If log_do_header() was called with overly long parameters, it'd generate
improper output. Essentially, it'd be truncated at random point, in particular
missing a newline at the end, so it'd run with the next field, usually MESSAGE=.
log_do_header is called with parameters from compiled code (file name, lien
nubmer, etc), so in practice this was unlikely to ever be a problem, but it is
possible. In particular, if systemd was compiled from sources in some deeply
nested directory (which happens for example in mock and other build roots), the
filename could be very long.
As a safety measure, let's truncate all parameters to 256 bytes. So we have
5 fields which are 256 bytes (plus the field name prefix), and a few other
fields with fixed width. This must always fit in the 2048 byte buffer.
I don't think there's much gain in calculating the required length precisely,
since it's a lot of fields and a few bytes allocated on the stack don't matter.
log.h really should only include the bare minimum of other headers, as
it is really pulled into pretty much everything else and already in
itself one of the most basic pieces of code we have.
Let's hence drop inclusion of:
1. sd-id128.h because it's entirely unneeded in current log.h
2. errno.h, dito.
3. sys/signalfd.h which we can replace by a simple struct forward
declaration
4. process-util.h which was needed for getpid_cached() which we now hide
in a funciton log_emergency_level() instead, which nicely abstracts
the details away.
5. sys/socket.h which was needed for struct iovec, but a simple struct
forward declaration suffices for that too.
Ultimately this actually makes our source tree larger (since users of
the functionality above must now include it themselves, log.h won't do
that for them), but I think it helps to untangle our web of includes a
tiny bit.
(Background: I'd like to isolate the generic bits of src/basic/ enough
so that we can do a git submodule import into casync for it)
This moves pretty much all uses of getpid() over to getpid_raw(). I
didn't specifically check whether the optimization is worth it for each
replacement, but in order to keep things simple and systematic I
switched over everything at once.
The single log level is split into an array of log levels. Which index in the
array is used can be determined for each compilation unit separately by setting
a macro before including log.h. All compilation units use the same index
(LOG_REALM_SYSTEMD), so there should be no functional change.
v2:
- the "realm" is squished into the level (upper bits that are not used by
priority or facility), and unsquished later in functions in log.c.
v3:
- rename REALM_PLUS_LEVEL to LOG_REALM_PLUS_LEVEL and REALM to LOG_REALM_REMOVE_LEVEL.
We don't have plural in the name of any other -util files and this
inconsistency trips me up every time I try to type this file name
from memory. "formats-util" is even hard to pronounce.