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Merge pull request #2905 from cgwalters/prepare-root-static-split

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Separate prepare-root static path + link to glib
This commit is contained in:
Colin Walters 2023-07-04 09:05:31 -04:00 committed by GitHub
commit 9104c54f2b
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3 changed files with 420 additions and 84 deletions
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26
Makefile-switchroot.am
View File

@ -15,6 +15,12 @@
# You should have received a copy of the GNU Lesser General Public
# License along with this library. If not, see <https://www.gnu.org/licenses/>.
ostree_prepare_root_SOURCES = \
src/switchroot/ostree-mount-util.h
ostree_prepare_root_CFLAGS =
ostree_prepare_root_CPPFLAGS = $(AM_CPPFLAGS)
ostree_prepare_root_LDADD =
if BUILDOPT_SYSTEMD
ostree_boot_PROGRAMS += ostree-remount
else
@ -23,15 +29,9 @@ else
check_PROGRAMS += ostree-remount
endif
ostree_prepare_root_SOURCES = \
src/switchroot/ostree-mount-util.h \
src/switchroot/ostree-prepare-root.c \
$(NULL)
ostree_prepare_root_CFLAGS =
ostree_prepare_root_CPPFLAGS = $(AM_CPPFLAGS)
ostree_prepare_root_LDADD =
if BUILDOPT_USE_STATIC_COMPILER
ostree_prepare_root_SOURCES += src/switchroot/ostree-prepare-root-static.c
# ostree-prepare-root can be used as init in a system without a populated /lib.
# To support this use case we need to link statically as we will be unable to
# locate libc.so at run time if it's not installed in /lib.
@ -45,12 +45,16 @@ if BUILDOPT_USE_STATIC_COMPILER
ostree_boot_SCRIPTS += ostree-prepare-root
ostree-prepare-root : $(ostree_prepare_root_SOURCES)
$(STATIC_COMPILER) -o $@ -static $(top_srcdir)/src/switchroot/ostree-prepare-root.c $(ostree_prepare_root_CPPFLAGS) $(AM_CFLAGS) $(DEFAULT_INCLUDES) -DOSTREE_PREPARE_ROOT_STATIC=1
$(STATIC_COMPILER) -o $@ -static $(top_srcdir)/src/switchroot/ostree-prepare-root-static.c $(ostree_prepare_root_CPPFLAGS) $(AM_CFLAGS) $(DEFAULT_INCLUDES) -DOSTREE_PREPARE_ROOT_STATIC=1
CLEANFILES += ostree-prepare-root
else
ostree_boot_PROGRAMS += ostree-prepare-root
ostree_prepare_root_CFLAGS += $(AM_CFLAGS) -Isrc/switchroot -I$(srcdir)/composefs
endif
ostree_prepare_root_SOURCES += src/switchroot/ostree-prepare-root.c
ostree_prepare_root_CPPFLAGS += $(OT_INTERNAL_GIO_UNIX_CFLAGS) -I $(srcdir)/libglnx
ostree_prepare_root_LDADD += $(AM_LDFLAGS) $(OT_INTERNAL_GIO_UNIX_LIBS) libglnx.la
endif # BUILDOPT_USE_STATIC_COMPILER
ostree_remount_SOURCES = \
src/switchroot/ostree-mount-util.h \
@ -65,7 +69,7 @@ endif
if BUILDOPT_SYSTEMD
ostree_prepare_root_CPPFLAGS += -DHAVE_SYSTEMD=1
ostree_prepare_root_LDADD += $(AM_LDFLAGS) $(LIBSYSTEMD_LIBS)
ostree_prepare_root_LDADD += $(LIBSYSTEMD_LIBS)
endif
# This is the "new mode" of using a generator for /var; see

390
src/switchroot/ostree-prepare-root-static.c Normal file
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@ -0,0 +1,390 @@
/* -*- c-file-style: "gnu" -*-
* Switch to new root directory and start init.
*
* Copyright 2011,2012,2013 Colin Walters <walters@verbum.org>
*
* Based on code from util-linux/sys-utils/switch_root.c,
* Copyright 2002-2009 Red Hat, Inc. All rights reserved.
* Authors:
* Peter Jones <pjones@redhat.com>
* Jeremy Katz <katzj@redhat.com>
*
* Relicensed with permission to LGPLv2+.
*
* SPDX-License-Identifier: LGPL-2.0+
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 this library. If not, see <https://www.gnu.org/licenses/>.
*/
/* The high level goal of this code is to run inside
* the initial ram disk (if one is in use) and set up the `/` mountpoint
* to be the deployment root, using the ostree= kernel commandline
* argument to find the target deployment root.
*
* It's really the heart of how ostree works - basically multiple
* hardlinked chroot() targets are maintained, this one does the equivalent
* of chroot().
*
* This -static.c variant of ostree-prepare-root is designed for
* the case where an initrd isn't used - instead the binary must be statically linked (and the
* kernel must have mounted the rootfs itself) - then we set things up and exec the real init
* directly. This can be popular in embedded systems to increase bootup speed.
*
* Note that as of lately, good tools exist for embedding an initramfs
* inside a kernel binary, and this can help avoid static linking.
*/
#include "config.h"
#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
// A temporary mount point
#define TMP_SYSROOT "/sysroot.tmp"
#include "ostree-mount-util.h"
static inline bool
sysroot_is_configured_ro (const char *sysroot)
{
char *config_path = NULL;
assert (asprintf (&config_path, "%s/ostree/repo/config", sysroot) != -1);
FILE *f = fopen (config_path, "r");
if (!f)
{
fprintf (stderr, "Missing expected repo config: %s\n", config_path);
free (config_path);
return false;
}
free (config_path);
bool ret = false;
char *line = NULL;
size_t len = 0;
/* Note getline() will reuse the previous buffer */
bool in_sysroot = false;
while (getline (&line, &len, f) != -1)
{
/* This is an awful hack to avoid depending on GLib in the
* initramfs right now.
*/
if (strstr (line, "[sysroot]") == line)
in_sysroot = true;
else if (*line == '[')
in_sysroot = false;
else if (in_sysroot && strstr (line, "readonly=true") == line)
{
ret = true;
break;
}
}
fclose (f);
free (line);
return ret;
}
static char *
resolve_deploy_path (const char *root_mountpoint)
{
char destpath[PATH_MAX];
struct stat stbuf;
char *deploy_path;
autofree char *ostree_target = get_ostree_target ();
if (snprintf (destpath, sizeof (destpath), "%s/%s", root_mountpoint, ostree_target) < 0)
err (EXIT_FAILURE, "failed to assemble ostree target path");
if (lstat (destpath, &stbuf) < 0)
err (EXIT_FAILURE, "Couldn't find specified OSTree root '%s'", destpath);
if (!S_ISLNK (stbuf.st_mode))
errx (EXIT_FAILURE, "OSTree target is not a symbolic link: %s", destpath);
deploy_path = realpath (destpath, NULL);
if (deploy_path == NULL)
err (EXIT_FAILURE, "realpath(%s) failed", destpath);
if (stat (deploy_path, &stbuf) < 0)
err (EXIT_FAILURE, "stat(%s) failed", deploy_path);
/* Quiet logs if there's no journal */
#ifdef USE_LIBSYSTEMD
const char *resolved_path = deploy_path + strlen (root_mountpoint);
sd_journal_send ("MESSAGE=Resolved OSTree target to: %s", deploy_path,
"MESSAGE_ID=" SD_ID128_FORMAT_STR,
SD_ID128_FORMAT_VAL (OSTREE_PREPARE_ROOT_DEPLOYMENT_MSG), "DEPLOYMENT_PATH=%s",
resolved_path, "DEPLOYMENT_DEVICE=%" PRIu64, (uint64_t)stbuf.st_dev,
"DEPLOYMENT_INODE=%" PRIu64, (uint64_t)stbuf.st_ino, NULL);
#endif
return deploy_path;
}
static int
pivot_root (const char *new_root, const char *put_old)
{
return syscall (__NR_pivot_root, new_root, put_old);
}
int
main (int argc, char *argv[])
{
char srcpath[PATH_MAX];
/* If we're pid 1, that means there's no initramfs; in this situation
* various defaults change:
*
* - Assume that the target root is /
* - Quiet logging as there's no journal
* etc.
*/
bool running_as_pid1 = (getpid () == 1);
assert (running_as_pid1);
const char *root_arg = "/";
root_arg = "/";
struct stat stbuf;
bool we_mounted_proc = false;
if (stat ("/proc/cmdline", &stbuf) < 0)
{
if (errno != ENOENT)
err (EXIT_FAILURE, "stat(\"/proc/cmdline\") failed");
/* We need /proc mounted for /proc/cmdline and realpath (on musl) to
* work: */
if (mount ("proc", "/proc", "proc", MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to mount proc on /proc");
we_mounted_proc = true;
}
/* This is the final target where we should prepare the rootfs. The usual
* case with systemd in the initramfs is that root_mountpoint = "/sysroot".
* In the fastboot embedded case we're pid1 and will setup / ourself, and
* then root_mountpoint = "/".
* */
const char *root_mountpoint = realpath (root_arg, NULL);
if (root_mountpoint == NULL)
err (EXIT_FAILURE, "realpath(\"%s\")", root_arg);
char *deploy_path = resolve_deploy_path (root_mountpoint);
if (we_mounted_proc)
{
/* Leave the filesystem in the state that we found it: */
if (umount ("/proc"))
err (EXIT_FAILURE, "failed to umount proc from /proc");
}
/* Query the repository configuration - this is an operating system builder
* choice. More info: https://github.com/ostreedev/ostree/pull/1767
*/
const bool sysroot_readonly = sysroot_is_configured_ro (root_arg);
const bool sysroot_currently_writable = !path_is_on_readonly_fs (root_arg);
/* Work-around for a kernel bug: for some reason the kernel
* refuses switching root if any file systems are mounted
* MS_SHARED. Hence remount them MS_PRIVATE here as a
* work-around.
*
* https://bugzilla.redhat.com/show_bug.cgi?id=847418 */
if (mount (NULL, "/", NULL, MS_REC | MS_PRIVATE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make \"/\" private mount");
if (mkdir (TMP_SYSROOT, 0755) < 0)
err (EXIT_FAILURE, "couldn't create temporary sysroot %s", TMP_SYSROOT);
/* Run in the deploy_path dir so we can use relative paths below */
if (chdir (deploy_path) < 0)
err (EXIT_FAILURE, "failed to chdir to deploy_path");
/* The deploy root starts out bind mounted to sysroot.tmp */
if (mount (deploy_path, TMP_SYSROOT, NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make initial bind mount %s", deploy_path);
/* This will result in a system with /sysroot read-only. Thus, two additional
* writable bind-mounts (for /etc and /var) are required later on. */
if (sysroot_readonly)
{
if (!sysroot_currently_writable)
errx (EXIT_FAILURE, "sysroot.readonly=true requires %s to be writable at this point",
root_arg);
/* Pass on the fact that we discovered a readonly sysroot to ostree-remount.service */
int fd = open (_OSTREE_SYSROOT_READONLY_STAMP, O_WRONLY | O_CREAT | O_CLOEXEC, 0644);
if (fd < 0)
err (EXIT_FAILURE, "failed to create %s", _OSTREE_SYSROOT_READONLY_STAMP);
(void)close (fd);
}
/* Prepare /boot.
* If /boot is on the same partition, use a bind mount to make it visible
* at /boot inside the deployment. */
if (snprintf (srcpath, sizeof (srcpath), "%s/boot/loader", root_mountpoint) < 0)
err (EXIT_FAILURE, "failed to assemble /boot/loader path");
if (lstat (srcpath, &stbuf) == 0 && S_ISLNK (stbuf.st_mode))
{
if (lstat ("boot", &stbuf) == 0 && S_ISDIR (stbuf.st_mode))
{
if (snprintf (srcpath, sizeof (srcpath), "%s/boot", root_mountpoint) < 0)
err (EXIT_FAILURE, "failed to assemble /boot path");
if (mount (srcpath, TMP_SYSROOT "/boot", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount %s to boot", srcpath);
}
}
/* Prepare /etc.
* No action required if sysroot is writable. Otherwise, a bind-mount for
* the deployment needs to be created and remounted as read/write. */
if (sysroot_readonly)
{
/* Bind-mount /etc (at deploy path), and remount as writable. */
if (mount ("etc", TMP_SYSROOT "/etc", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to prepare /etc bind-mount at /sysroot.tmp/etc");
if (mount (TMP_SYSROOT "/etc", TMP_SYSROOT "/etc", NULL, MS_BIND | MS_REMOUNT | MS_SILENT,
NULL)
< 0)
err (EXIT_FAILURE, "failed to make writable /etc bind-mount at /sysroot.tmp/etc");
}
/* Prepare /usr.
* It may be either just a read-only bind-mount, or a persistent overlayfs. */
if (lstat (".usr-ovl-work", &stbuf) == 0)
{
/* Do we have a persistent overlayfs for /usr? If so, mount it now. */
const char usr_ovl_options[]
= "lowerdir=" TMP_SYSROOT "/usr,upperdir=.usr-ovl-upper,workdir=.usr-ovl-work";
/* Except overlayfs barfs if we try to mount it on a read-only
* filesystem. For this use case I think admins are going to be
* okay if we remount the rootfs here, rather than waiting until
* later boot and `systemd-remount-fs.service`.
*/
if (path_is_on_readonly_fs (TMP_SYSROOT))
{
if (mount (TMP_SYSROOT, TMP_SYSROOT, NULL, MS_REMOUNT | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to remount rootfs writable (for overlayfs)");
}
if (mount ("overlay", TMP_SYSROOT "/usr", "overlay", MS_SILENT, usr_ovl_options) < 0)
err (EXIT_FAILURE, "failed to mount /usr overlayfs");
}
else
{
/* Otherwise, a read-only bind mount for /usr. (Not needed for composefs) */
if (mount (TMP_SYSROOT "/usr", TMP_SYSROOT "/usr", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr");
if (mount (TMP_SYSROOT "/usr", TMP_SYSROOT "/usr", NULL,
MS_BIND | MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL)
< 0)
err (EXIT_FAILURE, "failed to bind mount (class:readonly) /usr");
}
/* Prepare /var.
* When a read-only sysroot is configured, this adds a dedicated bind-mount (to itself)
* so that the stateroot location stays writable. */
if (sysroot_readonly)
{
/* Bind-mount /var (at stateroot path), and remount as writable. */
if (mount ("../../var", "../../var", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to prepare /var bind-mount at %s", srcpath);
if (mount ("../../var", "../../var", NULL, MS_BIND | MS_REMOUNT | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to make writable /var bind-mount at %s", srcpath);
}
/* When running under systemd, /var will be handled by a 'var.mount' unit outside
* of initramfs.
* Systemd auto-detection can be overridden by a marker file under /run. */
bool mount_var = true;
/* If required, bind-mount `/var` in the deployment to the "stateroot", which is
* the shared persistent directory for a set of deployments. More info:
* https://ostreedev.github.io/ostree/deployment/#stateroot-aka-osname-group-of-deployments-that-share-var
*/
if (mount_var)
{
if (mount ("../../var", TMP_SYSROOT "/var", NULL, MS_BIND | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to bind mount ../../var to var");
}
if (chdir (TMP_SYSROOT) < 0)
err (EXIT_FAILURE, "failed to chdir to " TMP_SYSROOT);
if (strcmp (root_mountpoint, "/") == 0)
{
/* pivot_root rotates two mount points around. In this instance . (the
* deploy location) becomes / and the existing / becomes /sysroot. We
* have to use pivot_root rather than mount --move in this instance
* because our deploy location is mounted as a subdirectory of the real
* sysroot, so moving sysroot would also move the deploy location. In
* reality attempting mount --move would fail with EBUSY. */
if (pivot_root (".", "sysroot") < 0)
err (EXIT_FAILURE, "failed to pivot_root to deployment");
}
else
{
/* In this instance typically we have our ready made-up up root at
* /sysroot.tmp and the physical root at /sysroot (root_mountpoint).
* We want to end up with our deploy root at /sysroot/ and the physical
* root under /sysroot/sysroot as systemd will be responsible for
* moving /sysroot to /.
*/
if (mount (root_mountpoint, "sysroot", NULL, MS_MOVE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to MS_MOVE '%s' to 'sysroot'", root_mountpoint);
if (mount (".", root_mountpoint, NULL, MS_MOVE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "failed to MS_MOVE %s to %s", ".", root_mountpoint);
if (chdir (root_mountpoint) < 0)
err (EXIT_FAILURE, "failed to chdir to %s", root_mountpoint);
if (rmdir (TMP_SYSROOT) < 0)
err (EXIT_FAILURE, "couldn't remove temporary sysroot %s", TMP_SYSROOT);
if (sysroot_readonly)
{
if (mount ("sysroot", "sysroot", NULL, MS_BIND | MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL)
< 0)
err (EXIT_FAILURE, "failed to make /sysroot read-only");
/* TODO(lucab): This will make the final '/' read-only.
* Stabilize read-only '/sysroot' first, then enable this additional hardening too.
*
* if (mount (".", ".", NULL, MS_BIND | MS_REMOUNT | MS_RDONLY | MS_SILENT, NULL) < 0)
* err (EXIT_FAILURE, "failed to make / read-only");
*/
}
}
/* The /sysroot mount needs to be private to avoid having a mount for e.g. /var/cache
* also propagate to /sysroot/ostree/deploy/$stateroot/var/cache
*
* Now in reality, today this is overridden by systemd: the *actual* way we fix this up
* is in ostree-remount.c. But let's do it here to express the semantics we want
* at the very start (perhaps down the line systemd will have compile/runtime option
* to say that the initramfs environment did everything right from the start).
*/
if (mount ("none", "sysroot", NULL, MS_PRIVATE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "remounting 'sysroot' private");
execl ("/sbin/init", "/sbin/init", NULL);
err (EXIT_FAILURE, "failed to exec init inside ostree");
}

88
src/switchroot/ostree-prepare-root.c
View File

@ -47,20 +47,16 @@
*
* # Running as pid 1
*
* There is also a secondary mode for this service when an initrd isn't
* used - instead the binary must be statically linked (and the kernel
* must have mounted the rootfs itself) - then we set things up and
* exec the real init directly. This can be popular in embedded
* systems to increase bootup speed.
* See ostree-prepare-root-static.c for this.
*/
#include "config.h"
#include <assert.h>
#include <ctype.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libglnx.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdio.h>
@ -110,44 +106,19 @@ typedef enum
OSTREE_COMPOSEFS_MODE_DIGEST, /* Always use and require specific digest */
} OstreeComposefsMode;
static inline bool
static bool
sysroot_is_configured_ro (const char *sysroot)
{
char *config_path = NULL;
assert (asprintf (&config_path, "%s/ostree/repo/config", sysroot) != -1);
FILE *f = fopen (config_path, "r");
if (!f)
g_autoptr (GError) local_error = NULL;
g_autofree char *repo_config_path = g_build_filename (sysroot, "ostree/repo/config", NULL);
g_autoptr (GKeyFile) repo_config = g_key_file_new ();
if (!g_key_file_load_from_file (repo_config, repo_config_path, G_KEY_FILE_NONE, &local_error))
{
fprintf (stderr, "Missing expected repo config: %s\n", config_path);
free (config_path);
g_printerr ("Failed to load %s: %s", repo_config_path, local_error->message);
return false;
}
free (config_path);
bool ret = false;
char *line = NULL;
size_t len = 0;
/* Note getline() will reuse the previous buffer */
bool in_sysroot = false;
while (getline (&line, &len, f) != -1)
{
/* This is an awful hack to avoid depending on GLib in the
* initramfs right now.
*/
if (strstr (line, "[sysroot]") == line)
in_sysroot = true;
else if (*line == '[')
in_sysroot = false;
else if (in_sysroot && strstr (line, "readonly=true") == line)
{
ret = true;
break;
}
}
fclose (f);
free (line);
return ret;
return g_key_file_get_boolean (repo_config, "sysroot", "readonly", NULL);
}
static char *
@ -194,27 +165,11 @@ main (int argc, char *argv[])
{
char srcpath[PATH_MAX];
/* If we're pid 1, that means there's no initramfs; in this situation
* various defaults change:
*
* - Assume that the target root is /
* - Quiet logging as there's no journal
* etc.
*/
bool running_as_pid1 = (getpid () == 1);
const char *root_arg = NULL;
bool we_mounted_proc = false;
if (running_as_pid1)
{
root_arg = "/";
}
else
{
if (argc < 2)
err (EXIT_FAILURE, "usage: ostree-prepare-root SYSROOT");
root_arg = argv[1];
}
if (argc < 2)
err (EXIT_FAILURE, "usage: ostree-prepare-root SYSROOT");
root_arg = argv[1];
#ifdef USE_LIBSYSTEMD
sd_journal_send ("MESSAGE=preparing sysroot at %s", root_arg, NULL);
#endif
@ -494,13 +449,8 @@ main (int argc, char *argv[])
err (EXIT_FAILURE, "failed to bind mount ../../var to var");
}
/* We only stamp /run now if we're running in an initramfs, i.e. we're
* not pid 1. Otherwise it's handled later via ostree-system-generator.
* https://mail.gnome.org/archives/ostree-list/2018-March/msg00012.html
* https://github.com/ostreedev/ostree/pull/1675
*/
if (!running_as_pid1)
touch_run_ostree ();
/* This can be used by other things to signal ostree is in use */
touch_run_ostree ();
if (chdir (TMP_SYSROOT) < 0)
err (EXIT_FAILURE, "failed to chdir to " TMP_SYSROOT);
@ -562,13 +512,5 @@ main (int argc, char *argv[])
if (mount ("none", "sysroot", NULL, MS_PRIVATE | MS_SILENT, NULL) < 0)
err (EXIT_FAILURE, "remounting 'sysroot' private");
if (running_as_pid1)
{
execl ("/sbin/init", "/sbin/init", NULL);
err (EXIT_FAILURE, "failed to exec init inside ostree");
}
else
{
exit (EXIT_SUCCESS);
}
exit (EXIT_SUCCESS);
}