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Systemd/src/gpt-auto-generator/gpt-auto-generator.c
Lennart Poettering 73b80ec2d9 gpt-auto-generator: automatically find the root disk of the system 
When run in an initrd and no root= argument is set (or is set to
root=gpt-auto) we will automatically look for the root partition on the
same disk the EFI ESP is located on.

Since we look for swap, /home and /srv on the disk the root partition is
located on, we hence have a fully discoverable chain:

    Firmware discovers the EFI ESP partition → the initrd discovers the
    root partition → the host OS discovers swap, /home, and /srv.

Note that this requires an EFI boot loader that sets the
LoaderDevicePartUUID EFI variable, such as Gummiboot.
2014-03-07 04:31:26 +01:00

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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/statfs.h>
#include <blkid/blkid.h>
#ifdef HAVE_LINUX_BTRFS_H
#include <linux/btrfs.h>
#endif
#include "sd-id128.h"
#include "libudev.h"
#include "path-util.h"
#include "util.h"
#include "mkdir.h"
#include "missing.h"
#include "udev-util.h"
#include "special.h"
#include "unit-name.h"
#include "virt.h"
#include "generator.h"
#include "gpt.h"
#include "fileio.h"
#include "efivars.h"
static const char *arg_dest = "/tmp";
static bool arg_enabled = true;
static bool arg_root_enabled = true;
static bool arg_root_rw = false;
DEFINE_TRIVIAL_CLEANUP_FUNC(blkid_probe, blkid_free_probe);
#define _cleanup_blkid_freep_probe_ _cleanup_(blkid_free_probep)
static int verify_gpt_partition(const char *node, sd_id128_t *type, unsigned *nr, char **fstype) {
_cleanup_blkid_freep_probe_ blkid_probe b = NULL;
const char *v;
int r;
errno = 0;
b = blkid_new_probe_from_filename(node);
if (!b)
return errno != 0 ? -errno : -ENOMEM;
blkid_probe_enable_superblocks(b, 1);
blkid_probe_set_superblocks_flags(b, BLKID_SUBLKS_TYPE);
blkid_probe_enable_partitions(b, 1);
blkid_probe_set_partitions_flags(b, BLKID_PARTS_ENTRY_DETAILS);
errno = 0;
r = blkid_do_safeprobe(b);
if (r == -2 || r == 1) /* no result or uncertain */
return -EBADSLT;
else if (r != 0)
return errno ? -errno : -EIO;
errno = 0;
r = blkid_probe_lookup_value(b, "PART_ENTRY_SCHEME", &v, NULL);
if (r != 0)
/* return 0 if we're not on GPT */
return errno ? -errno : 0;
if (strcmp(v, "gpt") != 0)
return 0;
if (type) {
errno = 0;
r = blkid_probe_lookup_value(b, "PART_ENTRY_TYPE", &v, NULL);
if (r != 0)
return errno ? -errno : -EIO;
r = sd_id128_from_string(v, type);
if (r < 0)
return r;
}
if (nr) {
errno = 0;
r = blkid_probe_lookup_value(b, "PART_ENTRY_NUMBER", &v, NULL);
if (r != 0)
return errno ? -errno : -EIO;
r = safe_atou(v, nr);
if (r < 0)
return r;
}
if (fstype) {
errno = 0;
r = blkid_probe_lookup_value(b, "TYPE", &v, NULL);
if (r != 0)
*fstype = NULL;
else {
char *fst;
fst = strdup(v);
if (!fst)
return -ENOMEM;
*fstype = fst;
}
}
return 1;
}
static int add_swap(const char *path, const char *fstype) {
_cleanup_free_ char *name = NULL, *unit = NULL, *lnk = NULL;
_cleanup_fclose_ FILE *f = NULL;
log_debug("Adding swap: %s %s", path, fstype);
name = unit_name_from_path(path, ".swap");
if (!name)
return log_oom();
unit = strjoin(arg_dest, "/", name, NULL);
if (!unit)
return log_oom();
f = fopen(unit, "wxe");
if (!f) {
log_error("Failed to create unit file %s: %m", unit);
return -errno;
}
fprintf(f,
"# Automatically generated by systemd-gpt-auto-generator\n\n"
"[Unit]\n"
"Description=Swap Partition\n"
"Documentation=man:systemd-gpt-auto-generator(8)\n\n"
"[Swap]\n"
"What=%s\n",
path);
fflush(f);
if (ferror(f)) {
log_error("Failed to write unit file %s: %m", unit);
return -errno;
}
lnk = strjoin(arg_dest, "/" SPECIAL_SWAP_TARGET ".wants/", name, NULL);
if (!lnk)
return log_oom();
mkdir_parents_label(lnk, 0755);
if (symlink(unit, lnk) < 0) {
log_error("Failed to create symlink %s: %m", lnk);
return -errno;
}
return 0;
}
static int add_cryptsetup(const char *id, const char *what, char **device) {
_cleanup_free_ char *e = NULL, *n = NULL, *p = NULL, *d = NULL, *to = NULL;
_cleanup_fclose_ FILE *f = NULL;
char *from, *ret;
int r;
assert(id);
assert(what);
assert(device);
d = unit_name_from_path(what, ".device");
if (!d)
return log_oom();
e = unit_name_escape(id);
if (!e)
return log_oom();
n = unit_name_build("systemd-cryptsetup", e, ".service");
if (!n)
return log_oom();
p = strjoin(arg_dest, "/", n, NULL);
if (!n)
return log_oom();
f = fopen(p, "wxe");
if (!f) {
log_error("Failed to create unit file %s: %m", p);
return -errno;
}
fprintf(f,
"# Automatically generated by systemd-gpt-auto-generator\n\n"
"[Unit]\n"
"Description=Cryptography Setup for %%I\n"
"Documentation=man:systemd-gpt-auto-generator(8) man:systemd-cryptsetup@.service(8)\n"
"DefaultDependencies=no\n"
"Conflicts=umount.target\n"
"BindsTo=dev-mapper-%%i.device %s\n"
"Before=umount.target cryptsetup.target\n"
"After=%s\n"
"IgnoreOnIsolate=true\n"
"After=systemd-readahead-collect.service systemd-readahead-replay.service\n\n"
"[Service]\n"
"Type=oneshot\n"
"RemainAfterExit=yes\n"
"TimeoutSec=0\n" /* the binary handles timeouts anyway */
"ExecStart=" SYSTEMD_CRYPTSETUP_PATH " attach '%s' '%s'\n"
"ExecStop=" SYSTEMD_CRYPTSETUP_PATH " detach '%s'\n",
d, d,
id, what,
id);
fflush(f);
if (ferror(f)) {
log_error("Failed to write file %s: %m", p);
return -errno;
}
from = strappenda("../", n);
to = strjoin(arg_dest, "/", d, ".wants/", n, NULL);
if (!to)
return log_oom();
mkdir_parents_label(to, 0755);
if (symlink(from, to) < 0) {
log_error("Failed to create symlink %s: %m", to);
return -errno;
}
free(to);
to = strjoin(arg_dest, "/cryptsetup.target.requires/", n, NULL);
if (!to)
return log_oom();
mkdir_parents_label(to, 0755);
if (symlink(from, to) < 0) {
log_error("Failed to create symlink %s: %m", to);
return -errno;
}
free(to);
to = strjoin(arg_dest, "/dev-mapper-", e, ".device.requires/", n, NULL);
if (!to)
return log_oom();
mkdir_parents_label(to, 0755);
if (symlink(from, to) < 0) {
log_error("Failed to create symlink %s: %m", to);
return -errno;
}
free(p);
p = strjoin(arg_dest, "/dev-mapper-", e, ".device.d/50-job-timeout-sec-0.conf", NULL);
if (!p)
return log_oom();
mkdir_parents_label(p, 0755);
r = write_string_file(p,
"# Automatically generated by systemd-gpt-auto-generator\n\n"
"[Unit]\n"
"JobTimeoutSec=0\n"); /* the binary handles timeouts anyway */
if (r < 0) {
log_error("Failed to write device drop-in: %s", strerror(-r));
return r;
}
ret = strappend("/dev/mapper/", id);
if (!ret)
return log_oom();
*device = ret;
return 0;
}
static int add_mount(
const char *id,
const char *what,
const char *where,
const char *fstype,
const char *options,
const char *description,
const char *post) {
_cleanup_free_ char *unit = NULL, *lnk = NULL, *crypto_what = NULL, *p = NULL;
_cleanup_fclose_ FILE *f = NULL;
int r;
assert(id);
assert(what);
assert(where);
assert(description);
if (path_is_mount_point(where, true) <= 0 &&
dir_is_empty(where) <= 0) {
log_debug("%s already populated, ignoring.", where);
return 0;
}
log_debug("Adding %s: %s %s", where, what, strna(fstype));
if (streq_ptr(fstype, "crypto_LUKS")) {
r = add_cryptsetup(id, what, &crypto_what);
if (r < 0)
return r;
what = crypto_what;
fstype = NULL;
}
unit = unit_name_from_path(where, ".mount");
if (!unit)
return log_oom();
p = strjoin(arg_dest, "/", unit, NULL);
if (!p)
return log_oom();
f = fopen(p, "wxe");
if (!f) {
log_error("Failed to create unit file %s: %m", unit);
return -errno;
}
fprintf(f,
"# Automatically generated by systemd-gpt-auto-generator\n\n"
"[Unit]\n"
"Description=%s\n"
"Documentation=man:systemd-gpt-auto-generator(8)\n",
description);
if (post)
fprintf(f, "Before=%s\n", post);
r = generator_write_fsck_deps(f, arg_dest, what, where, fstype);
if (r < 0)
return r;
fprintf(f,
"\n"
"[Mount]\n"
"What=%s\n"
"Where=%s\n",
what, where);
if (fstype)
fprintf(f, "Type=%s\n", fstype);
if (options)
fprintf(f, "Options=%s\n", options);
fflush(f);
if (ferror(f)) {
log_error("Failed to write unit file %s: %m", p);
return -errno;
}
if (post) {
lnk = strjoin(arg_dest, "/", post, ".requires/", unit, NULL);
if (!lnk)
return log_oom();
mkdir_parents_label(lnk, 0755);
if (symlink(p, lnk) < 0) {
log_error("Failed to create symlink %s: %m", lnk);
return -errno;
}
}
return 0;
}
static int enumerate_partitions(struct udev *udev, dev_t dev) {
_cleanup_udev_enumerate_unref_ struct udev_enumerate *e = NULL;
_cleanup_udev_device_unref_ struct udev_device *d = NULL;
_cleanup_free_ char *home = NULL, *home_fstype = NULL, *srv = NULL, *srv_fstype = NULL;
unsigned home_nr = (unsigned) -1, srv_nr = (unsigned )-1;
struct udev_list_entry *first, *item;
struct udev_device *parent = NULL;
int r, k;
e = udev_enumerate_new(udev);
if (!e)
return log_oom();
d = udev_device_new_from_devnum(udev, 'b', dev);
if (!d)
return log_oom();
parent = udev_device_get_parent(d);
if (!parent)
return log_oom();
r = udev_enumerate_add_match_parent(e, parent);
if (r < 0)
return log_oom();
r = udev_enumerate_add_match_subsystem(e, "block");
if (r < 0)
return log_oom();
r = udev_enumerate_scan_devices(e);
if (r < 0) {
log_error("Failed to enumerate partitions on /dev/block/%u:%u: %s", major(dev), minor(dev), strerror(-r));
return r;
}
r = 0;
first = udev_enumerate_get_list_entry(e);
udev_list_entry_foreach(item, first) {
_cleanup_udev_device_unref_ struct udev_device *q;
_cleanup_free_ char *fstype = NULL;
const char *node = NULL;
sd_id128_t type_id;
unsigned nr;
q = udev_device_new_from_syspath(udev, udev_list_entry_get_name(item));
if (!q)
return log_oom();
if (udev_device_get_devnum(q) == udev_device_get_devnum(d))
continue;
if (udev_device_get_devnum(q) == udev_device_get_devnum(parent))
continue;
node = udev_device_get_devnode(q);
if (!node)
return log_oom();
k = verify_gpt_partition(node, &type_id, &nr, &fstype);
if (k < 0) {
/* skip child devices which are not detected properly */
if (k == -EBADSLT)
continue;
log_error("Failed to verify GPT partition %s: %s", node, strerror(-k));
r = k;
continue;
}
if (k == 0)
continue;
if (sd_id128_equal(type_id, GPT_SWAP)) {
k = add_swap(node, fstype);
if (k < 0)
r = k;
} else if (sd_id128_equal(type_id, GPT_HOME)) {
/* We only care for the first /home partition */
if (home && nr >= home_nr)
continue;
home_nr = nr;
free(home);
home = strdup(node);
if (!home)
return log_oom();
free(home_fstype);
home_fstype = fstype;
fstype = NULL;
} else if (sd_id128_equal(type_id, GPT_SRV)) {
/* We only care for the first /srv partition */
if (srv && nr >= srv_nr)
continue;
srv_nr = nr;
free(srv);
srv = strdup(node);
if (!srv)
return log_oom();
free(srv_fstype);
srv_fstype = fstype;
fstype = NULL;
}
}
if (home && home_fstype) {
k = add_mount("home", home, "/home", home_fstype, NULL, "Home Partition", SPECIAL_LOCAL_FS_TARGET);
if (k < 0)
r = k;
}
if (srv && srv_fstype) {
k = add_mount("srv", srv, "/srv", srv_fstype, NULL, "Server Data Partition", SPECIAL_LOCAL_FS_TARGET);
if (k < 0)
r = k;
}
return r;
}
static int get_btrfs_block_device(const char *path, dev_t *dev) {
struct btrfs_ioctl_fs_info_args fsi = {};
_cleanup_close_ int fd = -1;
uint64_t id;
assert(path);
assert(dev);
fd = open(path, O_DIRECTORY|O_CLOEXEC);
if (fd < 0)
return -errno;
if (ioctl(fd, BTRFS_IOC_FS_INFO, &fsi) < 0)
return -errno;
/* We won't do this for btrfs RAID */
if (fsi.num_devices != 1)
return 0;
for (id = 1; id <= fsi.max_id; id++) {
struct btrfs_ioctl_dev_info_args di = {
.devid = id,
};
struct stat st;
if (ioctl(fd, BTRFS_IOC_DEV_INFO, &di) < 0) {
if (errno == ENODEV)
continue;
return -errno;
}
if (stat((char*) di.path, &st) < 0)
return -errno;
if (!S_ISBLK(st.st_mode))
return -ENODEV;
if (major(st.st_rdev) == 0)
return -ENODEV;
*dev = st.st_rdev;
return 1;
}
return -ENODEV;
}
static int get_block_device(const char *path, dev_t *dev) {
struct stat st;
struct statfs sfs;
assert(path);
assert(dev);
if (lstat(path, &st))
return -errno;
if (major(st.st_dev) != 0) {
*dev = st.st_dev;
return 1;
}
if (statfs(path, &sfs) < 0)
return -errno;
if (F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC))
return get_btrfs_block_device(path, dev);
return 0;
}
static int devno_to_devnode(struct udev *udev, dev_t devno, char **ret) {
_cleanup_udev_device_unref_ struct udev_device *d;
const char *t;
char *n;
d = udev_device_new_from_devnum(udev, 'b', devno);
if (!d)
return log_oom();
t = udev_device_get_devnode(d);
if (!t)
return -ENODEV;
n = strdup(t);
if (!n)
return -ENOMEM;
*ret = n;
return 0;
}
static int parse_proc_cmdline_item(const char *key, const char *value) {
int r;
assert(key);
if (STR_IN_SET(key, "systemd.gpt_auto", "rd.systemd.gpt_auto") && value) {
r = parse_boolean(value);
if (r < 0)
log_warning("Failed to parse gpt-auto switch %s. Ignoring.", value);
arg_enabled = r;
} else if (streq(key, "root") && value) {
/* Disable root disk logic if there's a root= value
* specified (unless it happens to be "gpt-auto") */
arg_root_enabled = streq(value, "gpt-auto");
} else if (streq(key, "rw") && !value)
arg_root_rw = true;
else if (streq(key, "ro") && !value)
arg_root_rw = false;
else if (startswith(key, "systemd.gpt-auto.") || startswith(key, "rd.systemd.gpt-auto."))
log_warning("Unknown kernel switch %s. Ignoring.", key);
return 0;
}
static int add_root_mount(void) {
#ifdef ENABLE_EFI
int r;
if (!is_efi_boot()) {
log_debug("Not a EFI boot, not creating root mount.");
return 0;
}
r = efi_loader_get_device_part_uuid(NULL);
if (r == -ENOENT) {
log_debug("EFI loader partition unknown, exiting.");
return 0;
} else if (r < 0) {
log_error("Failed to read ESP partition UUID: %s", strerror(-r));
return r;
}
/* OK, we have an ESP partition, this is fantastic, so let's
* wait for a root device to show up. A udev rule will create
* the link for us under the right name. */
return add_mount(
"root",
"/dev/disk/by-id/gpt-auto-root",
in_initrd() ? "/sysroot" : "/",
NULL,
arg_root_rw ? "rw" : "ro",
"Root Partition",
in_initrd() ? SPECIAL_INITRD_ROOT_FS_TARGET : SPECIAL_LOCAL_FS_TARGET);
#else
return 0;
#endif
}
static int add_mounts(void) {
_cleanup_udev_unref_ struct udev *udev = NULL;
_cleanup_free_ char *node = NULL;
dev_t devno;
int r;
r = get_block_device("/", &devno);
if (r < 0) {
log_error("Failed to determine block device of root file system: %s", strerror(-r));
return r;
} else if (r == 0) {
log_debug("Root file system not on a (single) block device.");
return 0;
}
udev = udev_new();
if (!udev)
return log_oom();
r = devno_to_devnode(udev, devno, &node);
if (r < 0) {
log_error("Failed to determine block device node from major/minor: %s", strerror(-r));
return r;
}
log_debug("Root device %s.", node);
r = verify_gpt_partition(node, NULL, NULL, NULL);
if (r < 0) {
log_error("Failed to verify GPT partition %s: %s", node, strerror(-r));
return r;
}
if (r == 0) {
log_debug("Not a GPT disk, exiting.");
return 0;
}
return enumerate_partitions(udev, devno);
}
int main(int argc, char *argv[]) {
int r = 0;
if (argc > 1 && argc != 4) {
log_error("This program takes three or no arguments.");
return EXIT_FAILURE;
}
if (argc > 1)
arg_dest = argv[3];
log_set_target(LOG_TARGET_SAFE);
log_parse_environment();
log_open();
umask(0022);
if (detect_container(NULL) > 0) {
log_debug("In a container, exiting.");
return EXIT_SUCCESS;
}
if (parse_proc_cmdline(parse_proc_cmdline_item) < 0)
return EXIT_FAILURE;
if (!arg_enabled) {
log_debug("Disabled, exiting.");
return EXIT_SUCCESS;
}
if (arg_root_enabled)
r = add_root_mount();
if (!in_initrd()) {
int k;
k = add_mounts();
if (k < 0)
r = k;
}
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}
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