On Wed, May 06, 2026 at 10:11:43AM +0800, Xie Yuanbin wrote:
> 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
> ```
This log can be made more readable:
```log
In function 'ppc_kallsyms_lookup_name',
./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)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
> 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 <[email protected]>
> Cc: Kees Cook <[email protected]>
Please, keep Cc list...
> Suggested-by: Christophe Leroy (CS GROUP) <[email protected]>
> Signed-off-by: Xie Yuanbin <[email protected]>
> ---
...somewhere here in the comments block. This will reduce unneeded churn
in the commit message when maintainer applies the patch.
> v1->v2: https://lore.kernel.org/[email protected]
> - Not use strlen()
--
With Best Regards,
Andy Shevchenko
