Re: [PATCH] kbuild: Add '-fno-builtin-wcslen'

[Kees Cook <kees@kernel.org>]

On Mon, Apr 07, 2025 at 04:22:12PM -0700, Nathan Chancellor wrote:
> A recent optimization change in LLVM [1] aims to transform certain loop
> idioms into calls to strlen() or wcslen(). This change transforms the
> first while loop in UniStrcat() into a call to wcslen(), breaking the
> build when UniStrcat() gets inlined into alloc_path_with_tree_prefix():
> 
>   ld.lld: error: undefined symbol: wcslen
>   >>> referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54)
>   >>>               vmlinux.o:(alloc_path_with_tree_prefix)
>   >>> referenced by nls_ucs2_utils.h:54 (fs/smb/client/../../nls/nls_ucs2_utils.h:54)
>   >>>               vmlinux.o:(alloc_path_with_tree_prefix)
> 
> Disable this optimization with '-fno-builtin-wcslen', which prevents the
> compiler from assuming that wcslen() is available in the kernel's C
> library
> 
> Cc: stable@vger.kernel.org
> Link: https://github.com/llvm/llvm-project/commit/9694844d7e36fd5e01011ab56b64f27b867aa72d [1]
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks for chasing this down. :)

Reviewed-by: Kees Cook <kees@kernel.org>

Since I have stuff queued for -rc2, do you want me to snag this too?

-- 
Kees Cook