[PATCH 1/2] kprobes: Allow architectures to override optinsn page allocation

[PATCH 1/2] kprobes: Allow architectures to override optinsn page allocation

[Christophe Leroy]

Some architectures like powerpc require a non standard
allocation of optinsn page, because module pages are
too far from the kernel for direct branches.

Define weak alloc_optinsn_page() and free_optinsn_page(), that
fall back on alloc_insn_page() and free_insn_page() when not
overriden by the architecture.

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 kernel/kprobes.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 745f08fdd7a6..8c0a6fdef771 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -321,11 +321,21 @@ int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
 }
 
 #ifdef CONFIG_OPTPROBES
+void __weak *alloc_optinsn_page(void)
+{
+	return alloc_insn_page();
+}
+
+void __weak free_optinsn_page(void *page)
+{
+	free_insn_page(page);
+}
+
 /* For optimized_kprobe buffer */
 struct kprobe_insn_cache kprobe_optinsn_slots = {
 	.mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
-	.alloc = alloc_insn_page,
-	.free = free_insn_page,
+	.alloc = alloc_optinsn_page,
+	.free = free_optinsn_page,
 	.sym = KPROBE_OPTINSN_PAGE_SYM,
 	.pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
 	/* .insn_size is initialized later */
-- 
2.25.0

[PATCH 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

[Christophe Leroy]

Commit 51c9c0843993 ("powerpc/kprobes: Implement Optprobes")
implemented a powerpc specific version of optinsn in order
to workaround the 32Mb limitation for direct branches.

Instead of implementing a dedicated powerpc version, use the
common optinsn and override the allocation and freeing functions.

This also indirectly remove the CLANG warning about
is_kprobe_ppc_optinsn_slot() not being use, and the powerpc will
now benefit from commit 5b485629ba0d ("kprobes, extable: Identify
kprobes trampolines as kernel text area")

Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/kernel/optprobes.c | 23 +++++------------------
 1 file changed, 5 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index cdf87086fa33..a370190cd02a 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -31,11 +31,9 @@
 #define TMPL_END_IDX		\
 	(optprobe_template_end - optprobe_template_entry)
 
-DEFINE_INSN_CACHE_OPS(ppc_optinsn);
-
 static bool insn_page_in_use;
 
-static void *__ppc_alloc_insn_page(void)
+void *alloc_optinsn_page(void)
 {
 	if (insn_page_in_use)
 		return NULL;
@@ -43,20 +41,11 @@ static void *__ppc_alloc_insn_page(void)
 	return &optinsn_slot;
 }
 
-static void __ppc_free_insn_page(void *page __maybe_unused)
+void free_optinsn_page(void *page)
 {
 	insn_page_in_use = false;
 }
 
-struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
-	.mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
-	.pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
-	/* insn_size initialized later */
-	.alloc = __ppc_alloc_insn_page,
-	.free = __ppc_free_insn_page,
-	.nr_garbage = 0,
-};
-
 /*
  * Check if we can optimize this probe. Returns NIP post-emulation if this can
  * be optimized and 0 otherwise.
@@ -136,7 +125,7 @@ NOKPROBE_SYMBOL(optimized_callback);
 void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
 {
 	if (op->optinsn.insn) {
-		free_ppc_optinsn_slot(op->optinsn.insn, 1);
+		free_optinsn_slot(op->optinsn.insn, 1);
 		op->optinsn.insn = NULL;
 	}
 }
@@ -203,14 +192,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	unsigned long nip, size;
 	int rc, i;
 
-	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
-
 	nip = can_optimize(p);
 	if (!nip)
 		return -EILSEQ;
 
 	/* Allocate instruction slot for detour buffer */
-	buff = get_ppc_optinsn_slot();
+	buff = get_optinsn_slot();
 	if (!buff)
 		return -ENOMEM;
 
@@ -297,7 +284,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
 	return 0;
 
 error:
-	free_ppc_optinsn_slot(buff, 0);
+	free_optinsn_slot(buff, 0);
 	return -ERANGE;
 
 }
-- 
2.25.0

Re: [PATCH 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

[kernel test robot]

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Hi Christophe,

I love your patch! Perhaps something to improve:

[auto build test WARNING on powerpc/next]
[also build test WARNING on linus/master v5.13-rc1 next-20210512]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-allyesconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/1cc4bb503e4ee4839247b767883c8b860b26413c
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
        git checkout 1cc4bb503e4ee4839247b767883c8b860b26413c
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/powerpc/kernel/optprobes.c:36:7: warning: no previous prototype for 'alloc_optinsn_page' [-Wmissing-prototypes]
      36 | void *alloc_optinsn_page(void)
         |       ^~~~~~~~~~~~~~~~~~
>> arch/powerpc/kernel/optprobes.c:44:6: warning: no previous prototype for 'free_optinsn_page' [-Wmissing-prototypes]
      44 | void free_optinsn_page(void *page)
         |      ^~~~~~~~~~~~~~~~~


vim +/alloc_optinsn_page +36 arch/powerpc/kernel/optprobes.c

    35	
  > 36	void *alloc_optinsn_page(void)
    37	{
    38		if (insn_page_in_use)
    39			return NULL;
    40		insn_page_in_use = true;
    41		return &optinsn_slot;
    42	}
    43	
  > 44	void free_optinsn_page(void *page)
    45	{
    46		insn_page_in_use = false;
    47	}
    48	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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Re: [PATCH 1/2] kprobes: Allow architectures to override optinsn page allocation

[kernel test robot]

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Hi Christophe,

I love your patch! Perhaps something to improve:

[auto build test WARNING on powerpc/next]
[also build test WARNING on linus/master v5.13-rc1 next-20210512]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: i386-randconfig-r012-20210512 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/0day-ci/linux/commit/2a1f135a9ce3c4d86d3bdefed561aa17760f430f
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
        git checkout 2a1f135a9ce3c4d86d3bdefed561aa17760f430f
        # save the attached .config to linux build tree
        make W=1 W=1 ARCH=i386 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> kernel/kprobes.c:324:14: warning: no previous prototype for 'alloc_optinsn_page' [-Wmissing-prototypes]
     324 | void __weak *alloc_optinsn_page(void)
         |              ^~~~~~~~~~~~~~~~~~
>> kernel/kprobes.c:329:13: warning: no previous prototype for 'free_optinsn_page' [-Wmissing-prototypes]
     329 | void __weak free_optinsn_page(void *page)
         |             ^~~~~~~~~~~~~~~~~


vim +/alloc_optinsn_page +324 kernel/kprobes.c

   322	
   323	#ifdef CONFIG_OPTPROBES
 > 324	void __weak *alloc_optinsn_page(void)
   325	{
   326		return alloc_insn_page();
   327	}
   328	
 > 329	void __weak free_optinsn_page(void *page)
   330	{
   331		free_insn_page(page);
   332	}
   333	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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Re: [PATCH 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

[kernel test robot]

[-- Attachment #1: Type: text/plain, Size: 2419 bytes --]

Hi Christophe,

I love your patch! Yet something to improve:

[auto build test ERROR on powerpc/next]
[also build test ERROR on linus/master v5.13-rc1 next-20210512]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-ppc64_defconfig (attached as .config)
compiler: powerpc64-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/0day-ci/linux/commit/1cc4bb503e4ee4839247b767883c8b860b26413c
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
        git checkout 1cc4bb503e4ee4839247b767883c8b860b26413c
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross W=1 ARCH=powerpc 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

>> arch/powerpc/kernel/optprobes.c:36:7: error: no previous prototype for 'alloc_optinsn_page' [-Werror=missing-prototypes]
      36 | void *alloc_optinsn_page(void)
         |       ^~~~~~~~~~~~~~~~~~
>> arch/powerpc/kernel/optprobes.c:44:6: error: no previous prototype for 'free_optinsn_page' [-Werror=missing-prototypes]
      44 | void free_optinsn_page(void *page)
         |      ^~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors


vim +/alloc_optinsn_page +36 arch/powerpc/kernel/optprobes.c

    35	
  > 36	void *alloc_optinsn_page(void)
    37	{
    38		if (insn_page_in_use)
    39			return NULL;
    40		insn_page_in_use = true;
    41		return &optinsn_slot;
    42	}
    43	
  > 44	void free_optinsn_page(void *page)
    45	{
    46		insn_page_in_use = false;
    47	}
    48	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 26845 bytes --]

Re: [PATCH 1/2] kprobes: Allow architectures to override optinsn page allocation

[Masami Hiramatsu]

On Wed, 12 May 2021 14:29:26 +0000 (UTC)
Christophe Leroy <christophe.leroy@csgroup.eu> wrote:

> Some architectures like powerpc require a non standard
> allocation of optinsn page, because module pages are
> too far from the kernel for direct branches.
> 
> Define weak alloc_optinsn_page() and free_optinsn_page(), that
> fall back on alloc_insn_page() and free_insn_page() when not
> overriden by the architecture.
> 

Looks good to me :)

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  kernel/kprobes.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 745f08fdd7a6..8c0a6fdef771 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -321,11 +321,21 @@ int kprobe_cache_get_kallsym(struct kprobe_insn_cache *c, unsigned int *symnum,
>  }
>  
>  #ifdef CONFIG_OPTPROBES
> +void __weak *alloc_optinsn_page(void)
> +{
> +	return alloc_insn_page();
> +}
> +
> +void __weak free_optinsn_page(void *page)
> +{
> +	free_insn_page(page);
> +}
> +
>  /* For optimized_kprobe buffer */
>  struct kprobe_insn_cache kprobe_optinsn_slots = {
>  	.mutex = __MUTEX_INITIALIZER(kprobe_optinsn_slots.mutex),
> -	.alloc = alloc_insn_page,
> -	.free = free_insn_page,
> +	.alloc = alloc_optinsn_page,
> +	.free = free_optinsn_page,
>  	.sym = KPROBE_OPTINSN_PAGE_SYM,
>  	.pages = LIST_HEAD_INIT(kprobe_optinsn_slots.pages),
>  	/* .insn_size is initialized later */
> -- 
> 2.25.0
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH 2/2] powerpc/kprobes: Replace ppc_optinsn by common optinsn

[Masami Hiramatsu]

On Wed, 12 May 2021 14:29:27 +0000 (UTC)
Christophe Leroy <christophe.leroy@csgroup.eu> wrote:

> Commit 51c9c0843993 ("powerpc/kprobes: Implement Optprobes")
> implemented a powerpc specific version of optinsn in order
> to workaround the 32Mb limitation for direct branches.
> 
> Instead of implementing a dedicated powerpc version, use the
> common optinsn and override the allocation and freeing functions.
> 
> This also indirectly remove the CLANG warning about
> is_kprobe_ppc_optinsn_slot() not being use, and the powerpc will
> now benefit from commit 5b485629ba0d ("kprobes, extable: Identify
> kprobes trampolines as kernel text area")
> 

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

> Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>  arch/powerpc/kernel/optprobes.c | 23 +++++------------------
>  1 file changed, 5 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
> index cdf87086fa33..a370190cd02a 100644
> --- a/arch/powerpc/kernel/optprobes.c
> +++ b/arch/powerpc/kernel/optprobes.c
> @@ -31,11 +31,9 @@
>  #define TMPL_END_IDX		\
>  	(optprobe_template_end - optprobe_template_entry)
>  
> -DEFINE_INSN_CACHE_OPS(ppc_optinsn);
> -
>  static bool insn_page_in_use;
>  
> -static void *__ppc_alloc_insn_page(void)
> +void *alloc_optinsn_page(void)
>  {
>  	if (insn_page_in_use)
>  		return NULL;
> @@ -43,20 +41,11 @@ static void *__ppc_alloc_insn_page(void)
>  	return &optinsn_slot;
>  }
>  
> -static void __ppc_free_insn_page(void *page __maybe_unused)
> +void free_optinsn_page(void *page)
>  {
>  	insn_page_in_use = false;
>  }
>  
> -struct kprobe_insn_cache kprobe_ppc_optinsn_slots = {
> -	.mutex = __MUTEX_INITIALIZER(kprobe_ppc_optinsn_slots.mutex),
> -	.pages = LIST_HEAD_INIT(kprobe_ppc_optinsn_slots.pages),
> -	/* insn_size initialized later */
> -	.alloc = __ppc_alloc_insn_page,
> -	.free = __ppc_free_insn_page,
> -	.nr_garbage = 0,
> -};
> -
>  /*
>   * Check if we can optimize this probe. Returns NIP post-emulation if this can
>   * be optimized and 0 otherwise.
> @@ -136,7 +125,7 @@ NOKPROBE_SYMBOL(optimized_callback);
>  void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
>  {
>  	if (op->optinsn.insn) {
> -		free_ppc_optinsn_slot(op->optinsn.insn, 1);
> +		free_optinsn_slot(op->optinsn.insn, 1);
>  		op->optinsn.insn = NULL;
>  	}
>  }
> @@ -203,14 +192,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	unsigned long nip, size;
>  	int rc, i;
>  
> -	kprobe_ppc_optinsn_slots.insn_size = MAX_OPTINSN_SIZE;
> -
>  	nip = can_optimize(p);
>  	if (!nip)
>  		return -EILSEQ;
>  
>  	/* Allocate instruction slot for detour buffer */
> -	buff = get_ppc_optinsn_slot();
> +	buff = get_optinsn_slot();
>  	if (!buff)
>  		return -ENOMEM;
>  
> @@ -297,7 +284,7 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
>  	return 0;
>  
>  error:
> -	free_ppc_optinsn_slot(buff, 0);
> +	free_optinsn_slot(buff, 0);
>  	return -ERANGE;
>  
>  }
> -- 
> 2.25.0
> 


-- 
Masami Hiramatsu <mhiramat@kernel.org>

Re: [PATCH 1/2] kprobes: Allow architectures to override optinsn page allocation

[Masami Hiramatsu]

On Thu, 13 May 2021 03:04:51 +0800
kernel test robot <lkp@intel.com> wrote:

> Hi Christophe,
> 
> I love your patch! Perhaps something to improve:
> 
> [auto build test WARNING on powerpc/next]
> [also build test WARNING on linus/master v5.13-rc1 next-20210512]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch]
> 
> url:    https://github.com/0day-ci/linux/commits/Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
> config: i386-randconfig-r012-20210512 (attached as .config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build):
>         # https://github.com/0day-ci/linux/commit/2a1f135a9ce3c4d86d3bdefed561aa17760f430f
>         git remote add linux-review https://github.com/0day-ci/linux
>         git fetch --no-tags linux-review Christophe-Leroy/kprobes-Allow-architectures-to-override-optinsn-page-allocation/20210512-223121
>         git checkout 2a1f135a9ce3c4d86d3bdefed561aa17760f430f
>         # save the attached .config to linux build tree
>         make W=1 W=1 ARCH=i386 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@intel.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> kernel/kprobes.c:324:14: warning: no previous prototype for 'alloc_optinsn_page' [-Wmissing-prototypes]
>      324 | void __weak *alloc_optinsn_page(void)
>          |              ^~~~~~~~~~~~~~~~~~
> >> kernel/kprobes.c:329:13: warning: no previous prototype for 'free_optinsn_page' [-Wmissing-prototypes]
>      329 | void __weak free_optinsn_page(void *page)
>          |             ^~~~~~~~~~~~~~~~~

Ah, we need a prototype for those in include/linux/kprobes.h
as same as alloc_insn_page() and free_insn_page().

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>