This wraps the call to org.freedesktop.DBus.Introspectable.Introspect.
Using "busctl call" directly is inconvenient because busctl escapes the
string before printing.
Example:
$ busctl introspect --xml org.freedesktop.systemd1 /org/freedesktop/systemd1 | pygmentize -lxml | less -RF
test-bus-introspect is also applied to the tables from test-bus-vtable.c.
test-bus-vtable.c is also used as C++ sources to produce test-bus-vtable-cc,
and our hashmap headers are not C++ compatible. So let's do the introspection
part only in the C version.
Just moving code around, in preparation to allow the content creation
part to be used in other places.
On the surface of things, introspect_path() should be in bus-introspect.c, but
introspect_path() uses many static helper functions in bus-objects.c, so moving
it would require all of them to be exposed, which is too much trouble.
test-bus-introspect is updated to actually write the closing bracket.
We would check the size of sd_bus_vtable entries, requring one of the two known
sizes. But we should be able to extend the structure in the future, by adding
new fields, without breaking backwards compatiblity.
Incidentally, this check was what caused -EINVAL failures before, when programs
were compiled with systemd-242 and run with older libsystemd.
In 856ad2a86b sd_bus_add_object_vtable() and
sd_bus_add_fallback_vtable() were changed to take an updated sd_bus_vtable[]
array with additional 'features' and 'names' fields in the union.
The commit tried to check whether the old or the new table format is used, by
looking at the vtable[0].x.start.element_size field, on the assumption that the
added fields caused the structure size to grow. Unfortunately, this assumption
was false, and on arm32 (at least), the structure size is unchanged.
In libsystemd we use symbol versioning and a major.minor.patch semantic
versioning of the library name (major equals the number in the so-name). When
systemd-242 was released, the minor number was (correctly) bumped, but this is
not enough, because no new symbols were added or symbol versions changed. This
means that programs compiled with the new systemd headers and library could be
successfully linked to older versions of the library. For example rpm only
looks at the so-name and the list of versioned symbols, completely ignoring the
major.minor numbers in the library name. But the older library does not
understand the new vtable format, and would return -EINVAL after failing the
size check (on those architectures where the structure size did change, i.e.
all 64 bit architectures).
To force new libsystemd (with the functions that take the updated
sd_bus_vtable[] format) to be used, let's pull in a dummy symbol from the table
definition. This is a bit wasteful, because a dummy pointer has to be stored,
but the effect is negligible. In particular, the pointer doesn't even change
the size of the structure because if fits in an unused area in the union.
The number stored in the new unsigned integer is not checked anywhere. If the
symbol exists, we already know we have the new version of the library, so an
additional check would not tell us anything.
An alternative would be to make sd_bus_add_{object,fallback}_vtable() versioned
symbols, using .symver linker annotations. We would provide
sd_bus_add_{object,fallback}_vtable@LIBSYSTEMD_221 (for backwards
compatibility) and e.g. sd_bus_add_{object,fallback}_vtable@@LIBSYSTEMD_242
(the default) with the new implementation. This would work too, but is more
work. We would have to version at least those two functions. And it turns out
that the .symver linker instructions have to located in the same compilation
unit as the function being annotated. We first compile libsystemd.a, and then
link it into libsystemd.so and various other targets, including
libsystemd-shared.so, and the nss modules. If the .symver annotations were
placed next to the function definitions (in bus-object.c), they would influence
all targets that link libsystemd.a, and cause problems, because those functions
should not be exported there. To export them only in libsystemd.so, compilation
would have to be rearranged, so that the functions exported in libsystemd.so
would not be present in libsystemd.a, but a separate compilation unit containg
them and the .symver annotations would be linked solely into libsystemd.so.
This is certainly possible, but more work than the approach in this patch.
856ad2a86b has one more issue: it relies on the
undefined fields in sd_bus_vtable[] array to be zeros. But the structure
contains a union, and fields of the union do not have to be zero-initalized by
the compiler. This means that potentially, we could have garbarge values there,
for example when reading the old vtable format definition from the new function
implementation. In practice this should not be an issue at all, because vtable
definitions are static data and are placed in the ro-data section, which is
fully initalized, so we know that those undefined areas will be zero. Things
would be different if somebody defined the vtable array on the heap or on the
stack. Let's just document that they should zero-intialize the unused areas
in this case.
The symbol checking code had to be updated because otherwise gcc warns about a
cast from unsigned to a pointer.
With gcc-9.0.1-0.10.fc30.x86_64:
../src/network/netdev/macsec.c: In function ‘config_parse_macsec_port’:
../src/network/netdev/macsec.c:584:24: warning: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Waddress-of-packed-member]
584 | dest = &c->sci.port;
| ^~~~~~~~~~~~
../src/network/netdev/macsec.c:592:24: warning: taking address of packed member of ‘struct <anonymous>’ may result in an unaligned pointer value [-Waddress-of-packed-member]
592 | dest = &b->sci.port;
| ^~~~~~~~~~~~
(The alignment was probably OK, but it's nicer to avoid the warning anyway.)
When shooting down a service with SIGABRT the user might want to have a
much longer stop timeout than on regular stops/shutdowns. Especially in
the face of short stop timeouts the time might not be sufficient to
write huge core dumps before the service is killed.
This commit adds a dedicated (Default)TimeoutAbortSec= timer that is
used when stopping a service via SIGABRT. In all other cases the
existing TimeoutStopSec= is used. The timer value is unset by default
to skip the special handling and use TimeoutStopSec= for state
'stop-watchdog' to keep the old behaviour.
If the service is in state 'stop-watchdog' and the service should be
stopped explicitly we still go to 'stop-sigterm' and re-apply the usual
TimeoutStopSec= timeout.
[zj: this is a subset of changes generated by clang-format, just the ones
I think improve readability or consistency.]
This is a part of https://github.com/systemd/systemd/pull/11811.
In cgroup v2 we have protection tunables -- currently MemoryLow and
MemoryMin (there will be more in future for other resources, too). The
design of these protection tunables requires not only intermediate
cgroups to propagate protections, but also the units at the leaf of that
resource's operation to accept it (by setting MemoryLow or MemoryMin).
This makes sense from an low-level API design perspective, but it's a
good idea to also have a higher-level abstraction that can, by default,
propagate these resources to children recursively. In this patch, this
happens by having descendants set memory.low to N if their ancestor has
DefaultMemoryLow=N -- assuming they don't set a separate MemoryLow
value.
Any affected unit can opt out of this propagation by manually setting
`MemoryLow` to some value in its unit configuration. A unit can also
stop further propagation by setting `DefaultMemoryLow=` with no
argument. This removes further propagation in the subtree, but has no
effect on the unit itself (for that, use `MemoryLow=0`).
Our use case in production is simplifying the configuration of machines
which heavily rely on memory protection tunables, but currently require
tweaking a huge number of unit files to make that a reality. This
directive makes that significantly less fragile, and decreases the risk
of misconfiguration.
After this patch is merged, I will implement DefaultMemoryMin= using the
same principles.
