diff options
author | Rob Landley <rob@landley.net> | 2005-10-28 02:55:50 +0400 |
---|---|---|
committer | Rob Landley <rob@landley.net> | 2005-10-28 02:55:50 +0400 |
commit | 0f34a821ab99e4936c7aa4974f58784442172211 (patch) | |
tree | 1341f988aa02110b3a997edc52e54bcc27ea1000 /util-linux/switch_root.c | |
parent | 2454ebd85ddbbdc0971e9b848032f66e23245ebe (diff) |
Add a switch_root utility (like kconfig's utils/run_init.c, although not
actuall using any of that code). This is needed because pivot_root doesn't
work right under initramfs. (See the menuconfig help.)
Diffstat (limited to 'util-linux/switch_root.c')
-rw-r--r-- | util-linux/switch_root.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/util-linux/switch_root.c b/util-linux/switch_root.c new file mode 100644 index 000000000..242699560 --- /dev/null +++ b/util-linux/switch_root.c @@ -0,0 +1,118 @@ +/* vi:set ts=4:*/ + +#include <dirent.h> +#include <fcntl.h> +#include <stdio.h> +#include <sys/mount.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <sys/vfs.h> +#include <unistd.h> + +#include "busybox.h" + +// Make up for header deficiencies. + +#ifndef RAMFS_MAGIC +#define RAMFS_MAGIC 0x858458f6 +#endif + +#ifndef TMPFS_MAGIC +#define TMPFS_MAGIC 0x01021994 +#endif + +#ifndef MS_MOVE +#define MS_MOVE 8192 +#endif + +dev_t rootdev; + +// Recursively delete contents of rootfs. + +static void delete_contents(char *directory) +{ + DIR *dir; + struct dirent *d; + struct stat st; + + // Don't descend into other filesystems + if (stat(directory,&st) || st.st_dev != rootdev) return; + + // Recursively delete the contents of directories. + if (S_ISDIR(st.st_mode)) { + if((dir = opendir(directory))) { + while ((d = readdir(dir))) { + char *newdir=d->d_name; + + // Skip . and .. + if(*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2]))) + continue; + + // Recurse to delete contents + newdir = alloca(strlen(directory) + strlen(d->d_name) + 2); + sprintf(newdir, "%s/%s", directory, d->d_name); + delete_contents(newdir); + } + closedir(dir); + + // Directory should now be empty. Zap it. + printf("rmdir %s\n",directory); // rmdir(directory); + } + + // It wasn't a directory. Zap it. + + } else printf("unlink %s\n",directory); //unlink(directory); +} + +int switch_root_main(int argc, char *argv[]) +{ + char *newroot, *console="/dev/console"; + struct stat st1, st2; + struct statfs stfs; + + // Parse args (-c console) + + bb_opt_complementally="-2"; + bb_getopt_ulflags(argc,argv,"c:",&console); + + // Change to new root directory and verify it's a different fs. + + newroot=argv[optind++]; + + if (chdir(newroot) || stat(".", &st1) || stat("/", &st2) || + st1.st_dev == st2.st_dev) + { + bb_error_msg_and_die("bad newroot %s",newroot); + } + rootdev=st2.st_dev; + + // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE + // we mean it. (I could make this a CONFIG option, but I would get email + // from all the people who WILL eat their filesystemss.) + + if (stat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) || + (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) || + getpid() != 1) + { + bb_error_msg_and_die("not rootfs"); + } + + // Zap everything out of rootdev + delete_contents("/"); + + // Overmount / with newdir + + if (mount(".", "/", NULL, MS_MOVE, NULL) || chdir("/")) + bb_error_msg_and_die("moving root"); + + // Reopen stdin/stdout/stderr to /dev/console + close(0); + if(open(console, O_RDWR) < 0) + bb_error_msg_and_die("Bad console '%s'",console); + dup2(0, 1); + dup2(0, 2); + + // Exec real init. (This is why we must be pid 1.) + execv(argv[optind],argv+optind+1); + bb_error_msg_and_die("Bad init '%s'",argv[optind]); +} |