include/asm/stackprotector.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 /*
0003  * GCC stack protector support.
0004  *
0005  * Stack protector works by putting predefined pattern at the start of
0006  * the stack frame and verifying that it hasn't been overwritten when
0007  * returning from the function.  The pattern is called stack canary
0008  * and gcc expects it to be defined by a global variable called
0009  * "__stack_chk_guard" on ARM.  This prevents SMP systems from using a
0010  * different value for each task unless we enable a GCC plugin that
0011  * replaces these symbol references with references to each task's own
0012  * value.
0013  */
0014
0015 #ifndef _ASM_STACKPROTECTOR_H
0016 #define _ASM_STACKPROTECTOR_H 1
0017
0018 #include <linux/random.h>
0019 #include <linux/version.h>
0020
0021 #include <asm/thread_info.h>
0022
0023 extern unsigned long __stack_chk_guard;
0024
0025 /*
0026  * Initialize the stackprotector canary value.
0027  *
0028  * NOTE: this must only be called from functions that never return,
0029  * and it must always be inlined.
0030  */
0031 static __always_inline void boot_init_stack_canary(void)
0032 {
0033     unsigned long canary;
0034
0035     /* Try to get a semi random initial value. */
0036     get_random_bytes(&canary, sizeof(canary));
0037     canary ^= LINUX_VERSION_CODE;
0038
0039     current->stack_canary = canary;
0040 #ifndef CONFIG_STACKPROTECTOR_PER_TASK
0041     __stack_chk_guard = current->stack_canary;
0042 #endif
0043 }
0044
0045 #endif  /* _ASM_STACKPROTECTOR_H */