arch/powerpc/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 PPC.  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
  14
  15 #include <linux/random.h>
  16 #include <linux/version.h>
  17 #include <asm/reg.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 ^= mftb();
  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 */