- Rename to script_get_shebang_interpreter and return
-EMEDIUMTYPE if the executable is not a script.
We nowadays utilize the scheme of making ret param
of getters optional, and use them directly as checkers.
- Don't unnecessarily read the whole line, but check
only the shebang first.
This brings two benefits: we will label the created file only if it is
actually created, and we can correctly delete any file we create again
on failure.
Given that we have the LabelOps abstraction these days, we can teach
write_string_file() to use it, which means we can get rid of
fileio-label.[ch] as a separate concept.
(The only reason that fileio-label.[ch] exists independently of
fileio.[ch] was that the former linekd to libselinux potentially, and
thus had to be in src/shared/ while the other always was in src/basic/.
But the LabelOps vtable provides us with a nice work-around)
let's rename the "_ts" flavour of these calls "_full" instead, exposing
the full functionality. And then keep two more minimal versions around:
one "_at" (which has the ts parameter suppressed, but keeps the dir_fd
one). And one without suffix (which supresses both).
Do the same for the label versions of these calls.
The return value of read_stripped_line() is changed. Before we'd return the
number of characters read, but that number was not meaningful after we called
strstrip(). So just return 0 if nothing was read (EOF), and 1 if something was
read (not EOF). All the callers were only checking for <0 or ==0.
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()
When READ_FULL_FILE_UNBASE64 (or READ_FULL_FILE_UNHEX) is specified,
setting size argument by caller is difficult, as it is hard to estimate
the encoded length.
This makes when size is specified with decoding option, let's read file
more, and check decoded size later with the specified size.
path_simplify_full()/path_simplify() are changed to allow a NULL path, for
which a NULL is returned. Generally, callers have already asserted before that
the argument is nonnull. This way path_simplify_full()/path_simplify() and
path_simplify_alloc() behave consistently.
In sd-device.c, logging in device_set_syspath() is intentionally dropped: other
branches don't log.
In mount-tool.c, logging in parse_argv() is changed to log the user-specified
value, not the simplified string. In an error message, we should show the
actual argument we got, not some transformed version.
Chasing symlinks is a core function that's used in a lot of places
so it deservers a less verbose names so let's rename it to chase()
and chaseat().
We also slightly change the pattern used for the chaseat() helpers
so we get chase_and_openat() and similar.
This is a combination of fdopen() and fd_reopen(). i.e. it first reopens
the fd, and then converts that into a FILE*.
We do this at various places already manually. let's move this into a
helper call of its own.
These combine strndup() + strspn()/strcspn() into one.
There are a bunch of strndupa() calls that could use similar treatment
(or should be converted to strdup[c]spn(), but this commit doesn't
bother with that.
-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.
Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state
Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.
In some places, initialization is dropped if unnecessary.
This way we can connect correctly to any AF_UNIX socket in the file
system, and even save some code. Yay!
This also adds some test code for this, that ensures read_file_full()
works correctly for AF_UNIX sockets that violate the 108 char limit.
Supporting sockets like this kinda matters I think, for the simple
reason that apps want to build socket paths via XDG_RUNTIME_DIR and
suchlike, and we should be able to connect to them, even via
non-normalized paths.
let's not make up new errors in these checks that validate if connect()
work at all. After all, we don't really know if the ENXIO we saw earlier
actually is really caused by the inode being an AF_UNIX socket, we just
have the suspicion...
We mishandled the case where the size we read from the file actually
matched the maximum size fully. In that case we cannot really make a
determination whether the file was fully read or only partially. In that
case let's do another loop, so that we operate with a buffer, and
we can detect the EOF (which will be signalled to us via a short read).
There's a very gradual increase of anonymous memory in systemd-journald that
blames to 2ac67221bb.
systemd-journald makes many calls to read /proc/PID/cmdline and
/proc/PID/status, both of which tend to be well under 4K. However the
combination of allocating 4M read buffers, then using `realloc()` to
shrink the buffer in `read_virtual_file()` appears to be creating
fragmentation in the heap (when combined with the other allocations
systemd-journald is doing).
To help mitigate this, try reading /proc with a 4K buffer as
`read_virtual_file()` did before 2ac67221bb.
If it isn't big enough then try again with the larger buffers.
When reading virtual files (i.e. procfs, sysfs, …) we currently put a
limit of 4M-1 on that. We have to pick something, and we have to read
these files in a single read() (since the kernel generally doesn't
support continuation read()s for them). 4M-1 is actually the maximum
size the kernel allows for reads from files in /proc/sys/, all larger
reads will result in an ENOMEM error (which is really weird, but the
kernel does what the kernel does). Hence 4M-1 sounds like a smart
choice.
However, we made one mistake here: in order to be able to detect EOFs
properly we actually read one byte more than we actually intend to
return: if that extra byte can be read, then we know the file is
actually larger than our limit and we can generate an EFBIG error from
that. However, if it cannot be read then we know EOF was hit, and we are
good. So ultimately after all we issued a single 4M read, which the
kernel then responds with ENOMEM to. And that means read_virtual_file()
actually doesn't work properly right now on /proc/sys/. Let's fix that.
The fix is simple, lower the limit of the the buffer we intend to return
by one, i.e. 4M-2. That way, the read() we'll issue is exactly as large
as the limit the kernel allows, and we still get safely detect EOF from
it.
Mike Yuan
gerblesh
Lennart Poettering
Zbigniew Jędrzejewski-Szmek
Yu Watanabe
Daan De Meyer
Dimitri Papadopoulos
Antony Deepak Thomas
Anita Zhang