arch/arm/include/asm/stackprotector.h

   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 <asm/thread_info.h>
  19
  20 extern unsigned long __stack_chk_guard;
  21
  22 /*
  23  * Initialize the stackprotector canary value.
  24  *
  25  * NOTE: this must only be called from functions that never return,
  26  * and it must always be inlined.
  27  */
  28 static __always_inline void boot_init_stack_canary(void)
  29 {
  30         unsigned long canary = get_random_canary();
  31
  32         current->stack_canary = canary;
  33 #ifndef CONFIG_STACKPROTECTOR_PER_TASK
  34         __stack_chk_guard = current->stack_canary;
  35 #endif
  36 }
  37
  38 #endif  /* _ASM_STACKPROTECTOR_H */