I was looking at strace for systemd-getty-generator and noticed the call to
faccessat2(3</sys>, "", W_OK, AT_EMPTY_PATH), even though we already did
fstatfs(3</sys>), which should give us all the necessary information. Let's
only do this additional check when it's likely to yield something useful, i.e.
for network fses and otherwise skip the syscall.
The call to statvfs is replaced by statfs because that gives us the .f_type
field and allows is_network_fs() to be called.
I'm a bit worried that the is_network_fs() is somewhat costly. This will be
improved in later commits.
This partially reverts e86a492ff0.
The function getdents64() was introduced in glibc-2.30, and our baseline
on glibc is 2.31. Hence, we can assume the function always exists.
The posix_getdents() wrapper was introduced for compatibility with musl.
However, even the latest release of musl does not provide posix_getdents()
yet. Also, even with musl, by defining _LARGEFILE64_SOURCE, we can get
getdents64() and struct dirent64. Hence, the wrapper is anyway not
necessary.
Now that the necessary functions from log.h have been moved to macro.h,
we can stop including log.h in macro.h. This requires modifying source
files all over the tree to include log.h instead.
glibc exports getdents64 syscall as is, but musl exports it as
posix_getdents(). Let's introduce a simple wrapper of posix_getdents().
Note, our baseline for glibc is 2.31. Hence, we can assume getdents64()
always defined when building with glibc.
struct statx in glibc header was introduced in glibc-2.28
(fd70af45528d59a00eb3190ef6706cb299488fcd), but at that time,
sys/stat.h conflicts with linux/stat.h. Since glibc-2.30
(5dad6ffbb2b76215cfcd38c3001778536ada8e8a), sys/stat.h includes
linux/stat.h if exists.
Since now our baseline of glibc is 2.31. Hence, we can drop workarounds
for struct statx by importing linux/stat.h from newer kernel (v6.14-rc4).
This is a follow-up for 945a8210c7 and
makes the st_dev check generic, so that we can reuse it some other
places. It also incorporates the non-NULL check now, to be a
comprehensive one-stop solution.
The helper is static inline so that compilers can optimize the redundant
checks away in case it is combined with other checks.
For anonymous inodes, the result would be 0, but
the struct stat is initialized obviously.
So let's switch to st_dev for the check, which
is guaranteed to be non-zero.
Also this is completely unnecessary for statx(),
since we check stx_mask first and that on its own
denotes that the struct is initialized.
When newer glibc is used, but kernel does not support statx(), then
glibc try to fallback with fstatat(). That's quite similar to our
implementation, but the supported flags are different, and if
unsupported flags are specified, it returns EINVAL.
Let's handle the case more gracefully.
Let's be more accurate about what this function does: it checks whether
the underlying reported inode is the same. Internally, this already uses
a better named stat_inode_same() call, hence let's similarly name the
wrapping function following the same logic.
Similar for files_same_at() and path_equal_or_same_files().
No code changes, just some renaming.
Normal users do not have permissions to access /proc/1/root, so
'systemd-detect-virt -r' fails, but the output, even at debug level
is cryptic:
$ SYSTEMD_LOG_LEVEL=debug build/systemd-detect-virt -r
Failed to check for chroot() environment: Permission denied
Let's make this a bit easier to figure out:
$ SYSTEMD_LOG_LEVEL=debug build/systemd-detect-virt -r
Cannot stat /proc/1/root: Permission denied
Failed to check for chroot() environment: Permission denied
I looked over other users of files_same(), and I think in general the message
at debug level is OK for them too.
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.
-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 is a follow-up for f470cb6d13 which in
turn is a follow-up for a068aceafb.
The latter started to honour hidden files when deciding whether a
directory is empty. The former reverted to the old behaviour to fix
issue #23220.
It introduced a bug though: when a directory contains a larger number of
hidden entries the getdents64() buffer will not suffice to read them,
since we just allocate three entries for it (which is definitely enough
if we just ignore the . + .. entries, but not ig we ignore more).
I think it's a bit confusing that dir_is_empty() can return true even if
rmdir() on the dir would return ENOTEMPTY. Hence, let's rework the
function to make it optional whether hidden files are ignored or not.
After all, I looking at the users of this function I am pretty sure in
more cases we want to honour hidden files.
