1. Take into account first 16B comparison for aligned strings
The previous version compares the first 16B and increments r4 by the number
of bytes until the address is 16B-aligned, then starts doing aligned loads at
that address. For aligned strings, this causes the first 16B to be compared
twice, because the increment is 0. Here we calculate the next 16B-aligned
address differently, which avoids that issue.
2. Use simple comparisons for the first ~192 bytes
The main loop is good for big strings, but comparing 16B each time is better
for smaller strings. So after aligning the address to 16 Bytes, we check
more 176B in 16B chunks. There may be some overlaps with the main loop for
unaligned strings, but we avoid using the more aggressive strategy too soon,
and also allow the loop to start at a 64B-aligned address. This greatly
benefits smaller strings and avoids overlapping checks if the string is
already aligned at a 64B boundary.
3. Reduce dependencies between load blocks caused by address calculation on loop
Doing a precise time tracing on the code showed many loads in the loop were
stalled waiting for updates to r4 from previous code blocks. This
implementation avoids that as much as possible by using 2 registers (r4 and
r5) to hold addresses to be used by different parts of the code.
Also, the previous code aligned the address to 16B, then to 64B by doing a
few 48B loops (if needed) until the address was aligned. The main loop could
not start until that 48B loop had finished and r4 was updated with the
current address. Here we calculate the address used by the loop very early,
so it can start sooner.
The main loop now uses 2 pointers 128B apart to make pointer updates less
frequent, and also unrolls 1 iteration to guarantee there is enough time
between iterations to update the pointers, reducing stalled cycles.
4. Use new P10 instructions
lxvp is used to load 32B with a single instruction, reducing contention in
the load queue.
vextractbm allows simplifying the tail code for the loop, replacing
vbpermq and avoiding having to generate a permute control vector.
Reviewed-by: Paul E Murphy <murphyp@linux.ibm.com> Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com> Reviewed-by: Lucas A. M. Magalhaes <lamm@linux.ibm.com>
nptl: Move setxid broadcast implementation into libc
The signal handler is exported as __nptl_setxid_sighandler, so
that the libpthread initialization code can install it. This
is sufficient for now because it is guarantueed to happen before
the first pthread_create call.
nptl: Move core condition variable functions into libc
Onl pthread_cond_clockwait did not have a forwarder, so it needs
a new symbol version.
Some complications arise due to the need to supply hidden aliases,
GLIBC_PRIVATE exports (for the C11 condition variable implementation
that still remains in libpthread) and 64-bit time_t stubs.
pthread_cond_broadcast, pthread_cond_signal, pthread_cond_timedwait,
pthread_cond_wait, pthread_cond_clockwait have been moved using
scripts/move-symbol-to-libc.py.
This is complicated because of a second compilation of
nptl/pthread_mutex_lock.c via nptl/pthread_mutex_cond_lock.c.
PTHREAD_MUTEX_VERSIONS is introduced to suppress symbol versions
in that case.
The symbols __pthread_mutex_lock, __pthread_mutex_unlock,
__pthread_mutex_init, __pthread_mutex_destroy, pthread_mutex_lock,
pthread_mutex_unlock, pthread_mutex_init, pthread_mutex_destroy
have been moved using scripts/move-symbol-to-libc.py.
The current approach is to do this optimizations at a higher level,
in generic code, so that single-threaded cases can be specifically
targeted.
Furthermore, using IS_IN (libc) as a compile-time indicator that
all locks are private is no longer correct once process-shared lock
implementations are moved into libc.
The generic <lowlevellock.h> is not compatible with assembler code
(obviously), so it's necessary to remove two long-unused #includes.
This is optimization is similar in spirit to the SINGLE_THREAD_P check
in the malloc implementation. Doing this in generic code allows us
to prioritize those cases which are likely to occur in single-threaded
programs (normal and recursive mutexes).
nptl: Move rwlock functions with forwarders into libc
The forwarders were only used internally, so new symbol versions
are needed. All symbols are moved at once because the forwarders
are no-ops if libpthread is not loaded, leading to inconsistencies
in case of a partial migration.
The symbols __pthread_rwlock_rdlock, __pthread_rwlock_unlock,
__pthread_rwlock_wrlock, pthread_rwlock_rdlock,
pthread_rwlock_unlock, pthread_rwlock_wrlock have been moved using
scripts/move-symbol-to-libc.py.
The __ symbol variants are turned into compat symbols, which is why they
do not receive a GLIBC_2.34 version.
nptl: Move part of TCB initialization from libpthread to __tls_init_tp
This initalization should only happen once for the main thread's TCB.
At present, auditors can achieve this by not linking against
libpthread. If libpthread becomes part of libc, doing this
initialization in libc would happen for every audit namespace,
or too late (if it happens from the main libc only). That's why
moving this code into ld.so seems the right thing to do, right after
the TCB initialization.
For !__ASSUME_SET_ROBUST_LIST ports, this also moves the symbol
__set_robust_list_avail into ld.so, as __nptl_set_robust_list_avail.
It also turned into a proper boolean flag.
Inline the __pthread_initialize_pids function because it seems no
longer useful as a separate function.
elf: Introduce __tls_init_tp for second-phase TCB initialization
TLS_INIT_TP is processor-specific, so it is not a good place to
put thread library initialization code (it would have to be repeated
for all CPUs). Introduce __tls_init_tp as a separate function,
to be called immediately after TLS_INIT_TP. Move the existing
stack list setup code for NPTL to this function.
dlfcn: dlerror needs to call free from the base namespace [BZ #24773]
Calling free directly may end up freeing a pointer allocated by the
dynamic loader using malloc from libc.so in the base namespace using
the allocator from libc.so in a secondary namespace, which results in
crashes.
This commit redirects the free call through GLRO and the dynamic
linker, to reach the correct namespace. It also cleans up the dlerror
handling along the way, so that pthread_setspecific is no longer
needed (which avoids triggering bug 24774).
dlfcn: Failures after dlmopen should not terminate process [BZ #24772]
Commit 9e78f6f6e7134a5f299cc8de77370218f8019237 ("Implement
_dl_catch_error, _dl_signal_error in libc.so [BZ #16628]") has the
side effect that distinct namespaces, as created by dlmopen, now have
separate implementations of the rtld exception mechanism. This means
that the call to _dl_catch_error from libdl in a secondary namespace
does not actually install an exception handler because the
thread-local variable catch_hook in the libc.so copy in the secondary
namespace is distinct from that of the base namepace. As a result, a
dlsym/dlopen/... failure in a secondary namespace terminates the process
with a dynamic linker error because it looks to the exception handler
mechanism as if no handler has been installed.
This commit restores GLRO (dl_catch_error) and uses it to set the
handler in the base namespace.
The pthread_exit symbol was moved using
scripts/move-symbol-to-libc.py. No new symbol version is needed
because there was a forwarder.
The new tests nptl/tst-pthread_exit-nothreads and
nptl/tst-pthread_exit-nothreads-static exercise the scenario
that pthread_exit is called without libpthread having been linked in.
This is not possible for the generic code, so these tests do not
live in sysdeps/pthread for now.
It's necessary to stub out __libc_disable_asynccancel and
__libc_enable_asynccancel via rtld-stubbed-symbols because the new
direct references to the unwinder result in symbol conflicts when the
rtld exception handling from libc is linked in during the construction
of librtld.map.
unwind-forcedunwind.c is merged into unwind-resume.c. libc now needs
the functions that were previously only used in libpthread.
The GLIBC_PRIVATE exports of __libc_longjmp and __libc_siglongjmp are
no longer needed, so switch them to hidden symbols.
The symbol __pthread_unwind_next has been moved using
scripts/move-symbol-to-libc.py.
This internal symbol is used as part of the longjmp implementation.
Rename the file from nptl/pt-cleanup.c to nptl/pthread_cleanup_upto.c
so that the pt-* files remain restricted to libpthread.
The definitions in libc are sufficient, the forwarders are no longer
needed.
The symbols have been moved using scripts/move-symbol-to-libc.py.
s390-linux-gnu and s390x-linux-gnu need a new version placeholder
to keep the GLIBC_2.19 symbol version in libpthread.
Tested on i386-linux-gnu, powerpc64le-linux-gnu, s390x-linux-gnu,
x86_64-linux-gnu. Built with build-many-glibcs.py.
nptl: Move legacy cancelation handling into libc as compat symbols
This affects _pthread_cleanup_pop, _pthread_cleanup_pop_restore,
_pthread_cleanup_push, _pthread_cleanup_push_defer. The symbols
have been moved using scripts/move-symbol-to-libc.py.
No new symbol versions are added because the symbols are turned into
compatibility symbols at the same time.
__pthread_cleanup_pop and __pthread_cleanup_push are added as
GLIBC_PRIVATE symbols because they are also used internally, for
glibc's own cancellation handling.
nptl: Move legacy unwinding implementation into libc
It is still used internally. Since unwinding is now available
unconditionally, avoid indirect calls through function pointers loaded
from the stack by inlining the non-cancellation cleanup code. This
avoids a regression in security hardening.
The out-of-line __libc_cleanup_routine implementation is no longer
needed because the inline definition is now static __always_inline.
Szabolcs Nagy [Thu, 11 Feb 2021 13:24:47 +0000 (13:24 +0000)]
elf: Remove lazy tlsdesc relocation related code
Remove generic tlsdesc code related to lazy tlsdesc processing since
lazy tlsdesc relocation is no longer supported. This includes removing
GL(dl_load_lock) from _dl_make_tlsdesc_dynamic which is only called at
load time when that lock is already held.
nptl_db: Support different libpthread/ld.so load orders (bug 27744)
libthread_db is loaded once GDB encounters libpthread, and at this
point, ld.so may not have been processed by GDB yet. As a result,
_rtld_global cannot be accessed by regular means from libthread_db.
To make this work until GDB can be fixed, acess _rtld_global through
a pointer stored in libpthread.
The new test does not reproduce bug 27744 with
--disable-hardcoded-path-in-tests, but is still a valid smoke test.
With --enable-hardcoded-path-in-tests, it is necessary to avoid
add-symbol-file because this can tickle a GDB bug.
No bug. This commit optimizes strlen-avx2.S. The optimizations are
mostly small things but they add up to roughly 10-30% performance
improvement for strlen. The results for strnlen are bit more
ambiguous. test-strlen, test-strnlen, test-wcslen, and test-wcsnlen
are all passing.
No bug. This commit optimizes strlen-evex.S. The
optimizations are mostly small things but they add up to roughly
10-30% performance improvement for strlen. The results for strnlen are
bit more ambiguous. test-strlen, test-strnlen, test-wcslen, and
test-wcsnlen are all passing.
No bug. This commit adds tests cases and benchmarks for page cross and
for memset to the end of the page without crossing. As well in
test-memset.c this commit adds sentinel on start/end of tstbuf to test
for overwrites
x86: Optimize less_vec evex and avx512 memset-vec-unaligned-erms.S
No bug. This commit adds optimized cased for less_vec memset case that
uses the avx512vl/avx512bw mask store avoiding the excessive
branches. test-memset and test-wmemset are passing.
benchtests: Fix pthread-locks test to produce valid json
The benchtests json allows {function {variant}} categorization of
results whereas the pthread-locks tests had {function {variant
{subvariant}}}, which broke validation. Fix that by serializing the
subvariants as variant-subvariant. Also update the schema to
recognize the new benchmark attributes after fixing the naming
conventions.
No Bug. This commit expanding the range of tests / benchmarks for
memmove and memcpy. The test expansion is mostly in the vein of
increasing the maximum size, increasing the number of unique
alignments tested, and testing both source < destination and vice
versa. The benchmark expansaion is just to increase the number of
unique alignments. test-memcpy, test-memccpy, test-mempcpy,
test-memmove, and tst-memmove-overflow all pass.
Fangrui Song [Fri, 16 Apr 2021 18:26:39 +0000 (11:26 -0700)]
Set the retain attribute on _elf_set_element if CC supports [BZ #27492]
So that text_set_element/data_set_element/bss_set_element defined
variables will be retained by the linker.
Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable
will not be optimized out; 'retain' prevents section garbage collection
if the linker support SHF_GNU_RETAIN.
GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C
identifier name sections to be GCed even if there are live
__start_/__stop_ references.
Without the change, there are some static linking problems, e.g.
_IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so
stdout is not flushed on exit.
Note: GCC may warning 'retain' attribute ignored while __has_attribute(retain)
is 1 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99587).
x86: Update large memcpy case in memmove-vec-unaligned-erms.S
No Bug. This commit updates the large memcpy case (no overlap). The
update is to perform memcpy on either 2 or 4 contiguous pages at
once. This 1) helps to alleviate the affects of false memory aliasing
when destination and source have a close 4k alignment and 2) In most
cases and for most DRAM units is a modestly more efficient access
pattern. These changes are a clear performance improvement for
VEC_SIZE =16/32, though more ambiguous for VEC_SIZE=64. test-memcpy,
test-memccpy, test-mempcpy, test-memmove, and tst-memmove-overflow all
pass.
Matheus Castanho [Wed, 17 Mar 2021 13:14:15 +0000 (10:14 -0300)]
powerpc: Add missing registers to clobbers list for syscalls [BZ #27623]
Some registers that can be clobbered by the kernel during a syscall are not
listed on the clobbers list in sysdeps/unix/sysv/linux/powerpc/sysdep.h.
For syscalls using sc:
- XER is zeroed by the kernel on exit
For syscalls using scv:
- XER is zeroed by the kernel on exit
- Different from the sc case, most CR fields can be clobbered (according to
the ELF ABI and the Linux kernel's syscall ABI for powerpc
(linux/Documentation/powerpc/syscall64-abi.rst)
The same should apply to vsyscalls, which effectively execute a function call
but are not currently adding these registers as clobbers either.
These are likely not causing issues today, but they should be added to the
clobbers list just in case things change on the kernel side in the future.
Reported-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>
misc: syslog: Assume MSG_NOSIGNAL support (BZ #17144)
MSG_NOSIGNAL was added on POSIX 2008 and Hurd seems to support it.
The SIGPIPE handling also makes the implementation not thread-safe
(due the sigaction usage).
Now that libsupport abstract Linux possible missing support (either
due FS limitation that can't handle 64 bit timestamp or architectures
that do not handle values larger than unsigned 32 bit values) the
tests can be turned generic.
Checked on x86_64-linux-gnu and i686-linux-gnu. I also built the
tests for i686-gnu.
Another issue is that ld auditing ignores DT_BIND_NOW and thus tries to
relocate tlsdesc lazily, but that does not work in a BIND_NOW module
due to missing DT_TLSDESC_PLT. Unconditionally relocating tlsdesc at
load time fixes this bug 27721 too.
Szabolcs Nagy [Wed, 30 Dec 2020 21:52:38 +0000 (21:52 +0000)]
elf: Refactor _dl_update_slotinfo to avoid use after free
map is not valid to access here because it can be freed by a concurrent
dlclose: during tls access (via __tls_get_addr) _dl_update_slotinfo is
called without holding dlopen locks. So don't check the modid of map.
The map == 0 and map != 0 code paths can be shared (avoiding the dtv
resize in case of map == 0 is just an optimization: larger dtv than
necessary would be fine too).
the generation counter update is not needed in the failure path.
That commit ensures allocation in _dl_add_to_slotinfo happens before
the demarcation point in dlopen (it is called twice, first time is for
allocation only where dlopen can still be reverted on failure, then
second time actual dtv updates are done which then cannot fail).
Szabolcs Nagy [Thu, 31 Dec 2020 12:24:38 +0000 (12:24 +0000)]
elf: Add a DTV setup test [BZ #27136]
The test dlopens a large number of modules with TLS, they are reused
from an existing test.
The test relies on the reuse of slotinfo entries after dlclose, without
bug 27135 fixed this needs a failing dlopen. With a slotinfo list that
has non-monotone increasing generation counters, bug 27136 can trigger.
Szabolcs Nagy [Wed, 30 Dec 2020 23:40:14 +0000 (23:40 +0000)]
elf: Fix a DTV setup issue [BZ #27136]
The max modid is a valid index in the dtv, it should not be skipped.
The bug is observable if the last module has modid == 64 and its
generation is same or less than the max generation of the previous
modules. Then dtv[0].counter implies dtv[64] is initialized but
it isn't. Fixes bug 27136.
Szabolcs Nagy [Tue, 2 Feb 2021 15:02:09 +0000 (15:02 +0000)]
Remove PR_TAGGED_ADDR_ENABLE from sys/prctl.h
The value of PR_TAGGED_ADDR_ENABLE was incorrect in the installed
headers and the prctl command macros were missing that are needed
for it to be useful (PR_SET_TAGGED_ADDR_CTRL). Linux headers have
the definitions since 5.4 so it's widely available, we don't need
to repeat these definitions. The remaining definitions are from
Linux 5.10.
To build glibc with --enable-memory-tagging, Linux 5.4 headers and
binutils 2.33.1 or newer is needed.
linux: sysconf: limit _SC_MAX_ARG to 6 MiB (BZ #25305)
Since Linux 4.13, kernel limits the maximum command line arguments
length to 6 MiB [1]. Normally the limit is still quarter of the maximum
stack size but if that limit exceeds 6 MiB it's clamped down.
glibc's __sysconf implementation for Linux platform is not aware of
this limitation and for stack sizes of over 24 MiB it returns higher
ARG_MAX than Linux will actually accept. This can be verified by
executing the following application on Linux 4.13 or newer:
On affected systems the program will report ARG_MAX as 10 MiB but
despite that executing /bin/true with a bit over 6 MiB of command line
arguments will fail with E2BIG error. Expected result is that ARG_MAX
is reported as 6 MiB.
Update the __sysconf function to clamp ARG_MAX value to 6 MiB if it
would otherwise exceed it. This resolves bug #25305 which was market
WONTFIX as suggested solution was to cap ARG_MAX at 128 KiB.
As an aside and point of comparison, bionic (a libc implementation for
Android systems) decided to resolve this issue by always returning 128
KiB ignoring any potential xargs regressions [2].
On older kernels this results in returning overly conservative value
but that's a safer option than being aggressive and returning invalid
value on recent systems. It's also worth noting that at this point
all supported Linux releases have the 6 MiB barrier so only someone
running an unsupported kernel version would get incorrectly truncated
result.
Dan Raymond [Tue, 13 Apr 2021 13:26:12 +0000 (10:26 -0300)]
misc: syslog: Fix calls to openlog() with LOG_KERN facility (BZ #3604)
POSIX states for syslog [1]:
"Values of the priority argument are formed by OR'ing together a
severity-level value and an optional facility value. If no
facility value is specified, the current default facility value is
used."
So the patch fixes an existing violation of the openlog interface contract
where it is ignoring the facility argument when the value is zero
It allows the use LOG_KERN by calling openlog prior syslog usage.
Paul Eggert [Mon, 12 Apr 2021 02:06:00 +0000 (19:06 -0700)]
Improve documentation for malloc etc. (BZ#27719)
Cover key corner cases (e.g., whether errno is set) that are well
settled in glibc, fix some examples to avoid integer overflow, and
update some other dated examples (code needed for K&R C, e.g.).
* manual/charset.texi (Non-reentrant String Conversion):
* manual/filesys.texi (Symbolic Links):
* manual/memory.texi (Allocating Cleared Space):
* manual/socket.texi (Host Names):
* manual/string.texi (Concatenating Strings):
* manual/users.texi (Setting Groups):
Use reallocarray instead of realloc, to avoid integer overflow issues.
* manual/filesys.texi (Scanning Directory Content):
* manual/memory.texi (The GNU Allocator, Hooks for Malloc):
* manual/tunables.texi:
Use code font for 'malloc' instead of roman font.
(Symbolic Links): Don't assume readlink return value fits in 'int'.
* manual/memory.texi (Memory Allocation and C, Basic Allocation)
(Malloc Examples, Alloca Example):
* manual/stdio.texi (Formatted Output Functions):
* manual/string.texi (Concatenating Strings, Collation Functions):
Omit pointer casts that are needed only in ancient K&R C.
* manual/memory.texi (Basic Allocation):
Say that malloc sets errno on failure.
Say "convert" rather than "cast", since casts are no longer needed.
* manual/memory.texi (Basic Allocation):
* manual/string.texi (Concatenating Strings):
In examples, use C99 declarations after statements for brevity.
* manual/memory.texi (Malloc Examples): Add portability notes for
malloc (0), errno setting, and PTRDIFF_MAX.
(Changing Block Size): Say that realloc (p, 0) acts like
(p ? (free (p), NULL) : malloc (0)).
Add xreallocarray example, since other examples can use it.
Add portability notes for realloc (0, 0), realloc (p, 0),
PTRDIFF_MAX, and improve notes for reallocating to the same size.
(Allocating Cleared Space): Reword now-confusing discussion
about replacement, and xref "Replacing malloc".
* manual/stdio.texi (Formatted Output Functions):
Don't assume message size fits in 'int'.
* manual/string.texi (Concatenating Strings):
Fix undefined behavior involving arithmetic on a freed pointer.
linux: Normalize and return timeout on select (BZ #27651)
The commit 2433d39b697, which added time64 support to select, changed
the function to use __NR_pselect6 (or __NR_pelect6_time64) on all
architectures. However, on architectures where the symbol was
implemented with __NR_select the kernel normalizes the passed timeout
instead of return EINVAL. For instance, the input timeval
{ 0, 5000000 } is interpreted as { 5, 0 }.
And as indicated by BZ #27651, this semantic seems to be expected
and changing it results in some performance issues (most likely
the program does not check the return code and keeps issuing
select with unormalized tv_usec argument).
To avoid a different semantic depending whether which syscall the
architecture used to issue, select now always normalize the timeout
input. This is a slight change for some ABIs (for instance aarch64).
Fix SXID_ERASE behavior in setuid programs (BZ #27471)
When parse_tunables tries to erase a tunable marked as SXID_ERASE for
setuid programs, it ends up setting the envvar string iterator
incorrectly, because of which it may parse the next tunable
incorrectly. Given that currently the implementation allows malformed
and unrecognized tunables pass through, it may even allow SXID_ERASE
tunables to go through.
This change revamps the SXID_ERASE implementation so that:
- Only valid tunables are written back to the tunestr string, because
of which children of SXID programs will only inherit a clean list of
identified tunables that are not SXID_ERASE.
- Unrecognized tunables get scrubbed off from the environment and
subsequently from the child environment.
- This has the side-effect that a tunable that is not identified by
the setxid binary, will not be passed on to a non-setxid child even
if the child could have identified that tunable. This may break
applications that expect this behaviour but expecting such tunables
to cross the SXID boundary is wrong. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Instead of passing GLIBC_TUNABLES via the environment, pass the
environment variable from parent to child. This allows us to test
multiple variables to ensure better coverage.
The test list currently only includes the case that's already being
tested. More tests will be added later. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
projects / thirdparty / glibc.git / log
