arch/arm64/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 unfortunately means that on SMP
  10  * we cannot have a different canary value per task.
  11  */
  12
  13 #ifndef __ASM_STACKPROTECTOR_H
  14 #define __ASM_STACKPROTECTOR_H
  15
  16 #include <linux/random.h>
  17 #include <linux/version.h>
  18
  19 extern unsigned long __stack_chk_guard;
  20
  21 /*
  22  * Initialize the stackprotector canary value.
  23  *
  24  * NOTE: this must only be called from functions that never return,
  25  * and it must always be inlined.
  26  */
  27 static __always_inline void boot_init_stack_canary(void)
  28 {
  29         unsigned long canary;
  30
  31         /* Try to get a semi random initial value. */
  32         get_random_bytes(&canary, sizeof(canary));
  33         canary ^= LINUX_VERSION_CODE;
  34         canary &= CANARY_MASK;
  35
  36         current->stack_canary = canary;
  37         if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK))
  38                 __stack_chk_guard = current->stack_canary;
  39 }
  40
  41 #endif  /* _ASM_STACKPROTECTOR_H */