arch/arm/include/asm/stackprotector.h

   1 /*
   2  * GCC stack protector support.
   3  *
   4  * Stack protector works by putting predefined pattern at the start of
   5  * the stack frame and verifying that it hasn't been overwritten when
   6  * returning from the function.  The pattern is called stack canary
   7  * and gcc expects it to be defined by a global variable called
   8  * "__stack_chk_guard" on ARM.  This unfortunately means that on SMP
   9  * we cannot have a different canary value per task.
  10  */
  11
  12 #ifndef _ASM_STACKPROTECTOR_H
  13 #define _ASM_STACKPROTECTOR_H 1
  14
  15 #include <linux/random.h>
  16 #include <linux/version.h>
  17
  18 extern unsigned long __stack_chk_guard;
  19
  20 /*
  21  * Initialize the stackprotector canary value.
  22  *
  23  * NOTE: this must only be called from functions that never return,
  24  * and it must always be inlined.
  25  */
  26 static __always_inline void boot_init_stack_canary(void)
  27 {
  28         unsigned long canary;
  29
  30         /* Try to get a semi random initial value. */
  31         get_random_bytes(&canary, sizeof(canary));
  32         canary ^= LINUX_VERSION_CODE;
  33
  34         current->stack_canary = canary;
  35         __stack_chk_guard = current->stack_canary;
  36 }
  37
  38 #endif  /* _ASM_STACKPROTECTOR_H */