[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Arnd Bergmann]

When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:

arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'

However, this combination is useless, as XIP_KERNEL implies that all the
RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
needed with XIP_KERNEL, and this patches enforces that using a Kconfig
dependency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
---
 arch/arm/mm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index fbf2296388ce..8894045caba9 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
 
 config DEBUG_RODATA
 	bool "Make kernel text and rodata read-only"
-	depends on MMU
+	depends on MMU && !XIP_KERNEL
 	default y if CPU_V7
 	help
 	  If this is set, kernel text and rodata memory will be made
-- 
2.7.0

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Arnd Bergmann]

When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:

arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'

However, this combination is useless, as XIP_KERNEL implies that all the
RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
needed with XIP_KERNEL, and this patches enforces that using a Kconfig
dependency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
---
 arch/arm/mm/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index fbf2296388ce..8894045caba9 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
 
 config DEBUG_RODATA
 	bool "Make kernel text and rodata read-only"
-	depends on MMU
+	depends on MMU && !XIP_KERNEL
 	default y if CPU_V7
 	help
 	  If this is set, kernel text and rodata memory will be made
-- 
2.7.0

[PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Arnd Bergmann]

The __start_rodata_section_aligned is only referenced by the
DEBUG_RODATA code, which is only used when the MMU is enabled,
but the definition fails on !MMU builds:

arch/arm/kernel/vmlinux.lds:702: undefined symbol `SECTION_SHIFT' referenced in expression

This hides the symbol whenever DEBUG_RODATA is disabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 64ac2e74f0b2 ("ARM: 8502/1: mm: mark section-aligned portion of rodata NX")
---
 arch/arm/kernel/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 2d7085ae1c2f..bb12933aee22 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -322,12 +322,14 @@ SECTIONS
 	STABS_DEBUG
 }
 
+#ifdef CONFIG_DEBUG_RODATA
 /*
  * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
  * be the first section-aligned location after __start_rodata. Otherwise,
  * it will be equal to __start_rodata.
  */
 __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
+#endif
 
 /*
  * These must never be empty
-- 
2.7.0

[PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Arnd Bergmann]

The __start_rodata_section_aligned is only referenced by the
DEBUG_RODATA code, which is only used when the MMU is enabled,
but the definition fails on !MMU builds:

arch/arm/kernel/vmlinux.lds:702: undefined symbol `SECTION_SHIFT' referenced in expression

This hides the symbol whenever DEBUG_RODATA is disabled.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 64ac2e74f0b2 ("ARM: 8502/1: mm: mark section-aligned portion of rodata NX")
---
 arch/arm/kernel/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 2d7085ae1c2f..bb12933aee22 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -322,12 +322,14 @@ SECTIONS
 	STABS_DEBUG
 }
 
+#ifdef CONFIG_DEBUG_RODATA
 /*
  * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
  * be the first section-aligned location after __start_rodata. Otherwise,
  * it will be equal to __start_rodata.
  */
 __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
+#endif
 
 /*
  * These must never be empty
-- 
2.7.0

Re: [PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Ard Biesheuvel]

On 16 February 2016 at 17:03, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig

s/patches/patch/

> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL
>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Ard Biesheuvel]

On 16 February 2016 at 17:03, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig

s/patches/patch/

> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL
>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>

Re: [PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Ard Biesheuvel]

On 16 February 2016 at 17:03, Arnd Bergmann <arnd@arndb.de> wrote:
> The __start_rodata_section_aligned is only referenced by the
> DEBUG_RODATA code, which is only used when the MMU is enabled,
> but the definition fails on !MMU builds:
>
> arch/arm/kernel/vmlinux.lds:702: undefined symbol `SECTION_SHIFT' referenced in expression
>
> This hides the symbol whenever DEBUG_RODATA is disabled.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 64ac2e74f0b2 ("ARM: 8502/1: mm: mark section-aligned portion of rodata NX")
> ---
>  arch/arm/kernel/vmlinux.lds.S | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index 2d7085ae1c2f..bb12933aee22 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -322,12 +322,14 @@ SECTIONS
>         STABS_DEBUG
>  }
>
> +#ifdef CONFIG_DEBUG_RODATA
>  /*
>   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
>   * be the first section-aligned location after __start_rodata. Otherwise,
>   * it will be equal to __start_rodata.
>   */
>  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> +#endif
>

Does

PROVIDE(__start_rodata_section_aligned = xxx);

do the trick as well? If it does, it's a bit cleaner.

[PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Ard Biesheuvel]

On 16 February 2016 at 17:03, Arnd Bergmann <arnd@arndb.de> wrote:
> The __start_rodata_section_aligned is only referenced by the
> DEBUG_RODATA code, which is only used when the MMU is enabled,
> but the definition fails on !MMU builds:
>
> arch/arm/kernel/vmlinux.lds:702: undefined symbol `SECTION_SHIFT' referenced in expression
>
> This hides the symbol whenever DEBUG_RODATA is disabled.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 64ac2e74f0b2 ("ARM: 8502/1: mm: mark section-aligned portion of rodata NX")
> ---
>  arch/arm/kernel/vmlinux.lds.S | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index 2d7085ae1c2f..bb12933aee22 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -322,12 +322,14 @@ SECTIONS
>         STABS_DEBUG
>  }
>
> +#ifdef CONFIG_DEBUG_RODATA
>  /*
>   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
>   * be the first section-aligned location after __start_rodata. Otherwise,
>   * it will be equal to __start_rodata.
>   */
>  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> +#endif
>

Does

PROVIDE(__start_rodata_section_aligned = xxx);

do the trick as well? If it does, it's a bit cleaner.

Re: [PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Arnd Bergmann]

On Tuesday 16 February 2016 17:12:52 Ard Biesheuvel wrote:
> > +#ifdef CONFIG_DEBUG_RODATA
> >  /*
> >   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
> >   * be the first section-aligned location after __start_rodata. Otherwise,
> >   * it will be equal to __start_rodata.
> >   */
> >  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> > +#endif
> >
> 
> Does
> 
> PROVIDE(__start_rodata_section_aligned = xxx);
> 
> do the trick as well? If it does, it's a bit cleaner.
> 

I would assume not, as the problem is that SECTION_SHIFT is a macro that
is not defined when the MMU is disabled.

	Arnd

[PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Arnd Bergmann]

On Tuesday 16 February 2016 17:12:52 Ard Biesheuvel wrote:
> > +#ifdef CONFIG_DEBUG_RODATA
> >  /*
> >   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
> >   * be the first section-aligned location after __start_rodata. Otherwise,
> >   * it will be equal to __start_rodata.
> >   */
> >  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
> > +#endif
> >
> 
> Does
> 
> PROVIDE(__start_rodata_section_aligned = xxx);
> 
> do the trick as well? If it does, it's a bit cleaner.
> 

I would assume not, as the problem is that SECTION_SHIFT is a macro that
is not defined when the MMU is disabled.

	Arnd

Re: [PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Ard Biesheuvel]

On 16 February 2016 at 17:34, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 16 February 2016 17:12:52 Ard Biesheuvel wrote:
>> > +#ifdef CONFIG_DEBUG_RODATA
>> >  /*
>> >   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
>> >   * be the first section-aligned location after __start_rodata. Otherwise,
>> >   * it will be equal to __start_rodata.
>> >   */
>> >  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
>> > +#endif
>> >
>>
>> Does
>>
>> PROVIDE(__start_rodata_section_aligned = xxx);
>>
>> do the trick as well? If it does, it's a bit cleaner.
>>
>
> I would assume not, as the problem is that SECTION_SHIFT is a macro that
> is not defined when the MMU is disabled.
>

I just tested it myself, and it in fact does work.

PROVIDE() means the expression is evaluated lazily, and SECTION_SHIFT
is just an undefined identifier in the linker script scope if the
preprocessor does not define it.

Anyway, I don't have a strong preference, so ack either way.

[PATCH 2/2] ARM: mm: hide __start_rodata_section_aligned for non-debug builds

[Ard Biesheuvel]

On 16 February 2016 at 17:34, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 16 February 2016 17:12:52 Ard Biesheuvel wrote:
>> > +#ifdef CONFIG_DEBUG_RODATA
>> >  /*
>> >   * Without CONFIG_DEBUG_ALIGN_RODATA, __start_rodata_section_aligned will
>> >   * be the first section-aligned location after __start_rodata. Otherwise,
>> >   * it will be equal to __start_rodata.
>> >   */
>> >  __start_rodata_section_aligned = ALIGN(__start_rodata, 1 << SECTION_SHIFT);
>> > +#endif
>> >
>>
>> Does
>>
>> PROVIDE(__start_rodata_section_aligned = xxx);
>>
>> do the trick as well? If it does, it's a bit cleaner.
>>
>
> I would assume not, as the problem is that SECTION_SHIFT is a macro that
> is not defined when the MMU is disabled.
>

I just tested it myself, and it in fact does work.

PROVIDE() means the expression is evaluated lazily, and SECTION_SHIFT
is just an undefined identifier in the linker script scope if the
preprocessor does not define it.

Anyway, I don't have a strong preference, so ack either way.

Re: [PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")

Oh, hm, I didn't see this before sending my fix for the rodata start issue.

> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL

If we do this, we need to probably clean up the xip linker script to
remove all the references to DEBUG_*RODATA too.

-Kees

>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")

Oh, hm, I didn't see this before sending my fix for the rodata start issue.

> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL

If we do this, we need to probably clean up the xip linker script to
remove all the references to DEBUG_*RODATA too.

-Kees

>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

Re: [PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")

For this and the 2/2 patch:

Acked-by: Kees Cook <keescook@chromium.org>

I've sent follow-up to clean up the XIP linker script too, if you want
to take that as the 3rd patch in this series of fixes.

-Kees

> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL
>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>
> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>
> However, this combination is useless, as XIP_KERNEL implies that all the
> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
> dependency.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")

For this and the 2/2 patch:

Acked-by: Kees Cook <keescook@chromium.org>

I've sent follow-up to clean up the XIP linker script too, if you want
to take that as the 3rd patch in this series of fixes.

-Kees

> ---
>  arch/arm/mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
> index fbf2296388ce..8894045caba9 100644
> --- a/arch/arm/mm/Kconfig
> +++ b/arch/arm/mm/Kconfig
> @@ -1039,7 +1039,7 @@ config ARCH_SUPPORTS_BIG_ENDIAN
>
>  config DEBUG_RODATA
>         bool "Make kernel text and rodata read-only"
> -       depends on MMU
> +       depends on MMU && !XIP_KERNEL
>         default y if CPU_V7
>         help
>           If this is set, kernel text and rodata memory will be made
> --
> 2.7.0
>



-- 
Kees Cook
Chrome OS & Brillo Security

Re: [PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 12:31 PM, Kees Cook <keescook@chromium.org> wrote:
> On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>>
>> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>>
>> However, this combination is useless, as XIP_KERNEL implies that all the
>> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
>> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
>> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
>> dependency.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
>
> For this and the 2/2 patch:
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
> I've sent follow-up to clean up the XIP linker script too, if you want
> to take that as the 3rd patch in this series of fixes.

Arnd, when you send your 2 patches to the tracker, can you also send
mine (so the ordering is correct)?

Thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security

[PATCH 1/2] ARM: mm: DEBUG_RODATA makes no sense with XIP_KERNEL

[Kees Cook]

On Tue, Feb 16, 2016 at 12:31 PM, Kees Cook <keescook@chromium.org> wrote:
> On Tue, Feb 16, 2016 at 8:03 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>> When CONFIG_DEBUG_ALIGN_RODATA is set, we get a link error:
>>
>> arch/arm/mm/built-in.o:(.data+0x4bc): undefined reference to `__start_rodata_section_aligned'
>>
>> However, this combination is useless, as XIP_KERNEL implies that all the
>> RODATA is already marked readonly, so both CONFIG_DEBUG_RODATA and
>> CONFIG_DEBUG_ALIGN_RODATA (which depends on the other) are not
>> needed with XIP_KERNEL, and this patches enforces that using a Kconfig
>> dependency.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> Fixes: 25362dc496ed ("ARM: 8501/1: mm: flip priority of CONFIG_DEBUG_RODATA")
>
> For this and the 2/2 patch:
>
> Acked-by: Kees Cook <keescook@chromium.org>
>
> I've sent follow-up to clean up the XIP linker script too, if you want
> to take that as the 3rd patch in this series of fixes.

Arnd, when you send your 2 patches to the tracker, can you also send
mine (so the ordering is correct)?

Thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security