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![Rasmus Villemoes](/assets/img/avatar_default.png)
Patch series "background initramfs unpacking, and CONFIG_MODPROBE_PATH", v3. These two patches are independent, but better-together. The second is a rather trivial patch that simply allows the developer to change "/sbin/modprobe" to something else - e.g. the empty string, so that all request_module() during early boot return -ENOENT early, without even spawning a usermode helper, needlessly synchronizing with the initramfs unpacking. The first patch delegates decompressing the initramfs to a worker thread, allowing do_initcalls() in main.c to proceed to the device_ and late_ initcalls without waiting for that decompression (and populating of rootfs) to finish. Obviously, some of those later calls may rely on the initramfs being available, so I've added synchronization points in the firmware loader and usermodehelper paths - there might be other places that would need this, but so far no one has been able to think of any places I have missed. There's not much to win if most of the functionality needed during boot is only available as modules. But systems with a custom-made .config and initramfs can boot faster, partly due to utilizing more than one cpu earlier, partly by avoiding known-futile modprobe calls (which would still trigger synchronization with the initramfs unpacking, thus eliminating most of the first benefit). This patch (of 2): Most of the boot process doesn't actually need anything from the initramfs, until of course PID1 is to be executed. So instead of doing the decompressing and populating of the initramfs synchronously in populate_rootfs() itself, push that off to a worker thread. This is primarily motivated by an embedded ppc target, where unpacking even the rather modest sized initramfs takes 0.6 seconds, which is long enough that the external watchdog becomes unhappy that it doesn't get attention soon enough. By doing the initramfs decompression in a worker thread, we get to do the device_initcalls and hence start petting the watchdog much sooner. Normal desktops might benefit as well. On my mostly stock Ubuntu kernel, my initramfs is a 26M xz-compressed blob, decompressing to around 126M. That takes almost two seconds: [ 0.201454] Trying to unpack rootfs image as initramfs... [ 1.976633] Freeing initrd memory: 29416K Before this patch, these lines occur consecutively in dmesg. With this patch, the timestamps on these two lines is roughly the same as above, but with 172 lines inbetween - so more than one cpu has been kept busy doing work that would otherwise only happen after the populate_rootfs() finished. Should one of the initcalls done after rootfs_initcall time (i.e., device_ and late_ initcalls) need something from the initramfs (say, a kernel module or a firmware blob), it will simply wait for the initramfs unpacking to be done before proceeding, which should in theory make this completely safe. But if some driver pokes around in the filesystem directly and not via one of the official kernel interfaces (i.e. request_firmware*(), call_usermodehelper*) that theory may not hold - also, I certainly might have missed a spot when sprinkling wait_for_initramfs(). So there is an escape hatch in the form of an initramfs_async= command line parameter. Link: https://lkml.kernel.org/r/20210313212528.2956377-1-linux@rasmusvillemoes.dk Link: https://lkml.kernel.org/r/20210313212528.2956377-2-linux@rasmusvillemoes.dk Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Cc: Jessica Yu <jeyu@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
734 lines
16 KiB
C
734 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/init.h>
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#include <linux/async.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/fcntl.h>
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#include <linux/delay.h>
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#include <linux/string.h>
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#include <linux/dirent.h>
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#include <linux/syscalls.h>
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#include <linux/utime.h>
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#include <linux/file.h>
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#include <linux/memblock.h>
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#include <linux/mm.h>
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#include <linux/namei.h>
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#include <linux/init_syscalls.h>
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static ssize_t __init xwrite(struct file *file, const char *p, size_t count,
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loff_t *pos)
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{
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ssize_t out = 0;
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/* sys_write only can write MAX_RW_COUNT aka 2G-4K bytes at most */
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while (count) {
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ssize_t rv = kernel_write(file, p, count, pos);
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if (rv < 0) {
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if (rv == -EINTR || rv == -EAGAIN)
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continue;
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return out ? out : rv;
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} else if (rv == 0)
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break;
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p += rv;
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out += rv;
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count -= rv;
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}
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return out;
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}
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static __initdata char *message;
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static void __init error(char *x)
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{
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if (!message)
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message = x;
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}
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static void panic_show_mem(const char *fmt, ...)
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{
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va_list args;
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show_mem(0, NULL);
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va_start(args, fmt);
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panic(fmt, args);
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va_end(args);
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}
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/* link hash */
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#define N_ALIGN(len) ((((len) + 1) & ~3) + 2)
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static __initdata struct hash {
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int ino, minor, major;
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umode_t mode;
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struct hash *next;
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char name[N_ALIGN(PATH_MAX)];
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} *head[32];
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static inline int hash(int major, int minor, int ino)
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{
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unsigned long tmp = ino + minor + (major << 3);
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tmp += tmp >> 5;
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return tmp & 31;
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}
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static char __init *find_link(int major, int minor, int ino,
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umode_t mode, char *name)
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{
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struct hash **p, *q;
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for (p = head + hash(major, minor, ino); *p; p = &(*p)->next) {
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if ((*p)->ino != ino)
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continue;
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if ((*p)->minor != minor)
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continue;
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if ((*p)->major != major)
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continue;
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if (((*p)->mode ^ mode) & S_IFMT)
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continue;
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return (*p)->name;
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}
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q = kmalloc(sizeof(struct hash), GFP_KERNEL);
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if (!q)
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panic_show_mem("can't allocate link hash entry");
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q->major = major;
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q->minor = minor;
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q->ino = ino;
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q->mode = mode;
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strcpy(q->name, name);
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q->next = NULL;
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*p = q;
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return NULL;
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}
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static void __init free_hash(void)
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{
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struct hash **p, *q;
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for (p = head; p < head + 32; p++) {
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while (*p) {
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q = *p;
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*p = q->next;
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kfree(q);
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}
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}
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}
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static long __init do_utime(char *filename, time64_t mtime)
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{
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struct timespec64 t[2];
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t[0].tv_sec = mtime;
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t[0].tv_nsec = 0;
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t[1].tv_sec = mtime;
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t[1].tv_nsec = 0;
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return init_utimes(filename, t);
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}
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static __initdata LIST_HEAD(dir_list);
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struct dir_entry {
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struct list_head list;
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char *name;
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time64_t mtime;
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};
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static void __init dir_add(const char *name, time64_t mtime)
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{
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struct dir_entry *de = kmalloc(sizeof(struct dir_entry), GFP_KERNEL);
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if (!de)
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panic_show_mem("can't allocate dir_entry buffer");
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INIT_LIST_HEAD(&de->list);
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de->name = kstrdup(name, GFP_KERNEL);
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de->mtime = mtime;
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list_add(&de->list, &dir_list);
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}
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static void __init dir_utime(void)
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{
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struct dir_entry *de, *tmp;
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list_for_each_entry_safe(de, tmp, &dir_list, list) {
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list_del(&de->list);
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do_utime(de->name, de->mtime);
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kfree(de->name);
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kfree(de);
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}
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}
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static __initdata time64_t mtime;
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/* cpio header parsing */
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static __initdata unsigned long ino, major, minor, nlink;
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static __initdata umode_t mode;
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static __initdata unsigned long body_len, name_len;
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static __initdata uid_t uid;
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static __initdata gid_t gid;
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static __initdata unsigned rdev;
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static void __init parse_header(char *s)
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{
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unsigned long parsed[12];
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char buf[9];
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int i;
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buf[8] = '\0';
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for (i = 0, s += 6; i < 12; i++, s += 8) {
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memcpy(buf, s, 8);
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parsed[i] = simple_strtoul(buf, NULL, 16);
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}
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ino = parsed[0];
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mode = parsed[1];
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uid = parsed[2];
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gid = parsed[3];
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nlink = parsed[4];
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mtime = parsed[5]; /* breaks in y2106 */
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body_len = parsed[6];
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major = parsed[7];
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minor = parsed[8];
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rdev = new_encode_dev(MKDEV(parsed[9], parsed[10]));
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name_len = parsed[11];
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}
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/* FSM */
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static __initdata enum state {
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Start,
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Collect,
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GotHeader,
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SkipIt,
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GotName,
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CopyFile,
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GotSymlink,
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Reset
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} state, next_state;
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static __initdata char *victim;
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static unsigned long byte_count __initdata;
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static __initdata loff_t this_header, next_header;
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static inline void __init eat(unsigned n)
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{
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victim += n;
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this_header += n;
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byte_count -= n;
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}
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static __initdata char *collected;
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static long remains __initdata;
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static __initdata char *collect;
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static void __init read_into(char *buf, unsigned size, enum state next)
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{
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if (byte_count >= size) {
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collected = victim;
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eat(size);
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state = next;
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} else {
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collect = collected = buf;
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remains = size;
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next_state = next;
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state = Collect;
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}
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}
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static __initdata char *header_buf, *symlink_buf, *name_buf;
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static int __init do_start(void)
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{
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read_into(header_buf, 110, GotHeader);
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return 0;
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}
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static int __init do_collect(void)
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{
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unsigned long n = remains;
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if (byte_count < n)
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n = byte_count;
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memcpy(collect, victim, n);
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eat(n);
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collect += n;
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if ((remains -= n) != 0)
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return 1;
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state = next_state;
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return 0;
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}
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static int __init do_header(void)
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{
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if (memcmp(collected, "070707", 6)==0) {
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error("incorrect cpio method used: use -H newc option");
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return 1;
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}
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if (memcmp(collected, "070701", 6)) {
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error("no cpio magic");
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return 1;
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}
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parse_header(collected);
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next_header = this_header + N_ALIGN(name_len) + body_len;
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next_header = (next_header + 3) & ~3;
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state = SkipIt;
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if (name_len <= 0 || name_len > PATH_MAX)
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return 0;
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if (S_ISLNK(mode)) {
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if (body_len > PATH_MAX)
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return 0;
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collect = collected = symlink_buf;
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remains = N_ALIGN(name_len) + body_len;
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next_state = GotSymlink;
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state = Collect;
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return 0;
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}
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if (S_ISREG(mode) || !body_len)
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read_into(name_buf, N_ALIGN(name_len), GotName);
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return 0;
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}
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static int __init do_skip(void)
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{
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if (this_header + byte_count < next_header) {
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eat(byte_count);
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return 1;
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} else {
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eat(next_header - this_header);
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state = next_state;
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return 0;
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}
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}
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static int __init do_reset(void)
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{
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while (byte_count && *victim == '\0')
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eat(1);
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if (byte_count && (this_header & 3))
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error("broken padding");
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return 1;
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}
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static void __init clean_path(char *path, umode_t fmode)
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{
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struct kstat st;
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if (!init_stat(path, &st, AT_SYMLINK_NOFOLLOW) &&
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(st.mode ^ fmode) & S_IFMT) {
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if (S_ISDIR(st.mode))
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init_rmdir(path);
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else
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init_unlink(path);
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}
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}
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static int __init maybe_link(void)
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{
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if (nlink >= 2) {
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char *old = find_link(major, minor, ino, mode, collected);
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if (old) {
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clean_path(collected, 0);
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return (init_link(old, collected) < 0) ? -1 : 1;
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}
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}
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return 0;
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}
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static __initdata struct file *wfile;
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static __initdata loff_t wfile_pos;
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static int __init do_name(void)
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{
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state = SkipIt;
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next_state = Reset;
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if (strcmp(collected, "TRAILER!!!") == 0) {
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free_hash();
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return 0;
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}
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clean_path(collected, mode);
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if (S_ISREG(mode)) {
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int ml = maybe_link();
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if (ml >= 0) {
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int openflags = O_WRONLY|O_CREAT;
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if (ml != 1)
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openflags |= O_TRUNC;
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wfile = filp_open(collected, openflags, mode);
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if (IS_ERR(wfile))
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return 0;
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wfile_pos = 0;
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vfs_fchown(wfile, uid, gid);
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vfs_fchmod(wfile, mode);
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if (body_len)
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vfs_truncate(&wfile->f_path, body_len);
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state = CopyFile;
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}
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} else if (S_ISDIR(mode)) {
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init_mkdir(collected, mode);
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init_chown(collected, uid, gid, 0);
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init_chmod(collected, mode);
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dir_add(collected, mtime);
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} else if (S_ISBLK(mode) || S_ISCHR(mode) ||
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S_ISFIFO(mode) || S_ISSOCK(mode)) {
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if (maybe_link() == 0) {
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init_mknod(collected, mode, rdev);
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init_chown(collected, uid, gid, 0);
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init_chmod(collected, mode);
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do_utime(collected, mtime);
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}
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}
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return 0;
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}
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static int __init do_copy(void)
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{
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if (byte_count >= body_len) {
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struct timespec64 t[2] = { };
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if (xwrite(wfile, victim, body_len, &wfile_pos) != body_len)
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error("write error");
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t[0].tv_sec = mtime;
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t[1].tv_sec = mtime;
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vfs_utimes(&wfile->f_path, t);
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fput(wfile);
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eat(body_len);
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state = SkipIt;
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return 0;
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} else {
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if (xwrite(wfile, victim, byte_count, &wfile_pos) != byte_count)
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error("write error");
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body_len -= byte_count;
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eat(byte_count);
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return 1;
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}
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}
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static int __init do_symlink(void)
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{
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collected[N_ALIGN(name_len) + body_len] = '\0';
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clean_path(collected, 0);
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init_symlink(collected + N_ALIGN(name_len), collected);
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init_chown(collected, uid, gid, AT_SYMLINK_NOFOLLOW);
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do_utime(collected, mtime);
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state = SkipIt;
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next_state = Reset;
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return 0;
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}
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static __initdata int (*actions[])(void) = {
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[Start] = do_start,
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[Collect] = do_collect,
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[GotHeader] = do_header,
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[SkipIt] = do_skip,
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[GotName] = do_name,
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[CopyFile] = do_copy,
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[GotSymlink] = do_symlink,
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[Reset] = do_reset,
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};
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static long __init write_buffer(char *buf, unsigned long len)
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{
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byte_count = len;
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victim = buf;
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while (!actions[state]())
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;
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return len - byte_count;
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}
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static long __init flush_buffer(void *bufv, unsigned long len)
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{
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char *buf = (char *) bufv;
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long written;
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long origLen = len;
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if (message)
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return -1;
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while ((written = write_buffer(buf, len)) < len && !message) {
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char c = buf[written];
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if (c == '0') {
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buf += written;
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len -= written;
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state = Start;
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} else if (c == 0) {
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buf += written;
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len -= written;
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state = Reset;
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} else
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error("junk within compressed archive");
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}
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return origLen;
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}
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|
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static unsigned long my_inptr; /* index of next byte to be processed in inbuf */
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#include <linux/decompress/generic.h>
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static char * __init unpack_to_rootfs(char *buf, unsigned long len)
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{
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long written;
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decompress_fn decompress;
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const char *compress_name;
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static __initdata char msg_buf[64];
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header_buf = kmalloc(110, GFP_KERNEL);
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symlink_buf = kmalloc(PATH_MAX + N_ALIGN(PATH_MAX) + 1, GFP_KERNEL);
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name_buf = kmalloc(N_ALIGN(PATH_MAX), GFP_KERNEL);
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if (!header_buf || !symlink_buf || !name_buf)
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panic_show_mem("can't allocate buffers");
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state = Start;
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this_header = 0;
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message = NULL;
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while (!message && len) {
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loff_t saved_offset = this_header;
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if (*buf == '0' && !(this_header & 3)) {
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state = Start;
|
|
written = write_buffer(buf, len);
|
|
buf += written;
|
|
len -= written;
|
|
continue;
|
|
}
|
|
if (!*buf) {
|
|
buf++;
|
|
len--;
|
|
this_header++;
|
|
continue;
|
|
}
|
|
this_header = 0;
|
|
decompress = decompress_method(buf, len, &compress_name);
|
|
pr_debug("Detected %s compressed data\n", compress_name);
|
|
if (decompress) {
|
|
int res = decompress(buf, len, NULL, flush_buffer, NULL,
|
|
&my_inptr, error);
|
|
if (res)
|
|
error("decompressor failed");
|
|
} else if (compress_name) {
|
|
if (!message) {
|
|
snprintf(msg_buf, sizeof msg_buf,
|
|
"compression method %s not configured",
|
|
compress_name);
|
|
message = msg_buf;
|
|
}
|
|
} else
|
|
error("invalid magic at start of compressed archive");
|
|
if (state != Reset)
|
|
error("junk at the end of compressed archive");
|
|
this_header = saved_offset + my_inptr;
|
|
buf += my_inptr;
|
|
len -= my_inptr;
|
|
}
|
|
dir_utime();
|
|
kfree(name_buf);
|
|
kfree(symlink_buf);
|
|
kfree(header_buf);
|
|
return message;
|
|
}
|
|
|
|
static int __initdata do_retain_initrd;
|
|
|
|
static int __init retain_initrd_param(char *str)
|
|
{
|
|
if (*str)
|
|
return 0;
|
|
do_retain_initrd = 1;
|
|
return 1;
|
|
}
|
|
__setup("retain_initrd", retain_initrd_param);
|
|
|
|
#ifdef CONFIG_ARCH_HAS_KEEPINITRD
|
|
static int __init keepinitrd_setup(char *__unused)
|
|
{
|
|
do_retain_initrd = 1;
|
|
return 1;
|
|
}
|
|
__setup("keepinitrd", keepinitrd_setup);
|
|
#endif
|
|
|
|
static bool __initdata initramfs_async = true;
|
|
static int __init initramfs_async_setup(char *str)
|
|
{
|
|
strtobool(str, &initramfs_async);
|
|
return 1;
|
|
}
|
|
__setup("initramfs_async=", initramfs_async_setup);
|
|
|
|
extern char __initramfs_start[];
|
|
extern unsigned long __initramfs_size;
|
|
#include <linux/initrd.h>
|
|
#include <linux/kexec.h>
|
|
|
|
void __init reserve_initrd_mem(void)
|
|
{
|
|
phys_addr_t start;
|
|
unsigned long size;
|
|
|
|
/* Ignore the virtul address computed during device tree parsing */
|
|
initrd_start = initrd_end = 0;
|
|
|
|
if (!phys_initrd_size)
|
|
return;
|
|
/*
|
|
* Round the memory region to page boundaries as per free_initrd_mem()
|
|
* This allows us to detect whether the pages overlapping the initrd
|
|
* are in use, but more importantly, reserves the entire set of pages
|
|
* as we don't want these pages allocated for other purposes.
|
|
*/
|
|
start = round_down(phys_initrd_start, PAGE_SIZE);
|
|
size = phys_initrd_size + (phys_initrd_start - start);
|
|
size = round_up(size, PAGE_SIZE);
|
|
|
|
if (!memblock_is_region_memory(start, size)) {
|
|
pr_err("INITRD: 0x%08llx+0x%08lx is not a memory region",
|
|
(u64)start, size);
|
|
goto disable;
|
|
}
|
|
|
|
if (memblock_is_region_reserved(start, size)) {
|
|
pr_err("INITRD: 0x%08llx+0x%08lx overlaps in-use memory region\n",
|
|
(u64)start, size);
|
|
goto disable;
|
|
}
|
|
|
|
memblock_reserve(start, size);
|
|
/* Now convert initrd to virtual addresses */
|
|
initrd_start = (unsigned long)__va(phys_initrd_start);
|
|
initrd_end = initrd_start + phys_initrd_size;
|
|
initrd_below_start_ok = 1;
|
|
|
|
return;
|
|
disable:
|
|
pr_cont(" - disabling initrd\n");
|
|
initrd_start = 0;
|
|
initrd_end = 0;
|
|
}
|
|
|
|
void __weak __init free_initrd_mem(unsigned long start, unsigned long end)
|
|
{
|
|
#ifdef CONFIG_ARCH_KEEP_MEMBLOCK
|
|
unsigned long aligned_start = ALIGN_DOWN(start, PAGE_SIZE);
|
|
unsigned long aligned_end = ALIGN(end, PAGE_SIZE);
|
|
|
|
memblock_free(__pa(aligned_start), aligned_end - aligned_start);
|
|
#endif
|
|
|
|
free_reserved_area((void *)start, (void *)end, POISON_FREE_INITMEM,
|
|
"initrd");
|
|
}
|
|
|
|
#ifdef CONFIG_KEXEC_CORE
|
|
static bool __init kexec_free_initrd(void)
|
|
{
|
|
unsigned long crashk_start = (unsigned long)__va(crashk_res.start);
|
|
unsigned long crashk_end = (unsigned long)__va(crashk_res.end);
|
|
|
|
/*
|
|
* If the initrd region is overlapped with crashkernel reserved region,
|
|
* free only memory that is not part of crashkernel region.
|
|
*/
|
|
if (initrd_start >= crashk_end || initrd_end <= crashk_start)
|
|
return false;
|
|
|
|
/*
|
|
* Initialize initrd memory region since the kexec boot does not do.
|
|
*/
|
|
memset((void *)initrd_start, 0, initrd_end - initrd_start);
|
|
if (initrd_start < crashk_start)
|
|
free_initrd_mem(initrd_start, crashk_start);
|
|
if (initrd_end > crashk_end)
|
|
free_initrd_mem(crashk_end, initrd_end);
|
|
return true;
|
|
}
|
|
#else
|
|
static inline bool kexec_free_initrd(void)
|
|
{
|
|
return false;
|
|
}
|
|
#endif /* CONFIG_KEXEC_CORE */
|
|
|
|
#ifdef CONFIG_BLK_DEV_RAM
|
|
static void __init populate_initrd_image(char *err)
|
|
{
|
|
ssize_t written;
|
|
struct file *file;
|
|
loff_t pos = 0;
|
|
|
|
unpack_to_rootfs(__initramfs_start, __initramfs_size);
|
|
|
|
printk(KERN_INFO "rootfs image is not initramfs (%s); looks like an initrd\n",
|
|
err);
|
|
file = filp_open("/initrd.image", O_WRONLY | O_CREAT, 0700);
|
|
if (IS_ERR(file))
|
|
return;
|
|
|
|
written = xwrite(file, (char *)initrd_start, initrd_end - initrd_start,
|
|
&pos);
|
|
if (written != initrd_end - initrd_start)
|
|
pr_err("/initrd.image: incomplete write (%zd != %ld)\n",
|
|
written, initrd_end - initrd_start);
|
|
fput(file);
|
|
}
|
|
#endif /* CONFIG_BLK_DEV_RAM */
|
|
|
|
static void __init do_populate_rootfs(void *unused, async_cookie_t cookie)
|
|
{
|
|
/* Load the built in initramfs */
|
|
char *err = unpack_to_rootfs(__initramfs_start, __initramfs_size);
|
|
if (err)
|
|
panic_show_mem("%s", err); /* Failed to decompress INTERNAL initramfs */
|
|
|
|
if (!initrd_start || IS_ENABLED(CONFIG_INITRAMFS_FORCE))
|
|
goto done;
|
|
|
|
if (IS_ENABLED(CONFIG_BLK_DEV_RAM))
|
|
printk(KERN_INFO "Trying to unpack rootfs image as initramfs...\n");
|
|
else
|
|
printk(KERN_INFO "Unpacking initramfs...\n");
|
|
|
|
err = unpack_to_rootfs((char *)initrd_start, initrd_end - initrd_start);
|
|
if (err) {
|
|
#ifdef CONFIG_BLK_DEV_RAM
|
|
populate_initrd_image(err);
|
|
#else
|
|
printk(KERN_EMERG "Initramfs unpacking failed: %s\n", err);
|
|
#endif
|
|
}
|
|
|
|
done:
|
|
/*
|
|
* If the initrd region is overlapped with crashkernel reserved region,
|
|
* free only memory that is not part of crashkernel region.
|
|
*/
|
|
if (!do_retain_initrd && initrd_start && !kexec_free_initrd())
|
|
free_initrd_mem(initrd_start, initrd_end);
|
|
initrd_start = 0;
|
|
initrd_end = 0;
|
|
|
|
flush_delayed_fput();
|
|
}
|
|
|
|
static ASYNC_DOMAIN_EXCLUSIVE(initramfs_domain);
|
|
static async_cookie_t initramfs_cookie;
|
|
|
|
void wait_for_initramfs(void)
|
|
{
|
|
if (!initramfs_cookie) {
|
|
/*
|
|
* Something before rootfs_initcall wants to access
|
|
* the filesystem/initramfs. Probably a bug. Make a
|
|
* note, avoid deadlocking the machine, and let the
|
|
* caller's access fail as it used to.
|
|
*/
|
|
pr_warn_once("wait_for_initramfs() called before rootfs_initcalls\n");
|
|
return;
|
|
}
|
|
async_synchronize_cookie_domain(initramfs_cookie + 1, &initramfs_domain);
|
|
}
|
|
EXPORT_SYMBOL_GPL(wait_for_initramfs);
|
|
|
|
static int __init populate_rootfs(void)
|
|
{
|
|
initramfs_cookie = async_schedule_domain(do_populate_rootfs, NULL,
|
|
&initramfs_domain);
|
|
if (!initramfs_async)
|
|
wait_for_initramfs();
|
|
return 0;
|
|
}
|
|
rootfs_initcall(populate_rootfs);
|