This is preparation for #28891, which adds a bunch more helpers around
"struct iovec", at which point this really deserves its own .c/.h file.
The idea is that we sooner or later can consider "struct iovec" as an
entirely generic mechanism to reference some binary blob, and is the
go-to type for this purpose whenever we need one.
We usually check return value of syscalls or glibc functions by it is
negative or not, something like that `if (stat(path, &st) < 0)`.
Let's also use the same style for lseek() and friends even the type of
their return value is off_t.
Note, fseeko() returns int, instead of off_t.
This simply checks if the specified PidRef refers to the process we are
running in.
(In case you wonder why this is not a static inline: to avoid cyclic
header inclusion problems between pidref.h + process-util.h)
Instead of mounting over, do an atomic swap using mount beneath, if
available. This way assets can be mounted again and again (e.g.:
updates) without leaking mounts.
For a given PID and namespace type, this helper function gives the PID
of the leader of the namespace containing the given PID. Use this in
systemd-coredump instead of using the existing get_mount_namespace_leader.
This helper will be used again in a later commit.
This setting indicates that the given unit wants to receive coredumps
for processes that crash within the cgroup of this unit. This setting
requires that Delegate= is also true, and therefore is only available
where Delegate= is available.
This will be used by systemd-coredump to support forwarding coredumps to
containers.
Currently we spawn services by forking a child process, doing a bunch
of work, and then exec'ing the service executable.
There are some advantages to this approach:
- quick: we immediately have access to all the enourmous amount of
state simply by virtue of sharing the memory with the parent
- easy to refactor and add features
- part of the same binary, will never be out of sync
There are however significant drawbacks:
- doing work after fork and before exec is against glibc's supported
case for several APIs we call
- copy-on-write trap: anytime any memory is touched in either parent
or child, a copy of that page will be triggered
- memory footprint of the child process will be memory footprint of
PID1, but using the cgroup memory limits of the unit
The last issue is especially problematic on resource constrained
systems where hard memory caps are enforced and swap is not allowed.
As soon as PID1 is under load, with no page out due to no swap, and a
service with a low MemoryMax= tries to start, hilarity ensues.
Add a new systemd-executor binary, that is able to receive all the
required state via memfd, deserialize it, prepare the appropriate
data structures and call exec_child.
Use posix_spawn which uses CLONE_VM + CLONE_VFORK, to ensure there is
no copy-on-write (same address space will be used, and parent process
will be frozen, until exec).
The sd-executor binary is pinned by FD on startup, so that we can
guarantee there will be no incompatibilities during upgrades.
This reworks the image discovery logic, and conceptually allows DDIs
that are both confext and sysext to exist. Previously we'd only extract
one type of exension data from a DDI, with this we allow to extract both
if both exist.
This doesn't add support for true "multi-modal" DDIs, that qualify as
various things at once, it just lays some ground work that ensures we at
least can dissect such images.
This reworks 484d26dac1 quite a bit.
This changes systemd-dissect's JSON output, but given the
version with the fields it changes/dops has never been released (as the
above patch was merged post-v254) this shouldn't be an issue.
We have the "tasks.max" cgroup attribute only if we run in a cgroup
namespace, but not on the host. Hence let's handle ENODATA silently
simply to reduce the debug noise generated.
Let's modernize and clean up search_and_fopen a bit: let's add support
for regular open() (instead of fopen()), as well as access() (if caller
just wants to check if a file exists without opening it.
This unifies much of the code involved, which previously was duplicated
in search_and_fopen() and search_and_fopen_nulstr()
Lennart Poettering
Mike Yuan
Yu Watanabe
Arseny Maslennikov
Luca Boccassi
Nick Rosbrook
Zbigniew Jędrzejewski-Szmek