cmd/rng.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * The 'rng' command prints bytes from the hardware random number generator.
   4  *
   5  * Copyright (c) 2019, Heinrich Schuchardt <[email protected]>
   6  */
   7 #include <command.h>
   8 #include <dm.h>
   9 #include <hexdump.h>
  10 #include <malloc.h>
  11 #include <rng.h>
  12
  13 static int do_rng(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
  14 {
  15         size_t n;
  16         u8 buf[64];
  17         int devnum;
  18         struct udevice *dev;
  19         int ret = CMD_RET_SUCCESS, err;
  20
  21         if (argc == 2 && !strcmp(argv[1], "list")) {
  22                 int idx = 0;
  23
  24                 uclass_foreach_dev_probe(UCLASS_RNG, dev) {
  25                         idx++;
  26                         printf("RNG #%d - %s\n", dev->seq_, dev->name);
  27                 }
  28
  29                 if (!idx) {
  30                         log_err("No RNG device\n");
  31                         return CMD_RET_FAILURE;
  32                 }
  33
  34                 return CMD_RET_SUCCESS;
  35         }
  36
  37         switch (argc) {
  38         case 1:
  39                 devnum = 0;
  40                 n = 0x40;
  41                 break;
  42         case 2:
  43                 devnum = hextoul(argv[1], NULL);
  44                 n = 0x40;
  45                 break;
  46         case 3:
  47                 devnum = hextoul(argv[1], NULL);
  48                 n = hextoul(argv[2], NULL);
  49                 break;
  50         default:
  51                 return CMD_RET_USAGE;
  52         }
  53
  54         if (uclass_get_device_by_seq(UCLASS_RNG, devnum, &dev) || !dev) {
  55                 printf("No RNG device\n");
  56                 return CMD_RET_FAILURE;
  57         }
  58
  59         if (!n)
  60                 return 0;
  61
  62         n = min(n, sizeof(buf));
  63
  64         err = dm_rng_read(dev, buf, n);
  65         if (err) {
  66                 puts(err == -EINTR ? "Abort\n" : "Reading RNG failed\n");
  67                 ret = CMD_RET_FAILURE;
  68         } else {
  69                 print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, buf, n);
  70         }
  71
  72         return ret;
  73 }
  74
  75 U_BOOT_CMD(
  76         rng, 3, 0, do_rng,
  77         "print bytes from the hardware random number generator",
  78         "list         - list all the probed rng devices\n"
  79         "rng [dev] [n]    - print n random bytes(max 64) read from dev\n"
  80 );