plat/rpi/common/rpi3_stack_protector.c

   1 /*
   2  * Copyright (c) 2017-2019, ARM Limited and Contributors. All rights reserved.
   3  *
   4  * SPDX-License-Identifier: BSD-3-Clause
   5  */
   6
   7 #include <stdint.h>
   8
   9 #include <lib/utils.h>
  10 #include <lib/utils_def.h>
  11
  12 #include <drivers/rpi3/rng/rpi3_rng.h>
  13
  14 /* Get 128 bits of entropy and fuse the values together to form the canary. */
  15 #define TRNG_NBYTES     16U
  16
  17 u_register_t plat_get_stack_protector_canary(void)
  18 {
  19         size_t i;
  20         u_register_t buf[TRNG_NBYTES / sizeof(u_register_t)];
  21         u_register_t ret = 0U;
  22
  23         rpi3_rng_read(buf, sizeof(buf));
  24
  25         for (i = 0U; i < ARRAY_SIZE(buf); i++)
  26                 ret ^= buf[i];
  27
  28         return ret;
  29 }