ddnuke.c

   1 /*
   2  * released into the public domain
   3  * written by Mike Frysinger <vapier>
   4  */
   5
   6 #define _FILE_OFFSET_BITS 64
   7 #define _LARGEFILE_SOURCE
   8 #define _LARGEFILE64_SOURCE
   9 #define _GNU_SOURCE
  10
  11 #include <fcntl.h>
  12 #include <inttypes.h>
  13 #include <locale.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <time.h>
  18 #include <unistd.h>
  19
  20 static const char zero[1024 * 1024];
  21
  22 #define errp(msg, args...) \
  23         do { \
  24                 printf("%s: " msg ": %m\n", argv[0], ## args); \
  25                 return 1; \
  26         } while (0)
  27
  28 static unsigned long long mbps(struct timespec *stime, struct timespec *etime, off_t len)
  29 {
  30         uint64_t dtime;
  31         clock_gettime(CLOCK_MONOTONIC, etime);
  32         dtime = ((etime->tv_sec - stime->tv_sec) * 1000 * 1000 * 1000) +
  33                 (etime->tv_nsec - stime->tv_nsec);
  34         *stime = *etime;
  35         return 1000 * len / dtime;
  36 }
  37
  38 int main(int argc, char *argv[])
  39 {
  40         off_t offset = 0;
  41         const char *file;
  42
  43         setlocale(LC_NUMERIC, "en_US");
  44
  45         switch (argc) {
  46         case 3:
  47                 offset = atoll(argv[2]);
  48         case 2:
  49                 file = argv[1];
  50                 break;
  51         default:
  52                 puts("Usage: ddnuke <dev> [offset in bytes]");
  53                 return 1;
  54         }
  55
  56         int fd = open(file, O_WRONLY);
  57         if (fd == -1)
  58                 errp("open(%s) failed", file);
  59
  60         if (lseek(fd, offset, SEEK_SET) != offset)
  61                 errp("lseek(%"PRIu64"u) failed", offset);
  62
  63         unsigned long long speed = 0;
  64         struct timespec stime, etime, itime;
  65         clock_gettime(CLOCK_MONOTONIC, &stime);
  66         itime = stime;
  67
  68         off_t pos = 0, last_pos = 0;
  69         ssize_t ret;
  70         int fsync_pos = 0;
  71         while (1) {
  72                 ret = write(fd, zero, sizeof(zero));
  73                 pos += ret;
  74                 if (ret != sizeof(zero)) {
  75                         printf("\ngot back %zi (wanted %zu)\n%'llu MB/s over entire run\n",
  76                                 ret, sizeof(zero), mbps(&itime, &etime, pos));
  77                         return 0;
  78                 }
  79
  80                 printf("%'llu bytes (%'llu MB/s)%20s\r", (unsigned long long)pos, speed, "");
  81
  82                 if ((++fsync_pos % 16) == 0) {
  83                         speed = mbps(&stime, &etime, pos - last_pos);
  84                         last_pos = pos;
  85                         fflush(stdout);
  86                         fsync(fd);
  87                 }
  88         }
  89
  90         return 0;
  91 }