Unroll slightly and enforce good instruction scheduling. This improves
performance on out-of-order machines. The unrolling allows for
pipelined multiplies.
As well, as an optional sysdep, reorder the operations and prevent
reassosiation for better scheduling and higher ILP. This commit
only adds the barrier for x86, although it should be either no
change or a win for any architecture.
Unrolling further started to induce slowdowns for sizes [0, 4]
but can help the loop so if larger sizes are the target further
unrolling can be beneficial.
Results for _dl_new_hash
Benchmarked on Tigerlake: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
Time as Geometric Mean of N=30 runs
Geometric of all benchmark New / Old: 0.674
type, length, New Time, Old Time, New Time / Old Time
fixed, 0, 2.865, 2.72, 1.053
fixed, 1, 3.567, 2.489, 1.433
fixed, 2, 2.577, 3.649, 0.706
fixed, 3, 3.644, 5.983, 0.609
fixed, 4, 4.211, 6.833, 0.616
fixed, 5, 4.741, 9.372, 0.506
fixed, 6, 5.415, 9.561, 0.566
fixed, 7, 6.649, 10.789, 0.616
fixed, 8, 8.081, 11.808, 0.684
fixed, 9, 8.427, 12.935, 0.651
fixed, 10, 8.673, 14.134, 0.614
fixed, 11, 10.69, 15.408, 0.694
fixed, 12, 10.789, 16.982, 0.635
fixed, 13, 12.169, 18.411, 0.661
fixed, 14, 12.659, 19.914, 0.636
fixed, 15, 13.526, 21.541, 0.628
fixed, 16, 14.211, 23.088, 0.616
fixed, 32, 29.412, 52.722, 0.558
fixed, 64, 65.41, 142.351, 0.459
fixed, 128, 138.505, 295.625, 0.469
fixed, 256, 291.707, 601.983, 0.485
random, 2, 12.698, 12.849, 0.988
random, 4, 16.065, 15.857, 1.013
random, 8, 19.564, 21.105, 0.927
random, 16, 23.919, 26.823, 0.892
random, 32, 31.987, 39.591, 0.808
random, 64, 49.282, 71.487, 0.689
random, 128, 82.23, 145.364, 0.566
random, 256, 152.209, 298.434, 0.51
Co-authored-by: Alexander Monakov <amonakov@ispras.ru>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
No change to the code other than moving the function to
dl-new-hash.h. Changed name so its now in the reserved namespace.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This avoids an alias violation later. This commit also fixes
an incorrect double-checked locking idiom in _nl_init_era_entries.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
We can call the cleanup functions directly from _nl_unload_locale
if we pass the category to it.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The function performs the same steps for ld_archive locales
(mapped from an archive), and this code is not performance-critical,
so the specialization does not add value.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This code path is exercised indirectly by some of the DNS stub
resolver tests, via their own use of xopen_memstream for constructing
strings describing result data. The relative lack of test suite
coverage became apparent when these tests starting failing after a
printf changes uncovered bug 28949.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
form_character and form_string processing a sufficiently similar
that the logic can be shared.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This simplies formatting and helps with debugging. It also allows
the use of localized COMPILE_WPRINTF preprocessor conditionals.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit e938c0274 "Don't add access size hints to fortifiable functions"
converted a few '__attr_access ((...))' into '__fortified_attr_access (...)'
calls.
But one of conversions had double parentheses of '__fortified_attr_access (...)'.
Noticed as a gnat6 build failure:
/<<NIX>>-glibc-2.34-210-dev/include/bits/string_fortified.h:110:50: error: macro "__fortified_attr_access" requires 3 arguments, but only 1 given
The change fixes parentheses.
This is seen when using compilers that do not support
__builtin___stpncpy_chk, e.g. gcc older than 4.7, clang older than 2.6
or some compiler not derived from gcc or clang.
Signed-off-by: Sergei Trofimovich <slyich@gmail.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
To check for the pidfd functions pidfd_open, pidfd_getfd, pid_send_signal,
and waitid with P_PIDFD.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
It was added on Linux 5.4 (3695eae5fee0605f316fbaad0b9e3de791d7dfaf)
to extend waitid to wait on pidfd.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was added on Linux 5.1(3eb39f47934f9d5a3027fe00d906a45fe3a15fad)
as a way to avoid the race condition of using kill (where PID might be
reused by the kernel between between obtaining the pid and sending the
signal).
If the siginfo_t argument is NULL then pidfd_send_signal is equivalent
to kill. If it is not NULL pidfd_send_signal is equivalent to
rt_sigqueueinfo.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was added on Linux 5.6 (8649c322f75c96e7ced2fec201e123b2b073bf09)
as a way to retrieve a file descriptors for another process though
pidfd (created either with CLONE_PIDFD or pidfd_getfd). The
functionality is similar to recvmmsg SCM_RIGHTS.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was added on Linux 5.3 (32fcb426ec001cb6d5a4a195091a8486ea77e2df)
as a way to retrieve a pid file descriptors for process that has not
been created CLONE_PIDFD (by usual fork/clone).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
A separate asm file is easier to maintain than a macro that expands to
inline asm.
The RTLD_START macro is only needed now because _dl_start is local in
rtld.c, but _start has to call it, if _dl_start was made hidden then it
could be empty.
_dl_skip_args is no longer needed.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This is for bug 23293 and it relies on the glibc test system running
tests via explicit ld.so invokation by default.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
_dl_skip_args is always 0, so the target specific code that modifies
argv after relro protection is applied is no longer used.
After the patch relro protection is applied to _dl_argv consistently
on all targets.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
When an executable is invoked as
./ld.so [ld.so-args] ./exe [exe-args]
then the argv is adujusted in ld.so before calling the entry point of
the executable so ld.so args are not visible to it. On most targets
this requires moving argv, env and auxv on the stack to ensure correct
stack alignment at the entry point. This had several issues:
- The code for this adjustment on the stack is written in asm as part
of the target specific ld.so _start code which is hard to maintain.
- The adjustment is done after _dl_start returns, where it's too late
to update GLRO(dl_auxv), as it is already readonly, so it points to
memory that was clobbered by the adjustment. This is bug 23293.
- _environ is also wrong in ld.so after the adjustment, but it is
likely not used after _dl_start returns so this is not user visible.
- _dl_argv was updated, but for this it was moved out of relro, which
changes security properties across targets unnecessarily.
This patch introduces a generic _dl_start_args_adjust function that
handles the argument adjustments after ld.so processed its own args
and before relro protection is applied.
The same algorithm is used on all targets, _dl_skip_args is now 0, so
existing target specific adjustment code is no longer used. The bug
affects aarch64, alpha, arc, arm, csky, ia64, nios2, s390-32 and sparc,
other targets don't need the change in principle, only for consistency.
The GNU Hurd start code relied on _dl_skip_args after dl_main returned,
now it checks directly if args were adjusted and fixes the Hurd startup
data accordingly.
Follow up patches can remove _dl_skip_args and DL_ARGV_NOT_RELRO.
Tested on aarch64-linux-gnu and cross tested on i686-gnu.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
SHT_RISCV_ATTRIBUTES, PT_RISCV_ATTRIBUTES, DT_RISCV_VARIANT_CC were
added in commit 0b6c675073
("Update RISC-V specific ELF definitions"). This caused the
elf/tst-glibcelf consistency check to fail.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The Linux version used by i686 and m68k provide three overrrides for
generic code:
1. DISTINGUISH_LIB_VERSIONS to print additional information when
libc5 is used by a dependency.
2. EXTRA_LD_ENVVARS to that enabled LD_LIBRARY_VERSION environment
variable.
3. EXTRA_UNSECURE_ENVVARS to add two environment variables related
to aout support.
None are really requires, it has some decades since libc5 or aout
suppported was removed and Linux even remove support for aout files.
The LD_LIBRARY_VERSION is also dead code, dl_correct_cache_id is not
used anywhere.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The kernel version check is used to avoid glibc to run on older
kernels where some syscall are not available and fallback code are
not enabled to handle graciously fail. However, it does not prevent
if the kernel does not correctly advertise its version through
vDSO note, uname or procfs.
Also kernel version checks are sometime not desirable by users,
where they want to deploy on different system with different kernel
version knowing the minimum set of syscall is always presented on
such systems.
The kernel version check has been removed along with the
LD_ASSUME_KERNEL environment variable. The minimum kernel used to
built glibc is still provided through NT_GNU_ABI_TAG ELF note and
also printed when libc.so is issued.
Checked on x86_64-linux-gnu.
Currently on Linux __get_nprocs_conf first tries to enumerate the
cpus present in the system by iterating on /sys/devices/system/cpuX
directories. This only enumerates the CPUs that are present in
system (but possibly offline), not taking in account possible CPU
that might added in the system through hotplugging.
Linux provides the maximum number of configured cpus on the
/sys/devices/system/cpu file. Although it might present a larger
value of possible active CPUs on some system (where kernel either
get the information from firmaware or is configured at boot time),
the information is what kernel presents to userland.
This also change the returned value of _SC_NPROCESSORS_CONF, which
aligns as the maximum configure cpu in the system.
Checked on x86_64-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This implements mmap fallback for a brk failure during TLS
allocation.
scripts/tls-elf-edit.py is updated to support the new patching method.
The script no longer requires that in the input object is of ET_DYN
type.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The check for an ISO C compiler assumes that anything GCC-like will
define __STDC__, even if it's actually a C++ compiler. That's currently
true for G++ and compilers like clang++ that also define __GNUC__, but
it might not always be true.
The C++ standard leaves it implementation-defined whether or not
__STDC__ is defined by C++ compilers. And really the check should be
"ISO C or ISO C++ conforming compiler" anyway. So only give an error if
__GNUC__ is defined and neither __STDC__ nor __cplusplus is defined.
Reviewed-by: Fangrui Song <maskray@google.com>
The fix c8ee1c85 introduced a -1 check for object size without also
checking that object size is a constant. Because of this, the tree
optimizer passes in gcc fail to fold away one of the branches in
__glibc_fortify and trips on a spurious Wstringop-overflow. The warning
itself is incorrect and the branch does go away eventually in DCE in the
rtl passes in gcc, but the constant check is a helpful hint to simplify
code early, so add it in.
Resolves: BZ #29141
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Both symbols are marked as legacy in POSIX.1-2001 and removed on
POSIX.1-2008, although the prototypes are defined for _GNU_SOURCE
or _DEFAULT_SOURCE.
GCC also replaces bcopy with a memmove and bzero with memset on default
configuration (to actually get a bzero libc call the code requires
to omit string.h inclusion and built with -fno-builtin), so it is
highly unlikely programs are actually calling libc bzero symbol.
On a recent Linux distro (Ubuntu 22.04), there is no bzero calls
by the installed binaries.
$ cat count_bstring.sh
#!/bin/bash
files=`IFS=':';for i in $PATH; do test -d "$i" && find "$i" -maxdepth 1 -executable -type f; done`
total=0
for file in $files; do
symbols=`objdump -R $file 2>&1`
if [ $? -eq 0 ]; then
ncalls=`echo $symbols | grep -w $1 | wc -l`
((total=total+ncalls))
if [ $ncalls -gt 0 ]; then
echo "$file: $ncalls"
fi
fi
done
echo "TOTAL=$total"
$ ./count_bstring.sh bzero
TOTAL=0
Checked on x86_64-linux-gnu.
Avoid fiddling with autoconf internals and use AC_DEFINE_UNQUOTED to
define macros in the configuration headers rather than handcoding an
equivalent shell sequence with the use of the `as_echo' undocumented
variable.
Switch to using AC_MSG_ERROR rather than `echo' and `exit' directly for
error handling. Owing to the lack of any kind of error annotation it
makes it difficult to spot the message in the flood in a parallel build
and neither it is logged in `config.log'.
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Avoid fiddling with autoconf internals and use AC_DEFINE_UNQUOTED to
define macros in the configuration headers rather than handcoding an
equivalent shell sequence with the use of the `as_echo' undocumented
variable.
Similarly use AC_MSG_ERROR for error handling rather than the internal
undocumented `as_fn_error' variable. Switch to using 1 as the exit code
as it makes no sense to refer $? in the contexts involved, it's not a
command failure handled there.
Switch to using AC_MSG_ERROR rather than `echo' and `exit' directly for
error handling. Owing to the lack of any kind of error annotation it
makes it difficult to spot the message in the flood in a parallel build
and neither it is logged in `config.log'.
Avoid fiddling with autoconf internals and use AC_DEFINE_UNQUOTED to
define macros in the configuration headers rather than handcoding an
equivalent shell sequence with the use of the `as_echo' undocumented
variable.
Switch to using AC_MSG_ERROR rather than `echo' and `exit' directly for
error handling. Owing to the lack of any kind of error annotation it
makes it difficult to spot the message in the flood in a parallel build
and neither it is logged in `config.log'.
The siglist.c is built with -fno-toplevel-reorder to avoid compiler
to reorder the compat assembly directives due an assembler
issue [1] (fixed on 2.39).
This patch removes the compiler flags by split the compat symbol
generation in two phases. First the __sys_siglist and __sys_sigabbrev
without any compat symbol directive is preprocessed to generate an
assembly source code. This generate assembly is then used as input
on a platform agnostic siglist.S which then creates the compat
definitions. This prevents compiler to move any compat directive
prior the _sys_errlist definition itself.
Checked on a make check run-built-tests=no on all affected ABIs.
Reviewed-by: Fangrui Song <maskray@google.com>
The errlist.c is built with -fno-toplevel-reorder to avoid compiler to
reorder the compat assembly directives due an assembler issue [1]
(fixed on 2.39).
This patch removes the compiler flags by split the compat symbol
generation in two phases. First the _sys_errlist_internal internal
without any compat symbol directive is preprocessed to generate an
assembly source code. This generate assembly is then used as input
on a platform agnostic errlist-data.S which then creates the compat
definitions. This prevents compiler to move any compat directive
prior the _sys_errlist_internal definition itself.
Checked on a make check run-built-tests=no on all affected ABIs.
[1] https://sourceware.org/bugzilla/show_bug.cgi?id=29012
The GNU implementation of wcrtomb assumes that there are at least
MB_CUR_MAX bytes available in the destination buffer passed to wcrtomb
as the first argument. This is not compatible with the POSIX
definition, which only requires enough space for the input wide
character.
This does not break much in practice because when users supply buffers
smaller than MB_CUR_MAX (e.g. in ncurses), they compute and dynamically
allocate the buffer, which results in enough spare space (thanks to
usable_size in malloc and padding in alloca) that no actual buffer
overflow occurs. However when the code is built with _FORTIFY_SOURCE,
it runs into the hard check against MB_CUR_MAX in __wcrtomb_chk and
hence fails. It wasn't evident until now since dynamic allocations
would result in wcrtomb not being fortified but since _FORTIFY_SOURCE=3,
that limitation is gone, resulting in such code failing.
To fix this problem, introduce an internal buffer that is MB_LEN_MAX
long and use that to perform the conversion and then copy the resultant
bytes into the destination buffer. Also move the fortification check
into the main implementation, which checks the result after conversion
and aborts if the resultant byte count is greater than the destination
buffer size.
One complication is that applications that assume the MB_CUR_MAX
limitation to be gone may not be able to run safely on older glibcs if
they use static destination buffers smaller than MB_CUR_MAX; dynamic
allocations will always have enough spare space that no actual overruns
will occur. One alternative to fixing this is to bump symbol version to
prevent them from running on older glibcs but that seems too strict a
constraint. Instead, since these users will only have made this
decision on reading the manual, I have put a note in the manual warning
them about the pitfalls of having static buffers smaller than
MB_CUR_MAX and running them on older glibc.
Benchmarking:
The wcrtomb microbenchmark shows significant increases in maximum
execution time for all locales, ranging from 10x for ar_SA.UTF-8 to
1.5x-2x for nearly everything else. The mean execution time however saw
practically no impact, with some results even being quicker, indicating
that cache locality has a much bigger role in the overhead.
Given that the additional copy uses a temporary buffer inside wcrtomb,
it's likely that a hot path will end up putting that buffer (which is
responsible for the additional overhead) in a similar place on stack,
giving the necessary cache locality to negate the overhead. However in
situations where wcrtomb ends up getting called at wildly different
spots on the call stack (or is on different call stacks, e.g. with
threads or different execution contexts) and is still a hotspot, the
performance lag will be visible.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
And keep the previous definition if it exists. This allows
disabling IA64_USE_NEW_STUB while keeping USE_DL_SYSINFO defined.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
