linux/arch/arm/include/asm/stackprotector.h
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   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * GCC stack protector support.
   4 *
   5 * Stack protector works by putting 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 stack canary
   8 * and gcc expects it to be defined by a global variable called
   9 * "__stack_chk_guard" on ARM.  This prevents SMP systems from using a
  10 * different value for each task unless we enable a GCC plugin that
  11 * replaces these symbol references with references to each task's own
  12 * value.
  13 */
  14
  15#ifndef _ASM_STACKPROTECTOR_H
  16#define _ASM_STACKPROTECTOR_H 1
  17
  18#include <linux/random.h>
  19#include <linux/version.h>
  20
  21#include <asm/thread_info.h>
  22
  23extern 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 */
  31static __always_inline void boot_init_stack_canary(void)
  32{
  33        unsigned long canary;
  34
  35        /* Try to get a semi random initial value. */
  36        get_random_bytes(&canary, sizeof(canary));
  37        canary ^= LINUX_VERSION_CODE;
  38
  39        current->stack_canary = canary;
  40#ifndef CONFIG_STACKPROTECTOR_PER_TASK
  41        __stack_chk_guard = current->stack_canary;
  42#else
  43        current_thread_info()->stack_canary = current->stack_canary;
  44#endif
  45}
  46
  47#endif  /* _ASM_STACKPROTECTOR_H */
  48