For libc syscall wrappers (pidfd_open, fsopen, openat2, etc.) we previously
gated the calls behind build-time HAVE_* checks. Replace these with shim
functions in src/libc/ that fall back to the raw syscall at runtime when the
loaded glibc lacks the symbol. The infrastructure lives in src/libc/libc-shim.h:
DEFINE_SYSCALL_SHIM falls back to a direct syscall, DEFINE_LIBC_SHIM returns
ENOSYS (for posix_spawn-family helpers that have no corresponding syscall), and
DEFINE_LIBC_ERRNO_SHIM sets errno=ENOSYS and returns -1 (for read/write-style
helpers). The weak reference to the libc symbol is bound via __asm__(\"name\")
rename so the bare libc identifier never appears as a C token — this avoids
both #undef boilerplate against override-header redirects and the resulting
-Wredundant-decls warning. Drop the corresponding cc.has_function() loop from
meson.build.
For optional libraries (libcryptsetup, libdw, libarchive), drop the per-symbol
HAVE_* checks. Always declare the prototypes, suppressing the redundant-decl
warnings via DISABLE_WARNING_REDUNDANT_DECLS and NOLINT, and resolve the symbols
after the main dlopen via a new DLSYM_OPTIONAL() helper that only assigns on
success. libcryptsetup's crypt_set_keyring_to_link / crypt_token_set_external_path
and libarchive's *_is_set wrappers use fallback functions as their pointer
initializers (returning -ENOSYS and 0 respectively), so call sites can invoke
the symbol unconditionally and just check for -ENOSYS where the \"not supported\"
distinction matters.
The same shim treatment applies to pidfd_spawn / posix_spawnattr_setcgroup_np
(src/libc/spawn.c) and epoll_pwait2 (src/libc/epoll.c), with corresponding
override headers in src/include/override/spawn.h and
src/include/override/sys/epoll.h. posix_spawn_wrapper() in process-util.c and
epoll_wait_usec() in sd-event.c now detect ENOSYS in the return value instead
of checking the function pointer, falling back to plain posix_spawn() and
epoll_wait() respectively. coredump-config and coredump-submit get a
dlopen_dw_has_dwfl_set_sysroot() helper. The kexec arch gate now uses
defined(__NR_kexec_file_load) directly; pidfd.h uses __has_include_next() to
decide whether to pull in glibc's header.
This lets binaries built against newer glibc / libcryptsetup / libdw /
libarchive headers still load and run on older targets where these symbols are
absent.
This makes __NR_kexec_file_load available on architectures where the kernel
UAPI headers don't define it, matching the runtime fallback path in
src/libc/kexec.c which is gated on #ifdef __NR_kexec_file_load.
A follow-up to the AddStorage / RemoveStorage series. ReplaceStorage
swaps the *backing file* of an already-attached storage device on a
running vmspawn-managed VM, leaving the guest-visible device frontend
(virtio-blk, virtio-scsi, nvme, scsi-cd) and every other property of
the device untouched. The intended use is to point an existing disk
at a new image without the guest seeing a hot-unplug/hot-plug cycle.
The signature mirrors AddStorage minus the 'config' field: the
device frontend doesn't change, only the backing behind it. Read-
only / read-write is derived from the new fd's O_ACCMODE; scsi-cd is
forced read-only to match the boot-time policy. S_ISBLK on the new
fd selects host_device vs file driver, matching AddStorage.
The QMP primitive is blockdev-reopen. It cannot change a file /
host_device node's 'filename' so we can't just point the existing
file node at a new fd, but it can swap a format node's 'file' child
to a different existing monitor-owned node by node-name reference
(case 3 in qemu/qapi/block-core.json:5034-5040). The chain is:
add-fd (host fd → new fdset)
blockdev-add (new file node, filename=/dev/fdset/N — fd-only)
remove-fd (release monitor's ref; new file holds the dup)
blockdev-reopen (format node, file = new file node-name)
blockdev-del (old file node; its dup release frees old fdset)
The reopen options must restate every option the original blockdev-
add emitted on the format node — blockdev-reopen resets any
unspecified option to its driver default. The 'file' field is a
node-name string reference, never a path.
No new errors and no new IDL types beyond the method itself;
everything is built on the existing NoSuchStorage / StorageImmutable
/ NotConnected / EBUSY vocabulary.
The series is:
vmspawn: split blockdev-add into separate file and format calls
Preparatory refactor. qemu/blockdev.c:3440 only marks the
top-level BDS returned by blockdev-add as monitor-owned;
inline children are NOT, so blockdev-del later rejects them
with "Node X is not owned by the monitor". Split into two
blockdev-add calls so the file node is independently
deletable. DriveInfo gains qmp_file_node_name and a
file_generation counter; the teardown helper deletes format
then file (file-first is rejected as "node used as 'file'
of Y"). The ephemeral path was already structured this way;
only the regular add path changes. Drops the now-unused
qmp_build_blockdev_add_inline().
shared/varlink-io.systemd.MachineInstance: add ReplaceStorage method
IDL only: ReplaceStorage(fileDescriptorIndex, name). No new
errors.
vmspawn: implement io.systemd.MachineInstance.ReplaceStorage
vmspawn_qmp_replace_block_device() entry point, ReplaceCtx
(refcounted, ReplaceCtxStateFlags for partial-state tracking)
and four async callbacks plus an idempotent replace_fail.
file_generation is bumped before issuing blockdev-add so
retries don't collide on node-name.
BLOCK_DEVICE_STATE_REPLACE_PENDING gates concurrent
Replace / Remove on the same drive. On reopen success the
trailing blockdev-del of the old file node fires from the
reopen callback; its failure logs a warning and still replies
success (the swap already committed; the orphan resolves at VM
exit). QMP disconnect mid-replace routes via
qmp_client_fail_pending → replace_fail → NotConnected.
test: integration test for io.systemd.MachineInstance.ReplaceStorage
TEST-87-AUX-UTILS-VM.replace-storage covers happy-path replace,
successive replaces (file_generation rotation), StorageImmutable
rejection on the boot-time drive, NoSuchStorage on unknown
names, InvalidParameter on malformed names, and clean
RemoveStorage after a replace (proves the new file node is
monitor-owned and the teardown order works). Backing files are
passed via 'varlinkctl --push-fd'; no machinectl front-end is
added in this round.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
JSON only supports string keys in objects, but D-Bus specification is a
bit more lenient and allows dict entries to have any basic type as key.
Let's stringify allowed non-string keys so that we can represent them as
JSON objects.
Relevant snippet from the D-Bus specification:
A DICT_ENTRY works exactly like a struct, but rather than parentheses
it uses curly braces, and it has more restrictions. The restrictions
are: it occurs only as an array element type; it has exactly two
single complete types inside the curly braces; the first single
complete type (the "key") must be a basic type rather than a container
type. Implementations must not accept dict entries outside of arrays,
must not accept dict entries with zero, one, or more than two fields,
and must not accept dict entries with non-basic-typed keys. A dict
entry is always a key-value pair.
Resolves: #32904
The local struct passed to sd_varlink_dispatch() was not
zero-initialized. Since sd_json_dispatch_full() does not call handlers
for absent optional fields, p.id could be left indeterminate when
the client omits the Id parameter, leading to use of uninitialized
memory.
Old gcc is confused about initialization:
In function ‘io_read_send’,
inlined from ‘walk_cgroups’ at ../src/report/report-cgroup.c:288:24:
../src/report/report-cgroup.c:167:21: error: ‘values[0]’ may be used uninitialized [-Werror=maybe-uninitialized]
167 | r = metric_build_send_unsigned(mf + i, link, unit, values[i], /* fields= */ NULL);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Maybe this helps.
Add io.systemd.Basic.OSRelease metric families that reports select fields
from os-release.
$ cat /etc/os-release
NAME="Fedora Linux"
VERSION="45 (Cloud Edition Prerelease)"
RELEASE_TYPE=development
ID=fedora
VERSION_ID=45
VERSION_CODENAME=""
PRETTY_NAME="Fedora Linux 45 (Cloud Edition Prerelease)"
ANSI_COLOR="0;38;2;60;110;180"
LOGO=fedora-logo-icon
CPE_NAME="cpe:/o:fedoraproject:fedora:45"
HOME_URL="https://fedoraproject.org/"
DOCUMENTATION_URL="https://docs.fedoraproject.org/en-US/fedora/rawhide/"
SUPPORT_URL="https://ask.fedoraproject.org/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"
REDHAT_BUGZILLA_PRODUCT="Fedora"
REDHAT_BUGZILLA_PRODUCT_VERSION=rawhide
REDHAT_SUPPORT_PRODUCT="Fedora"
REDHAT_SUPPORT_PRODUCT_VERSION=rawhide
SUPPORT_END=2027-11-24
VARIANT="Cloud Edition"
VARIANT_ID=cloud
$ varlinkctl call --more ./build/systemd-report-basic io.systemd.Metrics.List {} | jq --seq -c
...
{"name":"io.systemd.Basic.OSRelease.NAME","value":"Fedora Linux 44 (Workstation Edition)"}
{"name":"io.systemd.Basic.OSRelease.ID","value":"fedora"}
{"name":"io.systemd.Basic.OSRelease.CPE_NAME","value":"cpe:/o:fedoraproject:fedora:44"}
{"name":"io.systemd.Basic.OSRelease.VARIANT_ID","value":"workstation"}
{"name":"io.systemd.Basic.OSRelease.VERSION_ID","value":"44"}
{"name":"io.systemd.Basic.OSRelease.SUPPORT_END","value":"2027-05-19"}
I picked the fields that contain useful information about the specific
version/image/variant/experiment/flavour of the system. Also, either
NAME or PRETTY_NAME is included. This one is intended for human readers
to be able to identify the OS version easily.
Previously, we passed around information about the MetricFamily'ies
and the varlink connection in a helper structure. Having a hybrid of
const static and runtime stuff is iffy. Let's simplify things by passing
two separate parameters.
Also, in report-cgroup.c we built a cache of parsed values. This
requires additional storage requirements and introduces complexity when
dealing with population of the cache at the appropriate time.
This cache is not useful: for each cgroup, we generate a list of
metrics, and we have all the information at hand. The only reason
why we'd create the cache and not generate all the relevant replies
at once was that the helper functions called the .generate function
for each MetricFamily separately.
The MetricFamily interface is changed, so that metrics can be
defined without a .generate function. This is understood to mean
that the preceding metric family's .generate function will also
genarate this family. This allows us to define related metrics
nicely in a table:
{ METRIC_IO_SYSTEMD_CGROUP_PREFIX "CpuUsage", generate_func },
{ METRIC_IO_SYSTEMD_CGROUP_PREFIX "IOReadBytes", NULL },
{ METRIC_IO_SYSTEMD_CGROUP_PREFIX "IOReadOperations", NULL },
{ METRIC_IO_SYSTEMD_CGROUP_PREFIX "SomethingElse", generate_func2 },
...
When implementing .Describe, we list all the families. When implementing
.List, we only call those with .generate, and we get the same results
as before.
This allows the .generate functions to be simplified: instead of
keeping state, they just spit out all the metrics for a given
object in a tight loop.
The 'name' field on AddStorage and RemoveStorage was documented as
'<provider>:<volume>' and enforced via machine_storage_name_split() at
the varlink boundary. That form is only the convention machinectl
inherits from the StorageProvider routing path; the API itself only
needs a unique identifier the caller can re-use to detach the binding.
Drop the strict format check, require only a non-empty string, and
update the IDL docs to describe the field as a caller-supplied
identifier with machinectl's convention as a non-normative example.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
An fd opened O_PATH cannot be read, and an O_WRONLY fd cannot serve as
a backing file for a virtual disk image. Reject both at the bind-volume
entry point with -EBADF instead of letting the request proceed to QMP
where QEMU's file backend would fail to read from the fd. The
ReplaceStorage entry point grew the same checks in parallel.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Modelled on TEST-87-AUX-UTILS-VM.bind-volume.sh. Boots vmspawn with
one boot-time bind-volume, hot-adds a runtime volume via machinectl
bind-volume, then exercises ReplaceStorage:
1. happy-path replace of a runtime drive
2. successive replace (verify file_generation rotation — no
node-name collisions on the second swap)
3. replace of the boot-time drive must fail with StorageImmutable
4. replace of an unknown name must fail with NoSuchStorage
5. invalid name (no provider:volume separator) must fail with
InvalidParameter
6. unbind-volume after replace must succeed — proves the new file
node is monitor-owned and the format-then-file teardown order
in vmspawn_qmp_block_device_teardown() correctly cleans up both
blockdev nodes
Pushes the new backing file via varlinkctl --push-fd; the file is a
plain truncate'd image. Auto-discovered by run_subtests in
TEST-87-AUX-UTILS-VM.sh.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Wire up the runtime hot-swap Varlink method. The signature mirrors
AddStorage minus 'config': the device frontend (virtio-blk,
virtio-scsi, nvme, scsi-cd) doesn't change, only the backing file
behind it. Read-only/read-write may flip based on the new fd's
O_ACCMODE; scsi-cd is forced read-only to match the boot-time policy.
QMP sequence (entry: vmspawn_qmp_replace_block_device):
add-fd → on_replace_observe_stage
blockdev-add (new file) → on_replace_blockdev_add_complete
remove-fd (new fdset) → on_replace_observe_stage
blockdev-reopen (format) → on_replace_blockdev_reopen_complete
[commit + fire trailing del]
blockdev-del (old file) → on_replace_old_blockdev_del_complete
The reopen options must be a superset of every option that
qmp_build_blockdev_add_format() may emit, otherwise reopen rejects
'Cannot reset option X to default'. The 'file' field is a string
reference to the new file node — case 3 of the schema in
qemu/qapi/block-core.json:5034-5040 ("the current child is replaced
with that other node"). The format node's qmp_node_name is preserved
so the device frontend's drive=<X> binding does not move.
ReplaceCtx tracks the per-call state with a refcount mirroring the
add-stage drive-info pattern. On any pre-commit failure replace_fail
tears down whatever new-side state we created on the wire and replies
on drive->link via reply_qmp_error (disconnect → NotConnected). On
post-commit del failure we log a warning, leak the orphan, and reply
success — the swap itself succeeded and the leak resolves at VM exit.
file_generation is bumped before issuing blockdev-add so failed
attempts cannot collide on node-name when the user retries.
Errors:
NoSuchStorage - drive not in the registry
StorageImmutable - drive lacks QMP_DRIVE_REMOVABLE (boot-time)
EBUSY - add still pending or another replace/remove in flight
NotConnected - QMP transport disconnect during the chain
EIO - QEMU rejected blockdev-reopen
Also gates RemoveStorage on REPLACE_PENDING so a device_del cannot
race a mid-flight blockdev-reopen on the same drive.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Define the IDL for io.systemd.MachineInstance.ReplaceStorage, a
runtime hot-swap of an already-attached storage volume's backing
file. The signature mirrors AddStorage minus the 'config' field
because the device frontend (virtio-blk, virtio-scsi, nvme, scsi-cd)
does not change — only the backing file behind it.
The implementation lives in vmspawn (next commit) and uses QMP
blockdev-reopen to swap the file child of the existing format node.
The reused error vocabulary (NoSuchStorage, StorageImmutable,
NotConnected, plus the generic errno path) covers every failure
mode; no new errors are added.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
The current vmspawn_qmp_add_block_device() emits a single blockdev-add
that combines the format-level node ("vmspawn-N-storage") with an
inline file child. QEMU's qmp_blockdev_add() only marks the top-level
returned BDS as monitor-owned (qemu/blockdev.c:3440); inline children
are NOT, so qmp_blockdev_del() rejects them with "Node X is not owned
by the monitor" (qemu/blockdev.c:3513-3517).
To prepare for ReplaceStorage — which needs to swap the file child of
an existing format node via blockdev-reopen, and then blockdev-del the
old file node — make the file node monitor-owned by issuing it as its
own blockdev-add call. The 4-stage add chain becomes 5 stages:
add-fd
blockdev-add (file) → on_add_file_node_stage sets FILE_NODE_ADDED
blockdev-add (format) → on_add_format_node_stage sets BLOCKDEV_ADDED
remove-fd
device_add
DriveInfo gains qmp_file_node_name ("vmspawn-N-file-G", G a generation
counter bumped on every replace), file_generation, and a stashed
fdset_id so future ReplaceStorage can target both for cleanup.
vmspawn_qmp_block_device_teardown() now deletes both nodes in order —
format first, then file — because the format holds a strong reference
to its file child and a file-first del is rejected with "Node X is
busy: node is used as 'file' of Y".
Folds bridge->features VMSPAWN_QMP_FEATURE_IO_URING into the file
node's flags so the new path inherits io_uring just like the old
inline form did. The format-level options (read-only, discard,
discard-no-unref) are unchanged.
The ephemeral path is structurally already separate file+format with
monitor-owned children; no behavioural change there beyond the
on_add_blockdev_stage → on_add_format_node_stage rename.
Drops the now-unused qmp_build_blockdev_add_inline() helper.
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This is a series of commits which adds a feature needed by GNOME OS'
installer. This was show during All Systems Go 2025 talk:
https://cfp.all-systems-go.io/all-systems-go-2025/talk/QRJVL3/
To sum up this PR, this changes first systemd-repart to use BLKPG
partition instead of loop devices when possible. We need then to always
rescan the partitions to try remove partitions if it failed. We allow
encrypted partitions to stay activated and with a chosen name. And we
add a new partition configuration `BtrfsReplace=`.
Note that "replace" comes from the command `btrfs replace`. But in the
case of systemd-repart, maybe "inplace" or "move" would make more sense.
I open to suggestions.
If it is better I can split this into several PRs.
The commits:
## repart: Reuse the backing fd for fdisk
Because fdisk_assign_device tries to open block devices with O_EXCL,
when it does it blocks cryptsetup from using partition block devices for
the same disk.
Since we already have a file descriptor for the device, we can just
share it and use fdisk_assign_device_by_fd instead.
## repart: Use blkpg partitions instead of loop devices when possible
We will want to allow future features to keep some devices mounted or
active. So in order to avoid leaving a mess of many loop devices, we can
just already use the partition block device already.
## repart: Rescan disk on failure if we create blkpg partitions on the
fly
Since we did not write the partition table, then the created partitions
should get removed on error.
## repart: Allow keeping luks2 volumes opened
## repart: Add BtrfsReplace=
BtrfsReplace=/mntpnt will move the btrfs filesystem from mount point to
the partition created. After moving, it will resize to take the whole
partition.
This is useful for OS installers that move a live system into a disk and
do not require a reboot.
## repart: Add VolumeName=
When a luks2 device mapper is to be kept alive after execution of
systemd-cryptsetup, the name of the volume will be taken from this
value.
## test: Add test for repart's BtrfsReplace
$PATH might point to a systemd checkout containing
a newer version of systemd-journal-remote which we
should use, hence prefer an executable from $PATH
over the one from /usr/lib/systemd.
Even after switching the wait loop to a polling `journalctl --grep`, the
test still fails intermittently because the very first messages emitted by
the freshly-spawned systemd-networkd-wait-online process can carry stale
journald metadata. journald associates `_SYSTEMD_UNIT=` (and friends) with
each entry by reading `/proc/$pid/cgroup` of the originating PID; if those
messages are produced before journald notices the cgroup migration into the
new service, they get tagged with `_SYSTEMD_UNIT=init.scope`. The
`-u $unit` filter then fails to match them.
Capture a journal cursor before launching the unit, and grep using
`--after-cursor=` plus `SYSLOG_IDENTIFIER=systemd-networkd-wait-online`
instead of `-u $unit`. SYSLOG_IDENTIFIER is set by the program itself, so
it's not subject to the cgroup-discovery race. The cursor bounds the search
to entries produced by this invocation, so prior wait-online runs in
earlier testcases don't interfere.
Logs from the failing run showing the messages exist but are tagged with
the wrong unit:
[ 2570.948554] TEST-75-RESOLVED.sh[2178]: + unit=wait-online-dns-ede81407-b93b-459d-8e5d-69292b42d2ae.service
[ 2571.023162] TEST-75-RESOLVED.sh[2178]: + systemd-run -u wait-online-dns-ede81407-b93b-459d-8e5d-69292b42d2ae.service ...
[ 2571.049189] TEST-75-RESOLVED.sh[2178]: + timeout 30 bash -c 'until journalctl -b -u wait-online-dns-ede81407-b93b-459d-8e5d-69292b42d2ae.service --grep ...'
[ 2571.964986] systemd-networkd-wait-online[2190]: dns0: No DNS server is accessible.
[ 2601.051088] TEST-75-RESOLVED.sh[2178]: ++ cleanup
And for that 2571.964986 entry:
_SYSTEMD_CGROUP=/init.scope
_SYSTEMD_UNIT=init.scope
_EXE=/usr/lib/systemd/systemd-executor
_CMDLINE=/usr/lib/systemd/systemd-executor --deserialize 68 ...
SYSLOG_IDENTIFIER=systemd-networkd-wait-online
MESSAGE=dns0: No DNS server is accessible.
Follow-up for d4bc62713e
Co-developed-by: Claude Opus 4.7 <noreply@anthropic.com>
When an LSM (e.g. SELinux) denies an fd transfer or the receiver hits
RLIMIT_NOFILE, the kernel drops the fd(s) from the SCM_RIGHTS cmsg and
sets MSG_CTRUNC on the recvmsg(). recvmsg_safe() turns that into
-ECHRNG, which causes json_stream_read() to discard the data bytes
that were nevertheless received and the varlink server to silently
tear down the connection — leaving the caller waiting for a reply
that never comes.
Inline the recvmsg() call instead and, on MSG_CTRUNC, drop the partial
fds but keep the message data. The method handler will surface a clean
-ENXIO when it tries to peek the missing fd, which sd-varlink wraps as
io.systemd.System for the peer, instead of a hang. This matches the
recent sd-bus fix in 6c8de404c9 ('sd-bus: allow receiving messages with
MSG_CTRUNC set').
BlockDeviceReplace=/mntpnt will move the btrfs filesystem from mount point to
the partition created. After moving, it will resize to take the whole
partition.
This is useful for OS installers that move a live system into a disk and
do not require a reboot.
We will want to allow future features to keep some devices mounted or
active. So in order to avoid leaving a mess of many loop devices, we can
just already use the partition block device already.
Because fdisk_assign_device tries to open block devices with O_EXCL, when it
does it blocks cryptsetup from using partition block devices for the same
disk.
Since we already have a file descriptor for the device, we can just share it
and use fdisk_assign_device_by_fd instead.
This requires at least libfdisk 2.35 (part of util-linux) which was
released in 2020.
Daan De Meyer
Christian Brauner
Zbigniew Jędrzejewski-Szmek
Yu Watanabe
Frantisek Sumsal
Yaping Li
Christian Brauner
Luca Boccassi
Lennart Poettering
Valentin David
Bone NI