cmd/kaslrseed.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * The 'kaslrseed' command takes bytes from the hardware random number
   4  * generator and uses them to set the kaslr-seed value in the chosen node.
   5  *
   6  * Copyright (c) 2021, Chris Morgan <macromorgan@hotmail.com>
   7  */
   8
   9 #include <common.h>
  10 #include <command.h>
  11 #include <dm.h>
  12 #include <hexdump.h>
  13 #include <malloc.h>
  14 #include <rng.h>
  15 #include <fdt_support.h>
  16
  17 static int do_kaslr_seed(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
  18 {
  19         size_t n = 0x8;
  20         struct udevice *dev;
  21         u64 *buf;
  22         int nodeoffset;
  23         int ret = CMD_RET_SUCCESS;
  24
  25         if (uclass_get_device(UCLASS_RNG, 0, &dev) || !dev) {
  26                 printf("No RNG device\n");
  27                 return CMD_RET_FAILURE;
  28         }
  29
  30         buf = malloc(n);
  31         if (!buf) {
  32                 printf("Out of memory\n");
  33                 return CMD_RET_FAILURE;
  34         }
  35
  36         if (dm_rng_read(dev, buf, n)) {
  37                 printf("Reading RNG failed\n");
  38                 return CMD_RET_FAILURE;
  39         }
  40
  41         if (!working_fdt) {
  42                 printf("No FDT memory address configured. Please configure\n"
  43                        "the FDT address via \"fdt addr <address>\" command.\n"
  44                        "Aborting!\n");
  45                 return CMD_RET_FAILURE;
  46         }
  47
  48         ret = fdt_check_header(working_fdt);
  49         if (ret < 0) {
  50                 printf("fdt_chosen: %s\n", fdt_strerror(ret));
  51                 return CMD_RET_FAILURE;
  52         }
  53
  54         nodeoffset = fdt_find_or_add_subnode(working_fdt, 0, "chosen");
  55         if (nodeoffset < 0) {
  56                 printf("Reading chosen node failed\n");
  57                 return CMD_RET_FAILURE;
  58         }
  59
  60         ret = fdt_setprop(working_fdt, nodeoffset, "kaslr-seed", buf, sizeof(buf));
  61         if (ret < 0) {
  62                 printf("Unable to set kaslr-seed on chosen node: %s\n", fdt_strerror(ret));
  63                 return CMD_RET_FAILURE;
  64         }
  65
  66         free(buf);
  67
  68         return ret;
  69 }
  70
  71 #ifdef CONFIG_SYS_LONGHELP
  72 static char kaslrseed_help_text[] =
  73         "[n]\n"
  74         "  - append random bytes to chosen kaslr-seed node\n";
  75 #endif
  76
  77 U_BOOT_CMD(
  78         kaslrseed, 1, 0, do_kaslr_seed,
  79         "feed bytes from the hardware random number generator to the kaslr-seed",
  80         kaslrseed_help_text
  81 );