POSIX-1.2018 defines that getconf utility shall print symbolic constant
listed under the heading Maximum value and Minimum Values [1], however
current behaviour is to print the values using pathconf or sysconf,
which represents the specific implementation values instead of the
system agnostics ones.
Another issue is for such the symbolic constants, getconf handles them
as a path_var which requires an additional pathname (which does not
make sense for constants values).
The patch fixes it adding a new internal type, LIMITS_H, which only
prints the constant symbolic without requiring an additional path.
Only the values define in glibc provided limits.h plust the GNU
extensions are handled.
Checked on x86_64-linux-gnu.
[1] https://pubs.opengroup.org/onlinepubs/9699919799/utilities/getconf.html)
Tested-by: Yury Khrustalev <yury.khrustalev@arm.com>
Reviewed-by: Yury Khrustalev <yury.khrustalev@arm.com>
The ld.lld does not support the --no-error-execstack option, and it is
required only to suppress the linker warning while building tests. A new
configure macro, LIBC_TEST_LINKER_FEATURE, is added to check for linker
features using TEST_CC instead of CC.
Checked on x86_64-linux-gnu and aarch64-linux-gnu with gcc and
TEST_CC set to clang-18 and clan-21.
Reviewed-by: Sam James <sam@gentoo.org>
Linux supports multi-sized Transparent Huge Pages (mTHP). For the purpose
of this patch description, we call the block size mapped by a non-last
level pagetable level, the traditional THP size (2M for 4K basepage,
512M for 64K basepage). Linux now also supports intermediate THP sizes
mapped by the last level pagetable - we call that the mTHP size.
The support for mTHP in Linux has grown to be better and stable over time -
applications can benefit from reduced page faults and reduced kernel
memory management overhead, albeit at the cost of internal fragmentation.
We have observed consistent performance boosts with mTHP with little
variance.
As a result, enable 2M THP by default on Aarch64. This enables THP even if
user hasn't passed glibc.malloc.hugetlb=1. If user has passed it, we avoid
making the system call to check the hugepage size from sysfs, and override
it with the hardcoded 2MB.
There are two additional benefits of this patch, if the transparent
hugepage sysctl is set to madvise or always:
1) The THP size is now hardcoded to 2MB for Aarch64. This avoids a
syscall for fetching the THP size from sysfs.
2) On 64K basepage size systems, the traditional THP size is 512M, which
is unusable and impractical. We can instead benefit from the mTHP size of
2M. Apart from the usual benefit of THPs/mTHPs as described above, Aarch64
systems benefit from reduced TLB pressure on this mTHP size, commonly
known as the "contpte" size. If the application takes a pagefault, and
either the THP sysctl settings is "always", or the virtual memory area
has been madvise(MADV_HUGEPAGE)'d along with sysctl being "madvise", then
Linux will fault in a 2M mTHP, mapping contiguous pages into the pagetable,
and painting the pagetable entries with the cont-bit. This bit is a hint to
the hardware that the concerned pagetable entry maps a page which is part
of a set of contiguous pages - the TLB then only remembers a single entry
for this set of 2M/64K = 32 pages, because the physical address of any
other page in this contiguous set is computable by the TLB cached physical
address via a linear offset. Hence, what was only possible with the
traditional THP size, is now possible with the mTHP size.
We see a 6.25% performance improvement on SPEC.
If the sysctl is set to never, no transparent hugepages will be created by
the kernel. But, this patch still sets thp_pagesize = 2MB. The benefit is
that on MORECORE() invocation, we extend the heap by 2MB instead of 4KB,
potentially reducing the frequency of this syscall's invocation by 512x.
Note that, there is no difference in cost between an sbrk(2M) and sbrk(4K);
the kernel only does a virtual reservation and does not touch user physical
memory.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Currently, if the initial program break is not aligned to the system page
size, then we align the pointer down to the page size. If there is a gap
before the heap VMA, then such an adjustment means that the madvise() range
now contains a gap. The behaviour in the upstream kernel is currently this:
madvise() will return -ENOMEM, even though the operation will still succeed
in the sense that the VM_HUGEPAGE flag will be set on the heap VMA. We
*must not* depend on this behaviour - this is an internal kernel
implementation, and earlier kernels may possibly abort the operation
altogether.
The other case is that there is no gap, and as a result we may end up
setting the VM_HUGEPAGE flag on that other VMA too, which is an
unnecessary side effect.
Let us fix this by aligning the pointer up to the page size. We should
also subtract the pointer difference from the size, because if we don't,
since the pointer is now aligned up, the size may cross the heap VMA, thus
leading to the same problem but at the other end.
There is no need to check this new size against mp_.thp_pagesize to decide
whether to make the madvise() call. The reason we make this check at the
start of madvise_thp() is to check whether the size of the VMA is enough
to map THPs into it. Since that check has passed, all that we need to
ensure now is that q + size does not cross the heap VMA.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
The openat2 syscall was added on Linux 5.6, as an extension of openat.
Unlike other open-like functions, the kernel only provides the LFS
variant (so files larger than 4GB always succeed, unlike other
functions with an offset larger than off_t). Also, similar to other
open functions, the new symbol is a cancellable entrypoint.
The test case added only stress tests for some of the syscalls' provided
functionality, and it is based on an existing kernel self-test.
A fortify wrapper is added to verify the argument size if not larger
than the current support open_how struct.
Gnulib added an openat2 module, which uses read-only for the open_how
argument [1]. There is no clear indication whether the kernel will
indeed use the argument as in-out, how it would do so, or for which
kind of functionality [2]. Also, adding a potentially different prototype
than gnulib only would add extra unnecessary friction and extra
wrappers to handle it.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
[1] https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commit;h=0b97ffdf32bdab909d02449043447237273df75e
[2] https://sourceware.org/pipermail/libc-alpha/2025-September/169740.html
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The clang support is still experimental and not all testcases run
correctly. Only clang 18 and onwards is supported and only
for x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: Collin Funk <collin.funk1@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>
Clang issues a warning for double alias redirection, indicating that thei
original symbol is used even if a weak definition attempts to override it.
For instance, in the construction:
int __internal_impl (...) {}
weak_alias (__internal_impl, external_impl);
#if SOMETHING
weak_alias (external_impl, another_external_impl)
#endif
Clang warns that another_external_impl always resolves to __internal_impl,
even if external_impl is a weak reference. Using the internal symbol for
both aliases resolves this warning.
This issue also occurs with certain libc_hidden_def usage:
int __internal_impl (...) {}
weak_alias (__internal_impl, __internal_alias)
libc_hidden_weak (__internal_alias)
In this case, using a strong_alias is sufficient to avoid the warning
(since the alias is internal, there is no need to use a weak alias).
However, for the constructions like:
int __internal_impl (...) {}
weak_alias (__internal_impl, __internal_alias)
libc_hidden_def (__internal_alias)
weak_alias (__internal_impl, external_alias)
libc_hidden_def (external_alias)
Clang warns that the internal external_alias will always resolve to
__GI___internal_impl, even if a weak definition of __GI_internal_impl is
overridden. For this case, a new macro named static_weak_alias is used
to create a strong alias for SHARED, or a weak_alias otherwise.
With these changes, there is no need to check and enable the
-Wno-ignored-attributes suppression when using clang.
Checked with a build on affected ABIs, and a full check on aarch64,
armhf, i686, and x86_64.
Reviewed-by: Sam James <sam@gentoo.org>
Since the variadic prctl function takes at most 5 integer arguments which
are passed in the same integer registers on x32 as the function with 5
integer arguments, we can use assembly for prctl. Since upper 32-bits in
the last 4 arguments of pcrtl must be cleared to match the x32 prctl
syscall interface where the last 4 arguments are unsigned 64 bit longs,
implement prctl in assembly to clear upper 32-bits in the last 4 arguments
and add a test to verify it.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Commit 33eff78c8b caused issues in nbdkit
which had code similar to this to get the last line of the file:
while (getline (&line, &len, fp) != -1)
;
/* Process LINE. */
After that commit, line[0] would be equal to '\0' instead of containing
the last line of the file like before that commit. A recent POSIX issue
clarified that the behavior before and after that commit are allowed,
since the contents of LINE are unspecified after -1 is returned
[1]. However, some programs rely on the previous behavior.
This patch null terminates the buffer upon getdelim/getline's initial
allocation. This is compatible with previous glibc versions, while also
protecting the caller from reading uninitialized memory if the file is
empty, as long as getline/getdelim does the initial allocation.
[1] https://www.austingroupbugs.net/bug_view_page.php?bug_id=1953
Suggested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Vector variants of the new C23 rsqrt routines for both AdvSIMD and
SVE, as well as in both single and double precision.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Add benchtests for double precision vector rsqrt routine. They are
identical to those found in log2.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Add benchtests for vector single precision rsqrtf. They are
identical to those found in log2f.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The __builtin_fmod{f} and __builtin_remainder{f} were added on gcc 13,
and the minimum supported gcc is 12. This patch adds a configure test
to check whether the compiler enables inlining for fmod/remainder, and
uses inline assembly if not.
Checked on i686-linux-gnu wih gcc-12.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Report assertion failure if the alignment of external pthread structs is
lower than the internal version. This triggers on type mismatches like
in BZ #33632.
Reviewed-by: Yury Khrustalev <yury.khrustalev@arm.com>
Optimise AdvSIMD atanhf by vectorising the special case.
There are asymptotes at x = -1 and x = 1. So return inf for these.
Values for which |x| > 1, return NaN.
R.Throughput difference on V2 with GCC@15:
58-60% improvement in special cases.
No regression in fast pass.
Optimise AdvSIMD asinhf by vectorising the special case.
For values greater than 0x1p64, scale the input down first.
This is because the output will overflow with inputs greater than
or equal to this value as there is a squaring operation in the
algorithm.
To scale, do:
2asinh(sqrt[(x-1)/2])
Because:
2asinh(x) = +-acosh(2x^2 + 1)
Apply opposite operations in opposite order for x, and you get:
asinh(x) = 2acosh(sqrt[(x-1)/2]).
Found that using asinh instead of acosh also very closely
approximates asinh(x) for a high input x.
R.Throughput difference on V2 with GCC@15:
25-58% improvement in special cases.
4% regression in fast pass.
Optimise AdvSIMD acoshf by vectorising the special case.
For values greater than 0x1p64, scale the input down first.
This is because the output will overflow with inputs greater than
or equal to this value as there is a squaring operation in the
algorithm.
To scale, do:
2acosh(sqrt[(x+1)/2])
Because:
acosh(x) = 1/2acosh(2x^2 - 1) for x>=1.
Apply opposite operations in opposite order for x, and you get:
acosh(x) = 2acosh(sqrt[(x+1)/2]).
R.Throughput difference on V2 with GCC@15:
30-49% improvement in special cases.
2% regression in fast pass.
Check that the new tunable changes behaviour correctly:
* When BTI is enforced, any unmarked binary that is loaded
results in an error: either an abort or dlopen error when
this binary is loaded via dlopen.
* When BTI is not enforced, it is OK to load an unmarked
binary.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Add glibc.cpu.aarch64_bti tunable with 2 values:
- permissive (default)
- enforced
and use this tunable to enforce BTI marking on dependencies
when the enforced option is selected.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Tested-by: Jeremy Linton <jeremy.linton@arm.com>
We add configure checks for 3 things:
- Compiler (both CC and TEST_CC) supports -mbranch-protection=bti.
- Linker supports -z force-bti.
- The toolchain supplies object files and target libraries with
the BTI marking.
All three must be true in order for the tests to be valid, so
we check all flags and set the makefile variable accordingly.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Optimise AdvSIMD log10 by vectorising the special case.
For subnormal input values, use the same scaling technique as
described in the single precision equivalent.
Then check for inf, nan and x<=0.
Optimise AdvSIMD log2 by vectorising the special case.
For subnormal input values, use the same scaling technique as
described in the single precision equivalent.
Then check for inf, nan and x<=0.
Optimise AdvSIMD log by vectorising the special case.
For subnormal input values, use the same scaling technique as
described in the single precision equivalent.
Then check for inf, nan and x<=0.
Optimise AdvSIMD log10f by vectorising the special case.
Use scaling technique on subnormal values, then check for inf and
nan values.
The scaling technique will sqrt the input then multiply the output
by 2 because:
log(sqrt(x)) = 1/2(log(x)), so log(x) = 2log(sqrt(x))
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Optimise AdvSIMD log2f by vectorising the special case.
Use scaling technique on subnormal values, then check for inf and
nan values.
The scaling technique used will sqrt the input then multiply the
output by 2 because:
log(sqrt(x)) = 1/2 log(x), so log(x) = 2log(sqrt(x))
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Optimise AdvSIMD logf by vectorising the special case.
Use scaling technique on subnormal values, then check for inf and
nan values.
The scaling technique used will sqrt the input then multiply the
output by 2 because:
log(sqrt(x)) = 1/2 log(x), so log(x) = 2log(sqrt(x))
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Optimise AdvSIMD log1pf by vectorising the special case and by
reducing the range of values passed to the special case.
Previously, high values such as 0x1.1p127 where treated as special
cases, but now the special cases are for when the input is:
Less than or equal to -1
+/- INFINITY
+/- NaN
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
commit 8cd6efca5b
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Nov 20 15:30:06 2025 -0300
Add add_ssaaaa and sub_ssaaaa to gmp-arch.h
checks __WORDSIZE == 32 to decide if int128 should be used, which breaks
x32 which has int128 and __WORDSIZE == 32. Check BITS_PER_MP_LIMB == 32,
instead of __WORDSIZE == 32. This fixes BZ #33677.
Tested on x32, x86-64 and i686.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The TIME_MONOTONIC maps to POSIX's CLOCK_MONOTONIC, TIME_ACTIVE to
CLOCK_PROCESS_CPUTIME_ID, and TIME_THREAD_ACTIVE to
CLOCK_THREAD_CPUTIME_ID.
No Linux specific timer are added as extension.
Co-authored-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Paul Eggert <eggert@cs.ucla.edu>
commit 7fec8a5de6
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Thu Nov 13 14:26:08 2025 -0300
Revert __HAVE_64B_ATOMICS configure check
uses 64-bit atomic operations on sem_t if 64-bit atomics are supported.
But sem_t may be aligned to 32-bit on 32-bit architectures.
1. Add a macro, SEM_T_ALIGN, for sem_t alignment.
2. Add a macro, HAVE_UNALIGNED_64B_ATOMICS. Define it if unaligned 64-bit
atomic operations are supported.
3. Add a macro, USE_64B_ATOMICS_ON_SEM_T. Define to 1 if 64-bit atomic
operations are supported and SEM_T_ALIGN is at least 8-byte aligned or
HAVE_UNALIGNED_64B_ATOMICS is defined.
4. Assert that size and alignment of sem_t are not lower than those of
the internal struct new_sem.
5. Check USE_64B_ATOMICS_ON_SEM_T, instead of USE_64B_ATOMICS, when using
64-bit atomic operations on sem_t.
This fixes BZ #33632.
Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Use environment variables to provide mirror URLs to checkout
sources from Git. Each component has a corresponding env var
that will be used if it's present: <component>_GIT_MIRROR.
Note that '<component>' should be upper case, e.g. GLIBC.
Co-authored-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Allow to use custom mirror URLs to download tarballs from a mirror
of ftp.gnu.org using the FTP_GNU_ORG_MIRROR env variable (default
value is 'https://ftp.gnu.org').
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Test wrapper script was used twice: once to run the test
command and second time within the text command which
seems unnecessary and results in false errors when running
this test.
Fixes 332f8e62af
Reviewed-by: Frédéric Bérat <fberat@redhat.com>
The allocation_index was being incremented before checking if mmap()
succeeds. If mmap() fails, allocation_index would still be incremented,
creating a gap in the allocations tracking array and making
allocation_index inconsistent with the actual number of successful
allocations.
This fix moves the allocation_index increment to after the mmap()
success check, ensuring it only increments when an allocation actually
succeeds. This maintains proper tracking for leak detection and
prevents gaps in the allocations array.
Signed-off-by: Osama Abdelkader <osama.abdelkader@gmail.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The expression inptr + 1 can technically be invalid: if inptr == inend,
inptr may point one element past the end of an array.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
C23 defines library macros __STDC_VERSION_<header>_H__ to indicate
that a header has support for new / changed features from C23. Now
that all the required library features are implemented in glibc,
define these macros. I'm not sure this is sufficiently much of a
user-visible feature to be worth a mention in NEWS.
Tested for x86_64.
There are various optional C23 features we don't yet have, of which I
might look at the Annex H ones (floating-point encoding conversion
functions and _Float16 functions) next.
* Optional time bases TIME_MONOTONIC, TIME_ACTIVE, TIME_THREAD_ACTIVE.
See
<https://sourceware.org/pipermail/libc-alpha/2023-June/149264.html>
- we need to review / update that patch. (I think patch 2/2,
inventing new names for all the nonstandard CLOCK_* supported by the
Linux kernel, is rather more dubious.)
* Updating conform/ tests for C23.
* Defining the rounding mode macro FE_TONEARESTFROMZERO for RISC-V (as
far as I know, the only architecture supported by glibc that has
hardware support for this rounding mode for binary floating point)
and supporting it throughout glibc and its tests (especially the
string/numeric conversions in both directions that explicitly handle
each possible rounding mode, and various tests that do likewise).
* Annex H floating-point encoding conversion functions. (It's not
entirely clear which are optional even given support for Annex H;
there's some wording applied inconsistently about only being
required when non-arithmetic interchange formats are supported; see
the comments I raised on the WG14 reflector on 23 Oct 2025.)
* _Float16 functions (and other header and testcase support for this
type).
* Decimal floating-point support.
* Fully supporting __int128 and unsigned __int128 as integer types
wider than intmax_t, as permitted by C23. Would need doing in
coordination with GCC, see GCC bug 113887 for more discussion of
what's involved.
