1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * GCC stack protector support. 4 * 5 * Stack protector works by putting a predefined pattern at the start of 6 * the stack frame and verifying that it hasn't been overwritten when 7 * returning from the function. The pattern is called the stack canary 8 * and is a unique value for each task. 9 */ 10 11 #ifndef _ASM_STACKPROTECTOR_H 12 #define _ASM_STACKPROTECTOR_H 1 13 14 #ifdef CONFIG_STACKPROTECTOR 15 16 #include <asm/tsc.h> 17 #include <asm/processor.h> 18 #include <asm/percpu.h> 19 #include <asm/desc.h> 20 21 #include <linux/sched.h> 22 23 DECLARE_PER_CPU_CACHE_HOT(unsigned long, __stack_chk_guard); 24 25 /* 26 * Initialize the stackprotector canary value. 27 * 28 * NOTE: this must only be called from functions that never return 29 * and it must always be inlined. 30 * 31 * In addition, it should be called from a compilation unit for which 32 * stack protector is disabled. Alternatively, the caller should not end 33 * with a function call which gets tail-call optimized as that would 34 * lead to checking a modified canary value. 35 */ boot_init_stack_canary(void)36static __always_inline void boot_init_stack_canary(void) 37 { 38 unsigned long canary = get_random_canary(); 39 40 current->stack_canary = canary; 41 this_cpu_write(__stack_chk_guard, canary); 42 } 43 cpu_init_stack_canary(int cpu,struct task_struct * idle)44static inline void cpu_init_stack_canary(int cpu, struct task_struct *idle) 45 { 46 per_cpu(__stack_chk_guard, cpu) = idle->stack_canary; 47 } 48 49 #else /* STACKPROTECTOR */ 50 51 /* dummy boot_init_stack_canary() is defined in linux/stackprotector.h */ 52 cpu_init_stack_canary(int cpu,struct task_struct * idle)53static inline void cpu_init_stack_canary(int cpu, struct task_struct *idle) 54 { } 55 56 #endif /* STACKPROTECTOR */ 57 #endif /* _ASM_STACKPROTECTOR_H */ 58