1*c0c264aeSLaura Abbott /* 2*c0c264aeSLaura Abbott * GCC stack protector support. 3*c0c264aeSLaura Abbott * 4*c0c264aeSLaura Abbott * Stack protector works by putting predefined pattern at the start of 5*c0c264aeSLaura Abbott * the stack frame and verifying that it hasn't been overwritten when 6*c0c264aeSLaura Abbott * returning from the function. The pattern is called stack canary 7*c0c264aeSLaura Abbott * and gcc expects it to be defined by a global variable called 8*c0c264aeSLaura Abbott * "__stack_chk_guard" on ARM. This unfortunately means that on SMP 9*c0c264aeSLaura Abbott * we cannot have a different canary value per task. 10*c0c264aeSLaura Abbott */ 11*c0c264aeSLaura Abbott 12*c0c264aeSLaura Abbott #ifndef __ASM_STACKPROTECTOR_H 13*c0c264aeSLaura Abbott #define __ASM_STACKPROTECTOR_H 14*c0c264aeSLaura Abbott 15*c0c264aeSLaura Abbott #include <linux/random.h> 16*c0c264aeSLaura Abbott #include <linux/version.h> 17*c0c264aeSLaura Abbott 18*c0c264aeSLaura Abbott extern unsigned long __stack_chk_guard; 19*c0c264aeSLaura Abbott 20*c0c264aeSLaura Abbott /* 21*c0c264aeSLaura Abbott * Initialize the stackprotector canary value. 22*c0c264aeSLaura Abbott * 23*c0c264aeSLaura Abbott * NOTE: this must only be called from functions that never return, 24*c0c264aeSLaura Abbott * and it must always be inlined. 25*c0c264aeSLaura Abbott */ 26*c0c264aeSLaura Abbott static __always_inline void boot_init_stack_canary(void) 27*c0c264aeSLaura Abbott { 28*c0c264aeSLaura Abbott unsigned long canary; 29*c0c264aeSLaura Abbott 30*c0c264aeSLaura Abbott /* Try to get a semi random initial value. */ 31*c0c264aeSLaura Abbott get_random_bytes(&canary, sizeof(canary)); 32*c0c264aeSLaura Abbott canary ^= LINUX_VERSION_CODE; 33*c0c264aeSLaura Abbott 34*c0c264aeSLaura Abbott current->stack_canary = canary; 35*c0c264aeSLaura Abbott __stack_chk_guard = current->stack_canary; 36*c0c264aeSLaura Abbott } 37*c0c264aeSLaura Abbott 38*c0c264aeSLaura Abbott #endif /* _ASM_STACKPROTECTOR_H */ 39