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/* febootstrap-supermin-helper reimplementation in C.
* Copyright (C) 2009-2010 Red Hat Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* This very minimal init "script" goes in the mini-initrd used to
* boot the ext2-based appliance. Note we have no shell, so we cannot
* use system(3) to run external commands. In fact, we don't have
* very much at all, except this program, insmod.static, and some
* kernel modules.
*/
#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/wait.h>
/* Leave this enabled for now. When we get more confident in the boot
* process we can turn this off or make it configurable.
*/
#define verbose 1
static void print_uptime (void);
static void insmod (const char *filename);
static char line[1024];
void
main ()
{
print_uptime ();
fprintf (stderr, "febootstrap: ext2 mini initrd starting up\n");
/* Create some fixed directories. */
mkdir ("/dev", 0755);
mkdir ("/root", 0755);
mkdir ("/sys", 0755);
/* Mount /sys. */
if (verbose)
fprintf (stderr, "febootstrap: mounting /sys\n");
if (mount ("sysfs", "/sys", "sysfs", 0, "") == -1) {
perror ("mount: /sys");
exit (EXIT_FAILURE);
}
FILE *fp = fopen ("/modules", "r");
if (fp == NULL) {
perror ("fopen: /modules");
exit (EXIT_FAILURE);
}
while (fgets (line, sizeof line, fp)) {
size_t n = strlen (line);
if (n > 0 && line[n-1] == '\n')
line[--n] = '\0';
insmod (line);
}
fclose (fp);
/* Look for the ext2 filesystem device. It's always the last
* one that was added.
* XXX More than 25 devices?
*/
char path[] = "/sys/block/xdx/dev";
char class[3] = { 'v', 's', 'h' };
size_t i, j;
fp = NULL;
for (i = 0; i < sizeof class; ++i) {
for (j = 'z'; j >= 'a'; --j) {
path[11] = class[i];
path[13] = j;
fp = fopen (path, "r");
if (fp != NULL)
goto found;
}
}
fprintf (stderr,
"febootstrap: no ext2 root device found\n"
"Please include FULL verbose output in your bug report.\n");
exit (EXIT_FAILURE);
found:
if (verbose)
fprintf (stderr, "febootstrap: picked %s as root device\n", path);
fgets (line, sizeof line, fp);
int major = atoi (line);
char *p = line + strcspn (line, ":") + 1;
int minor = atoi (p);
fclose (fp);
if (umount ("/sys") == -1) {
perror ("umount: /sys");
exit (EXIT_FAILURE);
}
if (verbose)
fprintf (stderr, "febootstrap: creating /dev/root as block special %d:%d\n",
major, minor);
if (mknod ("/dev/root", S_IFBLK|0700, makedev (major, minor)) == -1) {
perror ("mknod: /dev/root");
exit (EXIT_FAILURE);
}
/* Mount new root and chroot to it. */
if (verbose)
fprintf (stderr, "febootstrap: mounting new root on /root\n");
if (mount ("/dev/root", "/root", "ext2", MS_NOATIME, "") == -1) {
perror ("mount: /root");
exit (EXIT_FAILURE);
}
/* Note that pivot_root won't work. See the note in
* Documentation/filesystems/ramfs-rootfs-initramfs.txt
* We could remove the old initramfs files, but let's not bother.
*/
if (verbose)
fprintf (stderr, "febootstrap: chroot\n");
if (chroot ("/root") == -1) {
perror ("chroot: /root");
exit (EXIT_FAILURE);
}
chdir ("/");
/* Run /init from ext2 filesystem. */
print_uptime ();
execl ("/init", "init", NULL);
perror ("execl: /init");
exit (EXIT_FAILURE);
}
static void
insmod (const char *filename)
{
if (verbose)
fprintf (stderr, "febootstrap: insmod %s\n", filename);
pid_t pid = fork ();
if (pid == -1) {
perror ("insmod: fork");
exit (EXIT_FAILURE);
}
if (pid == 0) { /* Child. */
execl ("/insmod.static", "insmod.static", filename, NULL);
perror ("insmod: execl");
_exit (EXIT_FAILURE);
}
/* Parent. */
int status;
if (wait (&status) == -1 ||
WEXITSTATUS (status) != 0)
perror ("insmod: wait");
/* but ignore the error, some will be because the device is not found */
}
/* Print contents of /proc/uptime. */
static void
print_uptime (void)
{
FILE *fp = fopen ("/proc/uptime", "r");
if (fp == NULL) {
perror ("/proc/uptime");
return;
}
fgets (line, sizeof line, fp);
fclose (fp);
fprintf (stderr, "febootstrap: uptime: %s", line);
}
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