130 lines
2.6 KiB
C
130 lines
2.6 KiB
C
/* This file contains some code to guess where we have to load the
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* RAM image device from, if started from CD. (In this case it's hard
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* to tell where this is without diving into BIOS heuristics.)
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*
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* There is some nasty hard-codery in here ( MINIX cd label) that can be
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* improved on.
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*
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* Changes:
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* Jul 14, 2005 Created (Ben Gras)
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* Feb 10, 2006 Changed into a standalone program (Philip Homburg)
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*/
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#define CD_SECTOR 2048
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#define SUPER_OFF 1024
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#define AT_MINORS 4
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#define MAGIC_OFF 24
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#include <errno.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "../../servers/fs/const.h"
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char pvd[CD_SECTOR];
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/*===========================================================================*
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* cdprobe *
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*===========================================================================*/
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int main(void)
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{
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int i, r, fd, minor, found;
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off_t pos;
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u16_t *magicp;
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char name1[]= "/dev/c0dX";
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char name2[]= "/dev/c0dXpY";
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found= 0;
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for(i = 0; i < AT_MINORS; i++) {
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name1[8]= '0' + i;
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fd = open(name1, O_RDONLY);
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if (fd < 0)
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{
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if (errno != ENXIO)
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{
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fprintf(stderr, "open '%s' failed: %s\n",
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name1, strerror(errno));
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}
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continue;
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}
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pos= lseek(fd, 16*CD_SECTOR, SEEK_SET);
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if (pos != 16*CD_SECTOR)
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{
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/* Strange, do we need to issue a warning? */
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close(fd);
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continue;
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}
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r = read(fd, pvd, sizeof(pvd));
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if (r != sizeof(pvd))
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{
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fprintf(stderr,
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"error reading CD label from '%s': %s\n",
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name1, strerror(errno));
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close(fd);
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continue;
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}
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close(fd);
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/* Check PVD ID. */
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if (pvd[0] != 1 || pvd[1] != 'C' || pvd[2] != 'D' ||
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pvd[3] != '0' || pvd[4] != '0' || pvd[5] != '1' ||
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pvd[6] != 1 ||
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strncmp(pvd + 40, "MINIX", 5) != 0) {
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continue;
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}
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/* 3. Both c0dXp1 and p2 should have a superblock. */
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found= 1; /* Assume everything is okay */
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for (minor = 1; minor <= 2; minor++) {
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name2[8]= '0' + i;
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name2[10]= '0' + minor;
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fd = open(name2, O_RDONLY);
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if (fd < 0)
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{
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if (errno != ENXIO)
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{
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fprintf(stderr,
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"open '%s' failed: %s\n",
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name2, strerror(errno));
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}
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found= 0;
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break;
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}
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r = read(fd, pvd, sizeof(pvd));
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if (r != sizeof(pvd))
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{
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fprintf(stderr,
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"error reading super block from '%s': %s\n",
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name2, strerror(errno));
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close(fd);
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found= 0;
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break;
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}
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close(fd);
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magicp= (u16_t *)&pvd[SUPER_OFF+MAGIC_OFF];
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if (*magicp != SUPER_V3)
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{
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fprintf(stderr, "bad super block on %s\n",
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name2);
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found= 0;
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break;
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}
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}
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if (found)
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{
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printf("%s\n", name1);
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exit(0);
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}
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}
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return 1;
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}
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