Rename atomic_exchange_rel/acq to use atomic_exchange_release/acquire
since these map to the standard C11 atomic builtins.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Replace atomic_decrement_and_test with atomic_fetch_add_relaxed.
These are simple counters which do not protect any shared data from
concurrent accesses. Also remove the unused file cond-perf.c.
Passes regress on AArch64.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Replace atomic_increment and atomic_increment_val with atomic_fetch_add_relaxed.
One case in sem_post.c uses release semantics (see comment above it).
The others are simple counters and do not protect any shared data from
concurrent accesses.
Passes regress on AArch64.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Remove the 4 uses of atomic_and and atomic_or with atomic_fetch_and_acquire
and atomic_fetch_or_acquire. This is preserves existing implied semantics,
however relaxed MO on FUTEX_OWNER_DIED accesses may be correct.
Passes regress on AArch64.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Replace the 3 uses of atomic_bit_set and atomic_bit_test_set with
atomic_fetch_or_relaxed. Using relaxed MO is correct since the
atomics are used to ensure memory is released only once.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
The main drive is to optimize the internal usage and required size
when sigset_t is embedded in other data structures. On Linux, the
current supported signal set requires up to 8 bytes (16 on mips),
was lower than the user defined sigset_t (128 bytes).
A new internal type internal_sigset_t is added, along with the
functions to operate on it similar to the ones for sigset_t. The
internal-signals.h is also refactored to remove unused functions
Besides small stack usage on some functions (posix_spawn, abort)
it lower the struct pthread by about 120 bytes (112 on mips).
Checked on x86_64-linux-gnu.
Reviewed-by: Arjun Shankar <arjun@redhat.com>
By adding an internal alias to avoid the GOT indirection.
On some architecture, __libc_single_thread may be accessed through
copy relocations and thus it requires to update also the copies
default copy.
This is done by adding a new internal macro,
libc_hidden_data_{proto,def}, which has an addition argument that
specifies the alias name (instead of default __GI_ one).
Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Fangrui Song <maskray@google.com>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
This tunable allows applications to register the rseq area instead
of glibc.
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
The rseq area is placed directly into struct pthread. rseq
registration failure is not treated as an error, so it is possible
that threads run with inconsistent registration status.
<sys/rseq.h> is not yet installed as a public header.
Co-Authored-By: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
__libc_signal_restore_set was in the wrong place: It also ran
when setjmp returned the second time (after pthread_exit or
pthread_cancel). This is observable with blocked pending
signals during thread exit.
Fixes commit b3cae39dcb
("nptl: Start new threads with all signals blocked [BZ #25098]").
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
As part of the fix for bug 12889, signals are blocked during
thread exit, so that application code cannot run on the thread that
is about to exit. This would cause problems if the application
expected signals to be delivered after the signal handler revealed
the thread to still exist, despite pthread_kill can no longer be used
to send signals to it. However, glibc internally uses the SIGSETXID
signal in a way that is incompatible with signal blocking, due to the
way the setxid handshake delays thread exit until the setxid operation
has completed. With a blocked SIGSETXID, the handshake can never
complete, causing a deadlock.
As a band-aid, restore the previous handshake protocol by not blocking
SIGSETXID during thread exit.
The new test sysdeps/pthread/tst-pthread-setuid-loop.c is based on
a downstream test by Martin Osvald.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
A new thread exit lock and flag are introduced. They are used to
detect that the thread is about to exit or has exited in
__pthread_kill_internal, and the signal is not sent in this case.
The test sysdeps/pthread/tst-pthread_cancel-select-loop.c is derived
from a downstream test originally written by Marek Polacek.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
We stopped adding "Contributed by" or similar lines in sources in 2012
in favour of git logs and keeping the Contributors section of the
glibc manual up to date. Removing these lines makes the license
header a bit more consistent across files and also removes the
possibility of error in attribution when license blocks or files are
copied across since the contributed-by lines don't actually reflect
reality in those cases.
Move all "Contributed by" and similar lines (Written by, Test by,
etc.) into a new file CONTRIBUTED-BY to retain record of these
contributions. These contributors are also mentioned in
manual/contrib.texi, so we just maintain this additional record as a
courtesy to the earlier developers.
The following scripts were used to filter a list of files to edit in
place and to clean up the CONTRIBUTED-BY file respectively. These
were not added to the glibc sources because they're not expected to be
of any use in future given that this is a one time task:
https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dchttps://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The clone3 system call (since Linux 5.3) provides a superset of the
functionality of clone and clone2. It also provides a number of API
improvements, including the ability to specify the size of the child's
stack area which can be used by kernel to compute the shadow stack size
when allocating the shadow stack. Add:
extern int __clone_internal (struct clone_args *__cl_args,
int (*__func) (void *__arg), void *__arg);
to provide an abstract interface for clone, clone2 and clone3.
1. Simplify stack management for thread creation by passing both stack
base and size to create_thread.
2. Consolidate clone vs clone2 differences into a single file.
3. Call __clone3 if HAVE_CLONE3_WAPPER is defined. If __clone3 returns
-1 with ENOSYS, fall back to clone or clone2.
4. Use only __clone_internal to clone a thread. Since the stack size
argument for create_thread is now unconditional, always pass stack size
to create_thread.
5. Enable the public clone3 wrapper in the future after it has been
added to all targets.
NB: Sandbox will return ENOSYS on clone3 in both Chromium:
The following revision refers to this bug:
218438259d
commit 218438259dd795456f0a48f67cbe5b4e520db88b
Author: Matthew Denton <mpdenton@chromium.org>
Date: Thu Jun 03 20:06:13 2021
Linux sandbox: return ENOSYS for clone3
Because clone3 uses a pointer argument rather than a flags argument, we
cannot examine the contents with seccomp, which is essential to
preventing sandboxed processes from starting other processes. So, we
won't be able to support clone3 in Chromium. This CL modifies the
BPF policy to return ENOSYS for clone3 so glibc always uses the fallback
to clone.
Bug: 1213452
Change-Id: I7c7c585a319e0264eac5b1ebee1a45be2d782303
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2936184
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Matthew Denton <mpdenton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#888980}
[modify] https://crrev.com/218438259dd795456f0a48f67cbe5b4e520db88b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
and Firefox:
https://hg.mozilla.org/integration/autoland/rev/ecb4011a0c76
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
As a result, is not necessary to specify __attribute__ ((nocommon))
on individual definitions.
GCC 10 defaults to -fno-common on all architectures except ARC,
but this change is compatible with older GCC versions and ARC, too.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This allows distributions to strip debugging information from
libc.so.6 without impacting the debugging experience.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The testcase provided on BZ#19366 may update __nptl_nthreads in a wrong
order, triggering an early process exit because the thread decrement
the value twice.
The issue is once the thread exits without acting on cancellation,
it decreaments '__nptl_nthreads' and then atomically set
'cancelhandling' with EXITING_BIT (thus preventing further cancellation
handler to act). The issue happens if a SIGCANCEL is received between
checking '__ntpl_nthreads' and setting EXITING_BIT. To avoid it, the
'__nptl_nthreads' decrement is moved after EXITING_BIT.
It does fully follow the POSIX XSH 2.9.5 Thread Cancellation under
the heading Thread Cancellation Cleanup Handlers that states that
when a cancellation request is acted upon, or when a thread calls
pthread_exit(), the thread first disables cancellation by setting its
cancelability state to PTHREAD_CANCEL_DISABLE and its cancelability type
to PTHREAD_CANCEL_DEFERRED. The issue is '__pthread_enable_asynccancel'
explicit enabled assynchrnous cancellation, so an interrupted syscall
within the cancellation cleanup handlers might see an invalid cancelling
type (a possible fix might be possible with my proposed solution to
BZ#12683).
Trying to come up with a test is quite hard since it requires to
mimic the timing issue described below, however I see that the
bug report reproducer does not early exit anymore.
Checked on x86_64-linux-gnu.
Now that cancellation is not used anymore to handle thread setup
creation failure, the sighandle can be installed only when
pthread_cancel is actually used.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
To setup either the thread scheduling parameters or affinity,
pthread_create enforce synchronization on created thread to wait until
its parent either release PD ownership or send a cancellation signal if
a failure occurs.
However, cancelling the thread does not deallocate the newly created
stack since cancellation expects that a pthread_join to deallocate any
allocated thread resouces (threads stack or TLS).
This patch changes on how the thread resource is deallocate in case of
failure to be synchronous, where the creating thread will signal the
created thread to exit early so it could be joined. The creating thread
will be reponsible for the resource cleanup before returning to the
caller.
To signal the creating thread that a failure has occured, an unused
'struct pthread' member, parent_cancelhandling_unsed, now indicates
whether the setup has failed so creating thread can proper exit.
This strategy also simplifies by not using thread cancellation and
thus not running libgcc_so load in the signal handler (which is
avoided in thread cancellation since 'pthread_cancel' is the one
responsible to dlopen libgcc_s). Another advantage is since the
early exit is move to first step at thread creation, the signal
mask is not already set and thus it can not act on change ID setxid
handler.
Checked on x86_64-linux-gnu and aarch64-linux-gnu.
The 'create_thread' function is moved to pthread_create.c. It removes
the START_THREAD_DEFN and START_THREAD_SELF macros and make the
lock usage more clear (no need to cross-reference multiple files).
No functional change.
The signal is sent to all threads, some of which may have switched
to very small stacks. If they have also installed an alternate
signal stack, SA_ONSTACK makes this work. The Go runtime needs this:
runtime: C.setuid/C.setgid smashes Go stack
<https://github.com/golang/go/issues/9400>
Doing this for SIGCANCEL is less obviously beneficial and needs further
testing.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The symbols were moved using scripts/move-symbol-to-libc.py.
The libpthread placeholder symbols need some changes because some
symbol versions have gone away completely. But
__errno_location@@GLIBC_2.0 still exists, so the GLIBC_2.0 version
is still there.
The internal __pthread_create symbol now points to the correct
function, so the sysdeps/nptl/thrd_create.c override is no longer
necessary.
There was an issue how the hidden alias of pthread_getattr_default_np
was defined, so this commit cleans up that aspects and removes the
GLIBC_PRIVATE export altogether.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
No abilist updates here because it is a GLIBC_PRIVATE symbol.
It's also necessary to move nptl_version into pthread_create, so
that it still ends up in static binaries.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Install signal handlers and unblock signals before pthread_create
creates the first thread.
create_thread in sysdeps/unix/sysv/linux/createthread.c can send
SIGCANCEL to the current thread, so the SIGCANCEL handler is currently
needed even if pthread_cancel is never called. (The way timer_create
uses SIGCANCEL does not need a signal handler; both SIG_DFL and SIG_IGN
dispositions should work.)
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This replaces the FREE_P macro with the __nptl_stack_in_use inline
function. stack_list_del is renamed to __nptl_stack_list_del,
stack_list_add to __nptl_stack_list_add, __deallocate_stack to
__nptl_deallocate_stack, free_stacks to __nptl_free_stacks.
It is convenient to move __libpthread_freeres into libc at the
same time. This removes the temporary __default_pthread_attr_freeres
export and restores full freeres coverage for __default_pthread_attr.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
This removes the DEBUGGING_P macro and the __pthread_debug variable.
The __find_in_stack_list function is now unused and deleted as well.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Previously, the source file nptl/cancellation.c was compiled multiple
times, for libc, libpthread, librt. This commit switches to a single
implementation, with new __pthread_enable_asynccancel@@GLIBC_PRIVATE,
__pthread_disable_asynccancel@@GLIBC_PRIVATE exports.
The almost-unused CANCEL_ASYNC and CANCEL_RESET macros are replaced
by LIBC_CANCEL_ASYNC and LIBC_CANCEL_ASYNC macros. They call the
__pthread_* functions unconditionally now. The macros are still
needed because shared code uses them; Hurd has different definitions.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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.
Fixes commit 1daccf403b ("nptl: Move
stack list variables into _rtld_global").
Tested-by: Emil Velikov <emil.velikov@collabora.com>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
Now __thread_gscope_wait (the function behind THREAD_GSCOPE_WAIT,
formerly __wait_lookup_done) can be implemented directly in ld.so,
eliminating the unprotected GL (dl_wait_lookup_done) function
pointer.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Building glibc with GCC 11 fails with (among other warnings) spurious
-Wstringop-overflow warnings from calls to setjmp and longjmp with a
pointer to a pthread_unwind_buf that is smaller than jmp_buf. As
discussed in bug 26647, the warning in libc-start.c is a false
positive, because setjmp and longjmp do not access anything (the
signal mask) beyond the common prefix of the two structures, so this
patch disables the warning for that call to setjmp, as well as for two
calls in NPTL code that produce the same warning and look like false
positives for the same reason.
Tested with build-many-glibcs.py for arm-linux-gnueabi, where this
allows the build to get further.
Reviewed-by: DJ Delorie <dj@redhat.com>
The kernel ABI is not finalized, and there are now various proposals
to change the size of struct rseq, which would make the glibc ABI
dependent on the version of the kernels used for building glibc.
This is of course not acceptable.
This reverts commit 48699da1c4 ("elf:
Support at least 32-byte alignment in static dlopen"), commit
8f4632deb3 ("Linux: rseq registration
tests"), commit 6e29cb3f61 ("Linux: Use
rseq in sched_getcpu if available"), and commit
0c76fc3c2b ("Linux: Perform rseq
registration at C startup and thread creation"), resolving the conflicts
introduced by the ARC port and the TLS static surplus changes.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
The variable is placed in libc.so, and it can be true only in
an outer libc, not libcs loaded via dlmopen or static dlopen.
Since thread creation from inner namespaces does not work,
pthread_create can update __libc_single_threaded directly.
Using __libc_early_init and its initial flag, implementation of this
variable is very straightforward. A future version may reset the flag
during fork (but not in an inner namespace), or after joining all
threads except one.
Reviewed-by: DJ Delorie <dj@redhat.com>
Register rseq TLS for each thread (including main), and unregister for
each thread (excluding main). "rseq" stands for Restartable Sequences.
See the rseq(2) man page proposed here:
https://lkml.org/lkml/2018/9/19/647
Those are based on glibc master branch commit 3ee1e0ec5c.
The rseq system call was merged into Linux 4.18.
The TLS_STATIC_SURPLUS define is increased to leave additional room for
dlopen'd initial-exec TLS, which keeps elf/tst-auditmany working.
The increase (76 bytes) is larger than 32 bytes because it has not been
increased in quite a while. The cost in terms of additional TLS storage
is quite significant, but it will also obscure some initial-exec-related
dlopen failures.
User provided stack should not be released nor madvised at
thread exit because it's owned by the user.
If the memory is shared or file based then MADV_DONTNEED
can have unwanted effects. With memory tagging on aarch64
linux the tags are dropped and thus it may invalidate
pointers.
Tested on aarch64-linux-gnu with MTE, it fixes
FAIL: nptl/tst-stack3
FAIL: nptl/tst-stack3-mem
This introduces the function __pthread_attr_extension to allocate the
extension space, which is freed by pthread_attr_destroy.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
union pthread_attr_transparent has always the correct size, even if
pthread_attr_t has padding that is not present in struct pthread_attr.
This should not result in an observable behavioral change. The
existing code appears to have been correct, but it was brittle because
it was not clear which functions were allowed to write to an entire
pthread_attr_t argument (e.g., by copying it).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
There is a race between __nptl_setxid and exiting detached thread, which
causes a deadlock on stack_cache_lock. The deadlock happens in this
state:
T1: setgroups -> __nptl_setxid (holding stack_cache_lock, waiting on cmdp->cntr == 0)
T2 (detached, exiting): start_thread -> __deallocate_stack (waiting on stack_cache_lock)
more threads waiting on stack_cache_lock in pthread_create
For non-detached threads, start_thread waits for its own setxid handler to
finish before exiting. Do this for detached threads as well.
New threads inherit the signal mask from the current thread. This
means that signal handlers can run on the newly created thread
immediately after the kernel has created the userspace thread, even
before glibc has initialized the TCB. Consequently, new threads can
observe uninitialized ctype data, among other things.
To address this, block all signals before starting the thread, and
pass the original signal mask to the start routine wrapper. On the
new thread, first perform all thread initialization, and then unblock
signals.
The cost of doing this is two rt_sigprocmask system calls on the old
thread, and one rt_sigprocmask system call on the new thread. (If
there was a way to clone a new thread with a signals disabled, this
could be brought down to one system call each.) The thread descriptor
increases in size, too, and sigset_t is fairly large. This increase
could be brought down by reusing space the in the descriptor which is
not needed before running user code, or by switching to an internal
sigset_t definition which only covers the signals supported by the
kernel definition. (Part of the thread descriptor size increase is
already offset by reduced stack usage in the thread start wrapper
routine after this commit.)
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Due to the built-in tables, __NR_set_robust_list is always defined
(although it may not be available at run time).
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
