Commit Graph

12 Commits

Author SHA1 Message Date
Adhemerval Zanella
89b53077d2 nptl: Fix Race conditions in pthread cancellation [BZ#12683]
The current racy approach is to enable asynchronous cancellation
before making the syscall and restore the previous cancellation
type once the syscall returns, and check if cancellation has happen
during the cancellation entrypoint.

As described in BZ#12683, this approach shows 2 problems:

  1. Cancellation can act after the syscall has returned from the
     kernel, but before userspace saves the return value.  It might
     result in a resource leak if the syscall allocated a resource or a
     side effect (partial read/write), and there is no way to program
     handle it with cancellation handlers.

  2. If a signal is handled while the thread is blocked at a cancellable
     syscall, the entire signal handler runs with asynchronous
     cancellation enabled.  This can lead to issues if the signal
     handler call functions which are async-signal-safe but not
     async-cancel-safe.

For the cancellation to work correctly, there are 5 points at which the
cancellation signal could arrive:

	[ ... )[ ... )[ syscall ]( ...
	   1      2        3    4   5

  1. Before initial testcancel, e.g. [*... testcancel)
  2. Between testcancel and syscall start, e.g. [testcancel...syscall start)
  3. While syscall is blocked and no side effects have yet taken
     place, e.g. [ syscall ]
  4. Same as 3 but with side-effects having occurred (e.g. a partial
     read or write).
  5. After syscall end e.g. (syscall end...*]

And libc wants to act on cancellation in cases 1, 2, and 3 but not
in cases 4 or 5.  For the 4 and 5 cases, the cancellation will eventually
happen in the next cancellable entrypoint without any further external
event.

The proposed solution for each case is:

  1. Do a conditional branch based on whether the thread has received
     a cancellation request;

  2. It can be caught by the signal handler determining that the saved
     program counter (from the ucontext_t) is in some address range
     beginning just before the "testcancel" and ending with the
     syscall instruction.

  3. SIGCANCEL can be caught by the signal handler and determine that
     the saved program counter (from the ucontext_t) is in the address
     range beginning just before "testcancel" and ending with the first
     uninterruptable (via a signal) syscall instruction that enters the
      kernel.

  4. In this case, except for certain syscalls that ALWAYS fail with
     EINTR even for non-interrupting signals, the kernel will reset
     the program counter to point at the syscall instruction during
     signal handling, so that the syscall is restarted when the signal
     handler returns.  So, from the signal handler's standpoint, this
     looks the same as case 2, and thus it's taken care of.

  5. For syscalls with side-effects, the kernel cannot restart the
     syscall; when it's interrupted by a signal, the kernel must cause
     the syscall to return with whatever partial result is obtained
     (e.g. partial read or write).

  6. The saved program counter points just after the syscall
     instruction, so the signal handler won't act on cancellation.
     This is similar to 4. since the program counter is past the syscall
     instruction.

So The proposed fixes are:

  1. Remove the enable_asynccancel/disable_asynccancel function usage in
     cancellable syscall definition and instead make them call a common
     symbol that will check if cancellation is enabled (__syscall_cancel
     at nptl/cancellation.c), call the arch-specific cancellable
     entry-point (__syscall_cancel_arch), and cancel the thread when
     required.

  2. Provide an arch-specific generic system call wrapper function
     that contains global markers.  These markers will be used in
     SIGCANCEL signal handler to check if the interruption has been
     called in a valid syscall and if the syscalls has side-effects.

     A reference implementation sysdeps/unix/sysv/linux/syscall_cancel.c
     is provided.  However, the markers may not be set on correct
     expected places depending on how INTERNAL_SYSCALL_NCS is
     implemented by the architecture.  It is expected that all
     architectures add an arch-specific implementation.

  3. Rewrite SIGCANCEL asynchronous handler to check for both canceling
     type and if current IP from signal handler falls between the global
     markers and act accordingly.

  4. Adjust libc code to replace LIBC_CANCEL_ASYNC/LIBC_CANCEL_RESET to
     use the appropriate cancelable syscalls.

  5. Adjust 'lowlevellock-futex.h' arch-specific implementations to
     provide cancelable futex calls.

Some architectures require specific support on syscall handling:

  * On i386 the syscall cancel bridge needs to use the old int80
    instruction because the optimized vDSO symbol the resulting PC value
    for an interrupted syscall points to an address outside the expected
    markers in __syscall_cancel_arch.  It has been discussed in LKML [1]
    on how kernel could help userland to accomplish it, but afaik
    discussion has stalled.

    Also, sysenter should not be used directly by libc since its calling
    convention is set by the kernel depending of the underlying x86 chip
    (check kernel commit 30bfa7b3488bfb1bb75c9f50a5fcac1832970c60).

  * mips o32 is the only kABI that requires 7 argument syscall, and to
    avoid add a requirement on all architectures to support it, mips
    support is added with extra internal defines.

Checked on aarch64-linux-gnu, arm-linux-gnueabihf, powerpc-linux-gnu,
powerpc64-linux-gnu, powerpc64le-linux-gnu, i686-linux-gnu, and
x86_64-linux-gnu.

[1] https://lkml.org/lkml/2016/3/8/1105
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
2024-08-23 14:27:43 -03:00
Florian Weimer
501bdb5dd6 Linux: Remove remnants of the getcpu cache
The getcpu cache was removed from the kernel in Linux 2.6.24.  glibc
support from the sched_getcpu implementation was removed in commit
dd26c44403 ("Consolidate sched_getcpu").
2020-05-16 15:47:51 +02:00
Adhemerval Zanella
17fd707f88 nptl: Remove x86_64 cancellation assembly implementations [BZ #25765]
All cancellable syscalls are done by C implementations, so there is no
no need to use a specialized implementation to optimize register usage.

It fixes BZ #25765.

Checked on x86_64-linux-gnu.
2020-04-03 10:47:59 -03:00
H.J. Lu
9aa3113a42 x86: Rename __glibc_reserved2 to ssp_base in tcbhead_t
This will be used to record the current shadow stack base for shadow
stack switching by getcontext, makecontext, setcontext and swapcontext.
If the target shadow stack base is the same as the current shadow stack
base, we unwind the shadow stack.  Otherwise it is a stack switch and
we look for a restore token to restore the target shadow stack.

	* sysdeps/i386/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
	* sysdeps/i386/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
	with ssp_base.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (SSP_BASE_OFFSET): New.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Replace __glibc_reserved2
	with ssp_base.
2018-07-25 04:39:39 -07:00
H.J. Lu
ebff9c5cfa x86: Rename __glibc_reserved1 to feature_1 in tcbhead_t [BZ #22563]
feature_1 has X86_FEATURE_1_IBT and X86_FEATURE_1_SHSTK bits for CET
run-time control.

CET_ENABLED, IBT_ENABLED and SHSTK_ENABLED are defined to 1 or 0 to
indicate that if CET, IBT and SHSTK are enabled.

<tls-setup.h> is added to set up thread-local data.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	[BZ #22563]
	* nptl/pthread_create.c: Include <tls-setup.h>.
	(__pthread_create_2_1): Call tls_setup_tcbhead.
	* sysdeps/generic/tls-setup.h: New file.
	* sysdeps/x86/nptl/tls-setup.h: Likewise.
	* sysdeps/i386/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (FEATURE_1_OFFSET):
	Likewise.
	* sysdeps/i386/nptl/tls.h (tcbhead_t): Rename __glibc_reserved1
	to feature_1.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Likewise.
	* sysdeps/x86/sysdep.h (X86_FEATURE_1_IBT): New.
	(X86_FEATURE_1_SHSTK): Likewise.
	(CET_ENABLED): Likewise.
	(IBT_ENABLED): Likewise.
	(SHSTK_ENABLED): Likewise.
2018-07-14 05:56:46 -07:00
H.J. Lu
0068c08588 nptl: Remove __ASSUME_PRIVATE_FUTEX
Since __ASSUME_PRIVATE_FUTEX is always defined, this patch removes the
!__ASSUME_PRIVATE_FUTEX paths.

Tested with build-many-glibcs.py.

	* nptl/allocatestack.c (allocate_stack): Remove the
	!__ASSUME_PRIVATE_FUTEX paths.
	* nptl/descr.h (header): Remove the !__ASSUME_PRIVATE_FUTEX path.
	* nptl/nptl-init.c (__pthread_initialize_minimal_internal):
	Likewise.
	* sysdeps/i386/nptl/tcb-offsets.sym (PRIVATE_FUTEX): Removed.
	* sysdeps/powerpc/nptl/tcb-offsets.sym (PRIVATE_FUTEX): Likewise.
	* sysdeps/sh/nptl/tcb-offsets.sym (PRIVATE_FUTEX): Likewise.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (PRIVATE_FUTEX): Likewise.
	* sysdeps/i386/nptl/tls.h: (tcbhead_t): Remve the
	!__ASSUME_PRIVATE_FUTEX path.
	* sysdeps/s390/nptl/tls.h (tcbhead_t): Likewise.
	* sysdeps/sparc/nptl/tls.h (tcbhead_t): Likewise.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Likewise.
	* sysdeps/unix/sysv/linux/i386/lowlevellock.S: Remove the
	!__ASSUME_PRIVATE_FUTEX macros.
	* sysdeps/unix/sysv/linux/lowlevellock-futex.h: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/cancellation.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/lowlevellock.S: Likewise.
	* sysdeps/unix/sysv/linux/kernel-features.h
	(__ASSUME_PRIVATE_FUTEX): Removed.
2018-05-17 04:25:10 -07:00
Carlos O'Donell
2ec0e7eade Revert Intel CET changes to __jmp_buf_tag (Bug 22743)
In commit cba595c350 and commit
f81ddabffd, ABI compatibility with
applications was broken by increasing the size of the on-stack
allocated __pthread_unwind_buf_t beyond the oringal size.
Applications only have the origianl space available for
__pthread_unwind_register, and __pthread_unwind_next to use,
any increase in the size of __pthread_unwind_buf_t causes these
functions to write beyond the original structure into other
on-stack variables leading to segmentation faults in common
applications like vlc. The only workaround is to version those
functions which operate on the old sized objects, but this must
happen in glibc 2.28.

Thank you to Andrew Senkevich, H.J. Lu, and Aurelien Jarno, for
submitting reports and tracking the issue down.

The commit reverts the above mentioned commits and testing on
x86_64 shows that the ABI compatibility is restored. A tst-cleanup1
regression test linked with an older glibc now passes when run
with the newly built glibc. Previously a tst-cleanup1 linked with
an older glibc would segfault when run with an affected glibc build.

Tested on x86_64 with no regressions.

Signed-off-by: Carlos O'Donell <carlos@redhat.com>
2018-01-25 23:43:46 -08:00
H.J. Lu
cba595c350 x86: Add feature_1 to tcbhead_t [BZ #22563]
On x86, padding in struct __jmp_buf_tag is used for shadow stack pointer
to support Shadow Stack in Intel Control-flow Enforcemen Technology.
cancel_jmp_buf has been updated to include saved_mask so that it is as
large as struct __jmp_buf_tag.  We must suport the old cancel_jmp_buf
in existing binaries.  Since symbol versioning doesn't work on
cancel_jmp_buf, feature_1 is added to tcbhead_t so that setjmp and
longjmp can check if shadow stack is enabled.  NB: Shadow stack is
enabled only if all modules are shadow stack enabled.

	[BZ #22563]
	* sysdeps/i386/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
	* sysdeps/i386/nptl/tls.h (tcbhead_t): Add feature_1.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Rename __glibc_unused1
	to feature_1.
2017-12-19 02:45:34 -08:00
Adhemerval Zanella
c579f48edb Remove cached PID/TID in clone
This patch remove the PID cache and usage in current GLIBC code.  Current
usage is mainly used a performance optimization to avoid the syscall,
however it adds some issues:

  - The exposed clone syscall will try to set pid/tid to make the new
    thread somewhat compatible with current GLIBC assumptions.  This cause
    a set of issue with new workloads and usecases (such as BZ#17214 and
    [1]) as well for new internal usage of clone to optimize other algorithms
    (such as clone plus CLONE_VM for posix_spawn, BZ#19957).

  - The caching complexity also added some bugs in the past [2] [3] and
    requires more effort of each port to handle such requirements (for
    both clone and vfork implementation).

  - Caching performance gain in mainly on getpid and some specific
    code paths.  The getpid performance leverage is questionable [4],
    either by the idea of getpid being a hotspot as for the getpid
    implementation itself (if it is indeed a justifiable hotspot a
    vDSO symbol could let to a much more simpler solution).

    Other usage is mainly for non usual code paths, such as pthread
    cancellation signal and handling.

For thread creation (on stack allocation) the code simplification in fact
adds some performance gain due the no need of transverse the stack cache
and invalidate each element pid.

Other thread usages will require a direct getpid syscall, such as
cancellation/setxid signal, thread cancellation, thread fail path (at
create_thread), and thread signal (pthread_kill and pthread_sigqueue).
However these are hardly usual hotspots and I think adding a syscall is
justifiable.

It also simplifies both the clone and vfork arch-specific implementation.
And by review each fork implementation there are some discrepancies that
this patch also solves:

  - microblaze clone/vfork does not set/reset the pid/tid field
  - hppa uses the default vfork implementation that fallback to fork.
    Since vfork is deprecated I do not think we should bother with it.

The patch also removes the TID caching in clone. My understanding for
such semantic is try provide some pthread usage after a user program
issue clone directly (as done by thread creation with CLONE_PARENT_SETTID
and pthread tid member).  However, as stated before in multiple discussions
threads, GLIBC provides clone syscalls without further supporting all this
semantics.

I ran a full make check on x86_64, x32, i686, armhf, aarch64, and powerpc64le.
For sparc32, sparc64, and mips I ran the basic fork and vfork tests from
posix/ folder (on a qemu system).  So it would require further testing
on alpha, hppa, ia64, m68k, nios2, s390, sh, and tile (I excluded microblaze
because it is already implementing the patch semantic regarding clone/vfork).

[1] https://codereview.chromium.org/800183004/
[2] https://sourceware.org/ml/libc-alpha/2006-07/msg00123.html
[3] https://sourceware.org/bugzilla/show_bug.cgi?id=15368
[4] http://yarchive.net/comp/linux/getpid_caching.html

	* sysdeps/nptl/fork.c (__libc_fork): Remove pid cache setting.
	* nptl/allocatestack.c (allocate_stack): Likewise.
	(__reclaim_stacks): Likewise.
	(setxid_signal_thread): Obtain pid through syscall.
	* nptl/nptl-init.c (sigcancel_handler): Likewise.
	(sighandle_setxid): Likewise.
	* nptl/pthread_cancel.c (pthread_cancel): Likewise.
	* sysdeps/unix/sysv/linux/pthread_kill.c (__pthread_kill): Likewise.
	* sysdeps/unix/sysv/linux/pthread_sigqueue.c (pthread_sigqueue):
	Likewise.
	* sysdeps/unix/sysv/linux/createthread.c (create_thread): Likewise.
	* sysdeps/unix/sysv/linux/getpid.c: Remove file.
	* nptl/descr.h (struct pthread): Change comment about pid value.
	* nptl/pthread_getattr_np.c (pthread_getattr_np): Remove thread
	pid assert.
	* sysdeps/unix/sysv/linux/pthread-pids.h (__pthread_initialize_pids):
	Do not set pid value.
	* nptl_db/td_ta_thr_iter.c (iterate_thread_list): Remove thread
	pid cache check.
	* nptl_db/td_thr_validate.c (td_thr_validate): Likewise.
	* sysdeps/aarch64/nptl/tcb-offsets.sym: Remove pid offset.
	* sysdeps/alpha/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/arm/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/hppa/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/i386/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/ia64/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/m68k/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/microblaze/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/mips/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/nios2/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/powerpc/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/s390/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/sh/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/sparc/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/tile/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/x86_64/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/clone.S: Remove pid and tid caching.
	* sysdeps/unix/sysv/linux/alpha/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/arm/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/hppa/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/ia64/clone2.S: Likewise.
	* sysdeps/unix/sysv/linux/mips/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/nios2/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sh/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/tile/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/aarch64/vfork.S: Remove pid set and reset.
	* sysdeps/unix/sysv/linux/alpha/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/arm/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/i386/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/ia64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/m68k/clone.S: Likewise.
	* sysdeps/unix/sysv/linux/m68k/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/mips/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/nios2/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sh/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/tile/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/vfork.S: Likewise.
	* sysdeps/unix/sysv/linux/tst-clone2.c (f): Remove direct pthread
	struct access.
	(clone_test): Remove function.
	(do_test): Rewrite to take in consideration pid is not cached anymore.
2016-11-24 19:38:51 -02:00
H.J. Lu
f3dcae82d5 Save and restore vector registers in x86-64 ld.so
This patch adds SSE, AVX and AVX512 versions of _dl_runtime_resolve
and _dl_runtime_profile, which save and restore the first 8 vector
registers used for parameter passing.  elf_machine_runtime_setup
selects the proper _dl_runtime_resolve or _dl_runtime_profile based
on _dl_x86_cpu_features.  It avoids race condition caused by
FOREIGN_CALL macros, which are only used for x86-64.

Performance impact of saving and restoring 8 vector registers are
negligible on Nehalem, Sandy Bridge, Ivy Bridge and Haswell when
ld.so is optimized with SSE2.

	[BZ #15128]
	* sysdeps/x86_64/Makefile [$(subdir) == elf] (tests): Add
	ifuncmain8.
	(modules-names): Add ifuncmod8.
	($(objpfx)ifuncmain8): New rule.
	* sysdeps/x86_64/dl-machine.h: Include <dl-procinfo.h> and
	<cpuid.h>.
	(elf_machine_runtime_setup): Use _dl_runtime_resolve_sse,
	_dl_runtime_resolve_avx, or _dl_runtime_resolve_avx512,
	_dl_runtime_profile_sse, _dl_runtime_profile_avx, or
	_dl_runtime_profile_avx512, based on HAS_ARCH_FEATURE.
	* sysdeps/x86_64/dl-trampoline.S: Rewrite.
	* sysdeps/x86_64/dl-trampoline.h: Likewise.
	* sysdeps/x86_64/ifuncmain8.c: New file.
	* sysdeps/x86_64/ifuncmod8.c: Likewise.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (RTLD_SAVESPACE_SSE):
	Removed.
	* sysdeps/x86_64/nptl/tls.h (__128bits): Removed.
	(tcbhead_t): Change rtld_must_xmm_save to __glibc_unused1.
	Change rtld_savespace_sse to __glibc_unused2.
	(RTLD_CHECK_FOREIGN_CALL): Removed.
	(RTLD_ENABLE_FOREIGN_CALL): Likewise.
	(RTLD_PREPARE_FOREIGN_CALL): Likewise.
	(RTLD_FINALIZE_FOREIGN_CALL): Likewise.
2015-08-25 04:34:13 -07:00
Joseph Myers
9bc6103d04 Include <kernel-features.h> explicitly where required.
This patch makes files using __ASSUME_* macros include
<kernel-features.h> explicitly, rather than relying on some other
header (such as tls.h, lowlevellock.h or pthreadP.h) to include it
implicitly.  (I omitted cases where I've already posted or am testing
the patch that stops the file from needing __ASSUME_* at all.)  This
accords with the general principle of making source files include the
headers for anything they use, and also helps make it safe to remove
<kernel-features.h> includes from any file that doesn't use
__ASSUME_* (some of those may be stray includes left behind after
increasing the minimum kernel version, others may never have been
needed or may have become obsolete after some other change).

Tested x86_64 that the disassembly of installed shared libraries is
unchanged by this patch.

	* nptl/pthread_cond_wait.c: Include <kernel-features.h>.
	* nptl/pthread_rwlock_timedrdlock.c: Likewise.
	* nptl/pthread_rwlock_timedwrlock.c: Likewise.
	* nptl/sysdeps/unix/sysv/linux/lowlevelrobustlock.c: Likewise.
	* nscd/nscd.c: Likewise.
	* sysdeps/i386/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/powerpc/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/sh/nptl/tcb-offsets.sym: Likewise.
	* sysdeps/x86_64/nptl/tcb-offsets.sym: Likewise.
2014-06-20 23:24:00 +00:00
Roland McGrath
14642b8511 Move x86_64 code out of nptl/ subdirectory. 2014-06-11 21:33:32 -07:00