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As tested by Gnulib's renameatu module.
Reported by Collin Funk on
https://sourceware.org/bugzilla/show_bug.cgi?id=32570
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C23 adds various <math.h> function families originally defined in TS
18661-4. Add the compoundn functions, which compute (1+X) to the
power Y for integer Y (and X at least -1). The integer exponent has
type long long int in C23; it was intmax_t in TS 18661-4, and as with
other interfaces changed after their initial appearance in the TS, I
don't think we need to support the original version of the interface.
Note that these functions are "compoundn" with a trailing "n", *not*
"compound" (CORE-MATH has the wrong name, for example).
As with pown, I strongly encourage searching for worst cases for ulps
error for these implementations (necessarily non-exhaustively, given
the size of the input space). I also expect a custom implementation
for a given format could be much faster as well as more accurate (I
haven't tested or benchmarked the CORE-MATH implementation for
binary32); this is one of the more complicated and less efficient
functions to implement in a type-generic way.
As with exp2m1 and exp10m1, this showed up places where the
powerpc64le IFUNC setup is not as self-contained as one might hope (in
this case, without the changes specific to powerpc64le, there were
undefined references to __GI___expf128).
Tested for x86_64 and x86, and with build-many-glibcs.py.
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It requires $(shared-thread-library). Fixes 0c342594237.
Checked on a i686-gnu build.
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These routines are not extensively used (gnulib documentation even
recommend use a replacement [1]), and there is already a POWER8
version that uses proper vectorized instructions.
[1] https://www.gnu.org/software/gnulib/manual/gnulib.html#C-strings
Checked with a build for some powerpc variations.
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>
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The glibc-hwcaps subdirectories are extended by "z17". Libraries are loaded if
the z17 facility bits are active:
- Miscellaneous-instruction-extensions facility 4
- Vector-enhancements-facility 3
- Vector-Packed-Decimal-Enhancement Facility 3
- CPU: Concurrent-Functions Facility
tst-glibc-hwcaps.c is extended in order to test z17 via new marker6.
In case of running on a z17 with a kernel not recognizing z17 yet,
AT_PLATFORM will be z900 but vector-bit in AT_HWCAP is set. This situation
is now recognized and this testcase does not fail.
A fatal glibc error is dumped if glibc was build with architecture
level set for z17, but run on an older machine (See dl-hwcap-check.h).
Note, you might get an SIGILL before this check if you don't use:
configure --with-rtld-early-cflags=-march=<older-machine>
ld.so --list-diagnostics now also dumps information about s390.cpu_features.
Independent from z17, the s390x kernel won't introduce new HWCAP-Bits if there
is no special handling needed in kernel itself. For z17, we don't have new
HWCAP flags, but have to check the facility bits retrieved by
stfle-instruction.
Instead of storing all the stfle-bits (currently four 64bit values) in the
cpu_features struct, we now only store those bits, which are needed within
glibc itself. Note that we have this list twice, one with original values and
the other one which can be filtered with GLIBC_TUNABLES=glibc.cpu.hwcaps.
Those new fields are stored in so far reserved space in cpu_features struct.
Thus processes started in between the update of glibc package and we e.g. have
a new ld.so and an old libc.so, won't crash. The glibc internal ifunc-resolvers
would not select the best optimized variant.
The users of stfle-bits are also updated:
- parsing of GLIBC_TUNABLES=glibc.cpu.hwcaps
- glibc internal ifunc-resolvers
- __libc_ifunc_impl_list
- sysconf
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The left shift overflows for 'int', use uint32_t instead. It syncs
with CORE-MATH commit bbfabd99.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use uint64_t instead. It syncs
with CORE-MATH commit d0a2be200cbc1344d800d9ef0ebee9ad67dd3ad8.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use uint32_t instead. It syncs
with CORE-MATH commit bbfabd993a71b049c210b0febfd06d18369fadc1.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int64_t', use unsigned instead. It syncs
with CORE-MATH commit f7c7408d1749ec2859ea249495af699359ae559b.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use uint64_t instead. It syncs
with CORE-MATH commit bbfabd99.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use a literal instead. It syncs
with OPTIMIZED-ROUTINES commit 0f87f607b976820ef41fe64d004fe67dc7af8236.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use uint64_t instead. It syncs
with CORE-MATH commit 4d6192d2.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The left shift overflows for 'int', use unsigned instead. It syncs
with CORE-MATH commit 4d6192d2.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
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The BZ 32653 fix (12a497c716f0a06be5946cabb8c3ec22a079771e) kept the
stack pointer zeroing from make_main_stack_executable on
_dl_make_stack_executable. However, previously the 'stack_endp'
pointed to temporary variable created before the call of
_dl_map_object_from_fd; while now we use the __libc_stack_end
directly.
Since pthread_getattr_np relies on correct __libc_stack_end, if
_dl_make_stack_executable is called (for instance, when
glibc.rtld.execstack=2 is set) __libc_stack_end will be set to zero,
and the call will always fail.
The __libc_stack_end zero was used a mitigation hardening, but since
52a01100ad011293197637e42b5be1a479a2f4ae it is used solely on
pthread_getattr_np code. So there is no point in zeroing anymore.
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Sam James <sam@gentoo.org>
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Hardware ctz instructions are available in the RISC-V Zbb and XTheadBb extension. With special `-march` flags defined, we can generate more simplified code compared to the generic implementation of `ffs`/`ffsll`.
Signed-off-by: Julian Zhu <julian.oerv@isrc.iscas.ac.cn>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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The <termio.h> interface is absolutely ancient: it was obsoleted by
<termios.h> already in the first version of POSIX (1988) and thus
predates the very first version of Linux. Unfortunately, some constant
macros are used both by <termio.h> and <termios.h>; particularly
problematic is the baud rate constants since the termio interface
*requires* that the baud rate is set via an enumeration as part of
c_cflag.
In preparation of revamping the termios interface to support the
arbitrary baud rate capability that the Linux kernel has supported
since 2008, remove <termio.h> in the hope that no one still uses this
archaic interface.
Note that there is no actual code in glibc to support termio: it is
purely an unabstracted ioctl() interface.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
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"Recent" GCC versions (since commit fc62716fe8d1, backported to stable
branches) emit a vzeroupper instruction at the end of functions
containing AVX instructions. This causes the tst-audit10 test to fail
on CPUs lacking AVX instructions, despite the AVX512F check. The crash
occurs in the pltenter function of tst-auditmod10b.c.
Fix that by moving the code guarded by the check_avx512 function into
specific functions using the target ("avx512f") attribute. Note that
since commit 5359c3bc91cc ("x86-64: Remove compiler -mavx512f check") it
is safe to assume that the compiler has AVX512F support, thus the
__AVX512F__ checks can be dropped.
Tested on non-AVX, AVX2 and AVX512F machines.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
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Linux 6.12 adds AT_RENAME_* aliases for RENAME_* flags for renameat2,
and also AT_HANDLE_MNT_ID_UNIQUE. Add the first set of aliases to
stdio.h alongside the RENAME_* names, and AT_HANDLE_MNT_ID_UNIQUE to
bits/fcntl-linux.h.
Tested for x86_64.
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8ef17919509e ("hurd: Fix EINVAL error on linking to a slash-trailing path
[BZ #32569]) made symlink return ENOTDIR, but the gnulib testsuite does
not recognize it for such a situation, and EEXIST is indeed more
comprehensible to users.
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This avoids SIGFPE handlers (or code longjmp-ed to) getting disturbed by the
exception that generated it.
Note: gcc's unwinding depends on the rpc_wait_trampoline/trampoline exact
code, so we here avoid breaking it.
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If __thread_get_state failed, there is no xstate level to check.
ok is 0 already and the memory exists, but better not read uninitialized
memory.
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If the process has never used fp before getting a signal, xstate is set
(and thus the x87 state is not initialized) but xstate->initialized is still
0, and we should not restore anything.
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* hurd/Makefile: add new tests
* hurd/test-sig-rpc-interrupted.c: check xstate save and restore in
the case where a signal is delivered to a thread which is waiting
for an rpc. This test implements the rpc interruption protocol used
by the hurd servers. It was so far passing on Debian thanks to the
local-intr-msg-clobber.diff patch, which is now obsolete.
* hurd/test-sig-xstate.c: check xstate save and restore in the case
where a signal is delivered to a running thread, making sure that
the xstate is modified in the signal handler.
* hurd/test-xstate.h: add helpers to test xstate
* sysdeps/mach/hurd/i386/bits/sigcontext.h: add xstate to the
sigcontext structure.
+ sysdeps/mach/hurd/i386/sigreturn.c: restore xstate from the saved
context
* sysdeps/mach/hurd/x86/trampoline.c: save xstate if
supported. Otherwise we fall back to the previous behaviour of
ignoring xstate.
* sysdeps/mach/hurd/x86_64/bits/sigcontext.h: add xstate to the
sigcontext structure.
* sysdeps/mach/hurd/x86_64/sigreturn.c: restore xstate from the saved
context
Signed-off-by: Luca Dariz <luca@orpolo.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Message-ID: <20250319171118.142163-1-luca@orpolo.org>
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Message-ID: <20250310084409.24177-1-zhmingluo@163.com>
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I misunderstood the recommendation from the hardware team about non-temporal
load/stores. It is still recommended to use them in memset for large sizes. It
was not recommended for their use with device memory and memset is already
not valid to be used with device memory.
This reverts commit e6590f0c86632c36c9a784cf96075f4be2e920d2.
Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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I misunderstood the recommendation from the hardware team about non-temporal
load/stores. It is still recommended to use them in memcpy for large sizes. It
was not recommended for their use with device memory and memcpy is already
not valid to be use with device memory.
This reverts commit eb5eeb47403e0a91de834868e501b4d62b8d2cb9.
Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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There is a spelling mistake in a puts statement. Fix it.
Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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Detect Intel Diamond Rapids and tune it similar to Intel Granite Rapids.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>
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Enable default tuning for unknown Intel processor.
Tested on x86, no regression.
Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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- Add ARROWLAKE model detection.
- Add PANTHERLAKE model detection.
- Add CLEARWATERFOREST model detection.
Intel® Architecture Instruction Set Extensions Programming Reference
https://cdrdv2.intel.com/v1/dl/getContent/671368 Section 1.2.
No regression, validated model detection on SDE.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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This is only needed for -mno-secure-plt, and this linkage mode
is not supported with powerpc64 and powerp64le.
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>
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As mentioned by the reporter in a pull request against gcc-mirror,
the THREEp96 constant in e_expl.c is incorrect, it is actually 0x3.p+94f128
rather than 0x3.p+96f128.
The algorithm uses that to compute the t2 integer (tval2), by whose
delta it adjusts the x+xl pair and then in the result uses the precomputed
exp value for that entry.
Using 0x3.p+94f128 rather than 0x3.p+96f128 results in tval2 sometimes
being one smaller, sometimes one larger than the desired value, thus can mean
the x+xl pair after adjustment will be larger in absolute value than it
should be.
DesWursters created a test program for this
https://github.com/DesWurstes/comparefloats
and his results were
total: 1135000000 not_equal: 4322 earlier_score: 674 later_score: 3648
I've modified this so with
https://sourceware.org/bugzilla/show_bug.cgi?id=32411#c3
so that it actually tests pseudo-random _Float128 values with range
(-16384.,16384) with strong bias on values larger than 0.0002 in absolute
value (so that tval1/tval2 aren't zero most of the time) and that gave
total: 10000000000 not_equal: 29861 earlier_score: 4606 later_score: 25255
So, in both cases, in most cases the change doesn't result in any differences,
and in those rare cases where does, about 85% have smaller ulp than without
the patch.
Additionally I've tried
https://sourceware.org/bugzilla/show_bug.cgi?id=32411#c4
and in 2 billion iterations it didn't find any case where x+xl after the
adjustments without this change would be smaller in absolute value compared
to x+xl after the adjustments with this change.
Reviewed-by: Joseph Myers <josmyers@redhat.com>
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From the bug report [1], multiple programs still require to dlopen
shared libraries with either missing PT_GNU_STACK or with the executable
bit set. Although, in some cases, it seems to be a hard-craft assembly
source without the required .note.GNU-stack marking (so the static linker
is forced to set the stack executable if the ABI requires it), other
cases seem that the library uses trampolines [2].
Unfortunately, READ_IMPLIES_EXEC is not an option since on some ABIs
(x86_64), the kernel clears the bit, making it unsupported. To avoid
reinstating the broken code that changes stack permission on dlopen
(0ca8785a28), this patch extends the glibc.rtld.execstack tunable to
allow an option to force an executable stack at the program startup.
The tunable is a security issue because it defeats the PT_GNU_STACK
hardening. It has the slight advantage of making it explicit by the
caller, and, as for other tunables, this is disabled for setuid binaries.
A tunable also allows us to eventually remove it, but from previous
experiences, it would require some time.
Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
[1] https://sourceware.org/bugzilla/show_bug.cgi?id=32653
[2] https://github.com/conda-forge/ctng-compiler-activation-feedstock/issues/143
Reviewed-by: Sam James <sam@gentoo.org>
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C2Y adds unsigned versions of the abs functions (see C2Y draft N3467 and
proposal N3349).
Tested for x86_64.
Signed-off-by: Lenard Mollenkopf <glibc@lenardmollenkopf.de>
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Scan xstate IDs up to the maximum supported xstate ID. Remove the
separate AMX xstate calculation. Instead, exclude the AMX space from
the start of TILECFG to the end of TILEDATA in xsave_state_size.
Completed validation on SKL/SKX/SPR/SDE and compared xsave state size
with "ld.so --list-diagnostics" option, no regression.
Co-Authored-By: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sunil K Pandey <skpgkp2@gmail.com>
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If the input buffer exceeds the stack auxiliary buffer, qsort will
malloc a temporary one to call mergesort. Since C++ standard does
allow the callback comparison function to throw [1], the glibc
implementation can potentially leak memory.
The fixes uses a pthread_cleanup_combined_push and
pthread_cleanup_combined_pop, so it can work with and without
exception enables. The qsort code path that calls malloc now
requires some extra setup and a call to __pthread_cleanup_push
anmd __pthread_cleanup_pop (which should be ok since they just
setup some buffer state).
Checked on x86_64-linux-gnu.
[1] https://timsong-cpp.github.io/cppwp/n4950/alg.c.library#4
Reviewed-by: DJ Delorie <dj@redhat.com>
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We mistakenly dropped the check in 27b96e069aad17cefea9437542180bff448ac3a0;
there's some other checks which we *can* drop, but let's worry about that
later.
Fixes the build on ppc64le where GCC is configured with --with-long-double-format=ieee.
Reviewed-by: Andreas Schwab <schwab@suse.de>
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Linux 6.14 has no new syscalls. Update the version number in
syscall-names.list to reflect that it is still current for 6.14.
Tested with build-many-glibcs.py.
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This fixes a test build failure on Hurd.
Fixes commit 145097dff170507fe73190e8e41194f5b5f7e6bf ("x86: Use separate
variable for TLSDESC XSAVE/XSAVEC state size (bug 32810)").
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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For all Linux distros with glibc 2.40 which I can find, GCC 14.2 is used
to compile glibc 2.40:
OS GCC URL
AOSC 14.2.0 https://aosc.io/
Arch Linux 14.2.0 https://archlinux.org/
ArchPOWER 14.2.0 https://archlinuxpower.org/
Artix 14.2.0 https://artixlinux.org/
Debian 14.2.0 https://www.debian.org/
Devuan 14.2.0 https://www.devuan.org/
Exherbo 14.2.0 https://www.exherbolinux.org/
Fedora 14.2.1 https://fedoraproject.org/
Gentoo 14.2.1 https://gentoo.org/
Kali Linux 14.2.0 https://www.kali.org/
KaOS 14.2.0 https://kaosx.us/
LiGurOS 14.2.0 https://liguros.gitlab.io/
Mageia 14.2.0 https://www.mageia.org/en/
Manjaro 14.2.0 https://manjaro.org/
NixOS 14.2.0 https://nixos.org/
openmamba 14.2.0 https://openmamba.org/
OpenMandriva 14.2.0 https://openmandriva.org/
openSUSE 14.2.0 https://www.opensuse.org/
Parabola 14.2.0 https://www.parabola.nu/
PLD Linux 14.2.0 https://pld-linux.org/
PureOS 14.2.0 https://pureos.net/
Raspbian 14.2.0 http://raspbian.org/
Slackware 14.2.0 http://www.slackware.com/
Solus 14.2.0 https://getsol.us/
T2 SDE 14.2.0 http://t2sde.org/
Ubuntu 14.2.0 https://www.ubuntu.com/
Wikidata 14.2.0 https://wikidata.org/
Support older versions of GCC to build glibc 2.42:
1. Need to work around bugs in older versions of GCC.
2. Can't use the new features in newer versions of GCC, which may be
required for new features, like _Float16 which requires GCC 12.1 or
above, in glibc,
The main benefit of supporting older versions of GCC is easier backport
of bug fixes to the older releases of glibc, which can be mitigated by
avoiding incompatible features in newer versions of GCC for critical bug
fixes. Require GCC 12.1 or newer to build. Remove GCC version check for
PowerPC and s390x.
TEST_CC and TEST_CXX can be used to test the glibc build with the older
versions of GCC.
For glibc developers who are using Linux OSes which don't come with GCC
12.1 or newer, they should build and install GCC 12.1 or newer to work
on glibc.
This fixes BZ #32539.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
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When libgcc is built with pac-ret, it requires to autenticate the
unwinding frame based on CFI information. The _dl_tlsdesc_dynamic
uses a custom calling convention, where it is responsible to save
and restore all registers it might use (even volatile).
The pac-ret support added by 1be3d6eb823d8b952fa54b7bbc90cbecb8981380
was added only on the slow-path, but the fast path also adds DWARF
Register Rule Instruction (cfi_adjust_cfa_offset) since it requires
to save/restore some auxiliary register. It seems that this is not
fully supported neither by libgcc nor AArch64 ABI [1].
Instead, move paciasp/autiasp to function prologue/epilogue to be
used on both fast and slow paths.
I also corrected the _dl_tlsdesc_dynamic comment description, it was
copied from i386 implementation without any adjustment.
Checked on aarch64-linux-gnu with a toolchain built with
--enable-standard-branch-protection on a system with pac-ret
support.
[1] https://github.com/ARM-software/abi-aa/blob/main/aadwarf64/aadwarf64.rst#id1
Reviewed-by: Yury Khrustalev <yury.khrustalev@arm.com>
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Previously, the initialization code reused the xsave_state_full_size
member of struct cpu_features for the TLSDESC state size. However,
the tunable processing code assumes that this member has the
original XSAVE (non-compact) state size, so that it can use its
value if XSAVEC is disabled via tunable.
This change uses a separate variable and not a struct member because
the value is only needed in ld.so and the static libc, but not in
libc.so. As a result, struct cpu_features layout does not change,
helping a future backport of this change.
Fixes commit 9b7091415af47082664717210ac49d51551456ab ("x86-64:
Update _dl_tlsdesc_dynamic to preserve AMX registers").
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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If we have to use XSAVE or XSAVEC trampolines, do not adjust the size
information they need. Technically, it is an operator error to try to
run with -XSAVE,-XSAVEC on such builds, but this change here disables
some unnecessary code with higher ISA levels and simplifies testing.
Related to commit befe2d3c4dec8be2cdd01a47132e47bdb7020922
("x86-64: Don't use SSE resolvers for ISA level 3 or above").
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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Reject invalid formatted scanf real input data the exponent part of
which is comprised of an exponent introducing character, optionally
followed by a sign, and with no actual digits following. Such data is a
prefix of, but not a matching input sequence and it is required by ISO C
to cause a matching failure.
Currently a matching success is instead incorrectly produced along with
the conversion result according to the input significand read and the
exponent of zero, with the significand and the exponent part wholly
consumed from input.
Correct an invalid `tstscanf.c' test accordingly that expects a matching
success for input data provided in the ISO C standard as an example for
a matching failure.
Enable input data that causes test failures without this fix in place.
Reviewed-by: Joseph Myers <josmyers@redhat.com>
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Reject invalid formatted scanf real input data that is comprised of a
hexadecimal prefix, optionally preceded by a sign, and with no actual
digits following owing to the field width restriction in effect. Such
data is a prefix of, but not a matching input sequence and it is
required by ISO C to cause a matching failure.
Currently a matching success is instead incorrectly produced along with
the conversion result of zero, with the prefix wholly consumed from
input. Where the end of input is marked by the end-of-file condition
rather than the field width restriction in effect a matching failure is
already correctly produced.
Enable input data that causes test failures without this fix in place.
Reviewed-by: Joseph Myers <josmyers@redhat.com>
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Reject invalid formatted scanf integer input data that is comprised of a
binary or hexadecimal prefix, optionally preceded by a sign, and with no
actual digits following. Such data is a prefix of, but not a matching
input sequence and it is required by ISO C to cause a matching failure.
Currently a matching success is instead incorrectly produced along with
the conversion result of zero, with the prefix wholly consumed from
input.
Enable input data that causes test failures without this fix in place.
Reviewed-by: Joseph Myers <josmyers@redhat.com>
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Add Makefile infrastructure, a format-specific test skeleton providing a
data comparison implementation that ignores bits of data representation
in memory that do not participate in holding floating-point data, and
`long double' real input data for targets using the Intel/Motorola
80-bit format.
Keep input data disabled and referring to BZ #12701 for entries that are
are currently incorrectly accepted as valid data, such as '0e', '0e+',
'0x', '0x8p', '0x0p-', etc.
Reviewed-by: Joseph Myers <josmyers@redhat.com>
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C23 adds various <math.h> function families originally defined in TS
18661-4. Add the pown functions, which are like pow but with an
integer exponent. That exponent has type long long int in C23; it was
intmax_t in TS 18661-4, and as with other interfaces changed after
their initial appearance in the TS, I don't think we need to support
the original version of the interface. The test inputs are based on
the subset of test inputs for pow that use integer exponents that fit
in long long.
As the first such template implementation that saves and restores the
rounding mode internally (to avoid possible issues with directed
rounding and intermediate overflows or underflows in the wrong
rounding mode), support also needed to be added for using
SET_RESTORE_ROUND* in such template function implementations. This
required math-type-macros-float128.h to include <fenv_private.h>, so
it can tell whether SET_RESTORE_ROUNDF128 is defined. In turn, the
include order with <fenv_private.h> included before <math_private.h>
broke loongarch builds, showing up that
sysdeps/loongarch/math_private.h is really a fenv_private.h file
(maybe implemented internally before the consistent split of those
headers in 2018?) and needed to be renamed to fenv_private.h to avoid
errors with duplicate macro definitions if <math_private.h> is
included after <fenv_private.h>.
The underlying implementation uses __ieee754_pow functions (called
more than once in some cases, where the exponent does not fit in the
floating type). I expect a custom implementation for a given format,
that only handles integer exponents but handles larger exponents
directly, could be faster and more accurate in some cases.
I encourage searching for worst cases for ulps error for these
implementations (necessarily non-exhaustively, given the size of the
input space).
Tested for x86_64 and x86, and with build-many-glibcs.py.
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