init/initramfs.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/init.h>
   3 #include <linux/async.h>
   4 #include <linux/fs.h>
   5 #include <linux/slab.h>
   6 #include <linux/types.h>
   7 #include <linux/fcntl.h>
   8 #include <linux/delay.h>
   9 #include <linux/string.h>
  10 #include <linux/dirent.h>
  11 #include <linux/syscalls.h>
  12 #include <linux/utime.h>
  13 #include <linux/file.h>
  14 #include <linux/memblock.h>
  15 #include <linux/mm.h>
  16 #include <linux/namei.h>
  17 #include <linux/init_syscalls.h>
  18 #include <linux/task_work.h>
  19 #include <linux/umh.h>
  20
  21 static __initdata bool csum_present;
  22 static __initdata u32 io_csum;
  23
  24 static ssize_t __init xwrite(struct file *file, const unsigned char *p,
  25                 size_t count, loff_t *pos)
  26 {
  27         ssize_t out = 0;
  28
  29         /* sys_write only can write MAX_RW_COUNT aka 2G-4K bytes at most */
  30         while (count) {
  31                 ssize_t rv = kernel_write(file, p, count, pos);
  32
  33                 if (rv < 0) {
  34                         if (rv == -EINTR || rv == -EAGAIN)
  35                                 continue;
  36                         return out ? out : rv;
  37                 } else if (rv == 0)
  38                         break;
  39
  40                 if (csum_present) {
  41                         ssize_t i;
  42
  43                         for (i = 0; i < rv; i++)
  44                                 io_csum += p[i];
  45                 }
  46
  47                 p += rv;
  48                 out += rv;
  49                 count -= rv;
  50         }
  51
  52         return out;
  53 }
  54
  55 static __initdata char *message;
  56 static void __init error(char *x)
  57 {
  58         if (!message)
  59                 message = x;
  60 }
  61
  62 static void panic_show_mem(const char *fmt, ...)
  63 {
  64         va_list args;
  65
  66         show_mem(0, NULL);
  67         va_start(args, fmt);
  68         panic(fmt, args);
  69         va_end(args);
  70 }
  71
  72 /* link hash */
  73
  74 #define N_ALIGN(len) ((((len) + 1) & ~3) + 2)
  75
  76 static __initdata struct hash {
  77         int ino, minor, major;
  78         umode_t mode;
  79         struct hash *next;
  80         char name[N_ALIGN(PATH_MAX)];
  81 } *head[32];
  82
  83 static inline int hash(int major, int minor, int ino)
  84 {
  85         unsigned long tmp = ino + minor + (major << 3);
  86         tmp += tmp >> 5;
  87         return tmp & 31;
  88 }
  89
  90 static char __init *find_link(int major, int minor, int ino,
  91                               umode_t mode, char *name)
  92 {
  93         struct hash **p, *q;
  94         for (p = head + hash(major, minor, ino); *p; p = &(*p)->next) {
  95                 if ((*p)->ino != ino)
  96                         continue;
  97                 if ((*p)->minor != minor)
  98                         continue;
  99                 if ((*p)->major != major)
 100                         continue;
 101                 if (((*p)->mode ^ mode) & S_IFMT)
 102                         continue;
 103                 return (*p)->name;
 104         }
 105         q = kmalloc(sizeof(struct hash), GFP_KERNEL);
 106         if (!q)
 107                 panic_show_mem("can't allocate link hash entry");
 108         q->major = major;
 109         q->minor = minor;
 110         q->ino = ino;
 111         q->mode = mode;
 112         strcpy(q->name, name);
 113         q->next = NULL;
 114         *p = q;
 115         return NULL;
 116 }
 117
 118 static void __init free_hash(void)
 119 {
 120         struct hash **p, *q;
 121         for (p = head; p < head + 32; p++) {
 122                 while (*p) {
 123                         q = *p;
 124                         *p = q->next;
 125                         kfree(q);
 126                 }
 127         }
 128 }
 129
 130 #ifdef CONFIG_INITRAMFS_PRESERVE_MTIME
 131 static void __init do_utime(char *filename, time64_t mtime)
 132 {
 133         struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } };
 134         init_utimes(filename, t);
 135 }
 136
 137 static void __init do_utime_path(const struct path *path, time64_t mtime)
 138 {
 139         struct timespec64 t[2] = { { .tv_sec = mtime }, { .tv_sec = mtime } };
 140         vfs_utimes(path, t);
 141 }
 142
 143 static __initdata LIST_HEAD(dir_list);
 144 struct dir_entry {
 145         struct list_head list;
 146         time64_t mtime;
 147         char name[];
 148 };
 149
 150 static void __init dir_add(const char *name, time64_t mtime)
 151 {
 152         size_t nlen = strlen(name) + 1;
 153         struct dir_entry *de;
 154
 155         de = kmalloc(sizeof(struct dir_entry) + nlen, GFP_KERNEL);
 156         if (!de)
 157                 panic_show_mem("can't allocate dir_entry buffer");
 158         INIT_LIST_HEAD(&de->list);
 159         strscpy(de->name, name, nlen);
 160         de->mtime = mtime;
 161         list_add(&de->list, &dir_list);
 162 }
 163
 164 static void __init dir_utime(void)
 165 {
 166         struct dir_entry *de, *tmp;
 167         list_for_each_entry_safe(de, tmp, &dir_list, list) {
 168                 list_del(&de->list);
 169                 do_utime(de->name, de->mtime);
 170                 kfree(de);
 171         }
 172 }
 173 #else
 174 static void __init do_utime(char *filename, time64_t mtime) {}
 175 static void __init do_utime_path(const struct path *path, time64_t mtime) {}
 176 static void __init dir_add(const char *name, time64_t mtime) {}
 177 static void __init dir_utime(void) {}
 178 #endif
 179
 180 static __initdata time64_t mtime;
 181
 182 /* cpio header parsing */
 183
 184 static __initdata unsigned long ino, major, minor, nlink;
 185 static __initdata umode_t mode;
 186 static __initdata unsigned long body_len, name_len;
 187 static __initdata uid_t uid;
 188 static __initdata gid_t gid;
 189 static __initdata unsigned rdev;
 190 static __initdata u32 hdr_csum;
 191
 192 static void __init parse_header(char *s)
 193 {
 194         unsigned long parsed[13];
 195         char buf[9];
 196         int i;
 197
 198         buf[8] = '\0';
 199         for (i = 0, s += 6; i < 13; i++, s += 8) {
 200                 memcpy(buf, s, 8);
 201                 parsed[i] = simple_strtoul(buf, NULL, 16);
 202         }
 203         ino = parsed[0];
 204         mode = parsed[1];
 205         uid = parsed[2];
 206         gid = parsed[3];
 207         nlink = parsed[4];
 208         mtime = parsed[5]; /* breaks in y2106 */
 209         body_len = parsed[6];
 210         major = parsed[7];
 211         minor = parsed[8];
 212         rdev = new_encode_dev(MKDEV(parsed[9], parsed[10]));
 213         name_len = parsed[11];
 214         hdr_csum = parsed[12];
 215 }
 216
 217 /* FSM */
 218
 219 static __initdata enum state {
 220         Start,
 221         Collect,
 222         GotHeader,
 223         SkipIt,
 224         GotName,
 225         CopyFile,
 226         GotSymlink,
 227         Reset
 228 } state, next_state;
 229
 230 static __initdata char *victim;
 231 static unsigned long byte_count __initdata;
 232 static __initdata loff_t this_header, next_header;
 233
 234 static inline void __init eat(unsigned n)
 235 {
 236         victim += n;
 237         this_header += n;
 238         byte_count -= n;
 239 }
 240
 241 static __initdata char *collected;
 242 static long remains __initdata;
 243 static __initdata char *collect;
 244
 245 static void __init read_into(char *buf, unsigned size, enum state next)
 246 {
 247         if (byte_count >= size) {
 248                 collected = victim;
 249                 eat(size);
 250                 state = next;
 251         } else {
 252                 collect = collected = buf;
 253                 remains = size;
 254                 next_state = next;
 255                 state = Collect;
 256         }
 257 }
 258
 259 static __initdata char *header_buf, *symlink_buf, *name_buf;
 260
 261 static int __init do_start(void)
 262 {
 263         read_into(header_buf, 110, GotHeader);
 264         return 0;
 265 }
 266
 267 static int __init do_collect(void)
 268 {
 269         unsigned long n = remains;
 270         if (byte_count < n)
 271                 n = byte_count;
 272         memcpy(collect, victim, n);
 273         eat(n);
 274         collect += n;
 275         if ((remains -= n) != 0)
 276                 return 1;
 277         state = next_state;
 278         return 0;
 279 }
 280
 281 static int __init do_header(void)
 282 {
 283         if (!memcmp(collected, "070701", 6)) {
 284                 csum_present = false;
 285         } else if (!memcmp(collected, "070702", 6)) {
 286                 csum_present = true;
 287         } else {
 288                 if (memcmp(collected, "070707", 6) == 0)
 289                         error("incorrect cpio method used: use -H newc option");
 290                 else
 291                         error("no cpio magic");
 292                 return 1;
 293         }
 294         parse_header(collected);
 295         next_header = this_header + N_ALIGN(name_len) + body_len;
 296         next_header = (next_header + 3) & ~3;
 297         state = SkipIt;
 298         if (name_len <= 0 || name_len > PATH_MAX)
 299                 return 0;
 300         if (S_ISLNK(mode)) {
 301                 if (body_len > PATH_MAX)
 302                         return 0;
 303                 collect = collected = symlink_buf;
 304                 remains = N_ALIGN(name_len) + body_len;
 305                 next_state = GotSymlink;
 306                 state = Collect;
 307                 return 0;
 308         }
 309         if (S_ISREG(mode) || !body_len)
 310                 read_into(name_buf, N_ALIGN(name_len), GotName);
 311         return 0;
 312 }
 313
 314 static int __init do_skip(void)
 315 {
 316         if (this_header + byte_count < next_header) {
 317                 eat(byte_count);
 318                 return 1;
 319         } else {
 320                 eat(next_header - this_header);
 321                 state = next_state;
 322                 return 0;
 323         }
 324 }
 325
 326 static int __init do_reset(void)
 327 {
 328         while (byte_count && *victim == '\0')
 329                 eat(1);
 330         if (byte_count && (this_header & 3))
 331                 error("broken padding");
 332         return 1;
 333 }
 334
 335 static void __init clean_path(char *path, umode_t fmode)
 336 {
 337         struct kstat st;
 338
 339         if (!init_stat(path, &st, AT_SYMLINK_NOFOLLOW) &&
 340             (st.mode ^ fmode) & S_IFMT) {
 341                 if (S_ISDIR(st.mode))
 342                         init_rmdir(path);
 343                 else
 344                         init_unlink(path);
 345         }
 346 }
 347
 348 static int __init maybe_link(void)
 349 {
 350         if (nlink >= 2) {
 351                 char *old = find_link(major, minor, ino, mode, collected);
 352                 if (old) {
 353                         clean_path(collected, 0);
 354                         return (init_link(old, collected) < 0) ? -1 : 1;
 355                 }
 356         }
 357         return 0;
 358 }
 359
 360 static __initdata struct file *wfile;
 361 static __initdata loff_t wfile_pos;
 362
 363 static int __init do_name(void)
 364 {
 365         state = SkipIt;
 366         next_state = Reset;
 367         if (strcmp(collected, "TRAILER!!!") == 0) {
 368                 free_hash();
 369                 return 0;
 370         }
 371         clean_path(collected, mode);
 372         if (S_ISREG(mode)) {
 373                 int ml = maybe_link();
 374                 if (ml >= 0) {
 375                         int openflags = O_WRONLY|O_CREAT;
 376                         if (ml != 1)
 377                                 openflags |= O_TRUNC;
 378                         wfile = filp_open(collected, openflags, mode);
 379                         if (IS_ERR(wfile))
 380                                 return 0;
 381                         wfile_pos = 0;
 382                         io_csum = 0;
 383
 384                         vfs_fchown(wfile, uid, gid);
 385                         vfs_fchmod(wfile, mode);
 386                         if (body_len)
 387                                 vfs_truncate(&wfile->f_path, body_len);
 388                         state = CopyFile;
 389                 }
 390         } else if (S_ISDIR(mode)) {
 391                 init_mkdir(collected, mode);
 392                 init_chown(collected, uid, gid, 0);
 393                 init_chmod(collected, mode);
 394                 dir_add(collected, mtime);
 395         } else if (S_ISBLK(mode) || S_ISCHR(mode) ||
 396                    S_ISFIFO(mode) || S_ISSOCK(mode)) {
 397                 if (maybe_link() == 0) {
 398                         init_mknod(collected, mode, rdev);
 399                         init_chown(collected, uid, gid, 0);
 400                         init_chmod(collected, mode);
 401                         do_utime(collected, mtime);
 402                 }
 403         }
 404         return 0;
 405 }
 406
 407 static int __init do_copy(void)
 408 {
 409         if (byte_count >= body_len) {
 410                 if (xwrite(wfile, victim, body_len, &wfile_pos) != body_len)
 411                         error("write error");
 412
 413                 do_utime_path(&wfile->f_path, mtime);
 414                 fput(wfile);
 415                 if (csum_present && io_csum != hdr_csum)
 416                         error("bad data checksum");
 417                 eat(body_len);
 418                 state = SkipIt;
 419                 return 0;
 420         } else {
 421                 if (xwrite(wfile, victim, byte_count, &wfile_pos) != byte_count)
 422                         error("write error");
 423                 body_len -= byte_count;
 424                 eat(byte_count);
 425                 return 1;
 426         }
 427 }
 428
 429 static int __init do_symlink(void)
 430 {
 431         collected[N_ALIGN(name_len) + body_len] = '\0';
 432         clean_path(collected, 0);
 433         init_symlink(collected + N_ALIGN(name_len), collected);
 434         init_chown(collected, uid, gid, AT_SYMLINK_NOFOLLOW);
 435         do_utime(collected, mtime);
 436         state = SkipIt;
 437         next_state = Reset;
 438         return 0;
 439 }
 440
 441 static __initdata int (*actions[])(void) = {
 442         [Start]         = do_start,
 443         [Collect]       = do_collect,
 444         [GotHeader]     = do_header,
 445         [SkipIt]        = do_skip,
 446         [GotName]       = do_name,
 447         [CopyFile]      = do_copy,
 448         [GotSymlink]    = do_symlink,
 449         [Reset]         = do_reset,
 450 };
 451
 452 static long __init write_buffer(char *buf, unsigned long len)
 453 {
 454         byte_count = len;
 455         victim = buf;
 456
 457         while (!actions[state]())
 458                 ;
 459         return len - byte_count;
 460 }
 461
 462 static long __init flush_buffer(void *bufv, unsigned long len)
 463 {
 464         char *buf = (char *) bufv;
 465         long written;
 466         long origLen = len;
 467         if (message)
 468                 return -1;
 469         while ((written = write_buffer(buf, len)) < len && !message) {
 470                 char c = buf[written];
 471                 if (c == '0') {
 472                         buf += written;
 473                         len -= written;
 474                         state = Start;
 475                 } else if (c == 0) {
 476                         buf += written;
 477                         len -= written;
 478                         state = Reset;
 479                 } else
 480                         error("junk within compressed archive");
 481         }
 482         return origLen;
 483 }
 484
 485 static unsigned long my_inptr; /* index of next byte to be processed in inbuf */
 486
 487 #include <linux/decompress/generic.h>
 488
 489 static char * __init unpack_to_rootfs(char *buf, unsigned long len)
 490 {
 491         long written;
 492         decompress_fn decompress;
 493         const char *compress_name;
 494         static __initdata char msg_buf[64];
 495
 496         header_buf = kmalloc(110, GFP_KERNEL);
 497         symlink_buf = kmalloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1, GFP_KERNEL);
 498         name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
 499
 500         if (!header_buf || !symlink_buf || !name_buf)
 501                 panic_show_mem("can't allocate buffers");
 502
 503         state = Start;
 504         this_header = 0;
 505         message = NULL;
 506         while (!message && len) {
 507                 loff_t saved_offset = this_header;
 508                 if (*buf == '0' && !(this_header & 3)) {
 509                         state = Start;
 510                         written = write_buffer(buf, len);
 511                         buf += written;
 512                         len -= written;
 513                         continue;
 514                 }
 515                 if (!*buf) {
 516                         buf++;
 517                         len--;
 518                         this_header++;
 519                         continue;
 520                 }
 521                 this_header = 0;
 522                 decompress = decompress_method(buf, len, &compress_name);
 523                 pr_debug("Detected %s compressed data\n", compress_name);
 524                 if (decompress) {
 525                         int res = decompress(buf, len, NULL, flush_buffer, NULL,
 526                                    &my_inptr, error);
 527                         if (res)
 528                                 error("decompressor failed");
 529                 } else if (compress_name) {
 530                         if (!message) {
 531                                 snprintf(msg_buf, sizeof msg_buf,
 532                                          "compression method %s not configured",
 533                                          compress_name);
 534                                 message = msg_buf;
 535                         }
 536                 } else
 537                         error("invalid magic at start of compressed archive");
 538                 if (state != Reset)
 539                         error("junk at the end of compressed archive");
 540                 this_header = saved_offset + my_inptr;
 541                 buf += my_inptr;
 542                 len -= my_inptr;
 543         }
 544         dir_utime();
 545         kfree(name_buf);
 546         kfree(symlink_buf);
 547         kfree(header_buf);
 548         return message;
 549 }
 550
 551 static int __initdata do_retain_initrd;
 552
 553 static int __init retain_initrd_param(char *str)
 554 {
 555         if (*str)
 556                 return 0;
 557         do_retain_initrd = 1;
 558         return 1;
 559 }
 560 __setup("retain_initrd", retain_initrd_param);
 561
 562 #ifdef CONFIG_ARCH_HAS_KEEPINITRD
 563 static int __init keepinitrd_setup(char *__unused)
 564 {
 565         do_retain_initrd = 1;
 566         return 1;
 567 }
 568 __setup("keepinitrd", keepinitrd_setup);
 569 #endif
 570
 571 static bool __initdata initramfs_async = true;
 572 static int __init initramfs_async_setup(char *str)
 573 {
 574         strtobool(str, &initramfs_async);
 575         return 1;
 576 }
 577 __setup("initramfs_async=", initramfs_async_setup);
 578
 579 extern char __initramfs_start[];
 580 extern unsigned long __initramfs_size;
 581 #include <linux/initrd.h>
 582 #include <linux/kexec.h>
 583
 584 void __init reserve_initrd_mem(void)
 585 {
 586         phys_addr_t start;
 587         unsigned long size;
 588
 589         /* Ignore the virtul address computed during device tree parsing */
 590         initrd_start = initrd_end = 0;
 591
 592         if (!phys_initrd_size)
 593                 return;
 594         /*
 595          * Round the memory region to page boundaries as per free_initrd_mem()
 596          * This allows us to detect whether the pages overlapping the initrd
 597          * are in use, but more importantly, reserves the entire set of pages
 598          * as we don't want these pages allocated for other purposes.
 599          */
 600         start = round_down(phys_initrd_start, PAGE_SIZE);
 601         size = phys_initrd_size + (phys_initrd_start - start);
 602         size = round_up(size, PAGE_SIZE);
 603
 604         if (!memblock_is_region_memory(start, size)) {
 605                 pr_err("INITRD: 0x%08llx+0x%08lx is not a memory region",
 606                        (u64)start, size);
 607                 goto disable;
 608         }
 609
 610         if (memblock_is_region_reserved(start, size)) {
 611                 pr_err("INITRD: 0x%08llx+0x%08lx overlaps in-use memory region\n",
 612                        (u64)start, size);
 613                 goto disable;
 614         }
 615
 616         memblock_reserve(start, size);
 617         /* Now convert initrd to virtual addresses */
 618         initrd_start = (unsigned long)__va(phys_initrd_start);
 619         initrd_end = initrd_start + phys_initrd_size;
 620         initrd_below_start_ok = 1;
 621
 622         return;
 623 disable:
 624         pr_cont(" - disabling initrd\n");
 625         initrd_start = 0;
 626         initrd_end = 0;
 627 }
 628
 629 void __weak __init free_initrd_mem(unsigned long start, unsigned long end)
 630 {
 631 #ifdef CONFIG_ARCH_KEEP_MEMBLOCK
 632         unsigned long aligned_start = ALIGN_DOWN(start, PAGE_SIZE);
 633         unsigned long aligned_end = ALIGN(end, PAGE_SIZE);
 634
 635         memblock_free((void *)aligned_start, aligned_end - aligned_start);
 636 #endif
 637
 638         free_reserved_area((void *)start, (void *)end, POISON_FREE_INITMEM,
 639                         "initrd");
 640 }
 641
 642 #ifdef CONFIG_KEXEC_CORE
 643 static bool __init kexec_free_initrd(void)
 644 {
 645         unsigned long crashk_start = (unsigned long)__va(crashk_res.start);
 646         unsigned long crashk_end   = (unsigned long)__va(crashk_res.end);
 647
 648         /*
 649          * If the initrd region is overlapped with crashkernel reserved region,
 650          * free only memory that is not part of crashkernel region.
 651          */
 652         if (initrd_start >= crashk_end || initrd_end <= crashk_start)
 653                 return false;
 654
 655         /*
 656          * Initialize initrd memory region since the kexec boot does not do.
 657          */
 658         memset((void *)initrd_start, 0, initrd_end - initrd_start);
 659         if (initrd_start < crashk_start)
 660                 free_initrd_mem(initrd_start, crashk_start);
 661         if (initrd_end > crashk_end)
 662                 free_initrd_mem(crashk_end, initrd_end);
 663         return true;
 664 }
 665 #else
 666 static inline bool kexec_free_initrd(void)
 667 {
 668         return false;
 669 }
 670 #endif /* CONFIG_KEXEC_CORE */
 671
 672 #ifdef CONFIG_BLK_DEV_RAM
 673 static void __init populate_initrd_image(char *err)
 674 {
 675         ssize_t written;
 676         struct file *file;
 677         loff_t pos = 0;
 678
 679         unpack_to_rootfs(__initramfs_start, __initramfs_size);
 680
 681         printk(KERN_INFO "rootfs image is not initramfs (%s); looks like an initrd\n",
 682                         err);
 683         file = filp_open("/initrd.image", O_WRONLY | O_CREAT, 0700);
 684         if (IS_ERR(file))
 685                 return;
 686
 687         written = xwrite(file, (char *)initrd_start, initrd_end - initrd_start,
 688                         &pos);
 689         if (written != initrd_end - initrd_start)
 690                 pr_err("/initrd.image: incomplete write (%zd != %ld)\n",
 691                        written, initrd_end - initrd_start);
 692         fput(file);
 693 }
 694 #endif /* CONFIG_BLK_DEV_RAM */
 695
 696 static void __init do_populate_rootfs(void *unused, async_cookie_t cookie)
 697 {
 698         /* Load the built in initramfs */
 699         char *err = unpack_to_rootfs(__initramfs_start, __initramfs_size);
 700         if (err)
 701                 panic_show_mem("%s", err); /* Failed to decompress INTERNAL initramfs */
 702
 703         if (!initrd_start || IS_ENABLED(CONFIG_INITRAMFS_FORCE))
 704                 goto done;
 705
 706         if (IS_ENABLED(CONFIG_BLK_DEV_RAM))
 707                 printk(KERN_INFO "Trying to unpack rootfs image as initramfs...\n");
 708         else
 709                 printk(KERN_INFO "Unpacking initramfs...\n");
 710
 711         err = unpack_to_rootfs((char *)initrd_start, initrd_end - initrd_start);
 712         if (err) {
 713 #ifdef CONFIG_BLK_DEV_RAM
 714                 populate_initrd_image(err);
 715 #else
 716                 printk(KERN_EMERG "Initramfs unpacking failed: %s\n", err);
 717 #endif
 718         }
 719
 720 done:
 721         /*
 722          * If the initrd region is overlapped with crashkernel reserved region,
 723          * free only memory that is not part of crashkernel region.
 724          */
 725         if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
 726                 free_initrd_mem(initrd_start, initrd_end);
 727         initrd_start = 0;
 728         initrd_end = 0;
 729
 730         flush_delayed_fput();
 731         task_work_run();
 732 }
 733
 734 static ASYNC_DOMAIN_EXCLUSIVE(initramfs_domain);
 735 static async_cookie_t initramfs_cookie;
 736
 737 void wait_for_initramfs(void)
 738 {
 739         if (!initramfs_cookie) {
 740                 /*
 741                  * Something before rootfs_initcall wants to access
 742                  * the filesystem/initramfs. Probably a bug. Make a
 743                  * note, avoid deadlocking the machine, and let the
 744                  * caller's access fail as it used to.
 745                  */
 746                 pr_warn_once("wait_for_initramfs() called before rootfs_initcalls\n");
 747                 return;
 748         }
 749         async_synchronize_cookie_domain(initramfs_cookie + 1, &initramfs_domain);
 750 }
 751 EXPORT_SYMBOL_GPL(wait_for_initramfs);
 752
 753 static int __init populate_rootfs(void)
 754 {
 755         initramfs_cookie = async_schedule_domain(do_populate_rootfs, NULL,
 756                                                  &initramfs_domain);
 757         usermodehelper_enable();
 758         if (!initramfs_async)
 759                 wait_for_initramfs();
 760         return 0;
 761 }
 762 rootfs_initcall(populate_rootfs);