arch/arm/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 prevents SMP systems from using a
  10  * different value for each task unless we enable a GCC plugin that
  11  * replaces these symbol references with references to each task's own
  12  * value.
  13  */
  14
  15 #ifndef _ASM_STACKPROTECTOR_H
  16 #define _ASM_STACKPROTECTOR_H 1
  17
  18 #include <linux/random.h>
  19 #include <linux/version.h>
  20
  21 #include <asm/thread_info.h>
  22
  23 extern unsigned long __stack_chk_guard;
  24
  25 /*
  26  * Initialize the stackprotector canary value.
  27  *
  28  * NOTE: this must only be called from functions that never return,
  29  * and it must always be inlined.
  30  */
  31 static __always_inline void boot_init_stack_canary(void)
  32 {
  33         unsigned long canary;
  34
  35         /* Try to get a semi random initial value. */
  36         get_random_bytes(&canary, sizeof(canary));
  37         canary ^= LINUX_VERSION_CODE;
  38
  39         current->stack_canary = canary;
  40 #ifndef CONFIG_STACKPROTECTOR_PER_TASK
  41         __stack_chk_guard = current->stack_canary;
  42 #else
  43         current_thread_info()->stack_canary = current->stack_canary;
  44 #endif
  45 }
  46
  47 #endif  /* _ASM_STACKPROTECTOR_H */