0001-kallsyms-strip-LTO-suffixes-from-static-functions.patch

0001-kallsyms-strip-LTO-suffixes-from-static-functions.patch

From 2a710a626354016cd0344b848adeedb6e31ae643 Mon Sep 17 00:00:00 2001
From: Nathan Chancellor <[email protected]>
Date: Tue, 21 Mar 2023 15:04:24 +0800
Subject: [PATCH] kallsyms: strip LTO suffixes from static functions

https://lore.kernel.org/all/[email protected]/#r
---
 kernel/kallsyms.c | 47 ++++++++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 14de0c7bf756..5d12ef9f23ca 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -159,25 +159,46 @@ static unsigned long kallsyms_sym_address(int idx)
 	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 }
 
-#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_THINLTO)
-/*
- * LLVM appends a hash to static function names when ThinLTO and CFI are
- * both enabled, which causes confusion and potentially breaks user space
- * tools, so we will strip the postfix from expanded symbol names.
- */
-static inline char *cleanup_symbol_name(char *s)
+static bool cleanup_symbol_name(char *s)
 {
-	char *res = NULL;
+	char *res;
+
+	if (!IS_ENABLED(CONFIG_LTO_CLANG))
+		return false;
 
+	/*
+	 * LLVM appends various suffixes for local functions and variables that must
+	 * be promoted to global scope as part of LTO.  This can break hooking of
+	 * static functions with kprobes. '.' is not a valid character in an
+	 * identifier in C. Suffixes observed:
+	 * - foo.llvm.[0-9a-f]
+	 * - foo.[0-9a-f]
+	 * - foo.[0-9a-f].cfi_jt
+	 */
+	res = strchr(s, '.');
+	if (res) {
+		*res = '\0';
+		return true;
+	}
+
+	if (!IS_ENABLED(CONFIG_CFI_CLANG) ||
+		!IS_ENABLED(CONFIG_THINLTO) ||
+	    CONFIG_CLANG_VERSION >= 130000)
+			return false;
+
+	/*
+	 * Prior to LLVM 13, the following suffixes were observed when thinLTO
+	 * and CFI are both enabled:
+	 * - foo$[0-9]
+	 */
 	res = strrchr(s, '$');
-	if (res)
+	if (res) {
 		*res = '\0';
+		return true;
+	}
 
-	return res;
+	return false;
 }
-#else
-static inline char *cleanup_symbol_name(char *s) { return NULL; }
-#endif
 
 /* Lookup the address for this symbol. Returns 0 if not found. */
 unsigned long kallsyms_lookup_name(const char *name)
-- 
2.40.0