arch/xtensa/include/asm/stackprotector.h

   1 /*
   2  * GCC stack protector support.
   3  *
   4  * (This is directly adopted from the ARM implementation)
   5  *
   6  * Stack protector works by putting predefined pattern at the start of
   7  * the stack frame and verifying that it hasn't been overwritten when
   8  * returning from the function.  The pattern is called stack canary
   9  * and gcc expects it to be defined by a global variable called
  10  * "__stack_chk_guard" on Xtensa.  This unfortunately means that on SMP
  11  * we cannot have a different canary value per task.
  12  */
  13
  14 #ifndef _ASM_STACKPROTECTOR_H
  15 #define _ASM_STACKPROTECTOR_H 1
  16
  17 #include <linux/random.h>
  18 #include <linux/version.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;
  31
  32         /* Try to get a semi random initial value. */
  33         get_random_bytes(&canary, sizeof(canary));
  34         canary ^= LINUX_VERSION_CODE;
  35
  36         current->stack_canary = canary;
  37         __stack_chk_guard = current->stack_canary;
  38 }
  39
  40 #endif  /* _ASM_STACKPROTECTOR_H */