kallsyms: Match symbols exactly with CONFIG_LTO_CLANG

With CONFIG_LTO_CLANG=y, the compiler may add .llvm.<hash> suffix to
function names to avoid duplication. APIs like kallsyms_lookup_name()
and kallsyms_on_each_match_symbol() tries to match these symbol names
without the .llvm.<hash> suffix, e.g., match "c_stop" with symbol
c_stop.llvm.17132674095431275852. This turned out to be problematic
for use cases that require exact match, for example, livepatch.

Fix this by making the APIs to match symbols exactly.

Also cleanup kallsyms_selftests accordingly.

Signed-off-by: Song Liu <song@kernel.org>
Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions")
Tested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20240807220513.3100483-3-song@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

1 files changed, 1 insertions, 21 deletions

diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c
index 2f84896a7bcb..873f7c445488 100644
--- a/kernel/kallsyms_selftest.c
+++ b/kernel/kallsyms_selftest.c
@@ -187,31 +187,11 @@ static void test_perf_kallsyms_lookup_name(void)
 		stat.min, stat.max, div_u64(stat.sum, stat.real_cnt));
 }
 
-static bool match_cleanup_name(const char *s, const char *name)
-{
-	char *p;
-	int len;
-
-	if (!IS_ENABLED(CONFIG_LTO_CLANG))
-		return false;
-
-	p = strstr(s, ".llvm.");
-	if (!p)
-		return false;
-
-	len = strlen(name);
-	if (p - s != len)
-		return false;
-
-	return !strncmp(s, name, len);
-}
-
 static int find_symbol(void *data, const char *name, unsigned long addr)
 {
 	struct test_stat *stat = (struct test_stat *)data;
 
-	if (strcmp(name, stat->name) == 0 ||
-	    (!stat->perf && match_cleanup_name(name, stat->name))) {
+	if (!strcmp(name, stat->name)) {
 		stat->real_cnt++;
 		stat->addr = addr;