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

[xur@google.com]

From: Rong Xu <xur@google.com>

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@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202606111233.kM8oo8Df-lkp@intel.com/
Signed-off-by: Rong Xu <xur@google.com>
---
 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