1 /* SPDX-License-Identifier: LGPL-2.1 OR MIT */
2 /*
3  * Stack protector support for NOLIBC
4  * Copyright (C) 2023 Thomas Weißschuh <linux@weissschuh.net>
5  */
6 
7 #ifndef _NOLIBC_STACKPROTECTOR_H
8 #define _NOLIBC_STACKPROTECTOR_H
9 
10 #include "compiler.h"
11 
12 #if defined(_NOLIBC_STACKPROTECTOR)
13 
14 #include "sys.h"
15 #include "stdlib.h"
16 
17 /* The functions in this header are using raw syscall macros to avoid
18  * triggering stack protector errors themselves
19  */
20 
21 __attribute__((weak,noreturn,section(".text.nolibc_stack_chk")))
__stack_chk_fail(void)22 void __stack_chk_fail(void)
23 {
24 	pid_t pid;
25 	my_syscall3(__NR_write, STDERR_FILENO, "!!Stack smashing detected!!\n", 28);
26 	pid = my_syscall0(__NR_getpid);
27 	my_syscall2(__NR_kill, pid, SIGABRT);
28 	for (;;);
29 }
30 
31 __attribute__((weak,noreturn,section(".text.nolibc_stack_chk")))
__stack_chk_fail_local(void)32 void __stack_chk_fail_local(void)
33 {
34 	__stack_chk_fail();
35 }
36 
37 __attribute__((weak,section(".data.nolibc_stack_chk")))
38 uintptr_t __stack_chk_guard;
39 
__stack_chk_init(void)40 static __no_stack_protector void __stack_chk_init(void)
41 {
42 	my_syscall3(__NR_getrandom, &__stack_chk_guard, sizeof(__stack_chk_guard), 0);
43 	/* a bit more randomness in case getrandom() fails, ensure the guard is never 0 */
44 	if (__stack_chk_guard != (uintptr_t) &__stack_chk_guard)
45 		__stack_chk_guard ^= (uintptr_t) &__stack_chk_guard;
46 }
47 #else /* !defined(_NOLIBC_STACKPROTECTOR) */
__stack_chk_init(void)48 static void __stack_chk_init(void) {}
49 #endif /* defined(_NOLIBC_STACKPROTECTOR) */
50 
51 #endif /* _NOLIBC_STACKPROTECTOR_H */
52