minix/commands/cdprobe/cdprobe.c

   1 /*
   2  * This file contains some code to guess where we have to load the
   3  * RAM image device from, if started from CD. (In this case it's hard
   4  * to tell where this is without diving into BIOS heuristics.)
   5  *
   6  * There is some nasty hard-codery in here ( MINIX cd label) that can be
   7  * improved on.
   8  *
   9  * Changes:
  10  *   Jul 14, 2005   Created (Ben Gras)
  11  *   Feb 10, 2006   Changed into a standalone program (Philip Homburg)
  12  *   May 25, 2015   Installation CD overhaul (Jean-Baptiste Boric)
  13  */
  14
  15 #define CD_SECTOR       2048
  16 #define SUPER_OFF       1024
  17 #define AT_MINORS       8
  18 #define MAGIC_OFF       24
  19
  20 #include <errno.h>
  21 #include <fcntl.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26
  27 int main(void)
  28 {
  29         const int probelist[AT_MINORS] = { 2, 3, 1, 0, 6, 7, 5, 4 };
  30         int controller, disk, r, fd;
  31         off_t pos;
  32         char name[] = "/dev/c0dX";
  33         char pvd[CD_SECTOR];
  34
  35         for(controller = 0; controller <= 1; controller++) {
  36                 name[6] = '0' + controller;
  37                 for(disk = 0; disk < AT_MINORS; disk++) {
  38                         name[8]= '0' + probelist[disk];
  39
  40                         fprintf(stderr, "Trying %s  \r", name);
  41                         fflush(stderr);
  42
  43                         fd = open(name, O_RDONLY);
  44                         if ((fd < 0) && (errno != ENXIO)) {
  45                                 fprintf(stderr, "open '%s' failed: %s\n",
  46                                         name, strerror(errno));
  47                                 continue;
  48                         }
  49
  50                         /* Try to read PVD. */
  51                         pos = lseek(fd, 16*CD_SECTOR, SEEK_SET);
  52                         if (pos != 16*CD_SECTOR) {
  53                                 close(fd);
  54                                 continue;
  55                         }
  56                         r = read(fd, pvd, sizeof(pvd));
  57                         close(fd);
  58                         if (r != sizeof(pvd)) {
  59                                 continue;
  60                         }
  61
  62                         /* Check PVD ID. */
  63                         if (pvd[0] !=  1  || pvd[1] != 'C' || pvd[2] != 'D' ||
  64                             pvd[3] != '0' || pvd[4] != '0' || pvd[5] != '1' ||
  65                             pvd[6] != 1 ||
  66                             strncmp(pvd + 40, "MINIX", 5) != 0) {
  67                                 continue;
  68                         }
  69
  70                         fprintf(stderr, "\nFound.\n");
  71                         printf("%s\n", name);
  72                         return 0;
  73                 }
  74         }
  75
  76         fprintf(stderr, "\nNot found.\n");
  77         return 1;
  78 }