1*4882a593Smuzhiyun /* 2*4882a593Smuzhiyun * GCC stack protector support. 3*4882a593Smuzhiyun * 4*4882a593Smuzhiyun * (This is directly adopted from the ARM implementation) 5*4882a593Smuzhiyun * 6*4882a593Smuzhiyun * Stack protector works by putting predefined pattern at the start of 7*4882a593Smuzhiyun * the stack frame and verifying that it hasn't been overwritten when 8*4882a593Smuzhiyun * returning from the function. The pattern is called stack canary 9*4882a593Smuzhiyun * and gcc expects it to be defined by a global variable called 10*4882a593Smuzhiyun * "__stack_chk_guard" on Xtensa. This unfortunately means that on SMP 11*4882a593Smuzhiyun * we cannot have a different canary value per task. 12*4882a593Smuzhiyun */ 13*4882a593Smuzhiyun 14*4882a593Smuzhiyun #ifndef _ASM_STACKPROTECTOR_H 15*4882a593Smuzhiyun #define _ASM_STACKPROTECTOR_H 1 16*4882a593Smuzhiyun 17*4882a593Smuzhiyun #include <linux/random.h> 18*4882a593Smuzhiyun #include <linux/version.h> 19*4882a593Smuzhiyun 20*4882a593Smuzhiyun extern unsigned long __stack_chk_guard; 21*4882a593Smuzhiyun 22*4882a593Smuzhiyun /* 23*4882a593Smuzhiyun * Initialize the stackprotector canary value. 24*4882a593Smuzhiyun * 25*4882a593Smuzhiyun * NOTE: this must only be called from functions that never return, 26*4882a593Smuzhiyun * and it must always be inlined. 27*4882a593Smuzhiyun */ boot_init_stack_canary(void)28*4882a593Smuzhiyunstatic __always_inline void boot_init_stack_canary(void) 29*4882a593Smuzhiyun { 30*4882a593Smuzhiyun unsigned long canary; 31*4882a593Smuzhiyun 32*4882a593Smuzhiyun /* Try to get a semi random initial value. */ 33*4882a593Smuzhiyun get_random_bytes(&canary, sizeof(canary)); 34*4882a593Smuzhiyun canary ^= LINUX_VERSION_CODE; 35*4882a593Smuzhiyun 36*4882a593Smuzhiyun current->stack_canary = canary; 37*4882a593Smuzhiyun __stack_chk_guard = current->stack_canary; 38*4882a593Smuzhiyun } 39*4882a593Smuzhiyun 40*4882a593Smuzhiyun #endif /* _ASM_STACKPROTECTOR_H */ 41