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 #include <asm/pointer_auth.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 #if defined(CONFIG_STACKPROTECTOR)
  31         unsigned long canary;
  32
  33         /* Try to get a semi random initial value. */
  34         get_random_bytes(&canary, sizeof(canary));
  35         canary ^= LINUX_VERSION_CODE;
  36         canary &= CANARY_MASK;
  37
  38         current->stack_canary = canary;
  39         if (!IS_ENABLED(CONFIG_STACKPROTECTOR_PER_TASK))
  40                 __stack_chk_guard = current->stack_canary;
  41 #endif
  42         ptrauth_thread_init_kernel(current);
  43         ptrauth_thread_switch_kernel(current);
  44 }
  45
  46 #endif  /* _ASM_STACKPROTECTOR_H */