libfstools/overlay.c

   1 /*
   2  * Copyright (C) 2014 John Crispin <blogic@openwrt.org>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License version 2.1
   6  * as published by the Free Software Foundation
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <sys/stat.h>
  15 #include <sys/types.h>
  16 #include <sys/mount.h>
  17
  18 #include <asm/byteorder.h>
  19
  20 #include <errno.h>
  21 #include <string.h>
  22 #include <stdio.h>
  23 #include <unistd.h>
  24 #include <stdlib.h>
  25 #include <glob.h>
  26 #include <errno.h>
  27 #include <dirent.h>
  28 #include <fcntl.h>
  29
  30 #include "libfstools.h"
  31 #include "volume.h"
  32
  33 #ifndef GLOB_ONLYDIR
  34 #define GLOB_ONLYDIR 0x100
  35 #endif
  36
  37 #define SWITCH_JFFS2 "/tmp/.switch_jffs2"
  38 #define OVERLAYDIR "/rom/overlay"
  39
  40 static bool keep_sysupgrade;
  41
  42 static int
  43 handle_rmdir(const char *dir)
  44 {
  45         struct dirent *dt;
  46         struct stat st;
  47         DIR *d;
  48         int fd;
  49
  50         d = opendir(dir);
  51         if (!d)
  52                 return -1;
  53
  54         fd = dirfd(d);
  55
  56         while ((dt = readdir(d)) != NULL) {
  57                 if (fstatat(fd, dt->d_name, &st, AT_SYMLINK_NOFOLLOW) || S_ISDIR(st.st_mode))
  58                         continue;
  59
  60                 if (keep_sysupgrade && !strcmp(dt->d_name, "sysupgrade.tgz"))
  61                         continue;
  62
  63                 unlinkat(fd, dt->d_name, 0);
  64         }
  65
  66         closedir(d);
  67         rmdir(dir);
  68
  69         return 0;
  70 }
  71
  72 void
  73 foreachdir(const char *dir, int (*cb)(const char*))
  74 {
  75         static char *globdir = NULL;
  76         static size_t globdirlen = 0;
  77         struct stat s = { 0 };
  78         size_t dirlen = strlen(dir);
  79         glob_t gl;
  80         int j;
  81
  82         if (dirlen + sizeof("/*") > globdirlen) {
  83                 /* Alloc extra 256 B to avoid too many reallocs */
  84                 size_t len = dirlen + sizeof("/*") + 256;
  85                 char *tmp;
  86
  87                 tmp = realloc(globdir, len);
  88                 if (!tmp)
  89                         return;
  90                 globdir = tmp;
  91                 globdirlen = len;
  92         }
  93
  94         sprintf(globdir, "%s/*", dir);
  95
  96         /* Include GLOB_MARK as callbacks expect a trailing slash */
  97         if (!glob(globdir, GLOB_NOESCAPE | GLOB_MARK | GLOB_ONLYDIR, NULL, &gl))
  98                 for (j = 0; j < gl.gl_pathc; j++) {
  99                         char *dir = gl.gl_pathv[j];
 100                         int len = strlen(gl.gl_pathv[j]);
 101                         int err;
 102
 103                         /* Quick way of skipping files */
 104                         if (dir[len - 1] != '/')
 105                                 continue;
 106
 107                         /* lstat needs path without a trailing slash */
 108                         if (len > 1)
 109                                 dir[len - 1] = '\0';
 110                         err = lstat(gl.gl_pathv[j], &s);
 111                         if (len > 1)
 112                                 dir[len - 1] = '/';
 113
 114                         if (!err && !S_ISLNK(s.st_mode))
 115                                 foreachdir(gl.gl_pathv[j], cb);
 116         }
 117         cb(dir);
 118 }
 119
 120 static void foreach_mount(int (*cb)(const char *, const char *))
 121 {
 122         FILE *fp = fopen("/proc/mounts", "r");
 123         static char line[256];
 124
 125         if (!fp)
 126                 return;
 127
 128         while (fgets(line, sizeof(line), fp)) {
 129                 char device[32], mount_point[32];
 130
 131                 if (sscanf(line, "%31s %31s %*s %*s %*u %*u", device, mount_point) == 2)
 132                         cb(device, mount_point);
 133         }
 134
 135         fclose(fp);
 136 }
 137
 138 void
 139 overlay_delete(const char *dir, bool _keep_sysupgrade)
 140 {
 141         keep_sysupgrade = _keep_sysupgrade;
 142         foreachdir(dir, handle_rmdir);
 143 }
 144
 145 static int
 146 overlay_mount(struct volume *v, char *fs)
 147 {
 148         if (mkdir("/tmp/overlay", 0755)) {
 149                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 150                 return -1;
 151         }
 152
 153         if (mount(v->blk, "/tmp/overlay", fs, MS_NOATIME, NULL)) {
 154                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n", fs, v->blk);
 155                 return -1;
 156         }
 157
 158         return 0;
 159 }
 160
 161 /**
 162  * move_mount - move mount point to the new root
 163  */
 164 static int move_mount(const char *device, const char *mount_point)
 165 {
 166         static const char *prefix = "/tmp/root/";
 167
 168         if (strncmp(mount_point, prefix, strlen(prefix)))
 169                 return 0;
 170
 171         return mount_move(prefix, "/", mount_point + strlen(prefix));
 172 }
 173
 174 static int
 175 switch2jffs(struct volume *v)
 176 {
 177         struct stat s;
 178         int ret, fd;
 179
 180         if (!stat(SWITCH_JFFS2, &s)) {
 181                 ULOG_ERR("jffs2 switch already running\n");
 182                 return -1;
 183         }
 184
 185         fd = creat(SWITCH_JFFS2, 0600);
 186         if (fd == -1) {
 187                 ULOG_ERR("failed - cannot create jffs2 switch mark: %m\n");
 188                 return -1;
 189         }
 190         close(fd);
 191
 192         ret = mount(v->blk, OVERLAYDIR, "jffs2", MS_NOATIME, NULL);
 193         unlink(SWITCH_JFFS2);
 194         if (ret) {
 195                 ULOG_ERR("failed - mount -t jffs2 %s %s: %m\n", v->blk, OVERLAYDIR);
 196                 return -1;
 197         }
 198
 199         if (mount("none", "/", NULL, MS_NOATIME | MS_REMOUNT, 0)) {
 200                 ULOG_ERR("failed - mount -o remount,ro none: %m\n");
 201                 return -1;
 202         }
 203
 204         if (system("cp -a /tmp/root/* /rom/overlay")) {
 205                 ULOG_ERR("failed - cp -a /tmp/root/* /rom/overlay: %m\n");
 206                 return -1;
 207         }
 208
 209         if (pivot("/rom", "/mnt")) {
 210                 ULOG_ERR("failed - pivot /rom /mnt: %m\n");
 211                 return -1;
 212         }
 213
 214         if (mount_move("/mnt", "/tmp/root", "")) {
 215                 ULOG_ERR("failed - mount -o move /mnt /tmp/root %m\n");
 216                 return -1;
 217         }
 218
 219         ret = fopivot("/overlay", "/rom");
 220
 221         /*
 222          * Besides copying overlay data from "tmpfs" to "jffs2" we should also
 223          * move mount points that user could create during JFFS2 formatting.
 224          * This has to happen after fopivot call because:
 225          * 1) It's trivial to find mount points to move then (/tmp/root/...).
 226          * 2) We can't do that earlier using /rom/overlay/upper/ as overlay(fs)
 227          *    doesn't support mounts. Mounting to upper dir don't make overlay
 228          *    /propagate/ files to the target dir.
 229          */
 230         foreach_mount(move_mount);
 231
 232         return ret;
 233 }
 234
 235 int
 236 handle_whiteout(const char *dir)
 237 {
 238         struct stat s;
 239         char link[256];
 240         ssize_t sz;
 241         struct dirent **namelist;
 242         int n;
 243
 244         n = scandir(dir, &namelist, NULL, NULL);
 245
 246         if (n < 1)
 247                 return -1;
 248
 249         while (n--) {
 250                 char file[256];
 251
 252                 snprintf(file, sizeof(file), "%s%s", dir, namelist[n]->d_name);
 253                 if (!lstat(file, &s) && S_ISLNK(s.st_mode)) {
 254                         sz = readlink(file, link, sizeof(link) - 1);
 255                         if (sz > 0) {
 256                                 char *orig;
 257
 258                                 link[sz] = '\0';
 259                                 orig = strstr(&file[1], "/");
 260                                 if (orig && !strcmp(link, "(overlay-whiteout)"))
 261                                         unlink(orig);
 262                         }
 263                 }
 264                 free(namelist[n]);
 265         }
 266         free(namelist);
 267
 268         return 0;
 269 }
 270
 271 static char *overlay_fs_name(int type)
 272 {
 273         switch (type) {
 274                 case FS_EXT4:
 275                         return "ext4";
 276                 case FS_F2FS:
 277                         return "f2fs";
 278                 case FS_UBIFS:
 279                         return "ubifs";
 280                 case FS_JFFS2:
 281                 default:
 282                         return "jffs2";
 283         }
 284 }
 285
 286 int
 287 jffs2_switch(struct volume *v)
 288 {
 289         char *mp, *fs_name;
 290         int type;
 291
 292         if (find_overlay_mount("overlayfs:/tmp/root"))
 293                 return -1;
 294
 295         if (find_filesystem("overlay")) {
 296                 ULOG_ERR("overlayfs not supported by kernel\n");
 297                 return -1;
 298         }
 299
 300         volume_init(v);
 301         mp = find_mount_point(v->blk, 0);
 302         if (mp) {
 303                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 304                 return -1;
 305         }
 306
 307         type = volume_identify(v);
 308         fs_name = overlay_fs_name(type);
 309
 310         switch (type) {
 311         case FS_NONE:
 312                 ULOG_ERR("no jffs2 marker found\n");
 313                 /* fall through */
 314
 315         case FS_DEADCODE:
 316                 if (switch2jffs(v))
 317                         return -1;
 318
 319                 ULOG_INFO("performing overlay whiteout\n");
 320                 umount2("/tmp/root", MNT_DETACH);
 321                 foreachdir("/overlay/", handle_whiteout);
 322
 323                 /* try hard to be in sync */
 324                 ULOG_INFO("synchronizing overlay\n");
 325                 if (system("cp -a /tmp/root/upper/* / 2>/dev/null"))
 326                         ULOG_ERR("failed to sync jffs2 overlay\n");
 327                 break;
 328
 329         case FS_EXT4:
 330         case FS_F2FS:
 331         case FS_UBIFS:
 332                 if (overlay_mount(v, fs_name))
 333                         return -1;
 334                 if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 335                         ULOG_ERR("switching to %s failed\n", fs_name);
 336                         return -1;
 337                 }
 338                 break;
 339         }
 340
 341         sync();
 342         fs_state_set("/overlay", FS_STATE_READY);
 343         return 0;
 344 }
 345
 346 static int overlay_mount_fs(struct volume *v, const char *overlay_mp)
 347 {
 348         char *fstype = overlay_fs_name(volume_identify(v));
 349
 350         if (mkdir(overlay_mp, 0755)) {
 351                 ULOG_ERR("failed to mkdir /tmp/overlay: %m\n");
 352                 return -1;
 353         }
 354
 355         if (mount(v->blk, overlay_mp, fstype,
 356 #ifdef OVL_MOUNT_FULL_ACCESS_TIME
 357                 MS_RELATIME,
 358 #else
 359                 MS_NOATIME,
 360 #endif
 361 #ifdef OVL_MOUNT_COMPRESS_ZLIB
 362                 "compr=zlib"
 363 #else
 364                 NULL
 365 #endif
 366                 )) {
 367                 ULOG_ERR("failed to mount -t %s %s /tmp/overlay: %m\n",
 368                          fstype, v->blk);
 369                 return -1;
 370         }
 371
 372         return 0;
 373 }
 374
 375 enum fs_state fs_state_get(const char *dir)
 376 {
 377         char *path;
 378         char valstr[16];
 379         uint32_t val;
 380         ssize_t len;
 381
 382         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 383         sprintf(path, "%s/.fs_state", dir);
 384         len = readlink(path, valstr, sizeof(valstr) - 1);
 385         if (len < 0)
 386                 return FS_STATE_UNKNOWN;
 387
 388         valstr[len] = 0;
 389         val = atoi(valstr);
 390
 391         if (val > __FS_STATE_LAST)
 392                 return FS_STATE_UNKNOWN;
 393
 394         return val;
 395 }
 396
 397
 398 int fs_state_set(const char *dir, enum fs_state state)
 399 {
 400         char valstr[16];
 401         char *path;
 402
 403         if (fs_state_get(dir) == state)
 404                 return 0;
 405
 406         path = alloca(strlen(dir) + 1 + sizeof("/.fs_state"));
 407         sprintf(path, "%s/.fs_state", dir);
 408         unlink(path);
 409         snprintf(valstr, sizeof(valstr), "%d", state);
 410
 411         return symlink(valstr, path);
 412 }
 413
 414
 415 int mount_overlay(struct volume *v)
 416 {
 417         const char *overlay_mp = "/tmp/overlay";
 418         char *mp, *fs_name;
 419         int err;
 420
 421         if (!v)
 422                 return -1;
 423
 424         mp = find_mount_point(v->blk, 0);
 425         if (mp) {
 426                 ULOG_ERR("rootfs_data:%s is already mounted as %s\n", v->blk, mp);
 427                 return -1;
 428         }
 429
 430         err = overlay_mount_fs(v, overlay_mp);
 431         if (err)
 432                 return err;
 433
 434         /*
 435          * Check for extroot config in overlay (rootfs_data) and if present then
 436          * prefer it over rootfs_data.
 437          */
 438         if (!mount_extroot(overlay_mp)) {
 439                 ULOG_INFO("switched to extroot\n");
 440                 return 0;
 441         }
 442
 443         switch (fs_state_get(overlay_mp)) {
 444         case FS_STATE_UNKNOWN:
 445                 fs_state_set(overlay_mp, FS_STATE_PENDING);
 446                 if (fs_state_get(overlay_mp) != FS_STATE_PENDING) {
 447                         ULOG_ERR("unable to set filesystem state\n");
 448                         break;
 449                 }
 450         case FS_STATE_PENDING:
 451                 ULOG_INFO("overlay filesystem has not been fully initialized yet\n");
 452                 overlay_delete(overlay_mp, true);
 453                 break;
 454         case FS_STATE_READY:
 455                 break;
 456         }
 457
 458         fs_name = overlay_fs_name(volume_identify(v));
 459         ULOG_INFO("switching to %s overlay\n", fs_name);
 460         if (mount_move("/tmp", "", "/overlay") || fopivot("/overlay", "/rom")) {
 461                 ULOG_ERR("switching to %s failed - fallback to ramoverlay\n", fs_name);
 462                 return ramoverlay();
 463         }
 464
 465         return -1;
 466 }