commands/loadramdisk/loadramdisk.c

   1 /*
   2 loadramdisk.c
   3
   4 Copy a device or file specified as argument to /dev/ram
   5 */
   6
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <unistd.h>
  13 #include <sys/ioctl.h>
  14
  15 #define RAM     "/dev/ram"
  16
  17 char buf[10240];
  18
  19 static unsigned long size_device(int fd);
  20
  21 int main(int argc, char *argv[])
  22 {
  23         unsigned long off, size;
  24         int r, s, fd, ramfd;
  25         char *src;
  26
  27         if (argc != 2)
  28         {
  29                 fprintf(stderr, "Usage: loadramdisk <file>\n");
  30                 exit(1);
  31         }
  32         src= argv[1];
  33         fd= open(src, O_RDONLY);
  34         if (fd < 0)
  35         {
  36                 fprintf(stderr, "Unable to open '%s': %s\n",
  37                         src, strerror(errno));
  38                 exit(1);
  39         }
  40
  41         /* Get the size of the device */
  42         errno= 0;
  43         size= size_device(fd);
  44         if (errno != 0)
  45         {
  46                 fprintf(stderr, "Lseek(end) failed on '%s': %s\n",
  47                         src, strerror(errno));
  48                 exit(1);
  49         }
  50         if (lseek(fd, 0, SEEK_SET) != 0)
  51         {
  52                 fprintf(stderr, "Lseek(0) failed on '%s': %s\n",
  53                         src, strerror(errno));
  54                 exit(1);
  55         }
  56
  57         ramfd= open(RAM, O_RDWR);
  58         if (ramfd < 0)
  59         {
  60                 fprintf(stderr, "Unable to open '%s': %s\n",
  61                         RAM, strerror(errno));
  62                 exit(1);
  63         }
  64         r= ioctl(ramfd, MIOCRAMSIZE, &size);
  65         if (r != 0)
  66         {
  67                 fprintf(stderr, "MIOCRAMSIZE %lu failed on '%s': %s\n",
  68                         size, RAM, strerror(errno));
  69                 exit(1);
  70         }
  71
  72         off= 0;
  73         while (off < size)
  74         {
  75                 r= read(fd, buf, sizeof(buf));
  76                 if (r <= 0)
  77                 {
  78                         fprintf(stderr, "error reading '%s': %s\n",
  79                                 src, r == 0 ? "unexpected EOF" :
  80                                 strerror(errno));
  81                         exit(1);
  82                 }
  83                 s= write(ramfd, buf, r);
  84                 if (s != r)
  85                 {
  86                         fprintf(stderr, "error writing to '%s': %s\n",
  87                                 s >= 0 ? "short write" : strerror(errno));
  88                         exit(1);
  89                 }
  90                 off += r;
  91         }
  92         exit(0);
  93 }
  94
  95 static unsigned long size_device(int fd)
  96 {
  97         char b;
  98         int r;
  99         unsigned long low, mid, high;
 100
 101         /* Try to find the size of a device using binary search */
 102         low= 0;
 103         high= -1;
 104
 105         while (mid= low+(high-low)/2, mid > low)
 106         {
 107                 if (lseek(fd, mid, SEEK_SET) != mid)
 108                 {
 109                         fprintf(stderr, "lseek to %lu failed: %s\n",
 110                                 mid, strerror(errno));
 111                         exit(1);
 112                 }
 113                 r= read(fd, &b, 1);
 114                 if (r < 0)
 115                 {
 116                         fprintf(stderr, "read failed at position %lu: %s\n",
 117                                 mid, strerror(errno));
 118                         exit(1);
 119                 }
 120                 if (r > 0)
 121                         low= mid;
 122                 else
 123                         high= mid;
 124         }
 125         return high;
 126 }