We had 'msghdr' and 'mh' in various places. Now 'const struct msghdr msghdr' is
used consistently. With structured init the variable is only used in the call
to sendmsg(), so let's make it a bit more descriptive.
In general we almost never hit those asserts in production code, so users see
them very rarely, if ever. But either way, we just need something that users
can pass to the developers.
We have quite a few of those asserts, and some have fairly nice messages, but
many are like "WTF?" or "???" or "unexpected something". The error that is
printed includes the file location, and function name. In almost all functions
there's at most one assert, so the function name alone is enough to identify
the failure for a developer. So we don't get much extra from the message, and
we might just as well drop them.
Dropping them makes our code a tiny bit smaller, and most importantly, improves
development experience by making it easy to insert such an assert in the code
without thinking how to phrase the argument.
We would try to return a value that could be nonzero only if the kernel
reported writing more bytes than we gave to it, hopefully a rare occurence.
Instead, assert that this doesn't happen.
Instead, return true if we got to the end of the iovec array. The caller
can use this information to know that the whole iovec array was written.
This allows one loop to be dropped in write_to_syslog().
Also drop _unlikely_: this function is called with very short arrays, and
it *is* likely that we trigger this condition. Let's just let the compiler
generate normal code without giving it a potentially false hint.
Commit 0b1f3c768c has introduced log_open()
calls after exec fails post-fork. However, the log_open() call itself could
change the value of errno, which, for me, manifested in:
$ coredumpctl gdb
...
Failed to invoke gdb: Success
Fix this by using PROTECT_ERRNO in log_open().
CLI tools may be used in a script. E.g., a script for monitoring a
service may use `systemctl`. Previously, if the kernel command line has
e.g. systemd.log-level=debug, then systemctl in the script produces
debugging logs when the script is invoked by a .service unit, but does
not when the script is running in a terminal. Then,
https://github.com/systemd/systemd/pull/18281#discussion_r561697482,
> I expect users to be (negatively) surprised.
In the previous commit, $SYSTEMD_EXEC_PID= is introduced. Then, we can
now detect whether a command is directly invoked by systemd or through
a script. Let's skip reading the kernel command line when a command is
invoked through a script.
This effectively reverts 41d1f469cf.
Before this, e.g., `networkctl reload` invoked by `systemctl reload systemd-networkd.service`
does not produce debugging logs even if systemd.log-level=debug is set. This fixes
the issue.
THis doesn't change the condition's logic at all, but is an attempt to
make things a bit more readable: instead of checking log_target !=
LOG_TARGET_AUTO let's actually list the targets where we want to
consider journal/syslog/kmsg, to make things a bit less confusing. After
all the message here is not to avoid them if LOG_TARGET_AUTO is set, but
to definitely do them in the other cases.
It always was the intention to expose this as trusted field _TID=, i.e.
automatically determine it from journald via some SCM_xyz field or so,
but this is never happened, and it's unlikely this will be added anytime
soon to the kernel either, hence let's just generate this sender side,
even if it means it's untrusted.
This was needed before commit 16e4fd87c5 added a
mode that opens the log fds for every single log message. This mode is used in
execute.c since then making the explicit call to log_open unnecessary.
This basically reverts ea89a119cd.
Presently, CLI utilities such as systemctl will check whether they have a tty
attached or not to decide whether to parse /proc/cmdline or EFI variable
SystemdOptions looking for systemd.log_* entries.
But this check will be misleading if these tools are being launched by a
daemon, such as a monitoring daemon or automation service that runs in
background.
Make log handling of CLI tools uniform by never checking /proc/cmdline or EFI
variables to determine the logging level.
Furthermore, introduce a new log_setup_cli() shortcut to set up common options
used by most command-line utilities.
In recent systemd-nspawn we wouldn't parse init args like systemd.log-level=debug.
This is because we wouldn't even look at /proc/1/cmdline.
$ systemd-nspawn -n cat /proc/1/stat
1 (cat) R 0 1 1 34816 ....
^^^^^
34816 is 136:0 a.k.a. /dev/pts/0.
And obviously CONFIG_LINE=0 is also not logged.
The way that log_syntax_internal now looks is becoming a bit crazy, but we
can't easily conditionalize on both unit and config_file, and we have different
types, so it's not easy to make this more compact.
We would log "(null):0: Failed to parse system call, ignoring: rseq" from
log_syntax_internal() from log_syntax() from seccomp_parse_syscall_filter_full()
from seccomp_parse_syscall_filter() from config_parse_syscall_filter(),
when generating the built-in @default whitelist. Since it was not based on the
unit file, we would not pass a file name.
So let's make sure that log_syntax() does not print "(null)" pointer (which is
iffy and ugly), and use the unit name as fallback or nothing if both are missing.
In principle, one of the two should be always available, since why use log_syntax()
otherwise, but let's make things more resilient by guarding against this case too.
log_syntax() is called from a thousand places, and often in error path, so it's
hard to verify all callers.
Zbigniew Jędrzejewski-Szmek
Sergey Bugaev
Yu Watanabe
Lennart Poettering
rnhmjoj
Franck Bui
Filipe Brandenburger
Daan De Meyer
Dan Streetman
Ivan Shapovalov