[PATCH 1/2] string: move __compiletime_strlen() to string.h

[PATCH 1/2] string: move __compiletime_strlen() to string.h

[Xie Yuanbin]

Move __compiletime_strlen() to string.h, so that others can use.

Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
---
 include/linux/fortify-string.h | 15 ---------------
 include/linux/string.h         | 15 +++++++++++++++
 lib/tests/fortify_kunit.c      |  3 ++-
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 171982e53c9a..c181dac26353 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -58,21 +58,6 @@ void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("
 void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
 void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?");
 
-#define __compiletime_strlen(p)					\
-({								\
-	char *__p = (char *)(p);				\
-	size_t __ret = SIZE_MAX;				\
-	const size_t __p_size = __member_size(p);		\
-	if (__p_size != SIZE_MAX &&				\
-	    __builtin_constant_p(*__p)) {			\
-		size_t __p_len = __p_size - 1;			\
-		if (__builtin_constant_p(__p[__p_len]) &&	\
-		    __p[__p_len] == '\0')			\
-			__ret = __builtin_strlen(__p);		\
-	}							\
-	__ret;							\
-})
-
 #if defined(__SANITIZE_ADDRESS__)
 
 #if !defined(CONFIG_CC_HAS_KASAN_MEMINTRINSIC_PREFIX) && !defined(CONFIG_GENERIC_ENTRY)
diff --git a/include/linux/string.h b/include/linux/string.h
index 1b564c36d721..fbae7d99bb6f 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -19,6 +19,21 @@ extern void *memdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *vmemdup_user(const void __user *, size_t) __realloc_size(2);
 extern void *memdup_user_nul(const void __user *, size_t);
 
+#define __compiletime_strlen(p)					\
+({								\
+	char *__p = (char *)(p);				\
+	size_t __ret = SIZE_MAX;				\
+	const size_t __p_size = __member_size(p);		\
+	if (__p_size != SIZE_MAX &&				\
+	    __builtin_constant_p(*__p)) {			\
+		size_t __p_len = __p_size - 1;			\
+		if (__builtin_constant_p(__p[__p_len]) &&	\
+		    __p[__p_len] == '\0')			\
+			__ret = __builtin_strlen(__p);		\
+	}							\
+	__ret;							\
+})
+
 /**
  * memdup_array_user - duplicate array from user space
  * @src: source address in user space
diff --git a/lib/tests/fortify_kunit.c b/lib/tests/fortify_kunit.c
index fc9c76f026d6..86181e3bd994 100644
--- a/lib/tests/fortify_kunit.c
+++ b/lib/tests/fortify_kunit.c
@@ -49,7 +49,8 @@ void fortify_add_kunit_error(int write);
 #include <linux/vmalloc.h>
 
 /* Handle being built without CONFIG_FORTIFY_SOURCE */
-#ifndef __compiletime_strlen
+#if defined(__NO_FORTIFY) || !defined(__OPTIMIZE__) || !defined(CONFIG_FORTIFY_SOURCE)
+# undef __compiletime_strlen
 # define __compiletime_strlen __builtin_strlen
 #endif
 
-- 
2.51.0

[PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Xie Yuanbin]

For strnlen(), if the compiler detects that the maxlen argument exceeds
the valid memory size of the input string object, a compilation error may
occur.

For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
__always_inline, using default ppc64_defconfig, and setting
CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n,
CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Then, when using gcc-15 for compilation,
the following error will be triggered:
```log
  CC      arch/powerpc/kernel/optprobes.o
In file included from ./arch/powerpc/include/asm/kprobes.h:24,
                 from ./include/linux/kprobes.h:31,
                 from arch/powerpc/kernel/optprobes.c:8:
In function ‘ppc_kallsyms_lookup_name’,
    inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
  232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function ‘ppc_kallsyms_lookup_name’,
    inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
  232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
```

Refer to the implementation of fortify's strnlen(). If the string length
is a compile-time constant, do not call the strnlen() function.

Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
---
 arch/powerpc/include/asm/text-patching.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h
index e7f14720f630..ce1b2131980a 100644
--- a/arch/powerpc/include/asm/text-patching.h
+++ b/arch/powerpc/include/asm/text-patching.h
@@ -228,8 +228,13 @@ static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
 	/* check for dot variant */
 	char dot_name[1 + KSYM_NAME_LEN];
 	bool dot_appended = false;
+	size_t n_len = __compiletime_strlen(name);
+	const size_t n_size = __member_size(name);
 
-	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
+	if (n_len == SIZE_MAX || KSYM_NAME_LEN < n_size)
+		n_len = strnlen(name, KSYM_NAME_LEN);
+	
+	if (n_len >= KSYM_NAME_LEN)
 		return 0;
 
 	if (name[0] != '.') {
-- 
2.51.0

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Andy Shevchenko]

On Thu, Feb 05, 2026 at 06:05:17PM +0800, Xie Yuanbin wrote:

First of all, when sending a series, always add a cover letter to explain
dependencies, goal, and how to route the series via the respective tree(s),
et cetera.

> For strnlen(), if the compiler detects that the maxlen argument exceeds
> the valid memory size of the input string object, a compilation error may
> occur.
> 
> For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
> __always_inline,

So, there is no issue in upstream without the mentioned change, right?

> using default ppc64_defconfig, and setting
> CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n,
> CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Then, when using gcc-15 for compilation,
> the following error will be triggered:
> ```log
>   CC      arch/powerpc/kernel/optprobes.o
> In file included from ./arch/powerpc/include/asm/kprobes.h:24,
>                  from ./include/linux/kprobes.h:31,
>                  from arch/powerpc/kernel/optprobes.c:8:
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> ```
> 
> Refer to the implementation of fortify's strnlen(). If the string length
> is a compile-time constant, do not call the strnlen() function.

I don't with the first patch this is a correct approach.
But I let others to comment, I assume Kees knows better
what's this and how it can be fixed without exporting
special macros.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Xie Yuanbin]

On Thu, 5 Feb 2026 18:40:08 +0200, Andy Shevchenko wrote:
>> For strnlen(), if the compiler detects that the maxlen argument exceeds
>> the valid memory size of the input string object, a compilation error may
>> occur.
>> 
>> For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
>> __always_inline,
>
> So, there is no issue in upstream without the mentioned change, right?

Yes. However, before the commit 889b3c1245de48ed0cac ("compiler: remove
CONFIG_OPTIMIZE_INLINING entirely") is merged, inline will be changed to
__always_inline, and this error will be directly triggered.

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Kees Cook]

On Thu, Feb 05, 2026 at 06:05:17PM +0800, Xie Yuanbin wrote:
> For strnlen(), if the compiler detects that the maxlen argument exceeds
> the valid memory size of the input string object, a compilation error may
> occur.
> 
> For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
> __always_inline, using default ppc64_defconfig, and setting
> CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n,
> CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Then, when using gcc-15 for compilation,
> the following error will be triggered:
> ```log
>   CC      arch/powerpc/kernel/optprobes.o
> In file included from ./arch/powerpc/include/asm/kprobes.h:24,
>                  from ./include/linux/kprobes.h:31,
>                  from arch/powerpc/kernel/optprobes.c:8:
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function ‘ppc_kallsyms_lookup_name’,
>     inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
>   232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>       |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> ```
> 
> Refer to the implementation of fortify's strnlen(). If the string length
> is a compile-time constant, do not call the strnlen() function.
> 
> Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
> ---
>  arch/powerpc/include/asm/text-patching.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h
> index e7f14720f630..ce1b2131980a 100644
> --- a/arch/powerpc/include/asm/text-patching.h
> +++ b/arch/powerpc/include/asm/text-patching.h
> @@ -228,8 +228,13 @@ static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
>  	/* check for dot variant */
>  	char dot_name[1 + KSYM_NAME_LEN];
>  	bool dot_appended = false;
> +	size_t n_len = __compiletime_strlen(name);
> +	const size_t n_size = __member_size(name);
>  
> -	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
> +	if (n_len == SIZE_MAX || KSYM_NAME_LEN < n_size)
> +		n_len = strnlen(name, KSYM_NAME_LEN);
> +	
> +	if (n_len >= KSYM_NAME_LEN)
>  		return 0;

Isn't it possible to do this and not need __compiletime_strlen at all?

	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));

?

>  
>  	if (name[0] != '.') {
> -- 
> 2.51.0
> 

-- 
Kees Cook

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Christophe Leroy (CS GROUP)]

Le 06/02/2026 à 19:26, Kees Cook a écrit :
> On Thu, Feb 05, 2026 at 06:05:17PM +0800, Xie Yuanbin wrote:
>> For strnlen(), if the compiler detects that the maxlen argument exceeds
>> the valid memory size of the input string object, a compilation error may
>> occur.
>>
>> For lastest linux-next source, changing ppc_kallsyms_lookup_name() to
>> __always_inline, using default ppc64_defconfig, and setting
>> CONFIG_EXPERT=y, CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n,
>> CONFIG_CC_OPTIMIZE_FOR_SIZE=y. Then, when using gcc-15 for compilation,
>> the following error will be triggered:
>> ```log
>>    CC      arch/powerpc/kernel/optprobes.o
>> In file included from ./arch/powerpc/include/asm/kprobes.h:24,
>>                   from ./include/linux/kprobes.h:31,
>>                   from arch/powerpc/kernel/optprobes.c:8:
>> In function ‘ppc_kallsyms_lookup_name’,
>>      inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
>> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
>>    232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> In function ‘ppc_kallsyms_lookup_name’,
>>      inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
>> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
>>    232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> cc1: all warnings being treated as errors
>> ```
>>
>> Refer to the implementation of fortify's strnlen(). If the string length
>> is a compile-time constant, do not call the strnlen() function.
>>
>> Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
>> ---
>>   arch/powerpc/include/asm/text-patching.h | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h
>> index e7f14720f630..ce1b2131980a 100644
>> --- a/arch/powerpc/include/asm/text-patching.h
>> +++ b/arch/powerpc/include/asm/text-patching.h
>> @@ -228,8 +228,13 @@ static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
>>   	/* check for dot variant */
>>   	char dot_name[1 + KSYM_NAME_LEN];
>>   	bool dot_appended = false;
>> +	size_t n_len = __compiletime_strlen(name);
>> +	const size_t n_size = __member_size(name);
>>   
>> -	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>> +	if (n_len == SIZE_MAX || KSYM_NAME_LEN < n_size)
>> +		n_len = strnlen(name, KSYM_NAME_LEN);
>> +	
>> +	if (n_len >= KSYM_NAME_LEN)
>>   		return 0;
> 
> Isn't it possible to do this and not need __compiletime_strlen at all?
> 
> 	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));

ppc_kallsyms_lookup_name() only has two callers and they call it with a 
built-in string. I think we can do something a lot simpler, something 
like (untested):

static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
{
	unsigned long addr = kallsyms_lookup_name(name);

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
		addr = ppc_function_entry((void *)addr);

	return addr;
}

#ifdef CONFIG_PPC64_ELF_ABI_V1
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
#else
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
#endif

Christophe

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Xie Yuanbin]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="y", Size: 1564 bytes --]

On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
> Le 06/02/2026 à 19:26, Kees Cook a écrit :
>>
>> Isn't it possible to do this and not need __compiletime_strlen at all?
>>
>> 	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));
>
> ppc_kallsyms_lookup_name() only has two callers and they call it with a
> built-in string. I think we can do something a lot simpler, something
> like (untested):
>
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
>
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
>
> 	return addr;
> }
>
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
> #else
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
> #endif
>
> Christophe

When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
the original non-dot symbol is missing.

What about this (Only the compilation test is performed):
```c
static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
{
	unsigned long addr = kallsyms_lookup_name(name);

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
		addr = ppc_function_entry((void *)addr);

	return addr;
}

#define ppc_kallsyms_lookup_name(x) ({					\
		unsigned long addr = 0;					\
		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
			addr = __ppc_kallsyms_lookup_name("." x);	\
		if (!addr)						\
			addr = __ppc_kallsyms_lookup_name(x);		\
		addr;							\
	})
```

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Christophe Leroy (CS GROUP)]

Le 09/02/2026 à 14:25, Xie Yuanbin a écrit :
> On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
>> Le 06/02/2026 à 19:26, Kees Cook a écrit :
>>>
>>> Isn't it possible to do this and not need __compiletime_strlen at all?
>>>
>>> 	n_len = strnlen(name, min(__member_size(name), KSYM_NAME_LEN));
>>
>> ppc_kallsyms_lookup_name() only has two callers and they call it with a
>> built-in string. I think we can do something a lot simpler, something
>> like (untested):
>>
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
>> #else
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
>> #endif
>>
>> Christophe
> 
> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
> the original non-dot symbol is missing.
> 
> What about this (Only the compilation test is performed):
> ```c
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
> 
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
> 
> 	return addr;
> }
> 
> #define ppc_kallsyms_lookup_name(x) ({					\
> 		unsigned long addr = 0;					\
> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
> 			addr = __ppc_kallsyms_lookup_name("." x);	\
> 		if (!addr)						\
> 			addr = __ppc_kallsyms_lookup_name(x);		\
> 		addr;							\
> 	})
> ```

Good point.

To avoid duplicating the string I'd suggest:

static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
{
	unsigned long addr = kallsyms_lookup_name(name);

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
		addr = kallsyms_lookup_name(name + 1);
	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
		addr = ppc_function_entry((void *)addr);

	return addr;
}

#ifdef CONFIG_PPC64_ELF_ABI_V1
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
#else
#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
#endif

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Xie Yuanbin]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="y", Size: 2382 bytes --]

On Mon, 9 Feb 2026 14:41:51 +0100, Christophe Leroy (CS GROUP) wrote:
> Le 09/02/2026 à 14:25, Xie Yuanbin a écrit :
>> On Fri, 6 Feb 2026 20:53:55 +0100, Christophe Leroy (CS GROUP) wrote:
>>> ppc_kallsyms_lookup_name() only has two callers and they call it with a
>>> built-in string. I think we can do something a lot simpler, something
>>> like (untested):
>>>
>>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>>> {
>>> 	unsigned long addr = kallsyms_lookup_name(name);
>>>
>>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>>> 		addr = ppc_function_entry((void *)addr);
>>>
>>> 	return addr;
>>> }
>>>
>>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." ## x);
>>> #else
>>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
>>> #endif
>>>
>>> Christophe
>>
>> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
>> the original non-dot symbol is missing.
>>
>> What about this (Only the compilation test is performed):
>> ```c
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #define ppc_kallsyms_lookup_name(x) ({					\
>> 		unsigned long addr = 0;					\
>> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
>> 			addr = __ppc_kallsyms_lookup_name("." x);	\
>> 		if (!addr)						\
>> 			addr = __ppc_kallsyms_lookup_name(x);		\
>> 		addr;							\
>> 	})
>> ```
>
> Good point.
>
> To avoid duplicating the string I'd suggest:
>
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
>
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
> 		addr = kallsyms_lookup_name(name + 1);
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
>
> 	return addr;
> }
>
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
> #else
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
> #endif

This seems good, but there seems to be an extra ';' after
'__ppc_kallsyms_lookup_name("." x)' ?

After removing the extra ';', I performed a compilation test,
no warnings.

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Xie Yuanbin]

Hi, Christophe Leroy!

On Mon, 9 Feb 2026 14:41:51 +0100, Christophe Leroy (CS GROUP) wrote:
> On 09/02/2026 14:25, Xie Yuanbin wrote:
>> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
>> the original non-dot symbol is missing.
>>
>> What about this (Only the compilation test is performed):
>> ```c
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #define ppc_kallsyms_lookup_name(x) ({					\
>> 		unsigned long addr = 0;					\
>> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
>> 			addr = __ppc_kallsyms_lookup_name("." x);	\
>> 		if (!addr)						\
>> 			addr = __ppc_kallsyms_lookup_name(x);		\
>> 		addr;							\
>> 	})
>> ```
>
> Good point.
>
> To avoid duplicating the string I'd suggest:
>
> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> {
> 	unsigned long addr = kallsyms_lookup_name(name);
>
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
> 		addr = kallsyms_lookup_name(name + 1);
> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> 		addr = ppc_function_entry((void *)addr);
>
> 	return addr;
> }
>
> #ifdef CONFIG_PPC64_ELF_ABI_V1
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
> #else
> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
> #endif

I would like to submit the modification as a new patch, and include you
as Co-developer. Do you agree?

Full of the patch:
```patch
From fbf07e5c1a97da7c8572435537f2b92213ede39d Mon Sep 17 00:00:00 2001
From: Xie Yuanbin <xieyuanbin1@huawei.com>
Date: Thu, 30 Apr 2026 14:15:26 +0800
Subject: [PATCH V2] powerpc/text-patching: simplify the implementation of ppc_kallsyms_lookup_name()

ppc_kallsyms_lookup_name() is called only twice in the kernel code, and
the parameters are all constant strings. strnlen(name, KSYM_NAME_LEN) is
called inside ppc_kallsyms_lookup_name(), when the compiler detects that
KSYM_NAME_LEN is larger then the constant strings,
the following error will be triggered:
```log
  CC      arch/powerpc/kernel/optprobes.o
In file included from ./arch/powerpc/include/asm/kprobes.h:24,
                 from ./include/linux/kprobes.h:31,
                 from arch/powerpc/kernel/optprobes.c:8:
In function ‘ppc_kallsyms_lookup_name’,
    inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
  232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function ‘ppc_kallsyms_lookup_name’,
    inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
  232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
```

The error can be reproduced in the following ways:
Use lastest linux-next source, change ppc_kallsyms_lookup_name() to
__always_inline, use default ppc64_defconfig, set CONFIG_EXPERT=y,
CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n, CONFIG_CC_OPTIMIZE_FOR_SIZE=y,
and use gcc-14 or a later version for compilation.

Since ppc_kallsyms_lookup_name() is called only twice in the kernel,
and the parameters are all constant strins, simplify the implementation
of ppc_kallsyms_lookup_name() and avoid calling strnlen().

Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Kees Cook <kees@kernel.org>
Co-developed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
---
v1->v2: https://lore.kernel.org/20260205100517.292858-2-xieyuanbin1@huawei.com
  - Not use strlen()

 arch/powerpc/include/asm/text-patching.h | 42 ++++++++----------------
 1 file changed, 17 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h
index e7f14720f630..2d3f698cb4f1 100644
--- a/arch/powerpc/include/asm/text-patching.h
+++ b/arch/powerpc/include/asm/text-patching.h
@@ -221,39 +221,23 @@ static inline unsigned long ppc_global_function_entry(void *func)
  * - For ABIv1, we lookup the dot variant.
  * - For ABIv2, we return the local entry point.
  */
-static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
-{
-	unsigned long addr;
-#ifdef CONFIG_PPC64_ELF_ABI_V1
-	/* check for dot variant */
-	char dot_name[1 + KSYM_NAME_LEN];
-	bool dot_appended = false;
-
-	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
-		return 0;
-
-	if (name[0] != '.') {
-		dot_name[0] = '.';
-		dot_name[1] = '\0';
-		strlcat(dot_name, name, sizeof(dot_name));
-		dot_appended = true;
-	} else {
-		dot_name[0] = '\0';
-		strlcat(dot_name, name, sizeof(dot_name));
-	}
-	addr = kallsyms_lookup_name(dot_name);
-	if (!addr && dot_appended)
-		/* Let's try the original non-dot symbol lookup	*/
-		addr = kallsyms_lookup_name(name);
-#elif defined(CONFIG_PPC64_ELF_ABI_V2)
-	addr = kallsyms_lookup_name(name);
-	if (addr)
-		addr = ppc_function_entry((void *)addr);
-#else
-	addr = kallsyms_lookup_name(name);
-#endif
-	return addr;
-}
+static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
+{
+	unsigned long addr = kallsyms_lookup_name(name);
+
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
+		addr = kallsyms_lookup_name(name + 1);
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
+		addr = ppc_function_entry((void *)addr);
+
+	return addr;
+}
+
+#ifdef CONFIG_PPC64_ELF_ABI_V1
+#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x)
+#else
+#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
+#endif
 
 /*
  * Some instruction encodings commonly used in dynamic ftracing
-- 
2.53.0
```

Re: [PATCH 2/2] powerpc/text-patching: Fix possible stringop-overread compilation error

[Christophe Leroy (CS GROUP)]

Le 30/04/2026 à 09:28, Xie Yuanbin a écrit :
> Hi, Christophe Leroy!
> 
> On Mon, 9 Feb 2026 14:41:51 +0100, Christophe Leroy (CS GROUP) wrote:
>> On 09/02/2026 14:25, Xie Yuanbin wrote:
>>> When CONFIG_PPC64_ELF_ABI_V1=y, it seems that the try of lookupinp
>>> the original non-dot symbol is missing.
>>>
>>> What about this (Only the compilation test is performed):
>>> ```c
>>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>>> {
>>> 	unsigned long addr = kallsyms_lookup_name(name);
>>>
>>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>>> 		addr = ppc_function_entry((void *)addr);
>>>
>>> 	return addr;
>>> }
>>>
>>> #define ppc_kallsyms_lookup_name(x) ({					\
>>> 		unsigned long addr = 0;					\
>>> 		if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1))		\
>>> 			addr = __ppc_kallsyms_lookup_name("." x);	\
>>> 		if (!addr)						\
>>> 			addr = __ppc_kallsyms_lookup_name(x);		\
>>> 		addr;							\
>>> 	})
>>> ```
>>
>> Good point.
>>
>> To avoid duplicating the string I'd suggest:
>>
>> static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
>> {
>> 	unsigned long addr = kallsyms_lookup_name(name);
>>
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
>> 		addr = kallsyms_lookup_name(name + 1);
>> 	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
>> 		addr = ppc_function_entry((void *)addr);
>>
>> 	return addr;
>> }
>>
>> #ifdef CONFIG_PPC64_ELF_ABI_V1
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x);
>> #else
>> #define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
>> #endif
> 
> I would like to submit the modification as a new patch, and include you
> as Co-developer. Do you agree?

Add me as Suggested-by: instead.

Thanks
Christophe

> 
> Full of the patch:
> ```patch
>  From fbf07e5c1a97da7c8572435537f2b92213ede39d Mon Sep 17 00:00:00 2001
> From: Xie Yuanbin <xieyuanbin1@huawei.com>
> Date: Thu, 30 Apr 2026 14:15:26 +0800
> Subject: [PATCH V2] powerpc/text-patching: simplify the implementation of ppc_kallsyms_lookup_name()
> 
> ppc_kallsyms_lookup_name() is called only twice in the kernel code, and
> the parameters are all constant strings. strnlen(name, KSYM_NAME_LEN) is
> called inside ppc_kallsyms_lookup_name(), when the compiler detects that
> KSYM_NAME_LEN is larger then the constant strings,
> the following error will be triggered:
> ```log
>    CC      arch/powerpc/kernel/optprobes.o
> In file included from ./arch/powerpc/include/asm/kprobes.h:24,
>                   from ./include/linux/kprobes.h:31,
>                   from arch/powerpc/kernel/optprobes.c:8:
> In function ‘ppc_kallsyms_lookup_name’,
>      inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:209:21:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 19 [-Werror=stringop-overread]
>    232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In function ‘ppc_kallsyms_lookup_name’,
>      inlined from ‘arch_prepare_optimized_kprobe’ at arch/powerpc/kernel/optprobes.c:210:22:
> ./arch/powerpc/include/asm/text-patching.h:232:13: error: ‘strnlen’ specified bound 512 exceeds source size 13 [-Werror=stringop-overread]
>    232 |         if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
>        |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> ```
> 
> The error can be reproduced in the following ways:
> Use lastest linux-next source, change ppc_kallsyms_lookup_name() to
> __always_inline, use default ppc64_defconfig, set CONFIG_EXPERT=y,
> CONFIG_PPC64_BIG_ENDIAN_ELF_ABI_V2=n, CONFIG_CC_OPTIMIZE_FOR_SIZE=y,
> and use gcc-14 or a later version for compilation.
> 
> Since ppc_kallsyms_lookup_name() is called only twice in the kernel,
> and the parameters are all constant strins, simplify the implementation
> of ppc_kallsyms_lookup_name() and avoid calling strnlen().
> 
> Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
> Cc: Kees Cook <kees@kernel.org>
> Co-developed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
> Signed-off-by: Xie Yuanbin <xieyuanbin1@huawei.com>
> ---
> v1->v2: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2F20260205100517.292858-2-xieyuanbin1%40huawei.com&data=05%7C02%7Cchristophe.leroy%40csgroup.eu%7C525ecaba66ea4e3b15f208dea68a3fa1%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639131309913493421%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=aaK9PO2mGdxM3vuJBVP0lcl6VKfqs3VKih5VPcG0IxI%3D&reserved=0
>    - Not use strlen()
> 
>   arch/powerpc/include/asm/text-patching.h | 42 ++++++++----------------
>   1 file changed, 17 insertions(+), 33 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/text-patching.h b/arch/powerpc/include/asm/text-patching.h
> index e7f14720f630..2d3f698cb4f1 100644
> --- a/arch/powerpc/include/asm/text-patching.h
> +++ b/arch/powerpc/include/asm/text-patching.h
> @@ -221,39 +221,23 @@ static inline unsigned long ppc_global_function_entry(void *func)
>    * - For ABIv1, we lookup the dot variant.
>    * - For ABIv2, we return the local entry point.
>    */
> -static inline unsigned long ppc_kallsyms_lookup_name(const char *name)
> -{
> -	unsigned long addr;
> -#ifdef CONFIG_PPC64_ELF_ABI_V1
> -	/* check for dot variant */
> -	char dot_name[1 + KSYM_NAME_LEN];
> -	bool dot_appended = false;
> -
> -	if (strnlen(name, KSYM_NAME_LEN) >= KSYM_NAME_LEN)
> -		return 0;
> -
> -	if (name[0] != '.') {
> -		dot_name[0] = '.';
> -		dot_name[1] = '\0';
> -		strlcat(dot_name, name, sizeof(dot_name));
> -		dot_appended = true;
> -	} else {
> -		dot_name[0] = '\0';
> -		strlcat(dot_name, name, sizeof(dot_name));
> -	}
> -	addr = kallsyms_lookup_name(dot_name);
> -	if (!addr && dot_appended)
> -		/* Let's try the original non-dot symbol lookup	*/
> -		addr = kallsyms_lookup_name(name);
> -#elif defined(CONFIG_PPC64_ELF_ABI_V2)
> -	addr = kallsyms_lookup_name(name);
> -	if (addr)
> -		addr = ppc_function_entry((void *)addr);
> -#else
> -	addr = kallsyms_lookup_name(name);
> -#endif
> -	return addr;
> -}
> +static inline unsigned long __ppc_kallsyms_lookup_name(const char *name)
> +{
> +	unsigned long addr = kallsyms_lookup_name(name);
> +
> +	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V1) && !addr)
> +		addr = kallsyms_lookup_name(name + 1);
> +	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2) && addr)
> +		addr = ppc_function_entry((void *)addr);
> +
> +	return addr;
> +}
> +
> +#ifdef CONFIG_PPC64_ELF_ABI_V1
> +#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name("." x)
> +#else
> +#define ppc_kallsyms_lookup_name(x)	__ppc_kallsyms_lookup_name(x)
> +#endif
>   
>   /*
>    * Some instruction encodings commonly used in dynamic ftracing