[821] | 1 | /* vi:set ts=4:*/
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| 2 | /* Copyright 2005 Rob Landley <rob@landley.net>
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| 3 | *
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| 4 | * Switch from rootfs to another filesystem as the root of the mount tree.
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| 5 | *
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| 6 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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| 7 | */
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| 8 |
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| 9 | #include "busybox.h"
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| 10 | #include <fcntl.h>
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| 11 | #include <string.h>
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| 12 | #include <sys/vfs.h>
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| 13 | #include <unistd.h>
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| 14 |
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| 15 |
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| 16 | // Make up for header deficiencies.
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| 17 |
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| 18 | #ifndef RAMFS_MAGIC
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| 19 | #define RAMFS_MAGIC 0x858458f6
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| 20 | #endif
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| 21 |
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| 22 | #ifndef TMPFS_MAGIC
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| 23 | #define TMPFS_MAGIC 0x01021994
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| 24 | #endif
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| 25 |
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| 26 | #ifndef MS_MOVE
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| 27 | #define MS_MOVE 8192
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| 28 | #endif
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| 29 |
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| 30 | dev_t rootdev;
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| 31 |
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| 32 | // Recursively delete contents of rootfs.
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| 33 |
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| 34 | static void delete_contents(char *directory)
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| 35 | {
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| 36 | DIR *dir;
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| 37 | struct dirent *d;
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| 38 | struct stat st;
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| 39 |
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| 40 | // Don't descend into other filesystems
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| 41 | if (lstat(directory,&st) || st.st_dev != rootdev) return;
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| 42 |
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| 43 | // Recursively delete the contents of directories.
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| 44 | if (S_ISDIR(st.st_mode)) {
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| 45 | if((dir = opendir(directory))) {
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| 46 | while ((d = readdir(dir))) {
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| 47 | char *newdir=d->d_name;
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| 48 |
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| 49 | // Skip . and ..
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| 50 | if(*newdir=='.' && (!newdir[1] || (newdir[1]=='.' && !newdir[2])))
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| 51 | continue;
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| 52 |
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| 53 | // Recurse to delete contents
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| 54 | newdir = alloca(strlen(directory) + strlen(d->d_name) + 2);
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| 55 | sprintf(newdir, "%s/%s", directory, d->d_name);
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| 56 | delete_contents(newdir);
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| 57 | }
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| 58 | closedir(dir);
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| 59 |
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| 60 | // Directory should now be empty. Zap it.
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| 61 | rmdir(directory);
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| 62 | }
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| 63 |
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| 64 | // It wasn't a directory. Zap it.
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| 65 |
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| 66 | } else unlink(directory);
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| 67 | }
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| 68 |
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| 69 | int switch_root_main(int argc, char *argv[])
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| 70 | {
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| 71 | char *newroot, *console=NULL;
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| 72 | struct stat st1, st2;
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| 73 | struct statfs stfs;
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| 74 |
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| 75 | // Parse args (-c console)
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| 76 |
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| 77 | bb_opt_complementally="-2";
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| 78 | bb_getopt_ulflags(argc,argv,"c:",&console);
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| 79 |
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| 80 | // Change to new root directory and verify it's a different fs.
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| 81 |
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| 82 | newroot=argv[optind++];
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| 83 |
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| 84 | if (chdir(newroot) || lstat(".", &st1) || lstat("/", &st2) ||
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| 85 | st1.st_dev == st2.st_dev)
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| 86 | {
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| 87 | bb_error_msg_and_die("bad newroot %s",newroot);
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| 88 | }
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| 89 | rootdev=st2.st_dev;
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| 90 |
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| 91 | // Additional sanity checks: we're about to rm -rf /, so be REALLY SURE
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| 92 | // we mean it. (I could make this a CONFIG option, but I would get email
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| 93 | // from all the people who WILL eat their filesystemss.)
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| 94 |
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| 95 | if (lstat("/init", &st1) || !S_ISREG(st1.st_mode) || statfs("/", &stfs) ||
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| 96 | (stfs.f_type != RAMFS_MAGIC && stfs.f_type != TMPFS_MAGIC) ||
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| 97 | getpid() != 1)
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| 98 | {
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| 99 | bb_error_msg_and_die("not rootfs");
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| 100 | }
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| 101 |
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| 102 | // Zap everything out of rootdev
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| 103 |
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| 104 | delete_contents("/");
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| 105 |
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| 106 | // Overmount / with newdir and chroot into it. The chdir is needed to
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| 107 | // recalculate "." and ".." links.
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| 108 |
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| 109 | if (mount(".", "/", NULL, MS_MOVE, NULL) || chroot(".") || chdir("/"))
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| 110 | bb_error_msg_and_die("moving root");
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| 111 |
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| 112 | // If a new console specified, redirect stdin/stdout/stderr to that.
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| 113 |
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| 114 | if (console) {
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| 115 | close(0);
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| 116 | if(open(console, O_RDWR) < 0)
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| 117 | bb_error_msg_and_die("Bad console '%s'",console);
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| 118 | dup2(0, 1);
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| 119 | dup2(0, 2);
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| 120 | }
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| 121 |
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| 122 | // Exec real init. (This is why we must be pid 1.)
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| 123 | execv(argv[optind],argv+optind);
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| 124 | bb_error_msg_and_die("Bad init '%s'",argv[optind]);
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| 125 | }
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