include/linux/stackprotector.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_STACKPROTECTOR_H
   3 #define _LINUX_STACKPROTECTOR_H 1
   4
   5 #include <linux/compiler.h>
   6 #include <linux/sched.h>
   7 #include <linux/random.h>
   8
   9 /*
  10  * On 64-bit architectures, protect against non-terminated C string overflows
  11  * by zeroing out the first byte of the canary; this leaves 56 bits of entropy.
  12  */
  13 #ifdef CONFIG_64BIT
  14 # ifdef __LITTLE_ENDIAN
  15 #  define CANARY_MASK 0xffffffffffffff00UL
  16 # else /* big endian, 64 bits: */
  17 #  define CANARY_MASK 0x00ffffffffffffffUL
  18 # endif
  19 #else /* 32 bits: */
  20 # define CANARY_MASK 0xffffffffUL
  21 #endif
  22
  23 static inline unsigned long get_random_canary(void)
  24 {
  25         return get_random_long() & CANARY_MASK;
  26 }
  27
  28 #if defined(CONFIG_STACKPROTECTOR) || defined(CONFIG_ARM64_PTR_AUTH)
  29 # include <asm/stackprotector.h>
  30 #else
  31 static inline void boot_init_stack_canary(void)
  32 {
  33 }
  34 #endif
  35
  36 #endif