| /* vi: set sw=4 ts=4: */ |
| /* Copyright 2005 Rob Landley <rob@landley.net> |
| * |
| * Switch from rootfs to another filesystem as the root of the mount tree. |
| * |
| * Licensed under GPL version 2, see file LICENSE in this tarball for details. |
| */ |
| |
| #include "busybox.h" |
| #include <sys/vfs.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(const char *directory) |
| { |
| DIR *dir; |
| struct dirent *d; |
| struct stat st; |
| |
| // Don't descend into other filesystems |
| if (lstat(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. |
| rmdir(directory); |
| } |
| |
| // It wasn't a directory. Zap it. |
| |
| } else unlink(directory); |
| } |
| |
| int switch_root_main(int argc, char **argv); |
| int switch_root_main(int argc, char **argv) |
| { |
| char *newroot, *console=NULL; |
| struct stat st1, st2; |
| struct statfs stfs; |
| |
| // Parse args (-c console) |
| |
| opt_complementary = "-2"; |
| getopt32(argc, argv, "c:", &console); |
| |
| // Change to new root directory and verify it's a different fs. |
| |
| newroot=argv[optind++]; |
| |
| if (chdir(newroot) || lstat(".", &st1) || lstat("/", &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 (lstat("/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 and chroot into it. The chdir is needed to |
| // recalculate "." and ".." links. |
| |
| if (mount(".", "/", NULL, MS_MOVE, NULL) || chroot(".") || chdir("/")) |
| bb_error_msg_and_die("moving root"); |
| |
| // If a new console specified, redirect stdin/stdout/stderr to that. |
| |
| if (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); |
| bb_error_msg_and_die("bad init '%s'", argv[optind]); |
| } |