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bin/admin-upgrade: add kexec support

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Adds a new `--kexec` flag to `ostree admin upgrade` which will cause
the deployment to be loaded into kexec after the upgrade completes.
It is particularly useful in conjunction with the `--reboot` flag to
perform a reboot into the new deployment without waiting for the
(often slow) firmware initialization to take place. (And in my case,
allows me to avoid a normal reboot, which can be unreliable on my
hardware).

After an image has been loaded (using the `kexec_file_load` syscall),
the `systemctl-reboot` command (which is called when the existing
`-r` flag is included) will trigger a kexec on the loaded image
rather than a normal reboot. From `systemctl(1)`:

  If a new kernel has been loaded via kexec --load, a kexec will be
  performed instead of a reboot, unless "SYSTEMCTL_SKIP_AUTO_KEXEC=1"
  has been set. If a new root file system has been set up on
  "/run/nextroot/", a soft-reboot will be performed instead of a
  reboot, unless "SYSTEMCTL_SKIP_AUTO_SOFT_REBOOT=1" has been set.

A good in-depth technical explanation of kexec can be found here:
https://web.archive.org/web/20090505132901/http://www.ibm.com/developerworks/linux/library/l-kexec.html

My implementation uses the `kexec_file_load` syscall rather than the
older `kexec_load` syscall, which allows the kernel to verify the
signatures of the new kernel. It is supported on Linux 3.17 and
newer. I assume this probably won't be an issue, but if it is, it's
not that hard to put a preprocessor directive around the kexec stuff
to disable it for older kernels. Even RHEL is new enough now to
not be an issue :)

Closes: #435
This commit is contained in:
Mary Strodl 2024-12-12 09:30:59 -05:00
parent 64a38aec8c
commit d5bd0e0035
No known key found for this signature in database
GPG Key ID: 23B7FC1590D8E30E
8 changed files with 113 additions and 4 deletions
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16
man/ostree-admin-switch.xml
View File

@ -65,6 +65,22 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
<title>Options</title>
<variablelist>
<varlistentry>
<term><option>--reboot</option>,<option>-r</option></term>
<listitem><para>
Reboot after a successful switch.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--kexec</option>,<option>-k</option></term>
<listitem><para>
Load new deployment into kexec after a successful switch.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--os</option>="STATEROOT"</term>

8
man/ostree-admin-upgrade.xml
View File

@ -112,6 +112,14 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--kexec</option>,<option>-k</option></term>
<listitem><para>
Load new deployment into kexec after a successful upgrade.
</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--allow-downgrade</option></term>

61
src/libostree/ostree-sysroot-deploy.c
View File

@ -30,6 +30,7 @@
#include <sys/poll.h>
#include <sys/socket.h>
#include <sys/statvfs.h>
#include <linux/kexec.h>
#ifdef HAVE_LIBMOUNT
#include <libmount.h>
@ -4265,3 +4266,63 @@ ostree_sysroot_deployment_set_mutable (OstreeSysroot *self, OstreeDeployment *de
return TRUE;
}
/**
* ostree_sysroot_deployment_kexec_load
* @self: Sysroot
* @deployment: Deployment to prepare a kexec for
* @cancellable: Cancellable
* @error: Error
*
* Prepare the specified deployment for a kexec.
*/
gboolean
ostree_sysroot_deployment_kexec_load (OstreeSysroot *self, OstreeDeployment *deployment,
GCancellable *cancellable, GError **error)
{
#ifdef SYS_kexec_file_load
GLNX_AUTO_PREFIX_ERROR ("Loading kernel into kexec", error);
OstreeBootconfigParser *bootconfig = ostree_deployment_get_bootconfig (deployment);
const char *kargs = ostree_bootconfig_parser_get(bootconfig, "options");
g_autofree char *deployment_dirpath = ostree_sysroot_get_deployment_dirpath (self, deployment);
glnx_autofd int deployment_dfd = -1;
if (!glnx_opendirat (self->sysroot_fd, deployment_dirpath, FALSE, &deployment_dfd, error))
return FALSE;
/* Find the kernel/initramfs in the tree */
g_autoptr (OstreeKernelLayout) kernel_layout = NULL;
if (!get_kernel_from_tree (self, deployment_dfd, &kernel_layout, cancellable, error))
return FALSE;
unsigned long flags = 0;
glnx_autofd int kernel_fd = -1;
glnx_autofd int initrd_fd = -1;
if (!glnx_openat_rdonly (kernel_layout->boot_dfd, kernel_layout->kernel_srcpath,
TRUE, &kernel_fd, error))
return FALSE;
/* initramfs is optional */
if (kernel_layout->initramfs_srcpath)
{
if (!glnx_openat_rdonly (kernel_layout->boot_dfd, kernel_layout->initramfs_srcpath,
TRUE, &initrd_fd, error))
{
return FALSE;
}
}
else
{
flags |= KEXEC_FILE_NO_INITRAMFS;
}
if (syscall (SYS_kexec_file_load, kernel_fd, initrd_fd, strlen (kargs) + 1, kargs, flags))
return glnx_throw_errno_prefix(error, "kexec_file_load");
return TRUE;
#else
g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
"This version of ostree is not compiled with kexec support");
return FALSE;
#endif // SYS_kexec_file_load
}

10
src/libostree/ostree-sysroot-upgrader.c
View File

@ -601,6 +601,7 @@ ostree_sysroot_upgrader_deploy (OstreeSysrootUpgrader *self, GCancellable *cance
/* Experimental flag to enable staging */
gboolean stage = (self->flags & OSTREE_SYSROOT_UPGRADER_FLAGS_STAGE) > 0
|| getenv ("OSTREE_EX_STAGE_DEPLOYMENTS") != NULL;
OstreeSysrootSimpleWriteDeploymentFlags write_deployment_flags = OSTREE_SYSROOT_SIMPLE_WRITE_DEPLOYMENT_FLAGS_NONE;
if (stage)
{
if (!ostree_sysroot_stage_tree (self->sysroot, self->osname, self->new_revision, self->origin,
@ -616,7 +617,12 @@ ostree_sysroot_upgrader_deploy (OstreeSysrootUpgrader *self, GCancellable *cance
return FALSE;
if (!ostree_sysroot_simple_write_deployment (self->sysroot, self->osname, new_deployment,
self->merge_deployment, 0, cancellable, error))
self->merge_deployment, write_deployment_flags, cancellable, error))
return FALSE;
if ((self->flags & OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC) > 0)
if (!ostree_sysroot_deployment_kexec_load(self->sysroot, new_deployment, cancellable, error))
return FALSE;
}
@ -635,6 +641,8 @@ ostree_sysroot_upgrader_flags_get_type (void)
"OSTREE_SYSROOT_UPGRADER_FLAGS_IGNORE_UNCONFIGURED", "ignore-unconfigured" },
{ OSTREE_SYSROOT_UPGRADER_FLAGS_STAGE, "OSTREE_SYSROOT_UPGRADER_FLAGS_STAGE",
"stage" },
{ OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC, "OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC",
"kexec" },
{ 0, NULL, NULL } };
GType g_define_type_id
= g_flags_register_static (g_intern_static_string ("OstreeSysrootUpgraderFlags"), values);

1
src/libostree/ostree-sysroot-upgrader.h
View File

@ -44,6 +44,7 @@ typedef enum
OSTREE_SYSROOT_UPGRADER_FLAGS_NONE = (1 << 0),
OSTREE_SYSROOT_UPGRADER_FLAGS_IGNORE_UNCONFIGURED = (1 << 1),
OSTREE_SYSROOT_UPGRADER_FLAGS_STAGE = (1 << 2),
OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC = (1 << 3),
} OstreeSysrootUpgraderFlags;
_OSTREE_PUBLIC

5
src/libostree/ostree-sysroot.h
View File

@ -268,4 +268,9 @@ gboolean ostree_sysroot_simple_write_deployment (OstreeSysroot *sysroot, const c
OstreeSysrootSimpleWriteDeploymentFlags flags,
GCancellable *cancellable, GError **error);
_OSTREE_PUBLIC
gboolean
ostree_sysroot_deployment_kexec_load (OstreeSysroot *self, OstreeDeployment *deployment,
GCancellable *cancellable, GError **error);
G_END_DECLS

8
src/ostree/ot-admin-builtin-switch.c
View File

@ -29,10 +29,12 @@
#include <unistd.h>
static gboolean opt_reboot;
static gboolean opt_kexec;
static char *opt_osname;
static GOptionEntry options[]
= { { "reboot", 'r', 0, G_OPTION_ARG_NONE, &opt_reboot, "Reboot after switching trees", NULL },
{ "kexec", 'k', 0, G_OPTION_ARG_NONE, &opt_kexec, "Stage new kernel in kexec", NULL },
{ "os", 0, 0, G_OPTION_ARG_STRING, &opt_osname,
"Use a different operating system root than the current one", "OSNAME" },
{ NULL } };
@ -56,8 +58,12 @@ ot_admin_builtin_switch (int argc, char **argv, OstreeCommandInvocation *invocat
const char *new_provided_refspec = argv[1];
OstreeSysrootUpgraderFlags flags = OSTREE_SYSROOT_UPGRADER_FLAGS_IGNORE_UNCONFIGURED;
if (opt_kexec)
flags |= OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC;
g_autoptr (OstreeSysrootUpgrader) upgrader = ostree_sysroot_upgrader_new_for_os_with_flags (
sysroot, opt_osname, OSTREE_SYSROOT_UPGRADER_FLAGS_IGNORE_UNCONFIGURED, cancellable, error);
sysroot, opt_osname, flags, cancellable, error);
if (!upgrader)
return FALSE;

8
src/ostree/ot-admin-builtin-upgrade.c
View File

@ -31,6 +31,7 @@
#include <unistd.h>
static gboolean opt_reboot;
static gboolean opt_kexec;
static gboolean opt_allow_downgrade;
static gboolean opt_pull_only;
static gboolean opt_deploy_only;
@ -42,6 +43,7 @@ static GOptionEntry options[] = {
{ "os", 0, 0, G_OPTION_ARG_STRING, &opt_osname,
"Use a different operating system root than the current one", "OSNAME" },
{ "reboot", 'r', 0, G_OPTION_ARG_NONE, &opt_reboot, "Reboot after a successful upgrade", NULL },
{ "kexec", 'k', 0, G_OPTION_ARG_NONE, &opt_kexec, "Stage new kernel in kexec", NULL },
{ "allow-downgrade", 0, 0, G_OPTION_ARG_NONE, &opt_allow_downgrade,
"Permit deployment of chronologically older trees", NULL },
{ "override-commit", 0, 0, G_OPTION_ARG_STRING, &opt_override_commit,
@ -72,16 +74,18 @@ ot_admin_builtin_upgrade (int argc, char **argv, OstreeCommandInvocation *invoca
"Cannot simultaneously specify --pull-only and --deploy-only");
return FALSE;
}
else if (opt_pull_only && opt_reboot)
else if (opt_pull_only && (opt_reboot || opt_kexec))
{
g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
"Cannot simultaneously specify --pull-only and --reboot");
"Cannot simultaneously specify --pull-only and --reboot or --kexec");
return FALSE;
}
OstreeSysrootUpgraderFlags flags = 0;
if (opt_stage)
flags |= OSTREE_SYSROOT_UPGRADER_FLAGS_STAGE;
if (opt_kexec)
flags |= OSTREE_SYSROOT_UPGRADER_FLAGS_KEXEC;
g_autoptr (OstreeSysrootUpgrader) upgrader = ostree_sysroot_upgrader_new_for_os_with_flags (
sysroot, opt_osname, flags, cancellable, error);