The tuning for non-temporal stores for memset vs memcpy is not always
the same. This includes both the exact value and whether non-temporal
stores are profitable at all for a given arch.
This patch add `x86_memset_non_temporal_threshold`. Currently we
disable non-temporal stores for non Intel vendors as the only
benchmarks showing its benefit have been on Intel hardware.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
C23 adds various <math.h> function families originally defined in TS
18661-4. Add the log2p1 functions (log2(1+x): like log1p, but for
base-2 logarithms).
This illustrates the intended structure of implementations of all
these function families: define them initially with a type-generic
template implementation. If someone wishes to add type-specific
implementations, it is likely such implementations can be both faster
and more accurate than the type-generic one and can then override it
for types for which they are implemented (adding benchmarks would be
desirable in such cases to demonstrate that a new implementation is
indeed faster).
The test inputs are copied from those for log1p. Note that these
changes make gen-auto-libm-tests depend on MPFR 4.2 (or later).
The bulk of the changes are fairly generic for any such new function.
(sysdeps/powerpc/nofpu/Makefile only needs changing for those
type-generic templates that use fabs.)
Tested for x86_64 and x86, and with build-many-glibcs.py.
The current IFUNC selection is always using the most recent
features which are available via AT_HWCAP. But in
some scenarios it is useful to adjust this selection.
The environment variable:
GLIBC_TUNABLES=glibc.cpu.hwcaps=-xxx,yyy,zzz,....
can be used to enable HWCAP feature yyy, disable HWCAP feature xxx,
where the feature name is case-sensitive and has to match the ones
used in sysdeps/loongarch/cpu-tunables.c.
Signed-off-by: caiyinyu <caiyinyu@loongson.cn>
This prints some information from struct cpu_features, and the midr_el1
and dczid_el0 system register contents on every CPU.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This is surprisingly difficult to implement if the goal is to produce
reasonably sized output. With the current approaches to output
compression (suppressing zeros and repeated results between CPUs,
folding ranges of identical subleaves, dealing with the %ecx
reflection issue), the output is less than 600 KiB even for systems
with 256 logical CPUs.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
* manual/search.texi (Array Search Function):
Correct the statement about lfind’s mean runtime:
it is proportional to a number (not that number),
and this is true only if random elements are searched for.
Relax the constraint on bsearch’s array argument:
POSIX says it need not be sorted, only partially sorted.
Say that the first arg passed to bsearch’s comparison function
is the key, and the second arg is an array element, as
POSIX requires. For bsearch and qsort, say that the
comparison function should not alter the array, as POSIX
requires. For qsort, say that the comparison function
must define a total order, as POSIX requires, that
it should not depend on element addresses, that
the original array index can be used for stable sorts,
and that if qsort still works if memory allocation fails.
Be more consistent in calling the array elements
“elements” rather than “objects”.
Co-authored-by: Zack Weinberg <zack@owlfolio.org>
In Linux 6.9 a new flag is added to allow for Per-io operations to
disable append mode even if a file was opened with the flag O_APPEND.
This is done with the new RWF_NOAPPEND flag.
This caused two test failures as these tests expected the flag 0x00000020
to be unused. Adding the flag definition now fixes these tests on Linux
6.9 (v6.9-rc1).
FAIL: misc/tst-preadvwritev2
FAIL: misc/tst-preadvwritev64v2
This patch adds the flag, adjusts the test and adds details to
documentation.
Link: https://lore.kernel.org/all/20200831153207.GO3265@brightrain.aerifal.cx/
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
It was raised on libc-help [1] that some Linux kernel interfaces expect
the libc to define __USE_TIME_BITS64 to indicate the time_t size for the
kABI. Different than defined by the initial y2038 design document [2],
the __USE_TIME_BITS64 is only defined for ABIs that support more than
one time_t size (by defining the _TIME_BITS for each module).
The 64 bit time_t redirects are now enabled using a different internal
define (__USE_TIME64_REDIRECTS). There is no expected change in semantic
or code generation.
Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, and
arm-linux-gnueabi
[1] https://sourceware.org/pipermail/libc-help/2024-January/006557.html
[2] https://sourceware.org/glibc/wiki/Y2038ProofnessDesign
Reviewed-by: DJ Delorie <dj@redhat.com>
"number of arguments, from zero to five" is wrong, because on Linux maximal number
of arguments is 6, not 5. Also, maximal number of arguments is kernel-dependent,
so let's not include it here at all.
Moreover, "Each kind of system call has a definite number of arguments" is questionable.
Think about SYS_open on Linux, which takes 2 or 3 arguments. Or SYS_clone on Linux x86_64, which
takes 2 to 5 arguments. So I propose to fully remove this sentence.
Signed-off-by: Askar Safin <safinaskar@zohomail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
* manual/search.texi (Comparison Functions, Array Sort Function):
Sort an array of long ints, not doubles, to avoid hassles
with NaNs.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
My recent change broke make pdf and in other documentation formats
results in weird rendering and invalid URL, all because of a forgotten
comma to separate @uref arguments.
WG14 decided to use the name C23 as the informal name of the next
revision of the C standard (notwithstanding the publication date in
2024). Update references to C2X in glibc to use the C23 name.
This is intended to update everything *except* where it involves
renaming files (the changes involving renaming tests are intended to
be done separately). In the case of the _ISOC2X_SOURCE feature test
macro - the only user-visible interface involved - support for that
macro is kept for backwards compatibility, while adding
_ISOC23_SOURCE.
Tested for x86_64.
The following patch uses the GCC 14 __builtin_stdc_* builtins in stdbit.h
for the type-generic macros, so that when compiled with GCC 14 or later,
it supports not just 8/16/32/64-bit unsigned integers, but also 128-bit
(if target supports them) and unsigned _BitInt (any supported precision).
And so that the macros don't expand arguments multiple times and can be
evaluated in constant expressions.
The new testcase is gcc's gcc/testsuite/gcc.dg/builtin-stdc-bit-1.c
adjusted to test stdbit.h and the type-generic macros in there instead
of the builtins and adjusted to use glibc test framework rather than
gcc style tests with __builtin_abort ().
Signed-off-by: Jakub Jelinek <jakub@redhat.com>
Reviewed-by: Joseph Myers <josmyers@redhat.com>
On the summary page the order of the function arguments was reversed, but it is
in correct order in the other places of the manual.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The increased malloc subsystem usage is a side effect of
commit d2123d6827 ("elf: Fix slow tls
access after dlopen [BZ #19924]").
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
The mergesort removal from qsort implementation (commit 03bf8357e8)
had the side-effect of making sorting nonstable. Although neither
POSIX nor C standard specify that qsort should be stable, it seems
that it has become an instance of Hyrum's law where multiple programs
expect it.
Also, the resulting introsort implementation is not faster than
the previous mergesort (which makes the change even less appealing).
This patch restores the previous mergesort implementation, with the
exception of machinery that checks the resulting allocation against
the _SC_PHYS_PAGES (it only adds complexity and the heuristic not
always make sense depending on the system configuration and load).
The alloca usage was replaced with a fixed-size buffer.
For the fallback mechanism, the implementation uses heapsort. It is
simpler than quicksort, and it does not suffer from adversarial
inputs. With memory overcommit, it should be rarely triggered.
The drawback is mergesort requires O(n) extra space, and since it is
allocated with malloc the function is AS-signal-unsafe. It should be
feasible to change it to use mmap, although I am not sure how urgent
it is. The heapsort is also nonstable, so programs that require a
stable sort would still be subject to this latent issue.
The tst-qsort5 is removed since it will not create quicksort adversarial
inputs with the current qsort_r implementation.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Add ELF_DYNAMIC_AFTER_RELOC to allow target specific processing after
relocation.
For x86-64, add
#define DT_X86_64_PLT (DT_LOPROC + 0)
#define DT_X86_64_PLTSZ (DT_LOPROC + 1)
#define DT_X86_64_PLTENT (DT_LOPROC + 3)
1. DT_X86_64_PLT: The address of the procedure linkage table.
2. DT_X86_64_PLTSZ: The total size, in bytes, of the procedure linkage
table.
3. DT_X86_64_PLTENT: The size, in bytes, of a procedure linkage table
entry.
With the r_addend field of the R_X86_64_JUMP_SLOT relocation set to the
memory offset of the indirect branch instruction.
Define ELF_DYNAMIC_AFTER_RELOC for x86-64 to rewrite the PLT section
with direct branch after relocation when the lazy binding is disabled.
PLT rewrite is disabled by default since SELinux may disallow modifying
code pages and ld.so can't detect it in all cases. Use
$ export GLIBC_TUNABLES=glibc.cpu.plt_rewrite=1
to enable PLT rewrite with 32-bit direct jump at run-time or
$ export GLIBC_TUNABLES=glibc.cpu.plt_rewrite=2
to enable PLT rewrite with 32-bit direct jump and on APX processors with
64-bit absolute jump at run-time.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
Since shadow stack is only supported for x86-64, ignore --enable-cet for
i386. Always setting $(enable-cet) for i386 to "no" to support
ifneq ($(enable-cet),no)
in x86 Makefiles. We can't use
ifeq ($(enable-cet),yes)
since $(enable-cet) can be "yes", "no" or "permissive".
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
C23 adds a header <stdbit.h> with various functions and type-generic
macros for bit-manipulation of unsigned integers (plus macro defines
related to endianness). Implement this header for glibc.
The functions have both inline definitions in the header (referenced
by macros defined in the header) and copies with external linkage in
the library (which are implemented in terms of those macros to avoid
duplication). They are documented in the glibc manual. Tests, as
well as verifying results for various inputs (of both the macros and
the out-of-line functions), verify the types of those results (which
showed up a bug in an earlier version with the type-generic macro
stdc_has_single_bit wrongly returning a promoted type), that the
macros can be used at top level in a source file (so don't use ({})),
that they evaluate their arguments exactly once, and that the macros
for the type-specific functions have the expected implicit conversions
to the relevant argument type.
Jakub previously referred to -Wconversion warnings in type-generic
macros, so I've included a test with -Wconversion (but the only
warnings I saw and fixed from that test were actually in inline
functions in the <stdbit.h> header - not anything coming from use of
the type-generic macros themselves).
This implementation of the type-generic macros does not handle
unsigned __int128, or unsigned _BitInt types with a width other than
that of a standard integer type (and C23 doesn't require the header to
handle such types either). Support for those types, using the new
type-generic built-in functions Jakub's added for GCC 14, can
reasonably be added in a followup (along of course with associated
tests).
This implementation doesn't do anything special to handle C++, or have
any tests of functionality in C++ beyond the existing tests that all
headers can be compiled in C++ code; it's not clear exactly what form
this header should take in C++, but probably not one using macros.
DIS ballot comment AT-107 asks for the word "count" to be added to the
names of the stdc_leading_zeros, stdc_leading_ones,
stdc_trailing_zeros and stdc_trailing_ones functions and macros. I
don't think it's likely to be accepted (accepting any technical
comments would mean having an FDIS ballot), but if it is accepted at
the WG14 meeting (22-26 January in Strasbourg, starting with DIS
ballot comment handling) then there would still be time to update
glibc for the renaming before the 2.39 release.
The new functions and header are placed in the stdlib/ directory in
glibc, rather than creating a new toplevel stdbit/ or putting them in
string/ alongside ffs.
Tested for x86_64 and x86.
The tunable privilege levels were a retrofit to try and keep the malloc
tunable environment variables' behavior unchanged across security
boundaries. However, CVE-2023-4911 shows how tricky can be
tunable parsing in a security-sensitive environment.
Not only parsing, but the malloc tunable essentially changes some
semantics on setuid/setgid processes. Although it is not a direct
security issue, allowing users to change setuid/setgid semantics is not
a good security practice, and requires extra code and analysis to check
if each tunable is safe to use on all security boundaries.
It also means that security opt-in features, like aarch64 MTE, would
need to be explicit enabled by an administrator with a wrapper script
or with a possible future system-wide tunable setting.
Co-authored-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: DJ Delorie <dj@redhat.com>
Since malloc debug support moved to a different library
(libc_malloc_debug.so), the glibc.malloc.check requires preloading the
debug library to enable it. It means that suid-debug support has not
been working since 2.34.
To restore its support, it would require to add additional information
and parsing to where to find libc_malloc_debug.so.
It is one thing less that might change AT_SECURE binaries' behavior
due to environment configurations.
Checked on x86_64-linux-gnu.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Remove the unused 'char *name;' from the example.
Use write instead of putchar to write input as it is read.
Example tested on x86_64 by compiling and running the example.
Tested by building the manual pdf and reviewing the results.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The latest implementations of memcpy are actually faster than the Falkor
implementations [1], so remove the falkor/phecda ifuncs for memcpy and
the now unused IS_FALKOR/IS_PHECDA defines.
[1] https://sourceware.org/pipermail/libc-alpha/2022-December/144227.html
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
The PR_SET_VMA_ANON_NAME support is only enabled through a configurable
kernel switch, mainly because assigning a name to a
anonymous virtual memory area might prevent that area from being
merged with adjacent virtual memory areas.
For instance, with the following code:
void *p1 = mmap (NULL,
1024 * 4096,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
-1,
0);
void *p2 = mmap (p1 + (1024 * 4096),
1024 * 4096,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
-1,
0);
The kernel will potentially merge both mappings resulting in only one
segment of size 0x800000. If the segment is names with
PR_SET_VMA_ANON_NAME with different names, it results in two mappings.
Although this will unlikely be an issue for pthread stacks and malloc
arenas (since for pthread stacks the guard page will result in
a PROT_NONE segment, similar to the alignment requirement for the arena
block), it still might prevent the mmap memory allocated for detail
malloc.
There is also another potential scalability issue, where the prctl
requires
to take the mmap global lock which is still not fully fixed in Linux
[1] (for pthread stacks and arenas, it is mitigated by the stack
cached and the arena reuse).
So this patch disables anonymous mapping annotations as default and
add a new tunable, glibc.mem.decorate_maps, can be used to enable
it.
[1] https://lwn.net/Articles/906852/
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
This patch removes the mergesort optimization on qsort implementation
and uses the introsort instead. The mergesort implementation has some
issues:
- It is as-safe only for certain types sizes (if total size is less
than 1 KB with large element sizes also forcing memory allocation)
which contradicts the function documentation. Although not required
by the C standard, it is preferable and doable to have an O(1) space
implementation.
- The malloc for certain element size and element number adds
arbitrary latency (might even be worse if malloc is interposed).
- To avoid trigger swap from memory allocation the implementation
relies on system information that might be virtualized (for instance
VMs with overcommit memory) which might lead to potentially use of
swap even if system advertise more memory than actually has. The
check also have the downside of issuing syscalls where none is
expected (although only once per execution).
- The mergesort is suboptimal on an already sorted array (BZ#21719).
The introsort implementation is already optimized to use constant extra
space (due to the limit of total number of elements from maximum VM
size) and thus can be used to avoid the malloc usage issues.
Resulting performance is slower due the usage of qsort, specially in the
worst-case scenario (partialy or sorted arrays) and due the fact
mergesort uses a slight improved swap operations.
This change also renders the BZ#21719 fix unrequired (since it is meant
to fix the sorted input performance degradation for mergesort). The
manual is also updated to indicate the function is now async-cancel
safe.
Checked on x86_64-linux-gnu.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>
All the crypt related functions, cryptographic algorithms, and
make requirements are removed, with only the exception of md5
implementation which is moved to locale folder since it is
required by localedef for integrity protection (libc's
locale-reading code does not check these, but localedef does
generate them).
Besides thec code itself, both internal documentation and the
manual is also adjusted. This allows to remove both --enable-crypt
and --enable-nss-crypt configure options.
Checked with a build for all affected ABIs.
Co-authored-by: Zack Weinberg <zack@owlfolio.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit add support for the new AVX10 cpu features:
https://cdrdv2-public.intel.com/784267/355989-intel-avx10-spec.pdf
We add checks for:
- `AVX10`: Check if AVX10 is present.
- `AVX10_{X,Y,Z}MM`: Check if a given vec class has AVX10 support.
`make check` passes and cpuid output was checked against GNR/DMR on an
emulator.
ISO C2x defines scanf length modifiers wN (for intN_t / int_leastN_t /
uintN_t / uint_leastN_t) and wfN (for int_fastN_t / uint_fastN_t).
Add support for those length modifiers, similar to the printf support
previously added.
Tested for x86_64 and x86.
And shorten the section/node names a bit, so that the menu
entries become easier to read.
Texinfo 6.5 fails to process the previous structure:
./dynlink.texi:56: warning: node `Dynamic Linker Introspection' is
next for `Dynamic Linker Diagnostics' in sectioning but not in menu
./dynlink.texi:56: warning: node up `Dynamic Linker Diagnostics'
in menu `Dynamic Linker Invocation' and
in sectioning `Dynamic Linker' differ
./dynlink.texi:1: node `Dynamic Linker' lacks menu item for
`Dynamic Linker Diagnostics' despite being its Up target
./dynlink.texi:226: warning: node prev `Dynamic Linker Introspection' in menu `Dynamic Linker Invocation'
and in sectioning `Dynamic Linker Diagnostics' differ
Texinfo 7.0.2 does not report an error.
This fixes commit f21962ddfc
("manual: Document ld.so --list-diagnostics output").
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This interface allows to obtain the associated process ID from the
process file descriptor. It is done by parsing the procps fdinfo
information. Its prototype is:
pid_t pidfd_getpid (int fd)
It returns the associated pid or -1 in case of an error and sets the
errno accordingly. The possible errno values are those from open, read,
and close (used on procps parsing), along with:
- EBADF if the FD is negative, does not have a PID associated, or if
the fdinfo fields contain a value larger than pid_t.
- EREMOTE if the PID is in a separate namespace.
- ESRCH if the process is already terminated.
Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PIDFD or waitid
support), Linux 5.4 (full support), and Linux 6.2.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Returning a pidfd allows a process to keep a race-free handle for a
child process, otherwise, the caller will need to either use pidfd_open
(which still might be subject to TOCTOU) or keep the old racy interface
base on pid_t.
To correct use pifd_spawn, the kernel must support not only returning
the pidfd with clone/clone3 but also waitid (P_PIDFD) (added on Linux
5.4). If kernel does not support the waitid, pidfd return ENOSYS.
It avoids the need to racy workarounds, such as reading the procfs
fdinfo to get the pid to use along with other wait interfaces.
These interfaces are similar to the posix_spawn and posix_spawnp, with
the only difference being it returns a process file descriptor (int)
instead of a process ID (pid_t). Their prototypes are:
int pidfd_spawn (int *restrict pidfd,
const char *restrict file,
const posix_spawn_file_actions_t *restrict facts,
const posix_spawnattr_t *restrict attrp,
char *const argv[restrict],
char *const envp[restrict])
int pidfd_spawnp (int *restrict pidfd,
const char *restrict path,
const posix_spawn_file_actions_t *restrict facts,
const posix_spawnattr_t *restrict attrp,
char *const argv[restrict_arr],
char *const envp[restrict_arr]);
A new symbol is used instead of a posix_spawn extension to avoid
possible issues with language bindings that might track the return
argument lifetime. Although on Linux pid_t and int are interchangeable,
POSIX only states that pid_t should be a signed integer.
Both symbols reuse the posix_spawn posix_spawn_file_actions_t and
posix_spawnattr_t, to void rehash posix_spawn API or add a new one. It
also means that both interfaces support the same attribute and file
actions, and a new flag or file action on posix_spawn is also added
automatically for pidfd_spawn.
Also, using posix_spawn plumbing allows the reusing of most of the
current testing with some changes:
- waitid is used instead of waitpid since it is a more generic
interface.
- tst-posix_spawn-setsid.c is adapted to take into consideration that
the caller can check for session id directly. The test now spawns
itself and writes the session id as a file instead.
- tst-spawn3.c need to know where pidfd_spawn is used so it keeps an
extra file description unused.
Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PIDFD or waitid
support), Linux 5.4 (full support), and Linux 6.2.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Parts of elf/tst-rtld-list-diagnostics.py have been copied from
scripts/tst-ld-trace.py.
The abnf module is entirely optional and used to verify the
ABNF grammar as included in the manual.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
