AT_EMPTY_PATH is a requirement to implement fstat over fstatat,
however it does not prevent the kernel to read the path argument.
It is not an issue, but on x86-64 with SMAP-capable CPUs the kernel is
forced to perform expensive user memory access. After that regular
lookup is performed which adds even more overhead.
Instead, issue the fstat syscall directly on LFS fstat implementation
(32 bit architectures will still continue to use statx, which is
required to have 64 bit time_t support). it should be even a
small performance gain on non x86_64, since there is no need
to handle the path argument.
Checked on x86_64-linux-gnu.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
Now that fstat is implemented on top fstatat we need to handle negative
inputs. The implementation now rejects AT_FDCWD, which would otherwise
be accepted by the kernel.
Checked on x86_64-linux-gnu and on i686-linux-gnu.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
A new struct __stat{64}_t64 type is added with the required
__timespec64 time definition. Only LFS is added, 64-bit time with
32-bit offsets is not supposed to be supported (no existing glibc
configuration supports such a combination). It is done with an extra
__NR_statx call plus a conversion to the new __stat{64}_t64 type.
The statx call is done only for 32-bit time_t ABIs.
Internally some extra routines to copy from/to struct stat{64}
to struct __stat{64} used on multiple implementations (stat, fstat,
lstat, and fstatat) are added on a extra implementation
(stat_t64_cp.c). Alse some extra routines to copy from statx to
__stat{64} is added on statx_cp.c.
Checked with a build for all affected ABIs. I also checked on x86_64,
i686, powerpc, powerpc64le, sparcv9, sparc64, s390, and s390x.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Both fstatat and fstata64 calls the old fxstatat and fxstatat64
repectivelly with _STAT_VER, the one currently exported as default
for all ABIs.
Checked with a build for all affected ABIs. I also checked on x86_64,
i686, powerpc, powerpc64le, sparcv9, sparc64, s390, and s390x.
Reviewed-by: Lukasz Majewski <lukma@denx.de>
