedefs

But yes, we could make a step in the direction of a common 'struct 
func_desc'. Let's see if I can do that.

Thanks for your comments.

Christophe

> 
>> Remove it.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/powerpc/include/asm/code-patching.h | 2 +-
>>   arch/powerpc/include/asm/types.h         | 6 ------
>>   arch/powerpc/kernel/signal_64.c          | 8 ++++----
>>   3 files changed, 5 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
>> index 4ba834599c4d..f3445188d319 100644
>> --- a/arch/powerpc/include/asm/code-patching.h
>> +++ b/arch/powerpc/include/asm/code-patching.h
>> @@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
>>   	 * function's descriptor. The first entry in the descriptor is the
>>   	 * address of the function text.
>>   	 */
>> -	return ((func_descr_t *)func)->entry;
>> +	return ((struct ppc64_opd_entry *)func)->addr;
>>   #else
>>   	return (unsigned long)func;
>>   #endif
>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>> index f1630c553efe..97da77bc48c9 100644
>> --- a/arch/powerpc/include/asm/types.h
>> +++ b/arch/powerpc/include/asm/types.h
>> @@ -23,12 +23,6 @@
>>   
>>   typedef __vector128 vector128;
>>   
>> -typedef struct {
>> -	unsigned long entry;
>> -	unsigned long toc;
>> -	unsigned long env;
>> -} func_descr_t;
> 
> I was a little concerned about going from a 3-element struct to a
> 2-element struct (as ppc64_opd_entry doesn't have an element for env) -
> but we don't seem to take the sizeof this anywhere, nor do we use env
> anywhere, nor do we do funky macro stuff with it in the signal handling
> code that might implictly use the 3rd element, so I guess this will
> work. Still, func_descr_t seems to describe the underlying ABI better
> than ppc64_opd_entry...
> 
>>   #endif /* __ASSEMBLY__ */
>>   
>>   #endif /* _ASM_POWERPC_TYPES_H */
>> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
>> index 1831bba0582e..63ddbe7b108c 100644
>> --- a/arch/powerpc/kernel/signal_64.c
>> +++ b/arch/powerpc/kernel/signal_64.c
>> @@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>>   		 * descriptor is the entry address of signal and the second
>>   		 * entry is the TOC value we need to use.
>>   		 */
>> -		func_descr_t __user *funct_desc_ptr =
>> -			(func_descr_t __user *) ksig->ka.sa.sa_handler;
>> +		struct ppc64_opd_entry __user *funct_desc_ptr =
>> +			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
>>   
>> -		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
>> -		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
>> +		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
>> +		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);
> 
> Likewise, r2 seems like a worse name than toc. I guess we could clean
> that up another time though.
> 
> Kind regards,
> Daniel
> 
>>   	}
>>   
>>   	/* enter the signal handler in native-endian mode */
>> -- 
>> 2.31.1

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Christophe Leroy]

Le 15/10/2021 à 00:17, Daniel Axtens a écrit :
> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
> 
>> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'
> 
> So, if I understand the overall direction of the series, you're
> consolidating powerpc around one single type for function descriptors,
> and then you're creating a generic typedef so that generic code can
> always do ((func_desc_t)x)->addr to get the address of a function out of
> a function descriptor regardless of arch. (And regardless of whether the
> arch uses function descriptors or not.)

An architecture not using function descriptors won't do much with 
((func_desc_t *)x)->addr. This is just done to allow building stuff 
regardless.

I prefer something like

	if (have_function_descriptors())
		addr = (func_desc_t *)ptr)->addr;
	else
		addr = ptr;

over

	#ifdef HAVE_FUNCTION_DESCRIPTORS
		addr = (func_desc_t *)ptr)->addr;
	#else
		addr = ptr;
	#endif

> 
> So:
> 
>   - why pick ppc64_opd_entry over func_descr_t?

Good question. At the begining it was because it was in UAPI headers, 
and also because it was the one used in our 
dereference_function_descriptor().

But at the end maybe that's not the more logical choice. I need to look 
a bit more.

> 
>   - Why not make our struct just called func_desc_t - why have a
>     ppc64_opd_entry type or a func_descr_t typedef?

Well ... you usually don't flag a struct name with _t, _t will most of 
the time refer to a typedef.

If I want to avoid typedef (I know they are deprecated in kernel coding 
stype), it means the name of the struct must be changed in every 
architecture and it becomes tricky and it adds more churn in them, which 
is what I want to avoid.

At the end we risk to end-up with a messy set of #ifdefs.

Maybe this can be done as a second step, but I would like to minimise 
impact in this series and focus on fixing lkdtm.


> 
>   - Should this patch wait until after you've made the generic
>     func_desc_t change and move directly to that new interface? (rather
>     than move from func_descr_t -> ppc64_opd_entry -> ...) Or is there a
>     particular reason arch specific code should use an arch-specific
>     struct or named type?

As mentioned in kernel coding style, typedefs reduce readability, see 
https://www.kernel.org/doc/html/latest/process/coding-style.html#typedefs

But yes, we could make a step in the direction of a common 'struct 
func_desc'. Let's see if I can do that.

Thanks for your comments.

Christophe

> 
>> Remove it.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/powerpc/include/asm/code-patching.h | 2 +-
>>   arch/powerpc/include/asm/types.h         | 6 ------
>>   arch/powerpc/kernel/signal_64.c          | 8 ++++----
>>   3 files changed, 5 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
>> index 4ba834599c4d..f3445188d319 100644
>> --- a/arch/powerpc/include/asm/code-patching.h
>> +++ b/arch/powerpc/include/asm/code-patching.h
>> @@ -110,7 +110,7 @@ static inline unsigned long ppc_function_entry(void *func)
>>   	 * function's descriptor. The first entry in the descriptor is the
>>   	 * address of the function text.
>>   	 */
>> -	return ((func_descr_t *)func)->entry;
>> +	return ((struct ppc64_opd_entry *)func)->addr;
>>   #else
>>   	return (unsigned long)func;
>>   #endif
>> diff --git a/arch/powerpc/include/asm/types.h b/arch/powerpc/include/asm/types.h
>> index f1630c553efe..97da77bc48c9 100644
>> --- a/arch/powerpc/include/asm/types.h
>> +++ b/arch/powerpc/include/asm/types.h
>> @@ -23,12 +23,6 @@
>>   
>>   typedef __vector128 vector128;
>>   
>> -typedef struct {
>> -	unsigned long entry;
>> -	unsigned long toc;
>> -	unsigned long env;
>> -} func_descr_t;
> 
> I was a little concerned about going from a 3-element struct to a
> 2-element struct (as ppc64_opd_entry doesn't have an element for env) -
> but we don't seem to take the sizeof this anywhere, nor do we use env
> anywhere, nor do we do funky macro stuff with it in the signal handling
> code that might implictly use the 3rd element, so I guess this will
> work. Still, func_descr_t seems to describe the underlying ABI better
> than ppc64_opd_entry...
> 
>>   #endif /* __ASSEMBLY__ */
>>   
>>   #endif /* _ASM_POWERPC_TYPES_H */
>> diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
>> index 1831bba0582e..63ddbe7b108c 100644
>> --- a/arch/powerpc/kernel/signal_64.c
>> +++ b/arch/powerpc/kernel/signal_64.c
>> @@ -933,11 +933,11 @@ int handle_rt_signal64(struct ksignal *ksig, sigset_t *set,
>>   		 * descriptor is the entry address of signal and the second
>>   		 * entry is the TOC value we need to use.
>>   		 */
>> -		func_descr_t __user *funct_desc_ptr >> -			(func_descr_t __user *) ksig->ka.sa.sa_handler;
>> +		struct ppc64_opd_entry __user *funct_desc_ptr >> +			(struct ppc64_opd_entry __user *)ksig->ka.sa.sa_handler;
>>   
>> -		err |= get_user(regs->ctr, &funct_desc_ptr->entry);
>> -		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
>> +		err |= get_user(regs->ctr, &funct_desc_ptr->addr);
>> +		err |= get_user(regs->gpr[2], &funct_desc_ptr->r2);
> 
> Likewise, r2 seems like a worse name than toc. I guess we could clean
> that up another time though.
> 
> Kind regards,
> Daniel
> 
>>   	}
>>   
>>   	/* enter the signal handler in native-endian mode */
>> -- 
>> 2.31.1

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 3:19 pm:
> 
> 
> Le 15/10/2021 à 00:17, Daniel Axtens a écrit :
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> 
>>> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'
>> 
>> So, if I understand the overall direction of the series, you're
>> consolidating powerpc around one single type for function descriptors,
>> and then you're creating a generic typedef so that generic code can
>> always do ((func_desc_t)x)->addr to get the address of a function out of
>> a function descriptor regardless of arch. (And regardless of whether the
>> arch uses function descriptors or not.)
> 
> An architecture not using function descriptors won't do much with 
> ((func_desc_t *)x)->addr. This is just done to allow building stuff 
> regardless.
> 
> I prefer something like
> 
> 	if (have_function_descriptors())
> 		addr = (func_desc_t *)ptr)->addr;
> 	else
> 		addr = ptr;

If you make a generic data type for architectures without function 
descriptors as such

typedef struct func_desc {
    char addr[0];
} func_desc_t;

Then you can do that with no if. The downside is your addr has to be 
char * and it's maybe not helpful to be so "clever".

>>   - why pick ppc64_opd_entry over func_descr_t?
> 
> Good question. At the begining it was because it was in UAPI headers, 
> and also because it was the one used in our 
> dereference_function_descriptor().
> 
> But at the end maybe that's not the more logical choice. I need to look 
> a bit more.

I would prefer the func_descr_t (with 'toc' and 'env') if you're going 
to change it.

Thanks,
Nick

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 3:19 pm:
> 
> 
> Le 15/10/2021 à 00:17, Daniel Axtens a écrit :
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> 
>>> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'
>> 
>> So, if I understand the overall direction of the series, you're
>> consolidating powerpc around one single type for function descriptors,
>> and then you're creating a generic typedef so that generic code can
>> always do ((func_desc_t)x)->addr to get the address of a function out of
>> a function descriptor regardless of arch. (And regardless of whether the
>> arch uses function descriptors or not.)
> 
> An architecture not using function descriptors won't do much with 
> ((func_desc_t *)x)->addr. This is just done to allow building stuff 
> regardless.
> 
> I prefer something like
> 
> 	if (have_function_descriptors())
> 		addr = (func_desc_t *)ptr)->addr;
> 	else
> 		addr = ptr;

If you make a generic data type for architectures without function 
descriptors as such

typedef struct func_desc {
    char addr[0];
} func_desc_t;

Then you can do that with no if. The downside is your addr has to be 
char * and it's maybe not helpful to be so "clever".

>>   - why pick ppc64_opd_entry over func_descr_t?
> 
> Good question. At the begining it was because it was in UAPI headers, 
> and also because it was the one used in our 
> dereference_function_descriptor().
> 
> But at the end maybe that's not the more logical choice. I need to look 
> a bit more.

I would prefer the func_descr_t (with 'toc' and 'env') if you're going 
to change it.

Thanks,
Nick

Re: [PATCH v2 03/13] powerpc: Remove func_descr_t

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 3:19 pm:
> 
> 
> Le 15/10/2021 à 00:17, Daniel Axtens a écrit :
>> Christophe Leroy <christophe.leroy@csgroup.eu> writes:
>> 
>>> 'func_descr_t' is redundant with 'struct ppc64_opd_entry'
>> 
>> So, if I understand the overall direction of the series, you're
>> consolidating powerpc around one single type for function descriptors,
>> and then you're creating a generic typedef so that generic code can
>> always do ((func_desc_t)x)->addr to get the address of a function out of
>> a function descriptor regardless of arch. (And regardless of whether the
>> arch uses function descriptors or not.)
> 
> An architecture not using function descriptors won't do much with 
> ((func_desc_t *)x)->addr. This is just done to allow building stuff 
> regardless.
> 
> I prefer something like
> 
> 	if (have_function_descriptors())
> 		addr = (func_desc_t *)ptr)->addr;
> 	else
> 		addr = ptr;

If you make a generic data type for architectures without function 
descriptors as such

typedef struct func_desc {
    char addr[0];
} func_desc_t;

Then you can do that with no if. The downside is your addr has to be 
char * and it's maybe not helpful to be so "clever".

>>   - why pick ppc64_opd_entry over func_descr_t?
> 
> Good question. At the begining it was because it was in UAPI headers, 
> and also because it was the one used in our 
> dereference_function_descriptor().
> 
> But at the end maybe that's not the more logical choice. I need to look 
> a bit more.

I would prefer the func_descr_t (with 'toc' and 'env') if you're going 
to change it.

Thanks,
Nick

[PATCH v2 04/13] powerpc: Prepare func_desc_t for refactorisation

[Christophe Leroy]

In preparation of making func_desc_t generic, change it to
a struct containing 'addr' element.

In addition this allows using single helpers common to ELFv1 and ELFv2.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/module_64.c | 34 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 82908c9be627..dc99a3f6cee2 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -33,19 +33,13 @@
 #ifdef PPC64_ELF_ABI_v2
 
 /* An address is simply the address of the function. */
-typedef unsigned long func_desc_t;
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func;
+	return (func_desc_t){addr};
 }
 
 /* PowerPC64 specific values for the Elf64_Sym st_other field.  */
@@ -68,15 +62,7 @@ typedef struct ppc64_opd_entry func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return *(struct ppc64_opd_entry *)addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return func_desc(addr).addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func.addr;
+	return *(func_desc_t *)addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -93,6 +79,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 }
 #endif
 
+static unsigned long func_addr(unsigned long addr)
+{
+	return func_desc(addr).addr;
+}
+
+static unsigned long stub_func_addr(func_desc_t func)
+{
+	return func.addr;
+}
+
 #define STUB_MAGIC 0x73747562 /* stub */
 
 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
-- 
2.31.1

[PATCH v2 04/13] powerpc: Prepare func_desc_t for refactorisation

[Christophe Leroy]

In preparation of making func_desc_t generic, change it to
a struct containing 'addr' element.

In addition this allows using single helpers common to ELFv1 and ELFv2.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/module_64.c | 34 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 82908c9be627..dc99a3f6cee2 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -33,19 +33,13 @@
 #ifdef PPC64_ELF_ABI_v2
 
 /* An address is simply the address of the function. */
-typedef unsigned long func_desc_t;
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func;
+	return (func_desc_t){addr};
 }
 
 /* PowerPC64 specific values for the Elf64_Sym st_other field.  */
@@ -68,15 +62,7 @@ typedef struct ppc64_opd_entry func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return *(struct ppc64_opd_entry *)addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return func_desc(addr).addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func.addr;
+	return *(func_desc_t *)addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -93,6 +79,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 }
 #endif
 
+static unsigned long func_addr(unsigned long addr)
+{
+	return func_desc(addr).addr;
+}
+
+static unsigned long stub_func_addr(func_desc_t func)
+{
+	return func.addr;
+}
+
 #define STUB_MAGIC 0x73747562 /* stub */
 
 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
-- 
2.31.1

[PATCH v2 04/13] powerpc: Prepare func_desc_t for refactorisation

[Christophe Leroy]

In preparation of making func_desc_t generic, change it to
a struct containing 'addr' element.

In addition this allows using single helpers common to ELFv1 and ELFv2.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/module_64.c | 34 +++++++++++++++------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 82908c9be627..dc99a3f6cee2 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -33,19 +33,13 @@
 #ifdef PPC64_ELF_ABI_v2
 
 /* An address is simply the address of the function. */
-typedef unsigned long func_desc_t;
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func;
+	return (func_desc_t){addr};
 }
 
 /* PowerPC64 specific values for the Elf64_Sym st_other field.  */
@@ -68,15 +62,7 @@ typedef struct ppc64_opd_entry func_desc_t;
 
 static func_desc_t func_desc(unsigned long addr)
 {
-	return *(struct ppc64_opd_entry *)addr;
-}
-static unsigned long func_addr(unsigned long addr)
-{
-	return func_desc(addr).addr;
-}
-static unsigned long stub_func_addr(func_desc_t func)
-{
-	return func.addr;
+	return *(func_desc_t *)addr;
 }
 static unsigned int local_entry_offset(const Elf64_Sym *sym)
 {
@@ -93,6 +79,16 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 }
 #endif
 
+static unsigned long func_addr(unsigned long addr)
+{
+	return func_desc(addr).addr;
+}
+
+static unsigned long stub_func_addr(func_desc_t func)
+{
+	return func.addr;
+}
+
 #define STUB_MAGIC 0x73747562 /* stub */
 
 /* Like PPC32, we need little trampolines to do > 24-bit jumps (into
-- 
2.31.1

[PATCH v2 05/13] ia64: Rename 'ip' to 'addr' in 'struct fdesc'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct fdesc' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/elf.h      | 2 +-
 arch/ia64/include/asm/sections.h | 2 +-
 arch/ia64/kernel/module.c        | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/ia64/include/asm/elf.h b/arch/ia64/include/asm/elf.h
index 6629301a2620..2ef5f9966ad1 100644
--- a/arch/ia64/include/asm/elf.h
+++ b/arch/ia64/include/asm/elf.h
@@ -226,7 +226,7 @@ struct got_entry {
  * Layout of the Function Descriptor
  */
 struct fdesc {
-	uint64_t ip;
+	uint64_t addr;
 	uint64_t gp;
 };
 
diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 3a033d2008b3..35f24e52149a 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -35,7 +35,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct fdesc *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->ip))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index 2cba53c1da82..4f6400cbf79e 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -602,15 +602,15 @@ get_fdesc (struct module *mod, uint64_t value, int *okp)
 		return value;
 
 	/* Look for existing function descriptor. */
-	while (fdesc->ip) {
-		if (fdesc->ip == value)
+	while (fdesc->addr) {
+		if (fdesc->addr == value)
 			return (uint64_t)fdesc;
 		if ((uint64_t) ++fdesc >= mod->arch.opd->sh_addr + mod->arch.opd->sh_size)
 			BUG();
 	}
 
 	/* Create new one */
-	fdesc->ip = value;
+	fdesc->addr = value;
 	fdesc->gp = mod->arch.gp;
 	return (uint64_t) fdesc;
 }
-- 
2.31.1

[PATCH v2 05/13] ia64: Rename 'ip' to 'addr' in 'struct fdesc'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct fdesc' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/elf.h      | 2 +-
 arch/ia64/include/asm/sections.h | 2 +-
 arch/ia64/kernel/module.c        | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/ia64/include/asm/elf.h b/arch/ia64/include/asm/elf.h
index 6629301a2620..2ef5f9966ad1 100644
--- a/arch/ia64/include/asm/elf.h
+++ b/arch/ia64/include/asm/elf.h
@@ -226,7 +226,7 @@ struct got_entry {
  * Layout of the Function Descriptor
  */
 struct fdesc {
-	uint64_t ip;
+	uint64_t addr;
 	uint64_t gp;
 };
 
diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 3a033d2008b3..35f24e52149a 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -35,7 +35,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct fdesc *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->ip))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index 2cba53c1da82..4f6400cbf79e 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -602,15 +602,15 @@ get_fdesc (struct module *mod, uint64_t value, int *okp)
 		return value;
 
 	/* Look for existing function descriptor. */
-	while (fdesc->ip) {
-		if (fdesc->ip = value)
+	while (fdesc->addr) {
+		if (fdesc->addr = value)
 			return (uint64_t)fdesc;
 		if ((uint64_t) ++fdesc >= mod->arch.opd->sh_addr + mod->arch.opd->sh_size)
 			BUG();
 	}
 
 	/* Create new one */
-	fdesc->ip = value;
+	fdesc->addr = value;
 	fdesc->gp = mod->arch.gp;
 	return (uint64_t) fdesc;
 }
-- 
2.31.1

[PATCH v2 05/13] ia64: Rename 'ip' to 'addr' in 'struct fdesc'

[Christophe Leroy]

There are three architectures with function descriptors, try to
have common names for the address they contain in order to
refactor some functions into generic functions later.

powerpc has 'funcaddr'
ia64 has 'ip'
parisc has 'addr'

Vote for 'addr' and update 'struct fdesc' accordingly.

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/elf.h      | 2 +-
 arch/ia64/include/asm/sections.h | 2 +-
 arch/ia64/kernel/module.c        | 6 +++---
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/ia64/include/asm/elf.h b/arch/ia64/include/asm/elf.h
index 6629301a2620..2ef5f9966ad1 100644
--- a/arch/ia64/include/asm/elf.h
+++ b/arch/ia64/include/asm/elf.h
@@ -226,7 +226,7 @@ struct got_entry {
  * Layout of the Function Descriptor
  */
 struct fdesc {
-	uint64_t ip;
+	uint64_t addr;
 	uint64_t gp;
 };
 
diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 3a033d2008b3..35f24e52149a 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -35,7 +35,7 @@ static inline void *dereference_function_descriptor(void *ptr)
 	struct fdesc *desc = ptr;
 	void *p;
 
-	if (!get_kernel_nofault(p, (void *)&desc->ip))
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
 		ptr = p;
 	return ptr;
 }
diff --git a/arch/ia64/kernel/module.c b/arch/ia64/kernel/module.c
index 2cba53c1da82..4f6400cbf79e 100644
--- a/arch/ia64/kernel/module.c
+++ b/arch/ia64/kernel/module.c
@@ -602,15 +602,15 @@ get_fdesc (struct module *mod, uint64_t value, int *okp)
 		return value;
 
 	/* Look for existing function descriptor. */
-	while (fdesc->ip) {
-		if (fdesc->ip == value)
+	while (fdesc->addr) {
+		if (fdesc->addr == value)
 			return (uint64_t)fdesc;
 		if ((uint64_t) ++fdesc >= mod->arch.opd->sh_addr + mod->arch.opd->sh_size)
 			BUG();
 	}
 
 	/* Create new one */
-	fdesc->ip = value;
+	fdesc->addr = value;
 	fdesc->gp = mod->arch.gp;
 	return (uint64_t) fdesc;
 }
-- 
2.31.1

[PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
HAVE_FUNCTION_DESCRIPTORS and use it instead of
'dereference_function_descriptor' macro to know
whether an arch has function descriptors.

To limit churn in one of the following patches, use
an #ifdef/#else construct with empty first part
instead of an #ifndef in asm-generic/sections.h

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 5 +++--
 arch/parisc/include/asm/sections.h  | 6 ++++--
 arch/powerpc/include/asm/sections.h | 6 ++++--
 include/asm-generic/sections.h      | 3 ++-
 include/linux/kallsyms.h            | 2 +-
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 35f24e52149a..6e55e545bf02 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -9,6 +9,9 @@
 
 #include <linux/elf.h>
 #include <linux/uaccess.h>
+
+#define HAVE_FUNCTION_DESCRIPTORS 1
+
 #include <asm-generic/sections.h>
 
 extern char __phys_per_cpu_start[];
@@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..85149a89ff3e 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -2,6 +2,10 @@
 #ifndef _PARISC_SECTIONS_H
 #define _PARISC_SECTIONS_H
 
+#ifdef CONFIG_64BIT
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
@@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
 
 #ifdef CONFIG_64BIT
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 void *dereference_function_descriptor(void *);
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 32e7035863ac..bba97b8c38cf 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -8,6 +8,10 @@
 
 #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
 
+#ifdef PPC64_ELF_ABI_v1
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 #include <asm-generic/sections.h>
 
 extern bool init_mem_is_free;
@@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 
 #ifdef PPC64_ELF_ABI_v1
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d16302d3eb59..b677e926e6b3 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
 extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
-#ifndef dereference_function_descriptor
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+#else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
 #endif
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index a1d6fc82d7f0..9f277baeb559 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
 
 static inline void *dereference_symbol_descriptor(void *ptr)
 {
-#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+#ifdef HAVE_FUNCTION_DESCRIPTORS
 	struct module *mod;
 
 	ptr = dereference_kernel_function_descriptor(ptr);
-- 
2.31.1

[PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
HAVE_FUNCTION_DESCRIPTORS and use it instead of
'dereference_function_descriptor' macro to know
whether an arch has function descriptors.

To limit churn in one of the following patches, use
an #ifdef/#else construct with empty first part
instead of an #ifndef in asm-generic/sections.h

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 5 +++--
 arch/parisc/include/asm/sections.h  | 6 ++++--
 arch/powerpc/include/asm/sections.h | 6 ++++--
 include/asm-generic/sections.h      | 3 ++-
 include/linux/kallsyms.h            | 2 +-
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 35f24e52149a..6e55e545bf02 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -9,6 +9,9 @@
 
 #include <linux/elf.h>
 #include <linux/uaccess.h>
+
+#define HAVE_FUNCTION_DESCRIPTORS 1
+
 #include <asm-generic/sections.h>
 
 extern char __phys_per_cpu_start[];
@@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..85149a89ff3e 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -2,6 +2,10 @@
 #ifndef _PARISC_SECTIONS_H
 #define _PARISC_SECTIONS_H
 
+#ifdef CONFIG_64BIT
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
@@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
 
 #ifdef CONFIG_64BIT
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 void *dereference_function_descriptor(void *);
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 32e7035863ac..bba97b8c38cf 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -8,6 +8,10 @@
 
 #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
 
+#ifdef PPC64_ELF_ABI_v1
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 #include <asm-generic/sections.h>
 
 extern bool init_mem_is_free;
@@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 
 #ifdef PPC64_ELF_ABI_v1
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d16302d3eb59..b677e926e6b3 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
 extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
-#ifndef dereference_function_descriptor
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+#else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
 #endif
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index a1d6fc82d7f0..9f277baeb559 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
 
 static inline void *dereference_symbol_descriptor(void *ptr)
 {
-#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+#ifdef HAVE_FUNCTION_DESCRIPTORS
 	struct module *mod;
 
 	ptr = dereference_kernel_function_descriptor(ptr);
-- 
2.31.1

[PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
HAVE_FUNCTION_DESCRIPTORS and use it instead of
'dereference_function_descriptor' macro to know
whether an arch has function descriptors.

To limit churn in one of the following patches, use
an #ifdef/#else construct with empty first part
instead of an #ifndef in asm-generic/sections.h

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 5 +++--
 arch/parisc/include/asm/sections.h  | 6 ++++--
 arch/powerpc/include/asm/sections.h | 6 ++++--
 include/asm-generic/sections.h      | 3 ++-
 include/linux/kallsyms.h            | 2 +-
 5 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 35f24e52149a..6e55e545bf02 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -9,6 +9,9 @@
 
 #include <linux/elf.h>
 #include <linux/uaccess.h>
+
+#define HAVE_FUNCTION_DESCRIPTORS 1
+
 #include <asm-generic/sections.h>
 
 extern char __phys_per_cpu_start[];
@@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index bb52aea0cb21..85149a89ff3e 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -2,6 +2,10 @@
 #ifndef _PARISC_SECTIONS_H
 #define _PARISC_SECTIONS_H
 
+#ifdef CONFIG_64BIT
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
@@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
 
 #ifdef CONFIG_64BIT
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 void *dereference_function_descriptor(void *);
 
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 32e7035863ac..bba97b8c38cf 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -8,6 +8,10 @@
 
 #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
 
+#ifdef PPC64_ELF_ABI_v1
+#define HAVE_FUNCTION_DESCRIPTORS 1
+#endif
+
 #include <asm-generic/sections.h>
 
 extern bool init_mem_is_free;
@@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 
 #ifdef PPC64_ELF_ABI_v1
 
-#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
-
 #undef dereference_function_descriptor
 static inline void *dereference_function_descriptor(void *ptr)
 {
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index d16302d3eb59..b677e926e6b3 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
 extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
-#ifndef dereference_function_descriptor
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+#else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
 #endif
diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
index a1d6fc82d7f0..9f277baeb559 100644
--- a/include/linux/kallsyms.h
+++ b/include/linux/kallsyms.h
@@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
 
 static inline void *dereference_symbol_descriptor(void *ptr)
 {
-#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
+#ifdef HAVE_FUNCTION_DESCRIPTORS
 	struct module *mod;
 
 	ptr = dereference_kernel_function_descriptor(ptr);
-- 
2.31.1

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
> HAVE_FUNCTION_DESCRIPTORS and use it instead of
> 'dereference_function_descriptor' macro to know
> whether an arch has function descriptors.
> 
> To limit churn in one of the following patches, use
> an #ifdef/#else construct with empty first part
> instead of an #ifndef in asm-generic/sections.h

Is it worth putting this into Kconfig if you're going to
change it? In any case

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 5 +++--
>  arch/parisc/include/asm/sections.h  | 6 ++++--
>  arch/powerpc/include/asm/sections.h | 6 ++++--
>  include/asm-generic/sections.h      | 3 ++-
>  include/linux/kallsyms.h            | 2 +-
>  5 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 35f24e52149a..6e55e545bf02 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -9,6 +9,9 @@
>  
>  #include <linux/elf.h>
>  #include <linux/uaccess.h>
> +
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +
>  #include <asm-generic/sections.h>
>  
>  extern char __phys_per_cpu_start[];
> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index bb52aea0cb21..85149a89ff3e 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -2,6 +2,10 @@
>  #ifndef _PARISC_SECTIONS_H
>  #define _PARISC_SECTIONS_H
>  
> +#ifdef CONFIG_64BIT
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  /* nothing to see, move along */
>  #include <asm-generic/sections.h>
>  
> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>  
>  #ifdef CONFIG_64BIT
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  void *dereference_function_descriptor(void *);
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 32e7035863ac..bba97b8c38cf 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -8,6 +8,10 @@
>  
>  #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>  
> +#ifdef PPC64_ELF_ABI_v1
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  #include <asm-generic/sections.h>
>  
>  extern bool init_mem_is_free;
> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  
>  #ifdef PPC64_ELF_ABI_v1
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index d16302d3eb59..b677e926e6b3 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>  extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
> -#ifndef dereference_function_descriptor
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +#else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
>  #endif
> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
> index a1d6fc82d7f0..9f277baeb559 100644
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>  
>  static inline void *dereference_symbol_descriptor(void *ptr)
>  {
> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>  	struct module *mod;
>  
>  	ptr = dereference_kernel_function_descriptor(ptr);
> -- 
> 2.31.1
> 
> 
> 

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
> HAVE_FUNCTION_DESCRIPTORS and use it instead of
> 'dereference_function_descriptor' macro to know
> whether an arch has function descriptors.
> 
> To limit churn in one of the following patches, use
> an #ifdef/#else construct with empty first part
> instead of an #ifndef in asm-generic/sections.h

Is it worth putting this into Kconfig if you're going to
change it? In any case

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 5 +++--
>  arch/parisc/include/asm/sections.h  | 6 ++++--
>  arch/powerpc/include/asm/sections.h | 6 ++++--
>  include/asm-generic/sections.h      | 3 ++-
>  include/linux/kallsyms.h            | 2 +-
>  5 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 35f24e52149a..6e55e545bf02 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -9,6 +9,9 @@
>  
>  #include <linux/elf.h>
>  #include <linux/uaccess.h>
> +
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +
>  #include <asm-generic/sections.h>
>  
>  extern char __phys_per_cpu_start[];
> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index bb52aea0cb21..85149a89ff3e 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -2,6 +2,10 @@
>  #ifndef _PARISC_SECTIONS_H
>  #define _PARISC_SECTIONS_H
>  
> +#ifdef CONFIG_64BIT
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  /* nothing to see, move along */
>  #include <asm-generic/sections.h>
>  
> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>  
>  #ifdef CONFIG_64BIT
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  void *dereference_function_descriptor(void *);
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 32e7035863ac..bba97b8c38cf 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -8,6 +8,10 @@
>  
>  #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>  
> +#ifdef PPC64_ELF_ABI_v1
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  #include <asm-generic/sections.h>
>  
>  extern bool init_mem_is_free;
> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  
>  #ifdef PPC64_ELF_ABI_v1
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index d16302d3eb59..b677e926e6b3 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>  extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
> -#ifndef dereference_function_descriptor
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +#else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
>  #endif
> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
> index a1d6fc82d7f0..9f277baeb559 100644
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>  
>  static inline void *dereference_symbol_descriptor(void *ptr)
>  {
> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>  	struct module *mod;
>  
>  	ptr = dereference_kernel_function_descriptor(ptr);
> -- 
> 2.31.1
> 
> 
> 

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
> HAVE_FUNCTION_DESCRIPTORS and use it instead of
> 'dereference_function_descriptor' macro to know
> whether an arch has function descriptors.
> 
> To limit churn in one of the following patches, use
> an #ifdef/#else construct with empty first part
> instead of an #ifndef in asm-generic/sections.h

Is it worth putting this into Kconfig if you're going to
change it? In any case

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 5 +++--
>  arch/parisc/include/asm/sections.h  | 6 ++++--
>  arch/powerpc/include/asm/sections.h | 6 ++++--
>  include/asm-generic/sections.h      | 3 ++-
>  include/linux/kallsyms.h            | 2 +-
>  5 files changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 35f24e52149a..6e55e545bf02 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -9,6 +9,9 @@
>  
>  #include <linux/elf.h>
>  #include <linux/uaccess.h>
> +
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +
>  #include <asm-generic/sections.h>
>  
>  extern char __phys_per_cpu_start[];
> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index bb52aea0cb21..85149a89ff3e 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -2,6 +2,10 @@
>  #ifndef _PARISC_SECTIONS_H
>  #define _PARISC_SECTIONS_H
>  
> +#ifdef CONFIG_64BIT
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  /* nothing to see, move along */
>  #include <asm-generic/sections.h>
>  
> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>  
>  #ifdef CONFIG_64BIT
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  void *dereference_function_descriptor(void *);
>  
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 32e7035863ac..bba97b8c38cf 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -8,6 +8,10 @@
>  
>  #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>  
> +#ifdef PPC64_ELF_ABI_v1
> +#define HAVE_FUNCTION_DESCRIPTORS 1
> +#endif
> +
>  #include <asm-generic/sections.h>
>  
>  extern bool init_mem_is_free;
> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  
>  #ifdef PPC64_ELF_ABI_v1
>  
> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> -
>  #undef dereference_function_descriptor
>  static inline void *dereference_function_descriptor(void *ptr)
>  {
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index d16302d3eb59..b677e926e6b3 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>  extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
> -#ifndef dereference_function_descriptor
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +#else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
>  #endif
> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
> index a1d6fc82d7f0..9f277baeb559 100644
> --- a/include/linux/kallsyms.h
> +++ b/include/linux/kallsyms.h
> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>  
>  static inline void *dereference_symbol_descriptor(void *ptr)
>  {
> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>  	struct module *mod;
>  
>  	ptr = dereference_kernel_function_descriptor(ptr);
> -- 
> 2.31.1
> 
> 
> 

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>> 'dereference_function_descriptor' macro to know
>> whether an arch has function descriptors.
>>
>> To limit churn in one of the following patches, use
>> an #ifdef/#else construct with empty first part
>> instead of an #ifndef in asm-generic/sections.h
> 
> Is it worth putting this into Kconfig if you're going to
> change it? In any case

That was what I wanted to do in the begining but how can I do that in 
Kconfig ?

#ifdef __powerpc64__
#if defined(_CALL_ELF) && _CALL_ELF == 2
#define PPC64_ELF_ABI_v2
#else
#define PPC64_ELF_ABI_v1
#endif
#endif /* __powerpc64__ */

#ifdef PPC64_ELF_ABI_v1
#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

Christophe

> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/ia64/include/asm/sections.h    | 5 +++--
>>   arch/parisc/include/asm/sections.h  | 6 ++++--
>>   arch/powerpc/include/asm/sections.h | 6 ++++--
>>   include/asm-generic/sections.h      | 3 ++-
>>   include/linux/kallsyms.h            | 2 +-
>>   5 files changed, 14 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
>> index 35f24e52149a..6e55e545bf02 100644
>> --- a/arch/ia64/include/asm/sections.h
>> +++ b/arch/ia64/include/asm/sections.h
>> @@ -9,6 +9,9 @@
>>   
>>   #include <linux/elf.h>
>>   #include <linux/uaccess.h>
>> +
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern char __phys_per_cpu_start[];
>> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>>   extern char __start_unwind[], __end_unwind[];
>>   extern char __start_ivt_text[], __end_ivt_text[];
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
>> index bb52aea0cb21..85149a89ff3e 100644
>> --- a/arch/parisc/include/asm/sections.h
>> +++ b/arch/parisc/include/asm/sections.h
>> @@ -2,6 +2,10 @@
>>   #ifndef _PARISC_SECTIONS_H
>>   #define _PARISC_SECTIONS_H
>>   
>> +#ifdef CONFIG_64BIT
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   /* nothing to see, move along */
>>   #include <asm-generic/sections.h>
>>   
>> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>>   
>>   #ifdef CONFIG_64BIT
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   void *dereference_function_descriptor(void *);
>>   
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 32e7035863ac..bba97b8c38cf 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -8,6 +8,10 @@
>>   
>>   #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>>   
>> +#ifdef PPC64_ELF_ABI_v1
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern bool init_mem_is_free;
>> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>>   
>>   #ifdef PPC64_ELF_ABI_v1
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index d16302d3eb59..b677e926e6b3 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>>   extern __visible const void __nosave_begin, __nosave_end;
>>   
>>   /* Function descriptor handling (if any).  Override in asm/sections.h */
>> -#ifndef dereference_function_descriptor
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>> +#else
>>   #define dereference_function_descriptor(p) ((void *)(p))
>>   #define dereference_kernel_function_descriptor(p) ((void *)(p))
>>   #endif
>> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
>> index a1d6fc82d7f0..9f277baeb559 100644
>> --- a/include/linux/kallsyms.h
>> +++ b/include/linux/kallsyms.h
>> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>>   
>>   static inline void *dereference_symbol_descriptor(void *ptr)
>>   {
>> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>>   	struct module *mod;
>>   
>>   	ptr = dereference_kernel_function_descriptor(ptr);
>> -- 
>> 2.31.1
>>
>>
>>

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>> 'dereference_function_descriptor' macro to know
>> whether an arch has function descriptors.
>>
>> To limit churn in one of the following patches, use
>> an #ifdef/#else construct with empty first part
>> instead of an #ifndef in asm-generic/sections.h
> 
> Is it worth putting this into Kconfig if you're going to
> change it? In any case

That was what I wanted to do in the begining but how can I do that in 
Kconfig ?

#ifdef __powerpc64__
#if defined(_CALL_ELF) && _CALL_ELF = 2
#define PPC64_ELF_ABI_v2
#else
#define PPC64_ELF_ABI_v1
#endif
#endif /* __powerpc64__ */

#ifdef PPC64_ELF_ABI_v1
#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

Christophe

> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/ia64/include/asm/sections.h    | 5 +++--
>>   arch/parisc/include/asm/sections.h  | 6 ++++--
>>   arch/powerpc/include/asm/sections.h | 6 ++++--
>>   include/asm-generic/sections.h      | 3 ++-
>>   include/linux/kallsyms.h            | 2 +-
>>   5 files changed, 14 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
>> index 35f24e52149a..6e55e545bf02 100644
>> --- a/arch/ia64/include/asm/sections.h
>> +++ b/arch/ia64/include/asm/sections.h
>> @@ -9,6 +9,9 @@
>>   
>>   #include <linux/elf.h>
>>   #include <linux/uaccess.h>
>> +
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern char __phys_per_cpu_start[];
>> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>>   extern char __start_unwind[], __end_unwind[];
>>   extern char __start_ivt_text[], __end_ivt_text[];
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
>> index bb52aea0cb21..85149a89ff3e 100644
>> --- a/arch/parisc/include/asm/sections.h
>> +++ b/arch/parisc/include/asm/sections.h
>> @@ -2,6 +2,10 @@
>>   #ifndef _PARISC_SECTIONS_H
>>   #define _PARISC_SECTIONS_H
>>   
>> +#ifdef CONFIG_64BIT
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   /* nothing to see, move along */
>>   #include <asm-generic/sections.h>
>>   
>> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>>   
>>   #ifdef CONFIG_64BIT
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   void *dereference_function_descriptor(void *);
>>   
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 32e7035863ac..bba97b8c38cf 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -8,6 +8,10 @@
>>   
>>   #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>>   
>> +#ifdef PPC64_ELF_ABI_v1
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern bool init_mem_is_free;
>> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>>   
>>   #ifdef PPC64_ELF_ABI_v1
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index d16302d3eb59..b677e926e6b3 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>>   extern __visible const void __nosave_begin, __nosave_end;
>>   
>>   /* Function descriptor handling (if any).  Override in asm/sections.h */
>> -#ifndef dereference_function_descriptor
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>> +#else
>>   #define dereference_function_descriptor(p) ((void *)(p))
>>   #define dereference_kernel_function_descriptor(p) ((void *)(p))
>>   #endif
>> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
>> index a1d6fc82d7f0..9f277baeb559 100644
>> --- a/include/linux/kallsyms.h
>> +++ b/include/linux/kallsyms.h
>> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>>   
>>   static inline void *dereference_symbol_descriptor(void *ptr)
>>   {
>> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>>   	struct module *mod;
>>   
>>   	ptr = dereference_kernel_function_descriptor(ptr);
>> -- 
>> 2.31.1
>>
>>
>>

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Christophe Leroy]

Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>> 'dereference_function_descriptor' macro to know
>> whether an arch has function descriptors.
>>
>> To limit churn in one of the following patches, use
>> an #ifdef/#else construct with empty first part
>> instead of an #ifndef in asm-generic/sections.h
> 
> Is it worth putting this into Kconfig if you're going to
> change it? In any case

That was what I wanted to do in the begining but how can I do that in 
Kconfig ?

#ifdef __powerpc64__
#if defined(_CALL_ELF) && _CALL_ELF == 2
#define PPC64_ELF_ABI_v2
#else
#define PPC64_ELF_ABI_v1
#endif
#endif /* __powerpc64__ */

#ifdef PPC64_ELF_ABI_v1
#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

Christophe

> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   arch/ia64/include/asm/sections.h    | 5 +++--
>>   arch/parisc/include/asm/sections.h  | 6 ++++--
>>   arch/powerpc/include/asm/sections.h | 6 ++++--
>>   include/asm-generic/sections.h      | 3 ++-
>>   include/linux/kallsyms.h            | 2 +-
>>   5 files changed, 14 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
>> index 35f24e52149a..6e55e545bf02 100644
>> --- a/arch/ia64/include/asm/sections.h
>> +++ b/arch/ia64/include/asm/sections.h
>> @@ -9,6 +9,9 @@
>>   
>>   #include <linux/elf.h>
>>   #include <linux/uaccess.h>
>> +
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern char __phys_per_cpu_start[];
>> @@ -27,8 +30,6 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>>   extern char __start_unwind[], __end_unwind[];
>>   extern char __start_ivt_text[], __end_ivt_text[];
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
>> index bb52aea0cb21..85149a89ff3e 100644
>> --- a/arch/parisc/include/asm/sections.h
>> +++ b/arch/parisc/include/asm/sections.h
>> @@ -2,6 +2,10 @@
>>   #ifndef _PARISC_SECTIONS_H
>>   #define _PARISC_SECTIONS_H
>>   
>> +#ifdef CONFIG_64BIT
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   /* nothing to see, move along */
>>   #include <asm-generic/sections.h>
>>   
>> @@ -9,8 +13,6 @@ extern char __alt_instructions[], __alt_instructions_end[];
>>   
>>   #ifdef CONFIG_64BIT
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   void *dereference_function_descriptor(void *);
>>   
>> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
>> index 32e7035863ac..bba97b8c38cf 100644
>> --- a/arch/powerpc/include/asm/sections.h
>> +++ b/arch/powerpc/include/asm/sections.h
>> @@ -8,6 +8,10 @@
>>   
>>   #define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed
>>   
>> +#ifdef PPC64_ELF_ABI_v1
>> +#define HAVE_FUNCTION_DESCRIPTORS 1
>> +#endif
>> +
>>   #include <asm-generic/sections.h>
>>   
>>   extern bool init_mem_is_free;
>> @@ -69,8 +73,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>>   
>>   #ifdef PPC64_ELF_ABI_v1
>>   
>> -#define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
>> -
>>   #undef dereference_function_descriptor
>>   static inline void *dereference_function_descriptor(void *ptr)
>>   {
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index d16302d3eb59..b677e926e6b3 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -59,7 +59,8 @@ extern char __noinstr_text_start[], __noinstr_text_end[];
>>   extern __visible const void __nosave_begin, __nosave_end;
>>   
>>   /* Function descriptor handling (if any).  Override in asm/sections.h */
>> -#ifndef dereference_function_descriptor
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>> +#else
>>   #define dereference_function_descriptor(p) ((void *)(p))
>>   #define dereference_kernel_function_descriptor(p) ((void *)(p))
>>   #endif
>> diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h
>> index a1d6fc82d7f0..9f277baeb559 100644
>> --- a/include/linux/kallsyms.h
>> +++ b/include/linux/kallsyms.h
>> @@ -57,7 +57,7 @@ static inline int is_ksym_addr(unsigned long addr)
>>   
>>   static inline void *dereference_symbol_descriptor(void *ptr)
>>   {
>> -#ifdef HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR
>> +#ifdef HAVE_FUNCTION_DESCRIPTORS
>>   	struct module *mod;
>>   
>>   	ptr = dereference_kernel_function_descriptor(ptr);
>> -- 
>> 2.31.1
>>
>>
>>

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
> 
> 
> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>> 'dereference_function_descriptor' macro to know
>>> whether an arch has function descriptors.
>>>
>>> To limit churn in one of the following patches, use
>>> an #ifdef/#else construct with empty first part
>>> instead of an #ifndef in asm-generic/sections.h
>> 
>> Is it worth putting this into Kconfig if you're going to
>> change it? In any case
> 
> That was what I wanted to do in the begining but how can I do that in 
> Kconfig ?
> 
> #ifdef __powerpc64__
> #if defined(_CALL_ELF) && _CALL_ELF == 2
> #define PPC64_ELF_ABI_v2
> #else
> #define PPC64_ELF_ABI_v1
> #endif
> #endif /* __powerpc64__ */
> 
> #ifdef PPC64_ELF_ABI_v1
> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

We have ELFv2 ABI / function descriptors iff big-endian so you could 
just select based on that.

I have a patch that makes the ABI version configurable which cleans
some of this up a bit, but that can be rebased on your series if we
ever merge it. Maybe just add BUILD_BUG_ONs in the above ifdef block
to ensure CONFIG_HAVE_FUNCTION_DESCRIPTORS was set the right way, so
I don't forget.

Thanks,
Nick

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
> 
> 
> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>> 'dereference_function_descriptor' macro to know
>>> whether an arch has function descriptors.
>>>
>>> To limit churn in one of the following patches, use
>>> an #ifdef/#else construct with empty first part
>>> instead of an #ifndef in asm-generic/sections.h
>> 
>> Is it worth putting this into Kconfig if you're going to
>> change it? In any case
> 
> That was what I wanted to do in the begining but how can I do that in 
> Kconfig ?
> 
> #ifdef __powerpc64__
> #if defined(_CALL_ELF) && _CALL_ELF == 2
> #define PPC64_ELF_ABI_v2
> #else
> #define PPC64_ELF_ABI_v1
> #endif
> #endif /* __powerpc64__ */
> 
> #ifdef PPC64_ELF_ABI_v1
> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

We have ELFv2 ABI / function descriptors iff big-endian so you could 
just select based on that.

I have a patch that makes the ABI version configurable which cleans
some of this up a bit, but that can be rebased on your series if we
ever merge it. Maybe just add BUILD_BUG_ONs in the above ifdef block
to ensure CONFIG_HAVE_FUNCTION_DESCRIPTORS was set the right way, so
I don't forget.

Thanks,
Nick

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
> 
> 
> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>> 'dereference_function_descriptor' macro to know
>>> whether an arch has function descriptors.
>>>
>>> To limit churn in one of the following patches, use
>>> an #ifdef/#else construct with empty first part
>>> instead of an #ifndef in asm-generic/sections.h
>> 
>> Is it worth putting this into Kconfig if you're going to
>> change it? In any case
> 
> That was what I wanted to do in the begining but how can I do that in 
> Kconfig ?
> 
> #ifdef __powerpc64__
> #if defined(_CALL_ELF) && _CALL_ELF == 2
> #define PPC64_ELF_ABI_v2
> #else
> #define PPC64_ELF_ABI_v1
> #endif
> #endif /* __powerpc64__ */
> 
> #ifdef PPC64_ELF_ABI_v1
> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1

We have ELFv2 ABI / function descriptors iff big-endian so you could 
just select based on that.

I have a patch that makes the ABI version configurable which cleans
some of this up a bit, but that can be rebased on your series if we
ever merge it. Maybe just add BUILD_BUG_ONs in the above ifdef block
to ensure CONFIG_HAVE_FUNCTION_DESCRIPTORS was set the right way, so
I don't forget.

Thanks,
Nick

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Nicholas Piggin's message of October 15, 2021 6:02 pm:
> Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
>> 
>> 
>> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>>> 'dereference_function_descriptor' macro to know
>>>> whether an arch has function descriptors.
>>>>
>>>> To limit churn in one of the following patches, use
>>>> an #ifdef/#else construct with empty first part
>>>> instead of an #ifndef in asm-generic/sections.h
>>> 
>>> Is it worth putting this into Kconfig if you're going to
>>> change it? In any case
>> 
>> That was what I wanted to do in the begining but how can I do that in 
>> Kconfig ?
>> 
>> #ifdef __powerpc64__
>> #if defined(_CALL_ELF) && _CALL_ELF == 2
>> #define PPC64_ELF_ABI_v2
>> #else
>> #define PPC64_ELF_ABI_v1
>> #endif
>> #endif /* __powerpc64__ */
>> 
>> #ifdef PPC64_ELF_ABI_v1
>> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> 
> We have ELFv2 ABI / function descriptors iff big-endian so you could 
> just select based on that.

Of course that should read ELFv1. To be clearer: BE is ELFv1 ABI and
LE is ELFv2 ABI.

Thanks,
Nick

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Nicholas Piggin's message of October 15, 2021 6:02 pm:
> Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
>> 
>> 
>> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>>> 'dereference_function_descriptor' macro to know
>>>> whether an arch has function descriptors.
>>>>
>>>> To limit churn in one of the following patches, use
>>>> an #ifdef/#else construct with empty first part
>>>> instead of an #ifndef in asm-generic/sections.h
>>> 
>>> Is it worth putting this into Kconfig if you're going to
>>> change it? In any case
>> 
>> That was what I wanted to do in the begining but how can I do that in 
>> Kconfig ?
>> 
>> #ifdef __powerpc64__
>> #if defined(_CALL_ELF) && _CALL_ELF == 2
>> #define PPC64_ELF_ABI_v2
>> #else
>> #define PPC64_ELF_ABI_v1
>> #endif
>> #endif /* __powerpc64__ */
>> 
>> #ifdef PPC64_ELF_ABI_v1
>> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> 
> We have ELFv2 ABI / function descriptors iff big-endian so you could 
> just select based on that.

Of course that should read ELFv1. To be clearer: BE is ELFv1 ABI and
LE is ELFv2 ABI.

Thanks,
Nick

Re: [PATCH v2 06/13] asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs

[Nicholas Piggin]

Excerpts from Nicholas Piggin's message of October 15, 2021 6:02 pm:
> Excerpts from Christophe Leroy's message of October 15, 2021 4:24 pm:
>> 
>> 
>> Le 15/10/2021 à 08:16, Nicholas Piggin a écrit :
>>> Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
>>>> Replace HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR by
>>>> HAVE_FUNCTION_DESCRIPTORS and use it instead of
>>>> 'dereference_function_descriptor' macro to know
>>>> whether an arch has function descriptors.
>>>>
>>>> To limit churn in one of the following patches, use
>>>> an #ifdef/#else construct with empty first part
>>>> instead of an #ifndef in asm-generic/sections.h
>>> 
>>> Is it worth putting this into Kconfig if you're going to
>>> change it? In any case
>> 
>> That was what I wanted to do in the begining but how can I do that in 
>> Kconfig ?
>> 
>> #ifdef __powerpc64__
>> #if defined(_CALL_ELF) && _CALL_ELF == 2
>> #define PPC64_ELF_ABI_v2
>> #else
>> #define PPC64_ELF_ABI_v1
>> #endif
>> #endif /* __powerpc64__ */
>> 
>> #ifdef PPC64_ELF_ABI_v1
>> #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
> 
> We have ELFv2 ABI / function descriptors iff big-endian so you could 
> just select based on that.

Of course that should read ELFv1. To be clearer: BE is ELFv1 ABI and
LE is ELFv2 ABI.

Thanks,
Nick

[PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Christophe Leroy]

We have three architectures using function descriptors, each with its
own name.

Add a common typedef that can be used in generic code.

Also add a stub typedef for architecture without function descriptors,
to avoid a forest of #ifdefs.

It replaces the similar func_desc_t previously defined in
arch/powerpc/kernel/module_64.c

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 1 +
 arch/parisc/include/asm/sections.h  | 2 ++
 arch/powerpc/include/asm/sections.h | 1 +
 arch/powerpc/kernel/module_64.c     | 8 --------
 include/asm-generic/sections.h      | 3 +++
 5 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 6e55e545bf02..1aaed8882294 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -11,6 +11,7 @@
 #include <linux/uaccess.h>
 
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct fdesc func_desc_t;
 
 #include <asm-generic/sections.h>
 
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 85149a89ff3e..37b34b357cb5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -3,7 +3,9 @@
 #define _PARISC_SECTIONS_H
 
 #ifdef CONFIG_64BIT
+#include <asm/elf.h>
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef Elf64_Fdesc func_desc_t;
 #endif
 
 /* nothing to see, move along */
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index bba97b8c38cf..1322d7b2f1a3 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -10,6 +10,7 @@
 
 #ifdef PPC64_ELF_ABI_v1
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct ppc64_opd_entry func_desc_t;
 #endif
 
 #include <asm-generic/sections.h>
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index dc99a3f6cee2..affda7698242 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -32,11 +32,6 @@
 
 #ifdef PPC64_ELF_ABI_v2
 
-/* An address is simply the address of the function. */
-typedef struct {
-	unsigned long addr;
-} func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return (func_desc_t){addr};
@@ -57,9 +52,6 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 }
 #else
 
-/* An address is address of the OPD entry, which contains address of fn. */
-typedef struct ppc64_opd_entry func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return *(func_desc_t *)addr;
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index b677e926e6b3..cbec7d5f1678 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -63,6 +63,9 @@ extern __visible const void __nosave_begin, __nosave_end;
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 #endif
 
 /* random extra sections (if any).  Override
-- 
2.31.1

[PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Christophe Leroy]

We have three architectures using function descriptors, each with its
own name.

Add a common typedef that can be used in generic code.

Also add a stub typedef for architecture without function descriptors,
to avoid a forest of #ifdefs.

It replaces the similar func_desc_t previously defined in
arch/powerpc/kernel/module_64.c

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 1 +
 arch/parisc/include/asm/sections.h  | 2 ++
 arch/powerpc/include/asm/sections.h | 1 +
 arch/powerpc/kernel/module_64.c     | 8 --------
 include/asm-generic/sections.h      | 3 +++
 5 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 6e55e545bf02..1aaed8882294 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -11,6 +11,7 @@
 #include <linux/uaccess.h>
 
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct fdesc func_desc_t;
 
 #include <asm-generic/sections.h>
 
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 85149a89ff3e..37b34b357cb5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -3,7 +3,9 @@
 #define _PARISC_SECTIONS_H
 
 #ifdef CONFIG_64BIT
+#include <asm/elf.h>
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef Elf64_Fdesc func_desc_t;
 #endif
 
 /* nothing to see, move along */
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index bba97b8c38cf..1322d7b2f1a3 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -10,6 +10,7 @@
 
 #ifdef PPC64_ELF_ABI_v1
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct ppc64_opd_entry func_desc_t;
 #endif
 
 #include <asm-generic/sections.h>
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index dc99a3f6cee2..affda7698242 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -32,11 +32,6 @@
 
 #ifdef PPC64_ELF_ABI_v2
 
-/* An address is simply the address of the function. */
-typedef struct {
-	unsigned long addr;
-} func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return (func_desc_t){addr};
@@ -57,9 +52,6 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 }
 #else
 
-/* An address is address of the OPD entry, which contains address of fn. */
-typedef struct ppc64_opd_entry func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return *(func_desc_t *)addr;
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index b677e926e6b3..cbec7d5f1678 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -63,6 +63,9 @@ extern __visible const void __nosave_begin, __nosave_end;
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 #endif
 
 /* random extra sections (if any).  Override
-- 
2.31.1

[PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Christophe Leroy]

We have three architectures using function descriptors, each with its
own name.

Add a common typedef that can be used in generic code.

Also add a stub typedef for architecture without function descriptors,
to avoid a forest of #ifdefs.

It replaces the similar func_desc_t previously defined in
arch/powerpc/kernel/module_64.c

Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 1 +
 arch/parisc/include/asm/sections.h  | 2 ++
 arch/powerpc/include/asm/sections.h | 1 +
 arch/powerpc/kernel/module_64.c     | 8 --------
 include/asm-generic/sections.h      | 3 +++
 5 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 6e55e545bf02..1aaed8882294 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -11,6 +11,7 @@
 #include <linux/uaccess.h>
 
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct fdesc func_desc_t;
 
 #include <asm-generic/sections.h>
 
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 85149a89ff3e..37b34b357cb5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -3,7 +3,9 @@
 #define _PARISC_SECTIONS_H
 
 #ifdef CONFIG_64BIT
+#include <asm/elf.h>
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef Elf64_Fdesc func_desc_t;
 #endif
 
 /* nothing to see, move along */
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index bba97b8c38cf..1322d7b2f1a3 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -10,6 +10,7 @@
 
 #ifdef PPC64_ELF_ABI_v1
 #define HAVE_FUNCTION_DESCRIPTORS 1
+typedef struct ppc64_opd_entry func_desc_t;
 #endif
 
 #include <asm-generic/sections.h>
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index dc99a3f6cee2..affda7698242 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -32,11 +32,6 @@
 
 #ifdef PPC64_ELF_ABI_v2
 
-/* An address is simply the address of the function. */
-typedef struct {
-	unsigned long addr;
-} func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return (func_desc_t){addr};
@@ -57,9 +52,6 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 }
 #else
 
-/* An address is address of the OPD entry, which contains address of fn. */
-typedef struct ppc64_opd_entry func_desc_t;
-
 static func_desc_t func_desc(unsigned long addr)
 {
 	return *(func_desc_t *)addr;
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index b677e926e6b3..cbec7d5f1678 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -63,6 +63,9 @@ extern __visible const void __nosave_begin, __nosave_end;
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
+typedef struct {
+	unsigned long addr;
+} func_desc_t;
 #endif
 
 /* random extra sections (if any).  Override
-- 
2.31.1

Re: [PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Arnd Bergmann]

On Thu, Oct 14, 2021 at 7:49 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> We have three architectures using function descriptors, each with its
> own name.
>
> Add a common typedef that can be used in generic code.
>
> Also add a stub typedef for architecture without function descriptors,
> to avoid a forest of #ifdefs.
>
> It replaces the similar func_desc_t previously defined in
> arch/powerpc/kernel/module_64.c
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Arnd Bergmann]

On Thu, Oct 14, 2021 at 7:49 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> We have three architectures using function descriptors, each with its
> own name.
>
> Add a common typedef that can be used in generic code.
>
> Also add a stub typedef for architecture without function descriptors,
> to avoid a forest of #ifdefs.
>
> It replaces the similar func_desc_t previously defined in
> arch/powerpc/kernel/module_64.c
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Acked-by: Arnd Bergmann <arnd@arndb.de>

Re: [PATCH v2 07/13] asm-generic: Define 'func_desc_t' to commonly describe function descriptors

[Arnd Bergmann]

On Thu, Oct 14, 2021 at 7:49 AM Christophe Leroy
<christophe.leroy@csgroup.eu> wrote:
>
> We have three architectures using function descriptors, each with its
> own name.
>
> Add a common typedef that can be used in generic code.
>
> Also add a stub typedef for architecture without function descriptors,
> to avoid a forest of #ifdefs.
>
> It replaces the similar func_desc_t previously defined in
> arch/powerpc/kernel/module_64.c
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Acked-by: Arnd Bergmann <arnd@arndb.de>

[PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Christophe Leroy]

dereference_function_descriptor() and
dereference_kernel_function_descriptor() are identical on the
three architectures implementing them.

Make them common and put them out-of-line in kernel/extable.c
which is one of the users and has similar type of functions.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 19 -------------------
 arch/parisc/include/asm/sections.h  |  9 ---------
 arch/parisc/kernel/process.c        | 21 ---------------------
 arch/powerpc/include/asm/sections.h | 23 -----------------------
 include/asm-generic/sections.h      |  2 ++
 kernel/extable.c                    | 23 ++++++++++++++++++++++-
 6 files changed, 24 insertions(+), 73 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 1aaed8882294..96c9bb500c34 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-	return dereference_function_descriptor(ptr);
-}
-
 #endif /* _ASM_IA64_SECTIONS_H */
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 37b34b357cb5..6b1fe22baaf5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
 
 extern char __alt_instructions[], __alt_instructions_end[];
 
-#ifdef CONFIG_64BIT
-
-#undef dereference_function_descriptor
-void *dereference_function_descriptor(void *);
-
-#undef dereference_kernel_function_descriptor
-void *dereference_kernel_function_descriptor(void *);
-#endif
-
 #endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 38ec4ae81239..7382576b52a8 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
 	return 0;
 }
 
-#ifdef CONFIG_64BIT
-void *dereference_function_descriptor(void *ptr)
-{
-	Elf64_Fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd ||
-			ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif
-
 static inline unsigned long brk_rnd(void)
 {
 	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 1322d7b2f1a3..fbfe1957edbe 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 		(unsigned long)_stext < end;
 }
 
-#ifdef PPC64_ELF_ABI_v1
-
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct ppc64_opd_entry *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif /* PPC64_ELF_ABI_v1 */
-
 #endif
 
 #endif /* __KERNEL__ */
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index cbec7d5f1678..76163883c6ff 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
 #ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr);
+void *dereference_kernel_function_descriptor(void *ptr);
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
diff --git a/kernel/extable.c b/kernel/extable.c
index b0ea5eb0c3b4..013ccffade11 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -3,6 +3,7 @@
    Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
 
 */
+#include <linux/elf.h>
 #include <linux/ftrace.h>
 #include <linux/memory.h>
 #include <linux/extable.h>
@@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
 }
 
 /*
- * On some architectures (PPC64, IA64) function pointers
+ * On some architectures (PPC64, IA64, PARISC) function pointers
  * are actually only tokens to some data that then holds the
  * real function address. As a result, to find if a function
  * pointer is part of the kernel text, we need to do some
  * special dereferencing first.
  */
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr)
+{
+	func_desc_t *desc = ptr;
+	void *p;
+
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
+		ptr = p;
+	return ptr;
+}
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif
+
 int func_ptr_is_kernel_text(void *ptr)
 {
 	unsigned long addr;
-- 
2.31.1

[PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Christophe Leroy]

dereference_function_descriptor() and
dereference_kernel_function_descriptor() are identical on the
three architectures implementing them.

Make them common and put them out-of-line in kernel/extable.c
which is one of the users and has similar type of functions.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 19 -------------------
 arch/parisc/include/asm/sections.h  |  9 ---------
 arch/parisc/kernel/process.c        | 21 ---------------------
 arch/powerpc/include/asm/sections.h | 23 -----------------------
 include/asm-generic/sections.h      |  2 ++
 kernel/extable.c                    | 23 ++++++++++++++++++++++-
 6 files changed, 24 insertions(+), 73 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 1aaed8882294..96c9bb500c34 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-	return dereference_function_descriptor(ptr);
-}
-
 #endif /* _ASM_IA64_SECTIONS_H */
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 37b34b357cb5..6b1fe22baaf5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
 
 extern char __alt_instructions[], __alt_instructions_end[];
 
-#ifdef CONFIG_64BIT
-
-#undef dereference_function_descriptor
-void *dereference_function_descriptor(void *);
-
-#undef dereference_kernel_function_descriptor
-void *dereference_kernel_function_descriptor(void *);
-#endif
-
 #endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 38ec4ae81239..7382576b52a8 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
 	return 0;
 }
 
-#ifdef CONFIG_64BIT
-void *dereference_function_descriptor(void *ptr)
-{
-	Elf64_Fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd ||
-			ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif
-
 static inline unsigned long brk_rnd(void)
 {
 	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 1322d7b2f1a3..fbfe1957edbe 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 		(unsigned long)_stext < end;
 }
 
-#ifdef PPC64_ELF_ABI_v1
-
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct ppc64_opd_entry *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif /* PPC64_ELF_ABI_v1 */
-
 #endif
 
 #endif /* __KERNEL__ */
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index cbec7d5f1678..76163883c6ff 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
 #ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr);
+void *dereference_kernel_function_descriptor(void *ptr);
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
diff --git a/kernel/extable.c b/kernel/extable.c
index b0ea5eb0c3b4..013ccffade11 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -3,6 +3,7 @@
    Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
 
 */
+#include <linux/elf.h>
 #include <linux/ftrace.h>
 #include <linux/memory.h>
 #include <linux/extable.h>
@@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
 }
 
 /*
- * On some architectures (PPC64, IA64) function pointers
+ * On some architectures (PPC64, IA64, PARISC) function pointers
  * are actually only tokens to some data that then holds the
  * real function address. As a result, to find if a function
  * pointer is part of the kernel text, we need to do some
  * special dereferencing first.
  */
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr)
+{
+	func_desc_t *desc = ptr;
+	void *p;
+
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
+		ptr = p;
+	return ptr;
+}
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif
+
 int func_ptr_is_kernel_text(void *ptr)
 {
 	unsigned long addr;
-- 
2.31.1

[PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Christophe Leroy]

dereference_function_descriptor() and
dereference_kernel_function_descriptor() are identical on the
three architectures implementing them.

Make them common and put them out-of-line in kernel/extable.c
which is one of the users and has similar type of functions.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/ia64/include/asm/sections.h    | 19 -------------------
 arch/parisc/include/asm/sections.h  |  9 ---------
 arch/parisc/kernel/process.c        | 21 ---------------------
 arch/powerpc/include/asm/sections.h | 23 -----------------------
 include/asm-generic/sections.h      |  2 ++
 kernel/extable.c                    | 23 ++++++++++++++++++++++-
 6 files changed, 24 insertions(+), 73 deletions(-)

diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
index 1aaed8882294..96c9bb500c34 100644
--- a/arch/ia64/include/asm/sections.h
+++ b/arch/ia64/include/asm/sections.h
@@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
 extern char __start_unwind[], __end_unwind[];
 extern char __start_ivt_text[], __end_ivt_text[];
 
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-	return dereference_function_descriptor(ptr);
-}
-
 #endif /* _ASM_IA64_SECTIONS_H */
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 37b34b357cb5..6b1fe22baaf5 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
 
 extern char __alt_instructions[], __alt_instructions_end[];
 
-#ifdef CONFIG_64BIT
-
-#undef dereference_function_descriptor
-void *dereference_function_descriptor(void *);
-
-#undef dereference_kernel_function_descriptor
-void *dereference_kernel_function_descriptor(void *);
-#endif
-
 #endif
diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
index 38ec4ae81239..7382576b52a8 100644
--- a/arch/parisc/kernel/process.c
+++ b/arch/parisc/kernel/process.c
@@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
 	return 0;
 }
 
-#ifdef CONFIG_64BIT
-void *dereference_function_descriptor(void *ptr)
-{
-	Elf64_Fdesc *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd ||
-			ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif
-
 static inline unsigned long brk_rnd(void)
 {
 	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
index 1322d7b2f1a3..fbfe1957edbe 100644
--- a/arch/powerpc/include/asm/sections.h
+++ b/arch/powerpc/include/asm/sections.h
@@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
 		(unsigned long)_stext < end;
 }
 
-#ifdef PPC64_ELF_ABI_v1
-
-#undef dereference_function_descriptor
-static inline void *dereference_function_descriptor(void *ptr)
-{
-	struct ppc64_opd_entry *desc = ptr;
-	void *p;
-
-	if (!get_kernel_nofault(p, (void *)&desc->addr))
-		ptr = p;
-	return ptr;
-}
-
-#undef dereference_kernel_function_descriptor
-static inline void *dereference_kernel_function_descriptor(void *ptr)
-{
-	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
-		return ptr;
-
-	return dereference_function_descriptor(ptr);
-}
-#endif /* PPC64_ELF_ABI_v1 */
-
 #endif
 
 #endif /* __KERNEL__ */
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index cbec7d5f1678..76163883c6ff 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
 
 /* Function descriptor handling (if any).  Override in asm/sections.h */
 #ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr);
+void *dereference_kernel_function_descriptor(void *ptr);
 #else
 #define dereference_function_descriptor(p) ((void *)(p))
 #define dereference_kernel_function_descriptor(p) ((void *)(p))
diff --git a/kernel/extable.c b/kernel/extable.c
index b0ea5eb0c3b4..013ccffade11 100644
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -3,6 +3,7 @@
    Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
 
 */
+#include <linux/elf.h>
 #include <linux/ftrace.h>
 #include <linux/memory.h>
 #include <linux/extable.h>
@@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
 }
 
 /*
- * On some architectures (PPC64, IA64) function pointers
+ * On some architectures (PPC64, IA64, PARISC) function pointers
  * are actually only tokens to some data that then holds the
  * real function address. As a result, to find if a function
  * pointer is part of the kernel text, we need to do some
  * special dereferencing first.
  */
+#ifdef HAVE_FUNCTION_DESCRIPTORS
+void *dereference_function_descriptor(void *ptr)
+{
+	func_desc_t *desc = ptr;
+	void *p;
+
+	if (!get_kernel_nofault(p, (void *)&desc->addr))
+		ptr = p;
+	return ptr;
+}
+
+void *dereference_kernel_function_descriptor(void *ptr)
+{
+	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
+		return ptr;
+
+	return dereference_function_descriptor(ptr);
+}
+#endif
+
 int func_ptr_is_kernel_text(void *ptr)
 {
 	unsigned long addr;
-- 
2.31.1

Re: [PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> dereference_function_descriptor() and
> dereference_kernel_function_descriptor() are identical on the
> three architectures implementing them.
> 
> Make them common and put them out-of-line in kernel/extable.c
> which is one of the users and has similar type of functions.

We should be moving more stuff out of extable.c (including all the
kernel address tests). lib/kimage.c or kelf.c or something. 

It could be after your series though.

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 19 -------------------
>  arch/parisc/include/asm/sections.h  |  9 ---------
>  arch/parisc/kernel/process.c        | 21 ---------------------
>  arch/powerpc/include/asm/sections.h | 23 -----------------------
>  include/asm-generic/sections.h      |  2 ++
>  kernel/extable.c                    | 23 ++++++++++++++++++++++-
>  6 files changed, 24 insertions(+), 73 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 1aaed8882294..96c9bb500c34 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -	return dereference_function_descriptor(ptr);
> -}
> -
>  #endif /* _ASM_IA64_SECTIONS_H */
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index 37b34b357cb5..6b1fe22baaf5 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
>  
>  extern char __alt_instructions[], __alt_instructions_end[];
>  
> -#ifdef CONFIG_64BIT
> -
> -#undef dereference_function_descriptor
> -void *dereference_function_descriptor(void *);
> -
> -#undef dereference_kernel_function_descriptor
> -void *dereference_kernel_function_descriptor(void *);
> -#endif
> -
>  #endif
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index 38ec4ae81239..7382576b52a8 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_64BIT
> -void *dereference_function_descriptor(void *ptr)
> -{
> -	Elf64_Fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd ||
> -			ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif
> -
>  static inline unsigned long brk_rnd(void)
>  {
>  	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 1322d7b2f1a3..fbfe1957edbe 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  		(unsigned long)_stext < end;
>  }
>  
> -#ifdef PPC64_ELF_ABI_v1
> -
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct ppc64_opd_entry *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif /* PPC64_ELF_ABI_v1 */
> -
>  #endif
>  
>  #endif /* __KERNEL__ */
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index cbec7d5f1678..76163883c6ff 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
>  #ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr);
> +void *dereference_kernel_function_descriptor(void *ptr);
>  #else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
> diff --git a/kernel/extable.c b/kernel/extable.c
> index b0ea5eb0c3b4..013ccffade11 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -3,6 +3,7 @@
>     Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
>  
>  */
> +#include <linux/elf.h>
>  #include <linux/ftrace.h>
>  #include <linux/memory.h>
>  #include <linux/extable.h>
> @@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
>  }
>  
>  /*
> - * On some architectures (PPC64, IA64) function pointers
> + * On some architectures (PPC64, IA64, PARISC) function pointers
>   * are actually only tokens to some data that then holds the
>   * real function address. As a result, to find if a function
>   * pointer is part of the kernel text, we need to do some
>   * special dereferencing first.
>   */
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr)
> +{
> +	func_desc_t *desc = ptr;
> +	void *p;
> +
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
> +		ptr = p;

I know you're just copying existing code. This seems a bit risky though. 
I don't think anything good could come of just treating the descriptor
address like a function entry address if we failed to load from it for
whatever reason.

Existing callers might be benign but the API is not good. It should
give a nice fail return or BUG. If we change that then we should also
change the name and pass the correct type to it too.

Thanks,
Nick

Re: [PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> dereference_function_descriptor() and
> dereference_kernel_function_descriptor() are identical on the
> three architectures implementing them.
> 
> Make them common and put them out-of-line in kernel/extable.c
> which is one of the users and has similar type of functions.

We should be moving more stuff out of extable.c (including all the
kernel address tests). lib/kimage.c or kelf.c or something. 

It could be after your series though.

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 19 -------------------
>  arch/parisc/include/asm/sections.h  |  9 ---------
>  arch/parisc/kernel/process.c        | 21 ---------------------
>  arch/powerpc/include/asm/sections.h | 23 -----------------------
>  include/asm-generic/sections.h      |  2 ++
>  kernel/extable.c                    | 23 ++++++++++++++++++++++-
>  6 files changed, 24 insertions(+), 73 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 1aaed8882294..96c9bb500c34 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -	return dereference_function_descriptor(ptr);
> -}
> -
>  #endif /* _ASM_IA64_SECTIONS_H */
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index 37b34b357cb5..6b1fe22baaf5 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
>  
>  extern char __alt_instructions[], __alt_instructions_end[];
>  
> -#ifdef CONFIG_64BIT
> -
> -#undef dereference_function_descriptor
> -void *dereference_function_descriptor(void *);
> -
> -#undef dereference_kernel_function_descriptor
> -void *dereference_kernel_function_descriptor(void *);
> -#endif
> -
>  #endif
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index 38ec4ae81239..7382576b52a8 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_64BIT
> -void *dereference_function_descriptor(void *ptr)
> -{
> -	Elf64_Fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd ||
> -			ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif
> -
>  static inline unsigned long brk_rnd(void)
>  {
>  	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 1322d7b2f1a3..fbfe1957edbe 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  		(unsigned long)_stext < end;
>  }
>  
> -#ifdef PPC64_ELF_ABI_v1
> -
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct ppc64_opd_entry *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif /* PPC64_ELF_ABI_v1 */
> -
>  #endif
>  
>  #endif /* __KERNEL__ */
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index cbec7d5f1678..76163883c6ff 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
>  #ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr);
> +void *dereference_kernel_function_descriptor(void *ptr);
>  #else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
> diff --git a/kernel/extable.c b/kernel/extable.c
> index b0ea5eb0c3b4..013ccffade11 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -3,6 +3,7 @@
>     Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
>  
>  */
> +#include <linux/elf.h>
>  #include <linux/ftrace.h>
>  #include <linux/memory.h>
>  #include <linux/extable.h>
> @@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
>  }
>  
>  /*
> - * On some architectures (PPC64, IA64) function pointers
> + * On some architectures (PPC64, IA64, PARISC) function pointers
>   * are actually only tokens to some data that then holds the
>   * real function address. As a result, to find if a function
>   * pointer is part of the kernel text, we need to do some
>   * special dereferencing first.
>   */
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr)
> +{
> +	func_desc_t *desc = ptr;
> +	void *p;
> +
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
> +		ptr = p;

I know you're just copying existing code. This seems a bit risky though. 
I don't think anything good could come of just treating the descriptor
address like a function entry address if we failed to load from it for
whatever reason.

Existing callers might be benign but the API is not good. It should
give a nice fail return or BUG. If we change that then we should also
change the name and pass the correct type to it too.

Thanks,
Nick

Re: [PATCH v2 08/13] asm-generic: Refactor dereference_[kernel]_function_descriptor()

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of October 14, 2021 3:49 pm:
> dereference_function_descriptor() and
> dereference_kernel_function_descriptor() are identical on the
> three architectures implementing them.
> 
> Make them common and put them out-of-line in kernel/extable.c
> which is one of the users and has similar type of functions.

We should be moving more stuff out of extable.c (including all the
kernel address tests). lib/kimage.c or kelf.c or something. 

It could be after your series though.

> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/ia64/include/asm/sections.h    | 19 -------------------
>  arch/parisc/include/asm/sections.h  |  9 ---------
>  arch/parisc/kernel/process.c        | 21 ---------------------
>  arch/powerpc/include/asm/sections.h | 23 -----------------------
>  include/asm-generic/sections.h      |  2 ++
>  kernel/extable.c                    | 23 ++++++++++++++++++++++-
>  6 files changed, 24 insertions(+), 73 deletions(-)
> 
> diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
> index 1aaed8882294..96c9bb500c34 100644
> --- a/arch/ia64/include/asm/sections.h
> +++ b/arch/ia64/include/asm/sections.h
> @@ -31,23 +31,4 @@ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_b
>  extern char __start_unwind[], __end_unwind[];
>  extern char __start_ivt_text[], __end_ivt_text[];
>  
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -	return dereference_function_descriptor(ptr);
> -}
> -
>  #endif /* _ASM_IA64_SECTIONS_H */
> diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
> index 37b34b357cb5..6b1fe22baaf5 100644
> --- a/arch/parisc/include/asm/sections.h
> +++ b/arch/parisc/include/asm/sections.h
> @@ -13,13 +13,4 @@ typedef Elf64_Fdesc func_desc_t;
>  
>  extern char __alt_instructions[], __alt_instructions_end[];
>  
> -#ifdef CONFIG_64BIT
> -
> -#undef dereference_function_descriptor
> -void *dereference_function_descriptor(void *);
> -
> -#undef dereference_kernel_function_descriptor
> -void *dereference_kernel_function_descriptor(void *);
> -#endif
> -
>  #endif
> diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c
> index 38ec4ae81239..7382576b52a8 100644
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -266,27 +266,6 @@ get_wchan(struct task_struct *p)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_64BIT
> -void *dereference_function_descriptor(void *ptr)
> -{
> -	Elf64_Fdesc *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd ||
> -			ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif
> -
>  static inline unsigned long brk_rnd(void)
>  {
>  	return (get_random_int() & BRK_RND_MASK) << PAGE_SHIFT;
> diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h
> index 1322d7b2f1a3..fbfe1957edbe 100644
> --- a/arch/powerpc/include/asm/sections.h
> +++ b/arch/powerpc/include/asm/sections.h
> @@ -72,29 +72,6 @@ static inline int overlaps_kernel_text(unsigned long start, unsigned long end)
>  		(unsigned long)_stext < end;
>  }
>  
> -#ifdef PPC64_ELF_ABI_v1
> -
> -#undef dereference_function_descriptor
> -static inline void *dereference_function_descriptor(void *ptr)
> -{
> -	struct ppc64_opd_entry *desc = ptr;
> -	void *p;
> -
> -	if (!get_kernel_nofault(p, (void *)&desc->addr))
> -		ptr = p;
> -	return ptr;
> -}
> -
> -#undef dereference_kernel_function_descriptor
> -static inline void *dereference_kernel_function_descriptor(void *ptr)
> -{
> -	if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd)
> -		return ptr;
> -
> -	return dereference_function_descriptor(ptr);
> -}
> -#endif /* PPC64_ELF_ABI_v1 */
> -
>  #endif
>  
>  #endif /* __KERNEL__ */
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index cbec7d5f1678..76163883c6ff 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -60,6 +60,8 @@ extern __visible const void __nosave_begin, __nosave_end;
>  
>  /* Function descriptor handling (if any).  Override in asm/sections.h */
>  #ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr);
> +void *dereference_kernel_function_descriptor(void *ptr);
>  #else
>  #define dereference_function_descriptor(p) ((void *)(p))
>  #define dereference_kernel_function_descriptor(p) ((void *)(p))
> diff --git a/kernel/extable.c b/kernel/extable.c
> index b0ea5eb0c3b4..013ccffade11 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -3,6 +3,7 @@
>     Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
>  
>  */
> +#include <linux/elf.h>
>  #include <linux/ftrace.h>
>  #include <linux/memory.h>
>  #include <linux/extable.h>
> @@ -159,12 +160,32 @@ int kernel_text_address(unsigned long addr)
>  }
>  
>  /*
> - * On some architectures (PPC64, IA64) function pointers
> + * On some architectures (PPC64, IA64, PARISC) function pointers
>   * are actually only tokens to some data that then holds the
>   * real function address. As a result, to find if a function
>   * pointer is part of the kernel text, we need to do some
>   * special dereferencing first.
>   */
> +#ifdef HAVE_FUNCTION_DESCRIPTORS
> +void *dereference_function_descriptor(void *ptr)
> +{
> +	func_desc_t *desc = ptr;
> +	void *p;
> +
> +	if (!get_kernel_nofault(p, (void *)&desc->addr))
> +		ptr = p;

I know you're just copying existing code. This seems a bit risky though. 
I don't think anything good could come of just treating the descriptor
address like a function entry address if we failed to load from it for
whatever reason.

Existing callers might be benign but the API is not good. It should
give a nice fail return or BUG. If we change that then we should also
change the name and pass the correct type to it too.

Thanks,
Nick

[PATCH v2 09/13] lkdtm: Force do_nothing() out of line

[Christophe Leroy]

LKDTM tests display that the run do_nothing() at a given
address, but in reality do_nothing() is inlined into the
caller.

Force it out of line so that it really runs text at the
displayed address.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..60b3b2fe929d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -21,7 +21,7 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
@@ -31,7 +31,7 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
-- 
2.31.1

[PATCH v2 09/13] lkdtm: Force do_nothing() out of line

[Christophe Leroy]

LKDTM tests display that the run do_nothing() at a given
address, but in reality do_nothing() is inlined into the
caller.

Force it out of line so that it really runs text at the
displayed address.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..60b3b2fe929d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -21,7 +21,7 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
@@ -31,7 +31,7 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
-- 
2.31.1

[PATCH v2 09/13] lkdtm: Force do_nothing() out of line

[Christophe Leroy]

LKDTM tests display that the run do_nothing() at a given
address, but in reality do_nothing() is inlined into the
caller.

Force it out of line so that it really runs text at the
displayed address.

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 2dede2ef658f..60b3b2fe929d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -21,7 +21,7 @@
 /* This is non-const, so it will end up in the .data section. */
 static u8 data_area[EXEC_SIZE];
 
-/* This is cost, so it will end up in the .rodata section. */
+/* This is const, so it will end up in the .rodata section. */
 static const unsigned long rodata = 0xAA55AA55;
 
 /* This is marked __ro_after_init, so it should ultimately be .rodata. */
@@ -31,7 +31,7 @@ static unsigned long ro_after_init __ro_after_init = 0x55AA5500;
  * This just returns to the caller. It is designed to be copied into
  * non-executable memory regions.
  */
-static void do_nothing(void)
+static noinline void do_nothing(void)
 {
 	return;
 }
-- 
2.31.1

[PATCH v2 10/13] lkdtm: Really write into kernel text in WRITE_KERN

[Christophe Leroy]

WRITE_KERN is supposed to overwrite some kernel text, namely
do_overwritten() function.

But at the time being it overwrites do_overwritten() function
descriptor, not function text.

Fix it by dereferencing the function descriptor to obtain
function text pointer.

And make do_overwritten() noinline so that it is really
do_overwritten() which is called by lkdtm_WRITE_KERN().

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 60b3b2fe929d..035fcca441f0 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
 #include <linux/mman.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 
 /* Whether or not to fill the target memory area with do_nothing(). */
 #define CODE_WRITE	true
@@ -37,7 +38,7 @@ static noinline void do_nothing(void)
 }
 
 /* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
 {
 	pr_info("do_overwritten wasn't overwritten!\n");
 	return;
@@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void)
 	size_t size;
 	volatile unsigned char *ptr;
 
-	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
-	ptr = (unsigned char *)do_overwritten;
+	size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+	       (unsigned long)dereference_function_descriptor(do_nothing);
+	ptr = dereference_function_descriptor(do_overwritten);
 
 	pr_info("attempting bad %zu byte write at %px\n", size, ptr);
 	memcpy((void *)ptr, (unsigned char *)do_nothing, size);
-- 
2.31.1

[PATCH v2 10/13] lkdtm: Really write into kernel text in WRITE_KERN

[Christophe Leroy]

WRITE_KERN is supposed to overwrite some kernel text, namely
do_overwritten() function.

But at the time being it overwrites do_overwritten() function
descriptor, not function text.

Fix it by dereferencing the function descriptor to obtain
function text pointer.

And make do_overwritten() noinline so that it is really
do_overwritten() which is called by lkdtm_WRITE_KERN().

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 60b3b2fe929d..035fcca441f0 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
 #include <linux/mman.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 
 /* Whether or not to fill the target memory area with do_nothing(). */
 #define CODE_WRITE	true
@@ -37,7 +38,7 @@ static noinline void do_nothing(void)
 }
 
 /* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
 {
 	pr_info("do_overwritten wasn't overwritten!\n");
 	return;
@@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void)
 	size_t size;
 	volatile unsigned char *ptr;
 
-	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
-	ptr = (unsigned char *)do_overwritten;
+	size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+	       (unsigned long)dereference_function_descriptor(do_nothing);
+	ptr = dereference_function_descriptor(do_overwritten);
 
 	pr_info("attempting bad %zu byte write at %px\n", size, ptr);
 	memcpy((void *)ptr, (unsigned char *)do_nothing, size);
-- 
2.31.1

[PATCH v2 10/13] lkdtm: Really write into kernel text in WRITE_KERN

[Christophe Leroy]

WRITE_KERN is supposed to overwrite some kernel text, namely
do_overwritten() function.

But at the time being it overwrites do_overwritten() function
descriptor, not function text.

Fix it by dereferencing the function descriptor to obtain
function text pointer.

And make do_overwritten() noinline so that it is really
do_overwritten() which is called by lkdtm_WRITE_KERN().

Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 60b3b2fe929d..035fcca441f0 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -10,6 +10,7 @@
 #include <linux/mman.h>
 #include <linux/uaccess.h>
 #include <asm/cacheflush.h>
+#include <asm/sections.h>
 
 /* Whether or not to fill the target memory area with do_nothing(). */
 #define CODE_WRITE	true
@@ -37,7 +38,7 @@ static noinline void do_nothing(void)
 }
 
 /* Must immediately follow do_nothing for size calculuations to work out. */
-static void do_overwritten(void)
+static noinline void do_overwritten(void)
 {
 	pr_info("do_overwritten wasn't overwritten!\n");
 	return;
@@ -113,8 +114,9 @@ void lkdtm_WRITE_KERN(void)
 	size_t size;
 	volatile unsigned char *ptr;
 
-	size = (unsigned long)do_overwritten - (unsigned long)do_nothing;
-	ptr = (unsigned char *)do_overwritten;
+	size = (unsigned long)dereference_function_descriptor(do_overwritten) -
+	       (unsigned long)dereference_function_descriptor(do_nothing);
+	ptr = dereference_function_descriptor(do_overwritten);
 
 	pr_info("attempting bad %zu byte write at %px\n", size, ptr);
 	memcpy((void *)ptr, (unsigned char *)do_nothing, size);
-- 
2.31.1

[PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Behind its location, lkdtm_EXEC_RODATA() executes
lkdtm_rodata_do_nothing() which is a real function,
not a copy of do_nothing().

So executes it directly instead of using execute_location().

This is necessary because following patch will fix execute_location()
to use a copy of the function descriptor of do_nothing() and
function descriptor of lkdtm_rodata_do_nothing() might be different.

And fix displayed addresses by dereferencing the function descriptors.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 035fcca441f0..5266dc28df6e 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
 
 void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	pr_info("attempting ok execution at %px\n",
+		dereference_function_descriptor(do_nothing));
+	do_nothing();
+
+	pr_info("attempting bad execution at %px\n",
+		dereference_function_descriptor(lkdtm_rodata_do_nothing));
+	lkdtm_rodata_do_nothing();
+	pr_err("FAIL: func returned\n");
 }
 
 void lkdtm_EXEC_USERSPACE(void)
-- 
2.31.1

[PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Behind its location, lkdtm_EXEC_RODATA() executes
lkdtm_rodata_do_nothing() which is a real function,
not a copy of do_nothing().

So executes it directly instead of using execute_location().

This is necessary because following patch will fix execute_location()
to use a copy of the function descriptor of do_nothing() and
function descriptor of lkdtm_rodata_do_nothing() might be different.

And fix displayed addresses by dereferencing the function descriptors.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 035fcca441f0..5266dc28df6e 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
 
 void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	pr_info("attempting ok execution at %px\n",
+		dereference_function_descriptor(do_nothing));
+	do_nothing();
+
+	pr_info("attempting bad execution at %px\n",
+		dereference_function_descriptor(lkdtm_rodata_do_nothing));
+	lkdtm_rodata_do_nothing();
+	pr_err("FAIL: func returned\n");
 }
 
 void lkdtm_EXEC_USERSPACE(void)
-- 
2.31.1

[PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Behind its location, lkdtm_EXEC_RODATA() executes
lkdtm_rodata_do_nothing() which is a real function,
not a copy of do_nothing().

So executes it directly instead of using execute_location().

This is necessary because following patch will fix execute_location()
to use a copy of the function descriptor of do_nothing() and
function descriptor of lkdtm_rodata_do_nothing() might be different.

And fix displayed addresses by dereferencing the function descriptors.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 035fcca441f0..5266dc28df6e 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
 
 void lkdtm_EXEC_RODATA(void)
 {
-	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
+	pr_info("attempting ok execution at %px\n",
+		dereference_function_descriptor(do_nothing));
+	do_nothing();
+
+	pr_info("attempting bad execution at %px\n",
+		dereference_function_descriptor(lkdtm_rodata_do_nothing));
+	lkdtm_rodata_do_nothing();
+	pr_err("FAIL: func returned\n");
 }
 
 void lkdtm_EXEC_USERSPACE(void)
-- 
2.31.1

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
> Behind its location, lkdtm_EXEC_RODATA() executes
> lkdtm_rodata_do_nothing() which is a real function,
> not a copy of do_nothing().
> 
> So executes it directly instead of using execute_location().
> 
> This is necessary because following patch will fix execute_location()
> to use a copy of the function descriptor of do_nothing() and
> function descriptor of lkdtm_rodata_do_nothing() might be different.
> 
> And fix displayed addresses by dereferencing the function descriptors.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

I still don't understand this -- it doesn't look needed at all given the
changes in patch 12. (i.e. everything is using
dereference_function_descriptor() now)

Can't this patch be dropped?

-Kees

> ---
>  drivers/misc/lkdtm/perms.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 035fcca441f0..5266dc28df6e 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
>  
>  void lkdtm_EXEC_RODATA(void)
>  {
> -	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
> +	pr_info("attempting ok execution at %px\n",
> +		dereference_function_descriptor(do_nothing));
> +	do_nothing();
> +
> +	pr_info("attempting bad execution at %px\n",
> +		dereference_function_descriptor(lkdtm_rodata_do_nothing));
> +	lkdtm_rodata_do_nothing();
> +	pr_err("FAIL: func returned\n");
>  }
>  
>  void lkdtm_EXEC_USERSPACE(void)
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
> Behind its location, lkdtm_EXEC_RODATA() executes
> lkdtm_rodata_do_nothing() which is a real function,
> not a copy of do_nothing().
> 
> So executes it directly instead of using execute_location().
> 
> This is necessary because following patch will fix execute_location()
> to use a copy of the function descriptor of do_nothing() and
> function descriptor of lkdtm_rodata_do_nothing() might be different.
> 
> And fix displayed addresses by dereferencing the function descriptors.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

I still don't understand this -- it doesn't look needed at all given the
changes in patch 12. (i.e. everything is using
dereference_function_descriptor() now)

Can't this patch be dropped?

-Kees

> ---
>  drivers/misc/lkdtm/perms.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 035fcca441f0..5266dc28df6e 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
>  
>  void lkdtm_EXEC_RODATA(void)
>  {
> -	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
> +	pr_info("attempting ok execution at %px\n",
> +		dereference_function_descriptor(do_nothing));
> +	do_nothing();
> +
> +	pr_info("attempting bad execution at %px\n",
> +		dereference_function_descriptor(lkdtm_rodata_do_nothing));
> +	lkdtm_rodata_do_nothing();
> +	pr_err("FAIL: func returned\n");
>  }
>  
>  void lkdtm_EXEC_USERSPACE(void)
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
> Behind its location, lkdtm_EXEC_RODATA() executes
> lkdtm_rodata_do_nothing() which is a real function,
> not a copy of do_nothing().
> 
> So executes it directly instead of using execute_location().
> 
> This is necessary because following patch will fix execute_location()
> to use a copy of the function descriptor of do_nothing() and
> function descriptor of lkdtm_rodata_do_nothing() might be different.
> 
> And fix displayed addresses by dereferencing the function descriptors.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

I still don't understand this -- it doesn't look needed at all given the
changes in patch 12. (i.e. everything is using
dereference_function_descriptor() now)

Can't this patch be dropped?

-Kees

> ---
>  drivers/misc/lkdtm/perms.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 035fcca441f0..5266dc28df6e 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -153,7 +153,14 @@ void lkdtm_EXEC_VMALLOC(void)
>  
>  void lkdtm_EXEC_RODATA(void)
>  {
> -	execute_location(lkdtm_rodata_do_nothing, CODE_AS_IS);
> +	pr_info("attempting ok execution at %px\n",
> +		dereference_function_descriptor(do_nothing));
> +	do_nothing();
> +
> +	pr_info("attempting bad execution at %px\n",
> +		dereference_function_descriptor(lkdtm_rodata_do_nothing));
> +	lkdtm_rodata_do_nothing();
> +	pr_err("FAIL: func returned\n");
>  }
>  
>  void lkdtm_EXEC_USERSPACE(void)
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 15/10/2021 à 23:32, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>> Behind its location, lkdtm_EXEC_RODATA() executes
>> lkdtm_rodata_do_nothing() which is a real function,
>> not a copy of do_nothing().
>>
>> So executes it directly instead of using execute_location().
>>
>> This is necessary because following patch will fix execute_location()
>> to use a copy of the function descriptor of do_nothing() and
>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>
>> And fix displayed addresses by dereferencing the function descriptors.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> 
> I still don't understand this -- it doesn't look needed at all given the
> changes in patch 12. (i.e. everything is using
> dereference_function_descriptor() now)

dereference_function_descriptor() only deals with the function address, 
not the function TOC.

do_nothing() is a function. It has a function descriptor with a given 
address (address of .do_nothing) and a given TOC, say TOC1.

lkdtm_rodata_do_nothing() is another function. It has its own function 
descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
and a given TOC, say TOC2.

If we use execute_location(), it will copy do_nothing() function 
descriptor and change the function address to the address of 
lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
with TOC1 instead of calling it with TOC2.

> 
> Can't this patch be dropped?

It is likely that the TOC will be the same for both functions, and 
anyway those functions are so simple that they don't use the TOC at all, 
so yes it would likely work without this patch but from my point of view 
it is incorrect to call one function with the TOC from the descriptor of 
another function.

If you thing we can take the risk, then I'm happy to drop the patch and 
replace it by

	execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)

Christophe

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 15/10/2021 à 23:32, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>> Behind its location, lkdtm_EXEC_RODATA() executes
>> lkdtm_rodata_do_nothing() which is a real function,
>> not a copy of do_nothing().
>>
>> So executes it directly instead of using execute_location().
>>
>> This is necessary because following patch will fix execute_location()
>> to use a copy of the function descriptor of do_nothing() and
>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>
>> And fix displayed addresses by dereferencing the function descriptors.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> 
> I still don't understand this -- it doesn't look needed at all given the
> changes in patch 12. (i.e. everything is using
> dereference_function_descriptor() now)

dereference_function_descriptor() only deals with the function address, 
not the function TOC.

do_nothing() is a function. It has a function descriptor with a given 
address (address of .do_nothing) and a given TOC, say TOC1.

lkdtm_rodata_do_nothing() is another function. It has its own function 
descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
and a given TOC, say TOC2.

If we use execute_location(), it will copy do_nothing() function 
descriptor and change the function address to the address of 
lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
with TOC1 instead of calling it with TOC2.

> 
> Can't this patch be dropped?

It is likely that the TOC will be the same for both functions, and 
anyway those functions are so simple that they don't use the TOC at all, 
so yes it would likely work without this patch but from my point of view 
it is incorrect to call one function with the TOC from the descriptor of 
another function.

If you thing we can take the risk, then I'm happy to drop the patch and 
replace it by

	execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)

Christophe

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 15/10/2021 à 23:32, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>> Behind its location, lkdtm_EXEC_RODATA() executes
>> lkdtm_rodata_do_nothing() which is a real function,
>> not a copy of do_nothing().
>>
>> So executes it directly instead of using execute_location().
>>
>> This is necessary because following patch will fix execute_location()
>> to use a copy of the function descriptor of do_nothing() and
>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>
>> And fix displayed addresses by dereferencing the function descriptors.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> 
> I still don't understand this -- it doesn't look needed at all given the
> changes in patch 12. (i.e. everything is using
> dereference_function_descriptor() now)

dereference_function_descriptor() only deals with the function address, 
not the function TOC.

do_nothing() is a function. It has a function descriptor with a given 
address (address of .do_nothing) and a given TOC, say TOC1.

lkdtm_rodata_do_nothing() is another function. It has its own function 
descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
and a given TOC, say TOC2.

If we use execute_location(), it will copy do_nothing() function 
descriptor and change the function address to the address of 
lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
with TOC1 instead of calling it with TOC2.

> 
> Can't this patch be dropped?

It is likely that the TOC will be the same for both functions, and 
anyway those functions are so simple that they don't use the TOC at all, 
so yes it would likely work without this patch but from my point of view 
it is incorrect to call one function with the TOC from the descriptor of 
another function.

If you thing we can take the risk, then I'm happy to drop the patch and 
replace it by

	execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)

Christophe

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 16/10/2021 à 08:41, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:32, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>>> Behind its location, lkdtm_EXEC_RODATA() executes
>>> lkdtm_rodata_do_nothing() which is a real function,
>>> not a copy of do_nothing().
>>>
>>> So executes it directly instead of using execute_location().
>>>
>>> This is necessary because following patch will fix execute_location()
>>> to use a copy of the function descriptor of do_nothing() and
>>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>>
>>> And fix displayed addresses by dereferencing the function descriptors.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>
>> I still don't understand this -- it doesn't look needed at all given the
>> changes in patch 12. (i.e. everything is using
>> dereference_function_descriptor() now)
> 
> dereference_function_descriptor() only deals with the function address, 
> not the function TOC.
> 
> do_nothing() is a function. It has a function descriptor with a given 
> address (address of .do_nothing) and a given TOC, say TOC1.
> 
> lkdtm_rodata_do_nothing() is another function. It has its own function 
> descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
> and a given TOC, say TOC2.
> 
> If we use execute_location(), it will copy do_nothing() function 
> descriptor and change the function address to the address of 
> lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
> with TOC1 instead of calling it with TOC2.
> 
>>
>> Can't this patch be dropped?
> 
> It is likely that the TOC will be the same for both functions, and 
> anyway those functions are so simple that they don't use the TOC at all, 
> so yes it would likely work without this patch but from my point of view 
> it is incorrect to call one function with the TOC from the descriptor of 
> another function.
> 
> If you thing we can take the risk, then I'm happy to drop the patch and 
> replace it by
> 
>      execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)
> 

Once we have patch 12 EXEC_RODATA works well on powerpc without this 
patch so I will drop this patch for now and will propose something else 
as a follow-up to my series.

Christophe

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 16/10/2021 à 08:41, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:32, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>>> Behind its location, lkdtm_EXEC_RODATA() executes
>>> lkdtm_rodata_do_nothing() which is a real function,
>>> not a copy of do_nothing().
>>>
>>> So executes it directly instead of using execute_location().
>>>
>>> This is necessary because following patch will fix execute_location()
>>> to use a copy of the function descriptor of do_nothing() and
>>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>>
>>> And fix displayed addresses by dereferencing the function descriptors.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>
>> I still don't understand this -- it doesn't look needed at all given the
>> changes in patch 12. (i.e. everything is using
>> dereference_function_descriptor() now)
> 
> dereference_function_descriptor() only deals with the function address, 
> not the function TOC.
> 
> do_nothing() is a function. It has a function descriptor with a given 
> address (address of .do_nothing) and a given TOC, say TOC1.
> 
> lkdtm_rodata_do_nothing() is another function. It has its own function 
> descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
> and a given TOC, say TOC2.
> 
> If we use execute_location(), it will copy do_nothing() function 
> descriptor and change the function address to the address of 
> lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
> with TOC1 instead of calling it with TOC2.
> 
>>
>> Can't this patch be dropped?
> 
> It is likely that the TOC will be the same for both functions, and 
> anyway those functions are so simple that they don't use the TOC at all, 
> so yes it would likely work without this patch but from my point of view 
> it is incorrect to call one function with the TOC from the descriptor of 
> another function.
> 
> If you thing we can take the risk, then I'm happy to drop the patch and 
> replace it by
> 
>      execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)
> 

Once we have patch 12 EXEC_RODATA works well on powerpc without this 
patch so I will drop this patch for now and will propose something else 
as a follow-up to my series.

Christophe

Re: [PATCH v2 11/13] lkdtm: Fix lkdtm_EXEC_RODATA()

[Christophe Leroy]

Le 16/10/2021 à 08:41, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:32, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:00AM +0200, Christophe Leroy wrote:
>>> Behind its location, lkdtm_EXEC_RODATA() executes
>>> lkdtm_rodata_do_nothing() which is a real function,
>>> not a copy of do_nothing().
>>>
>>> So executes it directly instead of using execute_location().
>>>
>>> This is necessary because following patch will fix execute_location()
>>> to use a copy of the function descriptor of do_nothing() and
>>> function descriptor of lkdtm_rodata_do_nothing() might be different.
>>>
>>> And fix displayed addresses by dereferencing the function descriptors.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>
>> I still don't understand this -- it doesn't look needed at all given the
>> changes in patch 12. (i.e. everything is using
>> dereference_function_descriptor() now)
> 
> dereference_function_descriptor() only deals with the function address, 
> not the function TOC.
> 
> do_nothing() is a function. It has a function descriptor with a given 
> address (address of .do_nothing) and a given TOC, say TOC1.
> 
> lkdtm_rodata_do_nothing() is another function. It has its own function 
> descriptor with a given address (address of .lkdtm_rodata_do_nothing) 
> and a given TOC, say TOC2.
> 
> If we use execute_location(), it will copy do_nothing() function 
> descriptor and change the function address to the address of 
> lkdtm_rodata_do_nothing(). So it will call lkdtm_rodata_do_nothing() 
> with TOC1 instead of calling it with TOC2.
> 
>>
>> Can't this patch be dropped?
> 
> It is likely that the TOC will be the same for both functions, and 
> anyway those functions are so simple that they don't use the TOC at all, 
> so yes it would likely work without this patch but from my point of view 
> it is incorrect to call one function with the TOC from the descriptor of 
> another function.
> 
> If you thing we can take the risk, then I'm happy to drop the patch and 
> replace it by
> 
>      execute_location(dereference_function_descriptor(lkdtm_rodata_do_nothing), CODE_AS_IS)
> 

Once we have patch 12 EXEC_RODATA works well on powerpc without this 
patch so I will drop this patch for now and will propose something else 
as a follow-up to my series.

Christophe

[PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

execute_location() and execute_user_location() intent
to copy do_nothing() text and execute it at a new location.
However, at the time being it doesn't copy do_nothing() function
but do_nothing() function descriptor which still points to the
original text. So at the end it still executes do_nothing() at
its original location allthough using a copied function descriptor.

So, fix that by really copying do_nothing() text and build a new
function descriptor by copying do_nothing() function descriptor and
updating the target address with the new location.

Also fix the displayed addresses by dereferencing do_nothing()
function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
 include/asm-generic/sections.h |  5 +++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 5266dc28df6e..96b3ebfcb8ed 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
+{
+	memcpy(fdesc, do_nothing, sizeof(*fdesc));
+	fdesc->addr = (unsigned long)dst;
+	barrier();
+
+	return fdesc;
+}
+
 static noinline void execute_location(void *dst, bool write)
 {
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
 	if (write == CODE_WRITE) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
+		memcpy(dst, do_nothing_text, EXEC_SIZE);
 		flush_icache_range((unsigned long)dst,
 				   (unsigned long)dst + EXEC_SIZE);
 	}
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
@@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
 
 	/* Intentionally crossing kernel/user memory boundary. */
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
-	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
+	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
 				   EXEC_SIZE, FOLL_WRITE);
 	if (copied < EXEC_SIZE)
 		return;
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 76163883c6ff..d225318538bd 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -70,6 +70,11 @@ typedef struct {
 } func_desc_t;
 #endif
 
+static inline bool have_function_descriptors(void)
+{
+	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
+}
+
 /* random extra sections (if any).  Override
  * in asm/sections.h */
 #ifndef arch_is_kernel_text
-- 
2.31.1

[PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

execute_location() and execute_user_location() intent
to copy do_nothing() text and execute it at a new location.
However, at the time being it doesn't copy do_nothing() function
but do_nothing() function descriptor which still points to the
original text. So at the end it still executes do_nothing() at
its original location allthough using a copied function descriptor.

So, fix that by really copying do_nothing() text and build a new
function descriptor by copying do_nothing() function descriptor and
updating the target address with the new location.

Also fix the displayed addresses by dereferencing do_nothing()
function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
 include/asm-generic/sections.h |  5 +++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 5266dc28df6e..96b3ebfcb8ed 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
+{
+	memcpy(fdesc, do_nothing, sizeof(*fdesc));
+	fdesc->addr = (unsigned long)dst;
+	barrier();
+
+	return fdesc;
+}
+
 static noinline void execute_location(void *dst, bool write)
 {
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
 	if (write = CODE_WRITE) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
+		memcpy(dst, do_nothing_text, EXEC_SIZE);
 		flush_icache_range((unsigned long)dst,
 				   (unsigned long)dst + EXEC_SIZE);
 	}
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
@@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
 
 	/* Intentionally crossing kernel/user memory boundary. */
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
-	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
+	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
 				   EXEC_SIZE, FOLL_WRITE);
 	if (copied < EXEC_SIZE)
 		return;
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 76163883c6ff..d225318538bd 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -70,6 +70,11 @@ typedef struct {
 } func_desc_t;
 #endif
 
+static inline bool have_function_descriptors(void)
+{
+	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
+}
+
 /* random extra sections (if any).  Override
  * in asm/sections.h */
 #ifndef arch_is_kernel_text
-- 
2.31.1

[PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

execute_location() and execute_user_location() intent
to copy do_nothing() text and execute it at a new location.
However, at the time being it doesn't copy do_nothing() function
but do_nothing() function descriptor which still points to the
original text. So at the end it still executes do_nothing() at
its original location allthough using a copied function descriptor.

So, fix that by really copying do_nothing() text and build a new
function descriptor by copying do_nothing() function descriptor and
updating the target address with the new location.

Also fix the displayed addresses by dereferencing do_nothing()
function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
 include/asm-generic/sections.h |  5 +++++
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 5266dc28df6e..96b3ebfcb8ed 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
+{
+	memcpy(fdesc, do_nothing, sizeof(*fdesc));
+	fdesc->addr = (unsigned long)dst;
+	barrier();
+
+	return fdesc;
+}
+
 static noinline void execute_location(void *dst, bool write)
 {
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
 	if (write == CODE_WRITE) {
-		memcpy(dst, do_nothing, EXEC_SIZE);
+		memcpy(dst, do_nothing_text, EXEC_SIZE);
 		flush_icache_range((unsigned long)dst,
 				   (unsigned long)dst + EXEC_SIZE);
 	}
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
@@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
 
 	/* Intentionally crossing kernel/user memory boundary. */
 	void (*func)(void) = dst;
+	func_desc_t fdesc;
+	void *do_nothing_text = dereference_function_descriptor(do_nothing);
 
-	pr_info("attempting ok execution at %px\n", do_nothing);
+	pr_info("attempting ok execution at %px\n", do_nothing_text);
 	do_nothing();
 
-	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
+	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
 				   EXEC_SIZE, FOLL_WRITE);
 	if (copied < EXEC_SIZE)
 		return;
 	pr_info("attempting bad execution at %px\n", func);
+	if (have_function_descriptors())
+		func = setup_function_descriptor(&fdesc, dst);
 	func();
 	pr_err("FAIL: func returned\n");
 }
diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
index 76163883c6ff..d225318538bd 100644
--- a/include/asm-generic/sections.h
+++ b/include/asm-generic/sections.h
@@ -70,6 +70,11 @@ typedef struct {
 } func_desc_t;
 #endif
 
+static inline bool have_function_descriptors(void)
+{
+	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
+}
+
 /* random extra sections (if any).  Override
  * in asm/sections.h */
 #ifndef arch_is_kernel_text
-- 
2.31.1

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
> execute_location() and execute_user_location() intent
> to copy do_nothing() text and execute it at a new location.
> However, at the time being it doesn't copy do_nothing() function
> but do_nothing() function descriptor which still points to the
> original text. So at the end it still executes do_nothing() at
> its original location allthough using a copied function descriptor.
> 
> So, fix that by really copying do_nothing() text and build a new
> function descriptor by copying do_nothing() function descriptor and
> updating the target address with the new location.
> 
> Also fix the displayed addresses by dereferencing do_nothing()
> function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>  include/asm-generic/sections.h |  5 +++++
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 5266dc28df6e..96b3ebfcb8ed 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> +{
> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> +	fdesc->addr = (unsigned long)dst;
> +	barrier();
> +
> +	return fdesc;
> +}

How about collapsing the "have_function_descriptors()" check into
setup_function_descriptor()?

static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
{
	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
		memcpy(fdesc, do_nothing, sizeof(*fdesc));
		fdesc->addr = (unsigned long)dst;
		barrier();
		return fdesc;
	} else {
		return dst;
	}
}

> +
>  static noinline void execute_location(void *dst, bool write)
>  {
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
>  	if (write == CODE_WRITE) {
> -		memcpy(dst, do_nothing, EXEC_SIZE);
> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>  		flush_icache_range((unsigned long)dst,
>  				   (unsigned long)dst + EXEC_SIZE);
>  	}
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }
> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>  
>  	/* Intentionally crossing kernel/user memory boundary. */
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>  				   EXEC_SIZE, FOLL_WRITE);
>  	if (copied < EXEC_SIZE)
>  		return;
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }


> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 76163883c6ff..d225318538bd 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -70,6 +70,11 @@ typedef struct {
>  } func_desc_t;
>  #endif
>  
> +static inline bool have_function_descriptors(void)
> +{
> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
> +}
> +
>  /* random extra sections (if any).  Override
>   * in asm/sections.h */
>  #ifndef arch_is_kernel_text

This hunk seems like it should live in a separate patch.

-- 
Kees Cook

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
> execute_location() and execute_user_location() intent
> to copy do_nothing() text and execute it at a new location.
> However, at the time being it doesn't copy do_nothing() function
> but do_nothing() function descriptor which still points to the
> original text. So at the end it still executes do_nothing() at
> its original location allthough using a copied function descriptor.
> 
> So, fix that by really copying do_nothing() text and build a new
> function descriptor by copying do_nothing() function descriptor and
> updating the target address with the new location.
> 
> Also fix the displayed addresses by dereferencing do_nothing()
> function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>  include/asm-generic/sections.h |  5 +++++
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 5266dc28df6e..96b3ebfcb8ed 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> +{
> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> +	fdesc->addr = (unsigned long)dst;
> +	barrier();
> +
> +	return fdesc;
> +}

How about collapsing the "have_function_descriptors()" check into
setup_function_descriptor()?

static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
{
	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
		memcpy(fdesc, do_nothing, sizeof(*fdesc));
		fdesc->addr = (unsigned long)dst;
		barrier();
		return fdesc;
	} else {
		return dst;
	}
}

> +
>  static noinline void execute_location(void *dst, bool write)
>  {
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
>  	if (write = CODE_WRITE) {
> -		memcpy(dst, do_nothing, EXEC_SIZE);
> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>  		flush_icache_range((unsigned long)dst,
>  				   (unsigned long)dst + EXEC_SIZE);
>  	}
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }
> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>  
>  	/* Intentionally crossing kernel/user memory boundary. */
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>  				   EXEC_SIZE, FOLL_WRITE);
>  	if (copied < EXEC_SIZE)
>  		return;
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }


> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 76163883c6ff..d225318538bd 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -70,6 +70,11 @@ typedef struct {
>  } func_desc_t;
>  #endif
>  
> +static inline bool have_function_descriptors(void)
> +{
> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
> +}
> +
>  /* random extra sections (if any).  Override
>   * in asm/sections.h */
>  #ifndef arch_is_kernel_text

This hunk seems like it should live in a separate patch.

-- 
Kees Cook

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
> execute_location() and execute_user_location() intent
> to copy do_nothing() text and execute it at a new location.
> However, at the time being it doesn't copy do_nothing() function
> but do_nothing() function descriptor which still points to the
> original text. So at the end it still executes do_nothing() at
> its original location allthough using a copied function descriptor.
> 
> So, fix that by really copying do_nothing() text and build a new
> function descriptor by copying do_nothing() function descriptor and
> updating the target address with the new location.
> 
> Also fix the displayed addresses by dereferencing do_nothing()
> function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>  include/asm-generic/sections.h |  5 +++++
>  2 files changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 5266dc28df6e..96b3ebfcb8ed 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> +{
> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> +	fdesc->addr = (unsigned long)dst;
> +	barrier();
> +
> +	return fdesc;
> +}

How about collapsing the "have_function_descriptors()" check into
setup_function_descriptor()?

static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
{
	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
		memcpy(fdesc, do_nothing, sizeof(*fdesc));
		fdesc->addr = (unsigned long)dst;
		barrier();
		return fdesc;
	} else {
		return dst;
	}
}

> +
>  static noinline void execute_location(void *dst, bool write)
>  {
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
>  	if (write == CODE_WRITE) {
> -		memcpy(dst, do_nothing, EXEC_SIZE);
> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>  		flush_icache_range((unsigned long)dst,
>  				   (unsigned long)dst + EXEC_SIZE);
>  	}
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }
> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>  
>  	/* Intentionally crossing kernel/user memory boundary. */
>  	void (*func)(void) = dst;
> +	func_desc_t fdesc;
> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>  
> -	pr_info("attempting ok execution at %px\n", do_nothing);
> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>  	do_nothing();
>  
> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>  				   EXEC_SIZE, FOLL_WRITE);
>  	if (copied < EXEC_SIZE)
>  		return;
>  	pr_info("attempting bad execution at %px\n", func);
> +	if (have_function_descriptors())
> +		func = setup_function_descriptor(&fdesc, dst);
>  	func();
>  	pr_err("FAIL: func returned\n");
>  }


> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
> index 76163883c6ff..d225318538bd 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -70,6 +70,11 @@ typedef struct {
>  } func_desc_t;
>  #endif
>  
> +static inline bool have_function_descriptors(void)
> +{
> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
> +}
> +
>  /* random extra sections (if any).  Override
>   * in asm/sections.h */
>  #ifndef arch_is_kernel_text

This hunk seems like it should live in a separate patch.

-- 
Kees Cook

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Le 15/10/2021 à 23:31, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>> execute_location() and execute_user_location() intent
>> to copy do_nothing() text and execute it at a new location.
>> However, at the time being it doesn't copy do_nothing() function
>> but do_nothing() function descriptor which still points to the
>> original text. So at the end it still executes do_nothing() at
>> its original location allthough using a copied function descriptor.
>>
>> So, fix that by really copying do_nothing() text and build a new
>> function descriptor by copying do_nothing() function descriptor and
>> updating the target address with the new location.
>>
>> Also fix the displayed addresses by dereferencing do_nothing()
>> function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>   include/asm-generic/sections.h |  5 +++++
>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 5266dc28df6e..96b3ebfcb8ed 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> +{
>> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> +	fdesc->addr = (unsigned long)dst;
>> +	barrier();
>> +
>> +	return fdesc;
>> +}
> 
> How about collapsing the "have_function_descriptors()" check into
> setup_function_descriptor()?
> 
> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> {
> 	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
> 		memcpy(fdesc, do_nothing, sizeof(*fdesc));
> 		fdesc->addr = (unsigned long)dst;
> 		barrier();
> 		return fdesc;
> 	} else {
> 		return dst;
> 	}
> }

Ok

> 
>> +
>>   static noinline void execute_location(void *dst, bool write)
>>   {
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>>   	if (write == CODE_WRITE) {
>> -		memcpy(dst, do_nothing, EXEC_SIZE);
>> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>>   		flush_icache_range((unsigned long)dst,
>>   				   (unsigned long)dst + EXEC_SIZE);
>>   	}
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
>> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>>   
>>   	/* Intentionally crossing kernel/user memory boundary. */
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
>> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>>   				   EXEC_SIZE, FOLL_WRITE);
>>   	if (copied < EXEC_SIZE)
>>   		return;
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
> 
> 
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index 76163883c6ff..d225318538bd 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -70,6 +70,11 @@ typedef struct {
>>   } func_desc_t;
>>   #endif
>>   
>> +static inline bool have_function_descriptors(void)
>> +{
>> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>> +}
>> +
>>   /* random extra sections (if any).  Override
>>    * in asm/sections.h */
>>   #ifndef arch_is_kernel_text
> 
> This hunk seems like it should live in a separate patch.
> 

Ok I move it in a previous patch.

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Le 15/10/2021 à 23:31, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>> execute_location() and execute_user_location() intent
>> to copy do_nothing() text and execute it at a new location.
>> However, at the time being it doesn't copy do_nothing() function
>> but do_nothing() function descriptor which still points to the
>> original text. So at the end it still executes do_nothing() at
>> its original location allthough using a copied function descriptor.
>>
>> So, fix that by really copying do_nothing() text and build a new
>> function descriptor by copying do_nothing() function descriptor and
>> updating the target address with the new location.
>>
>> Also fix the displayed addresses by dereferencing do_nothing()
>> function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>   include/asm-generic/sections.h |  5 +++++
>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 5266dc28df6e..96b3ebfcb8ed 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> +{
>> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> +	fdesc->addr = (unsigned long)dst;
>> +	barrier();
>> +
>> +	return fdesc;
>> +}
> 
> How about collapsing the "have_function_descriptors()" check into
> setup_function_descriptor()?
> 
> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> {
> 	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
> 		memcpy(fdesc, do_nothing, sizeof(*fdesc));
> 		fdesc->addr = (unsigned long)dst;
> 		barrier();
> 		return fdesc;
> 	} else {
> 		return dst;
> 	}
> }

Ok

> 
>> +
>>   static noinline void execute_location(void *dst, bool write)
>>   {
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>>   	if (write = CODE_WRITE) {
>> -		memcpy(dst, do_nothing, EXEC_SIZE);
>> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>>   		flush_icache_range((unsigned long)dst,
>>   				   (unsigned long)dst + EXEC_SIZE);
>>   	}
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
>> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>>   
>>   	/* Intentionally crossing kernel/user memory boundary. */
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
>> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>>   				   EXEC_SIZE, FOLL_WRITE);
>>   	if (copied < EXEC_SIZE)
>>   		return;
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
> 
> 
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index 76163883c6ff..d225318538bd 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -70,6 +70,11 @@ typedef struct {
>>   } func_desc_t;
>>   #endif
>>   
>> +static inline bool have_function_descriptors(void)
>> +{
>> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>> +}
>> +
>>   /* random extra sections (if any).  Override
>>    * in asm/sections.h */
>>   #ifndef arch_is_kernel_text
> 
> This hunk seems like it should live in a separate patch.
> 

Ok I move it in a previous patch.

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Le 15/10/2021 à 23:31, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>> execute_location() and execute_user_location() intent
>> to copy do_nothing() text and execute it at a new location.
>> However, at the time being it doesn't copy do_nothing() function
>> but do_nothing() function descriptor which still points to the
>> original text. So at the end it still executes do_nothing() at
>> its original location allthough using a copied function descriptor.
>>
>> So, fix that by really copying do_nothing() text and build a new
>> function descriptor by copying do_nothing() function descriptor and
>> updating the target address with the new location.
>>
>> Also fix the displayed addresses by dereferencing do_nothing()
>> function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>   include/asm-generic/sections.h |  5 +++++
>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 5266dc28df6e..96b3ebfcb8ed 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> +{
>> +	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> +	fdesc->addr = (unsigned long)dst;
>> +	barrier();
>> +
>> +	return fdesc;
>> +}
> 
> How about collapsing the "have_function_descriptors()" check into
> setup_function_descriptor()?
> 
> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
> {
> 	if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
> 		memcpy(fdesc, do_nothing, sizeof(*fdesc));
> 		fdesc->addr = (unsigned long)dst;
> 		barrier();
> 		return fdesc;
> 	} else {
> 		return dst;
> 	}
> }

Ok

> 
>> +
>>   static noinline void execute_location(void *dst, bool write)
>>   {
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>>   	if (write == CODE_WRITE) {
>> -		memcpy(dst, do_nothing, EXEC_SIZE);
>> +		memcpy(dst, do_nothing_text, EXEC_SIZE);
>>   		flush_icache_range((unsigned long)dst,
>>   				   (unsigned long)dst + EXEC_SIZE);
>>   	}
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
>> @@ -67,15 +80,19 @@ static void execute_user_location(void *dst)
>>   
>>   	/* Intentionally crossing kernel/user memory boundary. */
>>   	void (*func)(void) = dst;
>> +	func_desc_t fdesc;
>> +	void *do_nothing_text = dereference_function_descriptor(do_nothing);
>>   
>> -	pr_info("attempting ok execution at %px\n", do_nothing);
>> +	pr_info("attempting ok execution at %px\n", do_nothing_text);
>>   	do_nothing();
>>   
>> -	copied = access_process_vm(current, (unsigned long)dst, do_nothing,
>> +	copied = access_process_vm(current, (unsigned long)dst, do_nothing_text,
>>   				   EXEC_SIZE, FOLL_WRITE);
>>   	if (copied < EXEC_SIZE)
>>   		return;
>>   	pr_info("attempting bad execution at %px\n", func);
>> +	if (have_function_descriptors())
>> +		func = setup_function_descriptor(&fdesc, dst);
>>   	func();
>>   	pr_err("FAIL: func returned\n");
>>   }
> 
> 
>> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h
>> index 76163883c6ff..d225318538bd 100644
>> --- a/include/asm-generic/sections.h
>> +++ b/include/asm-generic/sections.h
>> @@ -70,6 +70,11 @@ typedef struct {
>>   } func_desc_t;
>>   #endif
>>   
>> +static inline bool have_function_descriptors(void)
>> +{
>> +	return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>> +}
>> +
>>   /* random extra sections (if any).  Override
>>    * in asm/sections.h */
>>   #ifndef arch_is_kernel_text
> 
> This hunk seems like it should live in a separate patch.
> 

Ok I move it in a previous patch.

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Hi Kees,

Le 16/10/2021 à 08:42, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:31, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>>> execute_location() and execute_user_location() intent
>>> to copy do_nothing() text and execute it at a new location.
>>> However, at the time being it doesn't copy do_nothing() function
>>> but do_nothing() function descriptor which still points to the
>>> original text. So at the end it still executes do_nothing() at
>>> its original location allthough using a copied function descriptor.
>>>
>>> So, fix that by really copying do_nothing() text and build a new
>>> function descriptor by copying do_nothing() function descriptor and
>>> updating the target address with the new location.
>>>
>>> Also fix the displayed addresses by dereferencing do_nothing()
>>> function descriptor.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>> ---
>>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>>   include/asm-generic/sections.h |  5 +++++
>>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>>> index 5266dc28df6e..96b3ebfcb8ed 100644
>>> --- a/drivers/misc/lkdtm/perms.c
>>> +++ b/drivers/misc/lkdtm/perms.c
>>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>>       return;
>>>   }
>>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>> +{
>>> +    memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>> +    fdesc->addr = (unsigned long)dst;
>>> +    barrier();
>>> +
>>> +    return fdesc;
>>> +}
>>
>> How about collapsing the "have_function_descriptors()" check into
>> setup_function_descriptor()?
>>
>> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> {
>>     if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
>>         memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>         fdesc->addr = (unsigned long)dst;
>>         barrier();
>>         return fdesc;
>>     } else {
>>         return dst;
>>     }
>> }
> 
> Ok
> 

...

>>
>>> diff --git a/include/asm-generic/sections.h 
>>> b/include/asm-generic/sections.h
>>> index 76163883c6ff..d225318538bd 100644
>>> --- a/include/asm-generic/sections.h
>>> +++ b/include/asm-generic/sections.h
>>> @@ -70,6 +70,11 @@ typedef struct {
>>>   } func_desc_t;
>>>   #endif
>>> +static inline bool have_function_descriptors(void)
>>> +{
>>> +    return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>>> +}
>>> +
>>>   /* random extra sections (if any).  Override
>>>    * in asm/sections.h */
>>>   #ifndef arch_is_kernel_text
>>
>> This hunk seems like it should live in a separate patch.
>>
> 
> Ok I move it in a previous patch.


Do you have any additional feedback or comment on series v3 ?

What's the way forward, should it go via LKDTM tree or via powerpc tree 
or another tree ? I see there are neither Ack-by nor Reviewed-by for the 
last 2 patches.

Thanks
Christophe

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Hi Kees,

Le 16/10/2021 à 08:42, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:31, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>>> execute_location() and execute_user_location() intent
>>> to copy do_nothing() text and execute it at a new location.
>>> However, at the time being it doesn't copy do_nothing() function
>>> but do_nothing() function descriptor which still points to the
>>> original text. So at the end it still executes do_nothing() at
>>> its original location allthough using a copied function descriptor.
>>>
>>> So, fix that by really copying do_nothing() text and build a new
>>> function descriptor by copying do_nothing() function descriptor and
>>> updating the target address with the new location.
>>>
>>> Also fix the displayed addresses by dereferencing do_nothing()
>>> function descriptor.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>> ---
>>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>>   include/asm-generic/sections.h |  5 +++++
>>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>>> index 5266dc28df6e..96b3ebfcb8ed 100644
>>> --- a/drivers/misc/lkdtm/perms.c
>>> +++ b/drivers/misc/lkdtm/perms.c
>>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>>       return;
>>>   }
>>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>> +{
>>> +    memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>> +    fdesc->addr = (unsigned long)dst;
>>> +    barrier();
>>> +
>>> +    return fdesc;
>>> +}
>>
>> How about collapsing the "have_function_descriptors()" check into
>> setup_function_descriptor()?
>>
>> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> {
>>     if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
>>         memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>         fdesc->addr = (unsigned long)dst;
>>         barrier();
>>         return fdesc;
>>     } else {
>>         return dst;
>>     }
>> }
> 
> Ok
> 

...

>>
>>> diff --git a/include/asm-generic/sections.h 
>>> b/include/asm-generic/sections.h
>>> index 76163883c6ff..d225318538bd 100644
>>> --- a/include/asm-generic/sections.h
>>> +++ b/include/asm-generic/sections.h
>>> @@ -70,6 +70,11 @@ typedef struct {
>>>   } func_desc_t;
>>>   #endif
>>> +static inline bool have_function_descriptors(void)
>>> +{
>>> +    return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>>> +}
>>> +
>>>   /* random extra sections (if any).  Override
>>>    * in asm/sections.h */
>>>   #ifndef arch_is_kernel_text
>>
>> This hunk seems like it should live in a separate patch.
>>
> 
> Ok I move it in a previous patch.


Do you have any additional feedback or comment on series v3 ?

What's the way forward, should it go via LKDTM tree or via powerpc tree 
or another tree ? I see there are neither Ack-by nor Reviewed-by for the 
last 2 patches.

Thanks
Christophe

Re: [PATCH v2 12/13] lkdtm: Fix execute_[user]_location()

[Christophe Leroy]

Hi Kees,

Le 16/10/2021 à 08:42, Christophe Leroy a écrit :
> 
> 
> Le 15/10/2021 à 23:31, Kees Cook a écrit :
>> On Thu, Oct 14, 2021 at 07:50:01AM +0200, Christophe Leroy wrote:
>>> execute_location() and execute_user_location() intent
>>> to copy do_nothing() text and execute it at a new location.
>>> However, at the time being it doesn't copy do_nothing() function
>>> but do_nothing() function descriptor which still points to the
>>> original text. So at the end it still executes do_nothing() at
>>> its original location allthough using a copied function descriptor.
>>>
>>> So, fix that by really copying do_nothing() text and build a new
>>> function descriptor by copying do_nothing() function descriptor and
>>> updating the target address with the new location.
>>>
>>> Also fix the displayed addresses by dereferencing do_nothing()
>>> function descriptor.
>>>
>>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>>> ---
>>>   drivers/misc/lkdtm/perms.c     | 25 +++++++++++++++++++++----
>>>   include/asm-generic/sections.h |  5 +++++
>>>   2 files changed, 26 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>>> index 5266dc28df6e..96b3ebfcb8ed 100644
>>> --- a/drivers/misc/lkdtm/perms.c
>>> +++ b/drivers/misc/lkdtm/perms.c
>>> @@ -44,19 +44,32 @@ static noinline void do_overwritten(void)
>>>       return;
>>>   }
>>> +static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>> +{
>>> +    memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>> +    fdesc->addr = (unsigned long)dst;
>>> +    barrier();
>>> +
>>> +    return fdesc;
>>> +}
>>
>> How about collapsing the "have_function_descriptors()" check into
>> setup_function_descriptor()?
>>
>> static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>> {
>>     if (__is_defined(HAVE_FUNCTION_DESCRIPTORS)) {
>>         memcpy(fdesc, do_nothing, sizeof(*fdesc));
>>         fdesc->addr = (unsigned long)dst;
>>         barrier();
>>         return fdesc;
>>     } else {
>>         return dst;
>>     }
>> }
> 
> Ok
> 

...

>>
>>> diff --git a/include/asm-generic/sections.h 
>>> b/include/asm-generic/sections.h
>>> index 76163883c6ff..d225318538bd 100644
>>> --- a/include/asm-generic/sections.h
>>> +++ b/include/asm-generic/sections.h
>>> @@ -70,6 +70,11 @@ typedef struct {
>>>   } func_desc_t;
>>>   #endif
>>> +static inline bool have_function_descriptors(void)
>>> +{
>>> +    return __is_defined(HAVE_FUNCTION_DESCRIPTORS);
>>> +}
>>> +
>>>   /* random extra sections (if any).  Override
>>>    * in asm/sections.h */
>>>   #ifndef arch_is_kernel_text
>>
>> This hunk seems like it should live in a separate patch.
>>
> 
> Ok I move it in a previous patch.


Do you have any additional feedback or comment on series v3 ?

What's the way forward, should it go via LKDTM tree or via powerpc tree 
or another tree ? I see there are neither Ack-by nor Reviewed-by for the 
last 2 patches.

Thanks
Christophe

[PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Add WRITE_OPD to check that you can't modify function
descriptors.

Gives the following result when function descriptors are
not protected:

	lkdtm: Performing direct entry WRITE_OPD
	lkdtm: attempting bad 16 bytes write at c00000000269b358
	lkdtm: FAIL: survived bad write
	lkdtm: do_nothing was hijacked!

Looks like a standard compiler barrier(); is not enough to force
GCC to use the modified function descriptor. Add to add a fake empty
inline assembly to force GCC to reload the function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/core.c  |  1 +
 drivers/misc/lkdtm/lkdtm.h |  1 +
 drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index fe6fd34b8caf..de092aa03b5d 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(WRITE_RO),
 	CRASHTYPE(WRITE_RO_AFTER_INIT),
 	CRASHTYPE(WRITE_KERN),
+	CRASHTYPE(WRITE_OPD),
 	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
 	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
 	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index c212a253edde..188bd0fd6575 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
 void lkdtm_WRITE_RO(void);
 void lkdtm_WRITE_RO_AFTER_INIT(void);
 void lkdtm_WRITE_KERN(void);
+void lkdtm_WRITE_OPD(void);
 void lkdtm_EXEC_DATA(void);
 void lkdtm_EXEC_STACK(void);
 void lkdtm_EXEC_KMALLOC(void);
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 96b3ebfcb8ed..3870bc82d40d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static noinline void do_almost_nothing(void)
+{
+	pr_info("do_nothing was hijacked!\n");
+}
+
 static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
 {
 	memcpy(fdesc, do_nothing, sizeof(*fdesc));
@@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
 	do_overwritten();
 }
 
+void lkdtm_WRITE_OPD(void)
+{
+	size_t size = sizeof(func_desc_t);
+	void (*func)(void) = do_nothing;
+
+	if (!have_function_descriptors()) {
+		pr_info("Platform doesn't have function descriptors.\n");
+		return;
+	}
+	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+	memcpy(do_nothing, do_almost_nothing, size);
+	pr_err("FAIL: survived bad write\n");
+
+	asm("" : "=m"(func));
+	func();
+}
+
 void lkdtm_EXEC_DATA(void)
 {
 	execute_location(data_area, CODE_WRITE);
-- 
2.31.1

[PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Add WRITE_OPD to check that you can't modify function
descriptors.

Gives the following result when function descriptors are
not protected:

	lkdtm: Performing direct entry WRITE_OPD
	lkdtm: attempting bad 16 bytes write at c00000000269b358
	lkdtm: FAIL: survived bad write
	lkdtm: do_nothing was hijacked!

Looks like a standard compiler barrier(); is not enough to force
GCC to use the modified function descriptor. Add to add a fake empty
inline assembly to force GCC to reload the function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/core.c  |  1 +
 drivers/misc/lkdtm/lkdtm.h |  1 +
 drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index fe6fd34b8caf..de092aa03b5d 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(WRITE_RO),
 	CRASHTYPE(WRITE_RO_AFTER_INIT),
 	CRASHTYPE(WRITE_KERN),
+	CRASHTYPE(WRITE_OPD),
 	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
 	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
 	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index c212a253edde..188bd0fd6575 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
 void lkdtm_WRITE_RO(void);
 void lkdtm_WRITE_RO_AFTER_INIT(void);
 void lkdtm_WRITE_KERN(void);
+void lkdtm_WRITE_OPD(void);
 void lkdtm_EXEC_DATA(void);
 void lkdtm_EXEC_STACK(void);
 void lkdtm_EXEC_KMALLOC(void);
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 96b3ebfcb8ed..3870bc82d40d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static noinline void do_almost_nothing(void)
+{
+	pr_info("do_nothing was hijacked!\n");
+}
+
 static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
 {
 	memcpy(fdesc, do_nothing, sizeof(*fdesc));
@@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
 	do_overwritten();
 }
 
+void lkdtm_WRITE_OPD(void)
+{
+	size_t size = sizeof(func_desc_t);
+	void (*func)(void) = do_nothing;
+
+	if (!have_function_descriptors()) {
+		pr_info("Platform doesn't have function descriptors.\n");
+		return;
+	}
+	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+	memcpy(do_nothing, do_almost_nothing, size);
+	pr_err("FAIL: survived bad write\n");
+
+	asm("" : "=m"(func));
+	func();
+}
+
 void lkdtm_EXEC_DATA(void)
 {
 	execute_location(data_area, CODE_WRITE);
-- 
2.31.1

[PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Add WRITE_OPD to check that you can't modify function
descriptors.

Gives the following result when function descriptors are
not protected:

	lkdtm: Performing direct entry WRITE_OPD
	lkdtm: attempting bad 16 bytes write at c00000000269b358
	lkdtm: FAIL: survived bad write
	lkdtm: do_nothing was hijacked!

Looks like a standard compiler barrier(); is not enough to force
GCC to use the modified function descriptor. Add to add a fake empty
inline assembly to force GCC to reload the function descriptor.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 drivers/misc/lkdtm/core.c  |  1 +
 drivers/misc/lkdtm/lkdtm.h |  1 +
 drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
index fe6fd34b8caf..de092aa03b5d 100644
--- a/drivers/misc/lkdtm/core.c
+++ b/drivers/misc/lkdtm/core.c
@@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
 	CRASHTYPE(WRITE_RO),
 	CRASHTYPE(WRITE_RO_AFTER_INIT),
 	CRASHTYPE(WRITE_KERN),
+	CRASHTYPE(WRITE_OPD),
 	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
 	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
 	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index c212a253edde..188bd0fd6575 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
 void lkdtm_WRITE_RO(void);
 void lkdtm_WRITE_RO_AFTER_INIT(void);
 void lkdtm_WRITE_KERN(void);
+void lkdtm_WRITE_OPD(void);
 void lkdtm_EXEC_DATA(void);
 void lkdtm_EXEC_STACK(void);
 void lkdtm_EXEC_KMALLOC(void);
diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
index 96b3ebfcb8ed..3870bc82d40d 100644
--- a/drivers/misc/lkdtm/perms.c
+++ b/drivers/misc/lkdtm/perms.c
@@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
 	return;
 }
 
+static noinline void do_almost_nothing(void)
+{
+	pr_info("do_nothing was hijacked!\n");
+}
+
 static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
 {
 	memcpy(fdesc, do_nothing, sizeof(*fdesc));
@@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
 	do_overwritten();
 }
 
+void lkdtm_WRITE_OPD(void)
+{
+	size_t size = sizeof(func_desc_t);
+	void (*func)(void) = do_nothing;
+
+	if (!have_function_descriptors()) {
+		pr_info("Platform doesn't have function descriptors.\n");
+		return;
+	}
+	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
+	memcpy(do_nothing, do_almost_nothing, size);
+	pr_err("FAIL: survived bad write\n");
+
+	asm("" : "=m"(func));
+	func();
+}
+
 void lkdtm_EXEC_DATA(void)
 {
 	execute_location(data_area, CODE_WRITE);
-- 
2.31.1

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
> Add WRITE_OPD to check that you can't modify function
> descriptors.
> 
> Gives the following result when function descriptors are
> not protected:
> 
> 	lkdtm: Performing direct entry WRITE_OPD
> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
> 	lkdtm: FAIL: survived bad write
> 	lkdtm: do_nothing was hijacked!
> 
> Looks like a standard compiler barrier(); is not enough to force
> GCC to use the modified function descriptor. Add to add a fake empty
> inline assembly to force GCC to reload the function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/core.c  |  1 +
>  drivers/misc/lkdtm/lkdtm.h |  1 +
>  drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index fe6fd34b8caf..de092aa03b5d 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>  	CRASHTYPE(WRITE_RO),
>  	CRASHTYPE(WRITE_RO_AFTER_INIT),
>  	CRASHTYPE(WRITE_KERN),
> +	CRASHTYPE(WRITE_OPD),
>  	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> index c212a253edde..188bd0fd6575 100644
> --- a/drivers/misc/lkdtm/lkdtm.h
> +++ b/drivers/misc/lkdtm/lkdtm.h
> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>  void lkdtm_WRITE_RO(void);
>  void lkdtm_WRITE_RO_AFTER_INIT(void);
>  void lkdtm_WRITE_KERN(void);
> +void lkdtm_WRITE_OPD(void);
>  void lkdtm_EXEC_DATA(void);
>  void lkdtm_EXEC_STACK(void);
>  void lkdtm_EXEC_KMALLOC(void);
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 96b3ebfcb8ed..3870bc82d40d 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static noinline void do_almost_nothing(void)
> +{
> +	pr_info("do_nothing was hijacked!\n");
> +}
> +
>  static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>  {
>  	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>  	do_overwritten();
>  }
>  
> +void lkdtm_WRITE_OPD(void)
> +{
> +	size_t size = sizeof(func_desc_t);
> +	void (*func)(void) = do_nothing;
> +
> +	if (!have_function_descriptors()) {
> +		pr_info("Platform doesn't have function descriptors.\n");

This should be more explicit ('xfail'):

	pr_info("XFAIL: platform doesn't use function descriptors.\n");

> +		return;
> +	}
> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
> +	memcpy(do_nothing, do_almost_nothing, size);
> +	pr_err("FAIL: survived bad write\n");
> +
> +	asm("" : "=m"(func));

Since this is a descriptor, I assume no icache flush is needed. Are
function descriptors strictly dcache? (Is anything besides just a
barrier needed?)

> +	func();
> +}
> +
>  void lkdtm_EXEC_DATA(void)
>  {
>  	execute_location(data_area, CODE_WRITE);
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
> Add WRITE_OPD to check that you can't modify function
> descriptors.
> 
> Gives the following result when function descriptors are
> not protected:
> 
> 	lkdtm: Performing direct entry WRITE_OPD
> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
> 	lkdtm: FAIL: survived bad write
> 	lkdtm: do_nothing was hijacked!
> 
> Looks like a standard compiler barrier(); is not enough to force
> GCC to use the modified function descriptor. Add to add a fake empty
> inline assembly to force GCC to reload the function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/core.c  |  1 +
>  drivers/misc/lkdtm/lkdtm.h |  1 +
>  drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index fe6fd34b8caf..de092aa03b5d 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>  	CRASHTYPE(WRITE_RO),
>  	CRASHTYPE(WRITE_RO_AFTER_INIT),
>  	CRASHTYPE(WRITE_KERN),
> +	CRASHTYPE(WRITE_OPD),
>  	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> index c212a253edde..188bd0fd6575 100644
> --- a/drivers/misc/lkdtm/lkdtm.h
> +++ b/drivers/misc/lkdtm/lkdtm.h
> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>  void lkdtm_WRITE_RO(void);
>  void lkdtm_WRITE_RO_AFTER_INIT(void);
>  void lkdtm_WRITE_KERN(void);
> +void lkdtm_WRITE_OPD(void);
>  void lkdtm_EXEC_DATA(void);
>  void lkdtm_EXEC_STACK(void);
>  void lkdtm_EXEC_KMALLOC(void);
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 96b3ebfcb8ed..3870bc82d40d 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static noinline void do_almost_nothing(void)
> +{
> +	pr_info("do_nothing was hijacked!\n");
> +}
> +
>  static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>  {
>  	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>  	do_overwritten();
>  }
>  
> +void lkdtm_WRITE_OPD(void)
> +{
> +	size_t size = sizeof(func_desc_t);
> +	void (*func)(void) = do_nothing;
> +
> +	if (!have_function_descriptors()) {
> +		pr_info("Platform doesn't have function descriptors.\n");

This should be more explicit ('xfail'):

	pr_info("XFAIL: platform doesn't use function descriptors.\n");

> +		return;
> +	}
> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
> +	memcpy(do_nothing, do_almost_nothing, size);
> +	pr_err("FAIL: survived bad write\n");
> +
> +	asm("" : "=m"(func));

Since this is a descriptor, I assume no icache flush is needed. Are
function descriptors strictly dcache? (Is anything besides just a
barrier needed?)

> +	func();
> +}
> +
>  void lkdtm_EXEC_DATA(void)
>  {
>  	execute_location(data_area, CODE_WRITE);
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Kees Cook]

On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
> Add WRITE_OPD to check that you can't modify function
> descriptors.
> 
> Gives the following result when function descriptors are
> not protected:
> 
> 	lkdtm: Performing direct entry WRITE_OPD
> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
> 	lkdtm: FAIL: survived bad write
> 	lkdtm: do_nothing was hijacked!
> 
> Looks like a standard compiler barrier(); is not enough to force
> GCC to use the modified function descriptor. Add to add a fake empty
> inline assembly to force GCC to reload the function descriptor.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  drivers/misc/lkdtm/core.c  |  1 +
>  drivers/misc/lkdtm/lkdtm.h |  1 +
>  drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>  3 files changed, 24 insertions(+)
> 
> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> index fe6fd34b8caf..de092aa03b5d 100644
> --- a/drivers/misc/lkdtm/core.c
> +++ b/drivers/misc/lkdtm/core.c
> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>  	CRASHTYPE(WRITE_RO),
>  	CRASHTYPE(WRITE_RO_AFTER_INIT),
>  	CRASHTYPE(WRITE_KERN),
> +	CRASHTYPE(WRITE_OPD),
>  	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>  	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
> index c212a253edde..188bd0fd6575 100644
> --- a/drivers/misc/lkdtm/lkdtm.h
> +++ b/drivers/misc/lkdtm/lkdtm.h
> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>  void lkdtm_WRITE_RO(void);
>  void lkdtm_WRITE_RO_AFTER_INIT(void);
>  void lkdtm_WRITE_KERN(void);
> +void lkdtm_WRITE_OPD(void);
>  void lkdtm_EXEC_DATA(void);
>  void lkdtm_EXEC_STACK(void);
>  void lkdtm_EXEC_KMALLOC(void);
> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
> index 96b3ebfcb8ed..3870bc82d40d 100644
> --- a/drivers/misc/lkdtm/perms.c
> +++ b/drivers/misc/lkdtm/perms.c
> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>  	return;
>  }
>  
> +static noinline void do_almost_nothing(void)
> +{
> +	pr_info("do_nothing was hijacked!\n");
> +}
> +
>  static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>  {
>  	memcpy(fdesc, do_nothing, sizeof(*fdesc));
> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>  	do_overwritten();
>  }
>  
> +void lkdtm_WRITE_OPD(void)
> +{
> +	size_t size = sizeof(func_desc_t);
> +	void (*func)(void) = do_nothing;
> +
> +	if (!have_function_descriptors()) {
> +		pr_info("Platform doesn't have function descriptors.\n");

This should be more explicit ('xfail'):

	pr_info("XFAIL: platform doesn't use function descriptors.\n");

> +		return;
> +	}
> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
> +	memcpy(do_nothing, do_almost_nothing, size);
> +	pr_err("FAIL: survived bad write\n");
> +
> +	asm("" : "=m"(func));

Since this is a descriptor, I assume no icache flush is needed. Are
function descriptors strictly dcache? (Is anything besides just a
barrier needed?)

> +	func();
> +}
> +
>  void lkdtm_EXEC_DATA(void)
>  {
>  	execute_location(data_area, CODE_WRITE);
> -- 
> 2.31.1
> 

-- 
Kees Cook

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Le 15/10/2021 à 23:35, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
>> Add WRITE_OPD to check that you can't modify function
>> descriptors.
>>
>> Gives the following result when function descriptors are
>> not protected:
>>
>> 	lkdtm: Performing direct entry WRITE_OPD
>> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
>> 	lkdtm: FAIL: survived bad write
>> 	lkdtm: do_nothing was hijacked!
>>
>> Looks like a standard compiler barrier(); is not enough to force
>> GCC to use the modified function descriptor. Add to add a fake empty
>> inline assembly to force GCC to reload the function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/core.c  |  1 +
>>   drivers/misc/lkdtm/lkdtm.h |  1 +
>>   drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>>   3 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
>> index fe6fd34b8caf..de092aa03b5d 100644
>> --- a/drivers/misc/lkdtm/core.c
>> +++ b/drivers/misc/lkdtm/core.c
>> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>>   	CRASHTYPE(WRITE_RO),
>>   	CRASHTYPE(WRITE_RO_AFTER_INIT),
>>   	CRASHTYPE(WRITE_KERN),
>> +	CRASHTYPE(WRITE_OPD),
>>   	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
>> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
>> index c212a253edde..188bd0fd6575 100644
>> --- a/drivers/misc/lkdtm/lkdtm.h
>> +++ b/drivers/misc/lkdtm/lkdtm.h
>> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>>   void lkdtm_WRITE_RO(void);
>>   void lkdtm_WRITE_RO_AFTER_INIT(void);
>>   void lkdtm_WRITE_KERN(void);
>> +void lkdtm_WRITE_OPD(void);
>>   void lkdtm_EXEC_DATA(void);
>>   void lkdtm_EXEC_STACK(void);
>>   void lkdtm_EXEC_KMALLOC(void);
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 96b3ebfcb8ed..3870bc82d40d 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static noinline void do_almost_nothing(void)
>> +{
>> +	pr_info("do_nothing was hijacked!\n");
>> +}
>> +
>>   static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>   {
>>   	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>>   	do_overwritten();
>>   }
>>   
>> +void lkdtm_WRITE_OPD(void)
>> +{
>> +	size_t size = sizeof(func_desc_t);
>> +	void (*func)(void) = do_nothing;
>> +
>> +	if (!have_function_descriptors()) {
>> +		pr_info("Platform doesn't have function descriptors.\n");
> 
> This should be more explicit ('xfail'):
> 
> 	pr_info("XFAIL: platform doesn't use function descriptors.\n");

Ok


> 
>> +		return;
>> +	}
>> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
>> +	memcpy(do_nothing, do_almost_nothing, size);
>> +	pr_err("FAIL: survived bad write\n");
>> +
>> +	asm("" : "=m"(func));
> 
> Since this is a descriptor, I assume no icache flush is needed. Are
> function descriptors strictly dcache? (Is anything besides just a
> barrier needed?)

No flush is needed, the code just loads the function address from memory 
into CTR, loads R2 and branch to CTR:

	 19c:	e9 21 00 70 	ld      r9,112(r1)
	 1a0:	e9 49 00 00 	ld      r10,0(r9)
	 1a4:	7d 49 03 a6 	mtctr   r10
	 1a8:	e8 49 00 08 	ld      r2,8(r9)
	 1ac:	4e 80 04 21 	bctrl


> 
>> +	func();
>> +}
>> +
>>   void lkdtm_EXEC_DATA(void)
>>   {
>>   	execute_location(data_area, CODE_WRITE);
>> -- 
>> 2.31.1
>>
> 

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Le 15/10/2021 à 23:35, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
>> Add WRITE_OPD to check that you can't modify function
>> descriptors.
>>
>> Gives the following result when function descriptors are
>> not protected:
>>
>> 	lkdtm: Performing direct entry WRITE_OPD
>> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
>> 	lkdtm: FAIL: survived bad write
>> 	lkdtm: do_nothing was hijacked!
>>
>> Looks like a standard compiler barrier(); is not enough to force
>> GCC to use the modified function descriptor. Add to add a fake empty
>> inline assembly to force GCC to reload the function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/core.c  |  1 +
>>   drivers/misc/lkdtm/lkdtm.h |  1 +
>>   drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>>   3 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
>> index fe6fd34b8caf..de092aa03b5d 100644
>> --- a/drivers/misc/lkdtm/core.c
>> +++ b/drivers/misc/lkdtm/core.c
>> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>>   	CRASHTYPE(WRITE_RO),
>>   	CRASHTYPE(WRITE_RO_AFTER_INIT),
>>   	CRASHTYPE(WRITE_KERN),
>> +	CRASHTYPE(WRITE_OPD),
>>   	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
>> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
>> index c212a253edde..188bd0fd6575 100644
>> --- a/drivers/misc/lkdtm/lkdtm.h
>> +++ b/drivers/misc/lkdtm/lkdtm.h
>> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>>   void lkdtm_WRITE_RO(void);
>>   void lkdtm_WRITE_RO_AFTER_INIT(void);
>>   void lkdtm_WRITE_KERN(void);
>> +void lkdtm_WRITE_OPD(void);
>>   void lkdtm_EXEC_DATA(void);
>>   void lkdtm_EXEC_STACK(void);
>>   void lkdtm_EXEC_KMALLOC(void);
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 96b3ebfcb8ed..3870bc82d40d 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static noinline void do_almost_nothing(void)
>> +{
>> +	pr_info("do_nothing was hijacked!\n");
>> +}
>> +
>>   static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>   {
>>   	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>>   	do_overwritten();
>>   }
>>   
>> +void lkdtm_WRITE_OPD(void)
>> +{
>> +	size_t size = sizeof(func_desc_t);
>> +	void (*func)(void) = do_nothing;
>> +
>> +	if (!have_function_descriptors()) {
>> +		pr_info("Platform doesn't have function descriptors.\n");
> 
> This should be more explicit ('xfail'):
> 
> 	pr_info("XFAIL: platform doesn't use function descriptors.\n");

Ok


> 
>> +		return;
>> +	}
>> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
>> +	memcpy(do_nothing, do_almost_nothing, size);
>> +	pr_err("FAIL: survived bad write\n");
>> +
>> +	asm("" : "=m"(func));
> 
> Since this is a descriptor, I assume no icache flush is needed. Are
> function descriptors strictly dcache? (Is anything besides just a
> barrier needed?)

No flush is needed, the code just loads the function address from memory 
into CTR, loads R2 and branch to CTR:

	 19c:	e9 21 00 70 	ld      r9,112(r1)
	 1a0:	e9 49 00 00 	ld      r10,0(r9)
	 1a4:	7d 49 03 a6 	mtctr   r10
	 1a8:	e8 49 00 08 	ld      r2,8(r9)
	 1ac:	4e 80 04 21 	bctrl


> 
>> +	func();
>> +}
>> +
>>   void lkdtm_EXEC_DATA(void)
>>   {
>>   	execute_location(data_area, CODE_WRITE);
>> -- 
>> 2.31.1
>>
> 

Re: [PATCH v2 13/13] lkdtm: Add a test for function descriptors protection

[Christophe Leroy]

Le 15/10/2021 à 23:35, Kees Cook a écrit :
> On Thu, Oct 14, 2021 at 07:50:02AM +0200, Christophe Leroy wrote:
>> Add WRITE_OPD to check that you can't modify function
>> descriptors.
>>
>> Gives the following result when function descriptors are
>> not protected:
>>
>> 	lkdtm: Performing direct entry WRITE_OPD
>> 	lkdtm: attempting bad 16 bytes write at c00000000269b358
>> 	lkdtm: FAIL: survived bad write
>> 	lkdtm: do_nothing was hijacked!
>>
>> Looks like a standard compiler barrier(); is not enough to force
>> GCC to use the modified function descriptor. Add to add a fake empty
>> inline assembly to force GCC to reload the function descriptor.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
>> ---
>>   drivers/misc/lkdtm/core.c  |  1 +
>>   drivers/misc/lkdtm/lkdtm.h |  1 +
>>   drivers/misc/lkdtm/perms.c | 22 ++++++++++++++++++++++
>>   3 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
>> index fe6fd34b8caf..de092aa03b5d 100644
>> --- a/drivers/misc/lkdtm/core.c
>> +++ b/drivers/misc/lkdtm/core.c
>> @@ -148,6 +148,7 @@ static const struct crashtype crashtypes[] = {
>>   	CRASHTYPE(WRITE_RO),
>>   	CRASHTYPE(WRITE_RO_AFTER_INIT),
>>   	CRASHTYPE(WRITE_KERN),
>> +	CRASHTYPE(WRITE_OPD),
>>   	CRASHTYPE(REFCOUNT_INC_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_ADD_OVERFLOW),
>>   	CRASHTYPE(REFCOUNT_INC_NOT_ZERO_OVERFLOW),
>> diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
>> index c212a253edde..188bd0fd6575 100644
>> --- a/drivers/misc/lkdtm/lkdtm.h
>> +++ b/drivers/misc/lkdtm/lkdtm.h
>> @@ -105,6 +105,7 @@ void __init lkdtm_perms_init(void);
>>   void lkdtm_WRITE_RO(void);
>>   void lkdtm_WRITE_RO_AFTER_INIT(void);
>>   void lkdtm_WRITE_KERN(void);
>> +void lkdtm_WRITE_OPD(void);
>>   void lkdtm_EXEC_DATA(void);
>>   void lkdtm_EXEC_STACK(void);
>>   void lkdtm_EXEC_KMALLOC(void);
>> diff --git a/drivers/misc/lkdtm/perms.c b/drivers/misc/lkdtm/perms.c
>> index 96b3ebfcb8ed..3870bc82d40d 100644
>> --- a/drivers/misc/lkdtm/perms.c
>> +++ b/drivers/misc/lkdtm/perms.c
>> @@ -44,6 +44,11 @@ static noinline void do_overwritten(void)
>>   	return;
>>   }
>>   
>> +static noinline void do_almost_nothing(void)
>> +{
>> +	pr_info("do_nothing was hijacked!\n");
>> +}
>> +
>>   static void *setup_function_descriptor(func_desc_t *fdesc, void *dst)
>>   {
>>   	memcpy(fdesc, do_nothing, sizeof(*fdesc));
>> @@ -143,6 +148,23 @@ void lkdtm_WRITE_KERN(void)
>>   	do_overwritten();
>>   }
>>   
>> +void lkdtm_WRITE_OPD(void)
>> +{
>> +	size_t size = sizeof(func_desc_t);
>> +	void (*func)(void) = do_nothing;
>> +
>> +	if (!have_function_descriptors()) {
>> +		pr_info("Platform doesn't have function descriptors.\n");
> 
> This should be more explicit ('xfail'):
> 
> 	pr_info("XFAIL: platform doesn't use function descriptors.\n");

Ok


> 
>> +		return;
>> +	}
>> +	pr_info("attempting bad %zu bytes write at %px\n", size, do_nothing);
>> +	memcpy(do_nothing, do_almost_nothing, size);
>> +	pr_err("FAIL: survived bad write\n");
>> +
>> +	asm("" : "=m"(func));
> 
> Since this is a descriptor, I assume no icache flush is needed. Are
> function descriptors strictly dcache? (Is anything besides just a
> barrier needed?)

No flush is needed, the code just loads the function address from memory 
into CTR, loads R2 and branch to CTR:

	 19c:	e9 21 00 70 	ld      r9,112(r1)
	 1a0:	e9 49 00 00 	ld      r10,0(r9)
	 1a4:	7d 49 03 a6 	mtctr   r10
	 1a8:	e8 49 00 08 	ld      r2,8(r9)
	 1ac:	4e 80 04 21 	bctrl


> 
>> +	func();
>> +}
>> +
>>   void lkdtm_EXEC_DATA(void)
>>   {
>>   	execute_location(data_area, CODE_WRITE);
>> -- 
>> 2.31.1
>>
> 

Re: [PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> PPC64/IA64/PARISC have function descriptors. LKDTM doesn't work
> on those three architectures because LKDTM messes up function
> descriptors with functions.

Just to nitpick, it's powerpc 64-bit using the ELFv1 ABI. [1]

The ELFv2 ABI [2] doesn't use function descriptors. (ELFv2 is used
primarily for ppc64le, but some people like musl support it for BE as
well.)

This doesn't affect the correctness or desirability of your changes, it
was just bugging me when I was reading the commit messages :-)

Kind regards,
Daniel

[1] See e.g. https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html
[2] https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf


> This series does some cleanup in the three architectures and
> refactors function descriptors so that it can then easily use it
> in a generic way in LKDTM.
>
> Patch 8 is not absolutely necessary but it is a good trivial cleanup.
>
> Changes in v2:
> - Addressed received comments
> - Moved dereference_[kernel]_function_descriptor() out of line
> - Added patches to remove func_descr_t and func_desc_t in powerpc
> - Using func_desc_t instead of funct_descr_t
> - Renamed HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to HAVE_FUNCTION_DESCRIPTORS
> - Added a new lkdtm test to check protection of function descriptors
>
> Christophe Leroy (13):
>   powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h
>   powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'
>   powerpc: Remove func_descr_t
>   powerpc: Prepare func_desc_t for refactorisation
>   ia64: Rename 'ip' to 'addr' in 'struct fdesc'
>   asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs
>   asm-generic: Define 'func_desc_t' to commonly describe function
>     descriptors
>   asm-generic: Refactor dereference_[kernel]_function_descriptor()
>   lkdtm: Force do_nothing() out of line
>   lkdtm: Really write into kernel text in WRITE_KERN
>   lkdtm: Fix lkdtm_EXEC_RODATA()
>   lkdtm: Fix execute_[user]_location()
>   lkdtm: Add a test for function descriptors protection
>
>  arch/ia64/include/asm/elf.h              |  2 +-
>  arch/ia64/include/asm/sections.h         | 25 ++-------
>  arch/ia64/kernel/module.c                |  6 +--
>  arch/parisc/include/asm/sections.h       | 17 +++---
>  arch/parisc/kernel/process.c             | 21 --------
>  arch/powerpc/include/asm/code-patching.h |  2 +-
>  arch/powerpc/include/asm/elf.h           |  6 +++
>  arch/powerpc/include/asm/sections.h      | 30 ++---------
>  arch/powerpc/include/asm/types.h         |  6 ---
>  arch/powerpc/include/uapi/asm/elf.h      |  8 ---
>  arch/powerpc/kernel/module_64.c          | 38 +++++--------
>  arch/powerpc/kernel/signal_64.c          |  8 +--
>  drivers/misc/lkdtm/core.c                |  1 +
>  drivers/misc/lkdtm/lkdtm.h               |  1 +
>  drivers/misc/lkdtm/perms.c               | 68 ++++++++++++++++++++----
>  include/asm-generic/sections.h           | 13 ++++-
>  include/linux/kallsyms.h                 |  2 +-
>  kernel/extable.c                         | 23 +++++++-
>  18 files changed, 138 insertions(+), 139 deletions(-)
>
> -- 
> 2.31.1

Re: [PATCH v2 00/13] Fix LKDTM for PPC64/IA64/PARISC

[Daniel Axtens]

Christophe Leroy <christophe.leroy@csgroup.eu> writes:

> PPC64/IA64/PARISC have function descriptors. LKDTM doesn't work
> on those three architectures because LKDTM messes up function
> descriptors with functions.

Just to nitpick, it's powerpc 64-bit using the ELFv1 ABI. [1]

The ELFv2 ABI [2] doesn't use function descriptors. (ELFv2 is used
primarily for ppc64le, but some people like musl support it for BE as
well.)

This doesn't affect the correctness or desirability of your changes, it
was just bugging me when I was reading the commit messages :-)

Kind regards,
Daniel

[1] See e.g. https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html
[2] https://openpowerfoundation.org/wp-content/uploads/2016/03/ABI64BitOpenPOWERv1.1_16July2015_pub4.pdf


> This series does some cleanup in the three architectures and
> refactors function descriptors so that it can then easily use it
> in a generic way in LKDTM.
>
> Patch 8 is not absolutely necessary but it is a good trivial cleanup.
>
> Changes in v2:
> - Addressed received comments
> - Moved dereference_[kernel]_function_descriptor() out of line
> - Added patches to remove func_descr_t and func_desc_t in powerpc
> - Using func_desc_t instead of funct_descr_t
> - Renamed HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR to HAVE_FUNCTION_DESCRIPTORS
> - Added a new lkdtm test to check protection of function descriptors
>
> Christophe Leroy (13):
>   powerpc: Move 'struct ppc64_opd_entry' back into asm/elf.h
>   powerpc: Rename 'funcaddr' to 'addr' in 'struct ppc64_opd_entry'
>   powerpc: Remove func_descr_t
>   powerpc: Prepare func_desc_t for refactorisation
>   ia64: Rename 'ip' to 'addr' in 'struct fdesc'
>   asm-generic: Use HAVE_FUNCTION_DESCRIPTORS to define associated stubs
>   asm-generic: Define 'func_desc_t' to commonly describe function
>     descriptors
>   asm-generic: Refactor dereference_[kernel]_function_descriptor()
>   lkdtm: Force do_nothing() out of line
>   lkdtm: Really write into kernel text in WRITE_KERN
>   lkdtm: Fix lkdtm_EXEC_RODATA()
>   lkdtm: Fix execute_[user]_location()
>   lkdtm: Add a test for function descriptors protection
>
>  arch/ia64/include/asm/elf.h              |  2 +-
>  arch/ia64/include/asm/sections.h         | 25 ++-------
>  arch/ia64/kernel/module.c                |  6 +--
>  arch/parisc/include/asm/sections.h       | 17 +++---
>  arch/parisc/kernel/process.c             | 21 --------
>  arch/powerpc/include/asm/code-patching.h |  2 +-
>  arch/powerpc/include/asm/elf.h           |  6 +++
>  arch/powerpc/include/asm/sections.h      | 30 ++---------
>  arch/powerpc/include/asm/types.h         |  6 ---
>  arch/powerpc/include/uapi/asm/elf.h      |  8 ---
>  arch/powerpc/kernel/module_64.c          | 38 +++++--------
>  arch/powerpc/kernel/signal_64.c          |  8 +--
>  drivers/misc/lkdtm/core.c                |  1 +
>  drivers/misc/lkdtm/lkdtm.h               |  1 +
>  drivers/misc/lkdtm/perms.c               | 68 ++++++++++++++++++++----
>  include/asm-generic/sections.h           | 13 ++++-
>  include/linux/kallsyms.h                 |  2 +-
>  kernel/extable.c                         | 23 +++++++-
>  18 files changed, 138 insertions(+), 139 deletions(-)
>
> -- 
> 2.31.1