This also switches all these notes to be defined via SD_ELF_NOTE_DLOPEN_ANCHORED().
Consequently, any notes added within unreachable or unused functions will be
automatically garbage-collected by the linker (--gc-sections) instead of
bloating the final binary.
E.g. unused p11-kit library dependency is now dropped from
systemd-repart.standalone binary.
Before:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE DESCRIPTION SONAME PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 recommended
blkid Support for block device identification libblkid.so.1 required
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 recommended
mount Support for mount enumeration libmount.so.1 required
fdisk Support for reading and writing partition tables libfdisk.so.1 required
blkid Support for block device identification libblkid.so.1 recommended
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 suggested
fdisk Support for reading and writing partition tables libfdisk.so.1 suggested
idn Support for internationalized domain names libidn2.so.0 suggested
mount Support for mount enumeration libmount.so.1 recommended
selinux Support for SELinux libselinux.so.1 recommended
tpm Support for TPM libtss2-esys.so.0 suggested
tpm Support for TPM libtss2-rc.so.0 suggested
tpm Support for TPM libtss2-mu.so.0 suggested
tpm Support for TPM libtss2-tcti-device.so.0 suggested
p11-kit Support for PKCS11 hardware tokens libp11-kit.so.0 suggested
```
After:
```
$ systemd-analyze dlopen-metadata build/systemd-repart.standalone
FEATURE DESCRIPTION SONAME PRIORITY
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 recommended
blkid Support for block device identification libblkid.so.1 required
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 recommended
mount Support for mount enumeration libmount.so.1 required
fdisk Support for reading and writing partition tables libfdisk.so.1 required
blkid Support for block device identification libblkid.so.1 recommended
libcrypto Support for cryptographic operations libcrypto.so.4 libcrypto.so.3 suggested
cryptsetup Support for disk encryption, integrity, and authentication libcryptsetup.so.12 suggested
fdisk Support for reading and writing partition tables libfdisk.so.1 suggested
mount Support for mount enumeration libmount.so.1 recommended
selinux Support for SELinux libselinux.so.1 recommended
tpm Support for TPM libtss2-esys.so.0 suggested
tpm Support for TPM libtss2-rc.so.0 suggested
tpm Support for TPM libtss2-mu.so.0 suggested
tpm Support for TPM libtss2-tcti-device.so.0 suggested
```
The inner map is created with a uint32_t key, but the update passed
&magic[i] where magic is a (possibly 64-bit) statfs_f_type_t. On
little-endian the low 32 bits happen to be read; on big-endian 64-bit
(s390x, ppc64 BE) the zero high word is read instead, so every
filesystem collides on key 0 (the allow/deny selector) and
RestrictFileSystems= is silently broken. Pass a truncated copy.
Follow-up for 184b4f78cf
Switch the executable-owned call sites from the plain dlopen_<lib>()
helpers to the new DLOPEN_<LIB>() macros, so that each binary that loads
an optional library at runtime now carries its own .note.dlopen note
instead of relying solely on libsystemd-shared. Each call site passes a
priority reflecting whether it hard-depends on the library (required) or
degrades gracefully without it (recommended).
Co-developed-by: Claude Opus 4.8 <noreply@anthropic.com>
Renames src/shared/bpf-dlopen.{c,h} to src/shared/bpf-util.{c,h} and
folds the former src/shared/bpf-compat.h (struct forward decl and
compat_bpf_map_create() helper) into the new header.
Aligns dlopen_bpf() with the standard wrapper pattern: drops the
manual dlopen_safe()/dlsym_many_or_warn()/TAKE_PTR(dl) plumbing and
the bespoke 'cached' int in favor of dlopen_many_sym_or_warn() inside
a FOREACH_STRING() soname-fallback loop.
Unifies declaration of the version-specific symbols (bpf_create_map,
bpf_map_create, bpf_object__next_map, bpf_token_create) into a single
DISABLE_WARNING_REDUNDANT_DECLS block in the header, and alphabetically
merges the DLSYM_PROTOTYPE list. DLSYM_OPTIONAL is used to load each
one — call sites already handle NULL (compat_bpf_map_create() and the
sym_bpf_object__next_map guard in userns-restrict.c). bpf_token_create
additionally defaults to a missing_bpf_token_create() stub returning
-ENOSYS, so callers can branch on the errno instead of NULL-checking
the pointer.
Updates test-bpf-token to match: drops the compile-time
LIBBPF_MAJOR_VERSION ≥ 1.5 gate and the direct <bpf/bpf.h> include in
favor of dlopen_bpf() + sym_bpf_token_create(), and treats -ENOSYS as
the test-skip path (covering both 'libbpf too old' and 'kernel lacks
BPF_TOKEN_CREATE support').
Add a new RestrictFileSystemAccess= boolean setting in the [Manager] section of
system.conf that enforces execution only from signed dm-verity block
devices and the initramfs during early boot.
When RestrictFileSystemAccess=yes is set, PID1 loads a BPF LSM program early in boot
that:
Integrity tracking (self-populating, no userspace involvement):
- bdev_setintegrity: records dm-verity signature status in a BPF hash
map when the kernel signals device integrity via
security_bdev_setintegrity()
- bdev_free_security: removes devices from the map on teardown
Execution enforcement (deny-default policy):
- bprm_check_security: blocks execve() from untrusted sources
- mmap_file: blocks PROT_EXEC mmap (shared libs, anonymous exec memory)
- file_mprotect: blocks W->X transitions (JIT, libffi, etc.)
Trust anchors:
- Signed dm-verity volumes (sig_valid flag in the BPF map)
- Initramfs (s_dev captured at load time, cleared after switch_root)
- Everything else is denied (tmpfs, procfs, sysfs, anonymous PROT_EXEC)
PID1 requires dm-verity require_signatures=1 to be enabled and refuses
to load the BPF program otherwise, ensuring the kernel enforces that all
dm-verity devices carry valid signatures.
After attach, PID1 extracts owned FDs from the skeleton (link FDs +
.bss map FD) and lets the skeleton be destroyed. The dup'd link FDs
keep programs attached via the kernel reference chain (link FD ->
bpf_link -> bpf_prog -> bpf_map). Destroying the skeleton unmaps the
.bss page from PID1's address space so no BPF state is readable via
/proc/1/mem. The .bss map FD is retained for targeted writes (clearing
initramfs_s_dev after switch_root via mmap).
Signed-off-by: Christian Brauner <brauner@kernel.org>
Every dlopen_xxx() helper now takes an int log_level argument. It is
passed through to dlopen_many_sym_or_warn() (which in turn propagates it
to dlopen_verbose() for the library-not-installed case), and is used by
the fallback stub when support for the library is not compiled in to
emit a "<lib> support is not compiled in." message at the caller's level.
Callers pass LOG_DEBUG when gracefully degrading, or a higher level when
the failure should surface, and no longer need to log redundantly at the
call site.
As part of this, dlopen_bpf_full() (which already took a log_level) is
merged into dlopen_bpf() rather than keeping both.
The static inline fallbacks used to live in the headers, which required
pulling log.h in from every header that declared a dlopen_xxx(). Move
them into the .c files instead: the declaration is always outside the
#if HAVE_XXX block, the impl sits outside the outer #if HAVE_XXX wrap
with its own internal #if HAVE_XXX/#else/#endif, and apparmor-util.c,
idn-util.c, libmount-util.c and pam-util.c are now always compiled so
they can host their stubs.
The six .bpf.c files and their shared .bpf.h headers now live directly
under src/bpf/, rather than scattered across src/core/bpf/<prog>/,
src/network/bpf/<prog>/ and src/nsresourced/bpf/<prog>/.
All BPF compilation logic — the BPF_FRAMEWORK determination (clang/gcc/
bpftool/llvm-strip lookups), flag and command construction, vmlinux.h
handling, the bpf_programs list and the loop that builds the unstripped
object, the stripped object and the skeleton header for each program —
moves into src/bpf/meson.build. The top-level meson.build only keeps
option handling and the libbpf dependency. subdir('src/bpf') is pulled
up before config.h generation so that BPF_FRAMEWORK, HAVE_VMLINUX_H and
ENABLE_SYSCTL_BPF land in conf in time.
Skeleton wrapper headers (<prog>-skel.h) are now emitted by a
configure_file() template (src/bpf/bpf-skel-wrapper.h.in) at meson
setup, replacing the previously checked-in shims of the same name.
Consumer #include paths are flattened:
"bpf/<prog>/<prog>-skel.h" becomes "<prog>-skel.h",
"bpf/<prog>/<prog>-api.bpf.h" becomes "<prog>-api.bpf.h". src/bpf is
added to includes so the shared BPF headers resolve.
sysctl-write-event.h, now shared between userspace (networkd-sysctl.c)
and BPF (sysctl-monitor.bpf.c) from a single location, gains guarded
includes so pid_t and uint64_t resolve on both sides: vmlinux.h in the
BPF case (selected via __bpf__), stdint.h + sys/types.h otherwise.
After 3988e2489a, the function is a simple
wrapper of bpf_dlopen() with logging. Let's introduce dlopen_bpf_full()
that takes log level, and replace cgroup_bpf_supported() with it.
Currently, if you boot PID 1 in a container you always see a complaint
that BPF LSM won't work. That's fine, and log worthy, but probably not
above debug level. After all this is a really common case, and we should
gracefully adopt to our execution environment.
In containers securityfs is typically not mounted. Our lsm-bpf code
so far detected this situation and claimed the kernel was lacking
lsm-bpf support. Which isn't quite true though, it might very well
support it. This made boots of systemd in systemd-nspawn a bit ugly,
because of the misleading log message at boot.
Let's improve things, and make clearer what is going on.
libbpf returns error codes from the kernel unmodified, and we don't understand
them so non-fatal ones are handled as hard errors.
Add a translation helper, and start by translating 524 to EOPNOTSUPP, which is
returned when nsresourced tries to use LSM BPF hooks that are not
implemented on a given arch (in this case, arm64 is misssing trampolines).
Fixes https://github.com/systemd/systemd/issues/32170
- drop unnecessary SYNTHETIC_ERRNO() when the logger does not propagate
error code,
- drop unnecessary '%m' in error message when the error code is
specified with SYNTHETIC_ERRNO(),
- add missing full stop at the end of log message,
- use RET_GATHER(),
- add missing ", ignoring.",
- upeercase the first letter, etc., etc...
This refactors the Unit structure a bit: all cgroup-related state fields
are moved to a new structure CGroupRuntime, which is only allocated as
we realize a cgroup.
This is both a nice cleanup and should make unit structures considerably
smaller that have no cgroup associated, because never realized or
because they belong to a unit type that doesn#t have cgroups anyway.
This makes things nicely symmetric:
ExecContext → static user configuration about execution
ExecRuntime → dynamic user state of execution
CGroupContext → static user configuration about cgroups
CGroupRuntime → dynamic user state of cgroups
And each time the XyzContext is part of the unit type structures such as
Service or Slice that need it, but the runtime object is only allocated
when a unit is started.
This file is a bit misnamed. What it actually implements is one specific
BPF LSM module, that restricts file systems. As such it really should be
named after that, and not primarily by the mechanism it uses for that.
With this our glue code is now named the same way as the actual bpf code
files in src/core/bpf/, thus things become a bit more symmetric.
This is particular relevant as we'll soon have another BPF LSM in our
tree, see #26826, and we should be able to distinguish them by name.
This commit just renames the files and does some dumb search/replace of
the string. A follow-up commit will name some functions more expressively
inside the files.
Yu Watanabe
Luca Boccassi
Daan De Meyer
Christian Brauner
Daan De Meyer
Lennart Poettering
Luca Boccassi