Re: [PATCH] modpost: Ignore Clang LTO suffixes in symbol matching

[Rong Xu]

A more direct fix for the warnings in
https://lore.kernel.org/oe-kbuild-all/202606111233.kM8oo8Df-lkp@xxxxxxxxx/
looks like the following. But I believe the solution provided in the
patch is more comprehensive.

-Rong

======
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index abbcd3fc1394..1f0a379b43c8 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -967,7 +967,7 @@ static int secref_whitelist(const char *fromsec,
const char *fromsym,
        /* symbols in data sections that may refer to any init/exit sections */
        if (match(fromsec, PATTERNS(DATA_SECTIONS)) &&
            match(tosec, PATTERNS(ALL_INIT_SECTIONS, ALL_EXIT_SECTIONS)) &&
-           match(fromsym, PATTERNS("*_ops", "*_console")))
+           match(fromsym, PATTERNS("*_ops", "*_ops.llvm.*", "*_console")))
                return 0;

        /* Check for pattern 3 */

On Mon, Jun 15, 2026 at 3:20 PM <xur@xxxxxxxxxx> wrote:
>
> From: Rong Xu <xur@xxxxxxxxxx>
>
> When building the kernel with Clang ThinLTO enabled, the compiler
> can mangle static variable names by appending suffixes such as
> ".llvm.<hash>" to prevent naming collisions across translation units.
>
> This name mangling breaks the section mismatch whitelisting in modpost.
> modpost relies on glob patterns (e.g., "*_ops" or "*_probe") to identify
> safe references between permanent data and initialization code. Because
> the LTO suffix modifies the end of the symbol name, legitimately
> whitelisted structures fail the match, resulting in false positive
> warnings.
>
> For example, a static pernet_operations struct triggers the following:
>
>   WARNING: modpost: vmlinux: section mismatch in reference: \
>   ping_v4_net_ops.llvm.5641696707737373282 (section: .data) -> \
>   ping_v4_proc_init_net (section: .init.text)
>
> Fix this by stripping ".llvm." suffixes from the symbol name in match().
>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Closes: https://lore.kernel.org/oe-kbuild-all/202606111233.kM8oo8Df-lkp@xxxxxxxxx/
> Signed-off-by: Rong Xu <xur@xxxxxxxxxx>
> ---
>  scripts/mod/modpost.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index abbcd3fc1394..1f5a64eeb048 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -727,6 +727,18 @@ static const char *sym_name(struct elf_info *elf, Elf_Sym *sym)
>  static bool match(const char *string, const char *const patterns[])
>  {
>         const char *pattern;
> +       char string_stripped[512];
> +       const char *ext = strstr(string, ".llvm.");
> +
> +       /*
> +        * Clang LTO can append .llvm.<hash> to a variable. Safely strip
> +        * the suffix so glob whitelists (like *_ops) work.
> +        */
> +       if (ext && (ext - string) < sizeof(string_stripped)) {
> +               strncpy(string_stripped, string, ext - string);
> +               string_stripped[ext - string] = '\0';
> +               string = string_stripped;
> +       }
>
>         while ((pattern = *patterns++)) {
>                 if (!fnmatch(pattern, string, 0))
>
> base-commit: 2b414a95b8f7307d42173ba9e580d6d3e2bcbfce
> --
> 2.54.0.1136.gdb2ca164c4-goog
>