Re: [PATCH] tracing: ring-buffer: allowlist clang-generated symbols

[Vincent Donnefort <vdonnefort@google.com>]

On Tue, Jun 16, 2026 at 06:42:03PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> In randconfig build testing using clang-22, I came across two
> sets of extra symbols in the ring buffer code that may get
> inserted by the compiler:
> 
> Unexpected symbols in kernel/trace/simple_ring_buffer.o:
>          U memset
> 
> Unexpected symbols in kernel/trace/simple_ring_buffer.o:
>                  U llvm_gcda_emit_arcs
>                  U llvm_gcda_emit_function
>                  U llvm_gcda_end_file
>                  U llvm_gcda_start_file
>                  U llvm_gcda_summary_info
>                  U llvm_gcov_init
> 
> Add all of these to the allowlist.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  kernel/trace/Makefile | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/Makefile b/kernel/trace/Makefile
> index f934ff586bd4..aa8564fb8ff4 100644
> --- a/kernel/trace/Makefile
> +++ b/kernel/trace/Makefile
> @@ -146,6 +146,7 @@ KASAN_SANITIZE_undefsyms_base.o := y

Would "GCOV_PROFILE_undefsyms_base.o := y" work?

>  
>  UNDEFINED_ALLOWLIST = __asan __gcov __kasan __kcsan __hwasan __sancov __sanitizer __tsan __ubsan __msan \
>  		      __aeabi_unwind_cpp __s390_indirect_jump __x86_indirect_thunk simple_ring_buffer \
> +		      memset llvm_gcda llvm_gcov \
>  		      $(shell $(NM) -u $(obj)/undefsyms_base.o 2>/dev/null | awk '{print $$2}')
>  
>  quiet_cmd_check_undefined = NM      $<
> -- 
> 2.39.5
>