Re: [PATCH V2] powerpc/text-patching: simplify the implementation of ppc_kallsyms_lookup_name()

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:

  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:

  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 <redacted>
Cc: Kees Cook <kees@kernel.org>

Please, keep Cc list...

Suggested-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Xie Yuanbin <redacted>
---

...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/20260205100517.292858-2-xieyuanbin1@huawei.com (local)
  - Not use strlen()

-- 
With Best Regards,
Andy Shevchenko