linux-kernel - [PATCH 2/6] tools/nolibc: disable function sanitizer for _start

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Message-Id: <20250416-nolibc-ubsan-v1-2-c4704bb23da7@weissschuh.net>
Date: Wed, 16 Apr 2025 20:40:17 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>, "Paul E. McKenney" <paulmck@...nel.org>, 
 Shuah Khan <shuah@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH 2/6] tools/nolibc: disable function sanitizer for
 _start_c()

Both constructors and main() may be executed with different function
signatures than they are actually using.
This is intentional but trips up UBSAN.

Disable the function sanitizer of UBSAN in _start_c().

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 tools/include/nolibc/crt.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/include/nolibc/crt.h b/tools/include/nolibc/crt.h
index c4b10103bbec50f1a3a0a4562e34fdbd1b43ce6f..961cfe777c3564e705dfdd581de828b374d05b0b 100644
--- a/tools/include/nolibc/crt.h
+++ b/tools/include/nolibc/crt.h
@@ -7,6 +7,8 @@
 #ifndef _NOLIBC_CRT_H
 #define _NOLIBC_CRT_H

+#include "compiler.h"
+
 char **environ __attribute__((weak));
 const unsigned long *_auxv __attribute__((weak));

@@ -25,6 +27,9 @@ extern void (*const __fini_array_end[])(void) __attribute__((weak));

 void _start_c(long *sp);
 __attribute__((weak,used))
+#if __nolibc_has_feature(undefined_behavior_sanitizer)
+	__attribute__((no_sanitize("function")))
+#endif
 void _start_c(long *sp)
 {
 	long argc;

-- 
2.49.0