Mike Frysinger [Fri, 7 Aug 2015 05:43:08 +0000 (01:43 -0400)]
hppa: _dl_symbol_address: add missing hidden def
Commit 2a6ad8142d14c998e6c5eb51418aac1f598b621e updated the headers and
the common dl-symaddr.c, but missed that hppa has its own dedicated source
file for this func. Update that too to fix build errors due to missing
exports of the symbol.
Samuel Thibault [Thu, 6 Aug 2015 23:38:39 +0000 (01:38 +0200)]
Fix gcrt0.o compilation
When static-start-installed-name is different from
start-installed-name, we must not use the shared objects.
* csu/Makefile
(extra-objs): Add gmon-start.o when building shared library and
$(static-start-installed-name) is different from
$(start-installed-name).
$(objpfx)g$(static-start-installed-name): When building shared
library and $(static-start-installed-name) is different from
$(static-start-installed-name), revert to non-shared rule,
i.e. using $(objpfx)% and gmon-start.o.
Joseph Myers [Thu, 6 Aug 2015 23:01:09 +0000 (23:01 +0000)]
Fix sinh missing underflows (bug 16519).
Similar to various other bugs in this area, some sinh implementations
do not raise the underflow exception for subnormal arguments, when the
result is tiny and inexact. This patch forces the exception in a
similar way to previous fixes.
Tested for x86_64, x86, mips64 and powerpc.
[BZ #16519]
* sysdeps/ieee754/dbl-64/e_sinh.c: Include <float.h>.
(__ieee754_sinh): Force underflow exception for arguments with
small absolute value.
* sysdeps/ieee754/flt-32/e_sinhf.c: Include <float.h>.
(__ieee754_sinhf): Force underflow exception for arguments with
small absolute value.
* sysdeps/ieee754/ldbl-128/e_sinhl.c: Include <float.h>.
(__ieee754_sinhl): Force underflow exception for arguments with
small absolute value.
* sysdeps/ieee754/ldbl-128ibm/e_sinhl.c: Include <float.h>.
(__ieee754_sinhl): Force underflow exception for arguments with
small absolute value.
* sysdeps/ieee754/ldbl-96/e_sinhl.c: Include <float.h>.
(__ieee754_sinhl): Force underflow exception for arguments with
small absolute value.
* math/auto-libm-test-in: Add more tests of sinh.
* math/auto-libm-test-out: Regenerated.
* sysdeps/i386/fpu/libm-test-ulps: Update.
Mike Frysinger [Thu, 6 Aug 2015 06:44:44 +0000 (02:44 -0400)]
fix missing ctype.h include
This file uses isspace but doesn't include ctype.h leading to:
isomac.c: In function 'get_null_defines':
isomac.c:305:30: warning: implicit declaration of function 'isspace' [-Wimplicit-function-declaration]
for (end = start + 1; !isspace (*end) && *end != '\0'; ++end)
Arjun Shankar [Mon, 3 Aug 2015 16:14:21 +0000 (16:14 +0000)]
Modify several tests to use test-skeleton.c
These tests were skipped by the use-test-skeleton conversion done in
commit 29955b5d because they did not have an `int main (void)'
declaration. Instead their `main' functions were declared with arguments
(i.e. argc, argv) even though they didn't use them.
Remove these arguments and include the test skeleton in these tests.
Zack Weinberg [Thu, 6 Aug 2015 02:35:28 +0000 (22:35 -0400)]
Correct comments about the history of <regexp.h>
In the "Kill regexp.h" thread, Joseph dug up more accurate information
about exactly which editions of the Single Unix Standard included and
deprecated this header.
H.J. Lu [Sun, 12 Jul 2015 21:38:58 +0000 (14:38 -0700)]
Align stack to 16 bytes when calling __setcontext
Don't use pop to restore %rdi so that stack is aligned to 16 bytes
when calling __setcontext.
[BZ #18661]
* sysdeps/unix/sysv/linux/x86_64/__start_context.S
(__start_context): Don't use pop to restore %rdi so that stack
is aligned to 16 bytes when calling __setcontext.
Wilco Dijkstra [Wed, 5 Aug 2015 14:24:06 +0000 (15:24 +0100)]
Improve memccpy performance by using memchr/memcpy/mempcpy rather than
a byte loop. Overall performance on bench-memccpy is > 2x faster when
using the C implementation of memchr and an optimized memcpy.
Wilco Dijkstra [Wed, 5 Aug 2015 14:15:28 +0000 (15:15 +0100)]
This patch improves strncpy performance by using strnlen/memcpy rather than a byte loop. Performance
on bench-strncpy is 1.9-2.1x faster on average. I tried several variations, and using a tailcall and
calling memset conditionally gave the best overall results.
Wilco Dijkstra [Wed, 5 Aug 2015 13:57:37 +0000 (14:57 +0100)]
Improve fesetenv performance by avoiding unnecessary FPSR/FPCR reads/writes.
It uses the same logic as the ARM version. The common case removes 1 FPSR
and 1 FPCR read. For FE_DFL_ENV and FE_NOMASK_ENV a FPCR read is avoided in
case the FPCR does not change.
for (cnt = 0; cnt < __LC_LAST; ++cnt)
if (cnt != LC_ALL)
{
lia->data[cnt] = _nl_intern_locale_data (cnt,
results[cnt].addr,
results[cnt].len);
if (__glibc_likely (lia->data[cnt] != NULL))
{
...
}
}
lia->data[cnt] can be NULL, which happens to en_US.UTF-8 with
LC_COLLATE. But this won't happen if glibc is configured with
--enable-hardcoded-path-in-tests. We should also check
dead->data[category] != NULL.
* locale/loadarchive.c (_nl_archive_subfreeres): Also check
dead->data[category] != NULL.
Joseph Myers [Wed, 5 Aug 2015 15:01:58 +0000 (15:01 +0000)]
Fix powf (close to -1, large) (bug 18647).
The flt-32 implementation of powf wrongly uses x-1 instead of |x|-1
when computing log (x) for the case where |x| is close to 1 and y is
large. This patch fixes the logic accordingly. Relevant tests
existed for x close to 1, and corresponding tests are added for x
close to -1, as well as for some new variant cases.
Tested for x86_64 and x86.
[BZ #18647]
* sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): For large y
and |x| close to 1, use absolute value of x when computing log.
* math/auto-libm-test-in: Add more tests of pow.
* math/auto-libm-test-out: Regenerated.
it looks like the best options is to remove locale timezone information
from locales which currently provide it (in incomplete or incorrect
fashion) rather than to start duplicating tzdata info in glibc.
Mike Frysinger [Tue, 4 Aug 2015 11:26:46 +0000 (07:26 -0400)]
test-skeleton: add usage information
I keep trying to run tests with --help and then remembering that does
nothing when it throws an error. That means I have to dig into the
source when I want to refer to flags or env vars and re-read a good
amount of code to find the nested locations.
Make this all much more user friendly with a usage screen that gets
printed out whenever an unknown option is specified.
On arches that set _STACK_GROWS_UP, the stacktop variable is declared
and set, but never actually used. Refactor the code a bit so that the
variable is only declared/set under _STACK_GROWS_DOWN settings.
Zack Weinberg [Sat, 1 Aug 2015 18:38:05 +0000 (14:38 -0400)]
Deprecate the use of regexp.h
<regexp.h> (not to be confused with <regex.h>) is an obsolete and
frankly horrible regular expression-matching API. It was part of SVID
but was withdrawn in Issue 5 (for reference, we're on Issue 7 now).
It doesn't do anything you can't do with <regex.h>, and using it
involves defining a bunch of macros before including the header.
Moreover, the code in regexp.h that uses those macros has been buggy
since its creation (in 1996) and no one has noticed, which indicates
to me that there are no users. (Specifically, RETURN() is used in a
whole bunch of cases where it should have been ERROR().)
The header is given a warning and marked deprecated for 2.22.
See:
https://sourceware.org/ml/libc-alpha/2015-07/msg00862.html and
https://sourceware.org/ml/libc-alpha/2015-07/msg00871.html.
Mike Frysinger [Thu, 30 Jul 2015 02:55:43 +0000 (22:55 -0400)]
hppa: fix sysdep.h header setup
The semi-recent SYSCALL_CANCEL inclusion broke hppa due to the sysdep.h
headers not including the unix/sysdep.h headers. Rework the includes so
we match the other ports:
* hppa/sysdep.h:
- Do not include sys/syscall.h as the unix sysdep.h headers do it.
- Do not include config.h as libc-symbols.h does it, and it has no
#ifdef multiple-include protection, and it breaks when some files
do things like #undef __OPTIMIZE__.
* sysdeps/unix/sysv/linux/hppa/sysdep-cancel.h:
- Drop the generic/sysdep.h as the unix sysdep.h headers include it.
* sysdeps/unix/sysv/linux/hppa/sysdep.h:
- Change to the unix & core hppa sysdep header stacks.
- Undef a few defines that the core headers already set up for us.
Mike Frysinger [Thu, 30 Jul 2015 03:01:01 +0000 (23:01 -0400)]
hppa: rewrite INLINE_SYSCALL
The semi-recent SYSCALL_CANCEL macro imposes a slight nuance on the
implementation of INLINE_SYSCALL: the nr argument cannot be expanded
directly but must be passed on to another macro which may expand it.
Most arches don't notice because INLINE_SYSCALL is defined in terms
of INTERNAL_SYSCALL which has the additional layer of expansion, but
on hppa, it was attempting to expand it directly. That causes build
errors like so:
../sysdeps/unix/sysv/linux/sigsuspend.c: In function '__sigsuspend':
../sysdeps/unix/sysv/linux/sigsuspend.c:31:62: error:
implicit declaration of function 'LOAD_ARGS___SYSCALL_NARGS'
../sysdeps/unix/sysv/linux/sigsuspend.c:31:304: error:
called object 'LOAD_ARGS___SYSCALL_NARGS(set, 8)' is not a function
So rewrite hppa's INLINE_SYSCALL to use INTERNAL_SYSCALL like other
arches do. This is also a nice clean up as the two macros had quite
a bit of duplicated logic.
H.J. Lu [Wed, 29 Jul 2015 18:57:54 +0000 (11:57 -0700)]
Extend local PLT reference check
On x86, linker in binutils 2.26 and newer consolidates R_*_JUMP_SLOT with
R_*_GLOB_DAT relocation against the same symbol. This patch extends
local PLT reference check to support alternate relocations.
[BZ #18078]
* scripts/check-localplt.awk: Support alternate relocations.
* scripts/localplt.awk: Also check relocations in DT_RELA/DT_REL
sections.
* sysdeps/unix/sysv/linux/i386/localplt.data: Mark free and
malloc entries with + REL R_386_GLOB_DAT.
* sysdeps/x86_64/localplt.data: New file.
Way back in 2005 the atomic_exchange_and_add function was cleaned up to
avoid the explicit size checking and instead let gcc handle things itself.
Unfortunately that change ended up leaving beyond a cast to int, even when
the incoming value was a long. This has flown under the radar for a long
time due to the function not being heavily used in the tree (especially as
a full 64bit field), but a recent change to semaphores made some nptl tests
fail reliably. This is due to the code packing two 32bit values into one
64bit variable (where the high 32bits contained the number of waiters), and
then the whole variable being atomically updated between threads. On ia64,
that meant we never atomically updated the count, so sometimes the sem_post
would not wake up the waiters.
Mike Frysinger [Tue, 28 Jul 2015 04:15:18 +0000 (00:15 -0400)]
ia64: clean up old kernel headers cruft
This define made more sense in the pre-sanitized kernel headers days,
but since we require kernel versions that are sanitized, we don't need
this hack anymore.
Mike Frysinger [Tue, 28 Jul 2015 03:43:09 +0000 (23:43 -0400)]
pwd.h: revert __nonnull markings on putpwent [BZ #18641]
This function actually checks for NULL arguments and the API has been
tenatively documented as using EINVAL in that case. We can debate
leaving it this way, but it should be done after the pending release.
Joseph Myers [Mon, 27 Jul 2015 23:59:08 +0000 (23:59 +0000)]
Mark bug 2981 (elf/tst-audit* fail on MIPS) as fixed.
Changes in support of -fno-plt also cause the elf/tst-audit* tests to
start passing on MIPS. This patch duly marks the relevant bug as
fixed in ChangeLog and NEWS.
Use IE model for static variables in libc.so, libpthread.so and rtld
The recently introduced TLS variables in the thread-local destructor
implementation (__cxa_thread_atexit_impl) used the default GD access
model, resulting in a call to __tls_get_addr. This causes a deadlock
with recent changes to the way TLS is initialized because DTV
allocations are delayed and hence despite knowing the offset to the
variable inside its TLS block, the thread has to take the global rtld
lock to safely update the TLS offset.
This causes deadlocks when a thread is instantiated and joined inside
a destructor of a dlopen'd DSO. The correct long term fix is to
somehow not take the lock, but that will need a lot deeper change set
to alter the way in which the big rtld lock is used.
Instead, this patch just eliminates the call to __tls_get_addr for the
thread-local variables inside libc.so, libpthread.so and rtld by
building all of their units with -mtls-model=initial-exec.
There were concerns that the static storage for TLS is limited and
hence we should not be using it. Additionally, dynamically loaded
modules may result in libc.so looking for this static storage pretty
late in static binaries. Both concerns are valid when using TLSDESC
since that is where one may attempt to allocate a TLS block from
static storage for even those variables that are not IE. They're not
very strong arguments for the traditional TLS model though, since it
assumes that the static storage would be used sparingly and definitely
not by default. Hence, for now this would only theoretically affect
ARM architectures.
The impact is hence limited to statically linked binaries that dlopen
modules that in turn load libc.so, all that on arm hardware. It seems
like a small enough impact to justify fixing the larger problem that
currently affects everything everywhere.
This still does not solve the original problem completely. That is,
it is still possible to deadlock on the big rtld lock with a small
tweak to the test case attached to this patch. That problem is
however not a regression in 2.22 and hence could be tackled as a
separate project. The test case is picked up as is from Alex's patch.
This change has been tested to verify that it does not cause any
issues on x86_64.
ChangeLog:
[BZ #18457]
* nptl/Makefile (tests): New test case tst-join7.
(modules-names): New test case module tst-join7mod.
* nptl/tst-join7.c: New file.
* nptl/tst-join7mod.c: New file.
* Makeconfig (tls-model): Pass -ftls-model=initial-exec for
all translation units in libc.so, libpthread.so and rtld.
Szabolcs Nagy [Fri, 24 Jul 2015 09:05:07 +0000 (10:05 +0100)]
[ARM][BZ #17711] Fix extern protected data handling
Fixes elf/tst-protected1a and elf/tst-protected1b tests.
Depends on a gcc patch that makes protected visibility data non-local:
https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01871.html
and on a binutils patch so R_*_GLOB_DAT relocs are used for it:
https://sourceware.org/ml/binutils/2015-07/msg00247.html
Szabolcs Nagy [Fri, 24 Jul 2015 08:57:32 +0000 (09:57 +0100)]
[AArch64][BZ #17711] Fix extern protected data handling
Fixes elf/tst-protected1a and elf/tst-protected1b tests.
Depends on a gcc patch that makes protected visibility data non-local:
https://gcc.gnu.org/ml/gcc-patches/2015-07/msg01871.html
and on a binutils patch so R_*_GLOB_DAT relocs are used for it:
https://sourceware.org/ml/binutils/2015-07/msg00246.html
glibc supports the deprecated matherr hook for math error reporting. The
conform tests take this into consideration and whitelist this symbol when
running linknamespace tests.
The ia64 libm code has long provided two additional hooks in this space:
matherrf (for floats)
matherrl (for long doubles)
Which causes the conform tests to fail with chains that all look like:
[initial] __atan2 ->
[libm.a(e_atan2.o)] __libm_error_support ->
[libm.a(libm_error.o)] matherrf
We can't (losslessly) redirect existing usage of these funcs to matherr
because the structure passed in is different -- matherr uses a struct with
doubles while matherrf/matherrl use floats and long doubles respectively.
Plus, this has been part of the exported ABI since glibc-2.2.3, so it
doesn't feel right to change it so late.
Until we get around to obsoleting matherr entirely, whitelist these two
additional ia64 symbols.
Also use l_tls_dtor_count to decide on object unload (BZ #18657)
When an TLS destructor is registered, we set the DF_1_NODELETE flag to
signal that the object should not be destroyed. We then clear the
DF_1_NODELETE flag when all destructors are called, which is wrong -
the flag could have been set by other means too.
This patch replaces this use of the flag by using l_tls_dtor_count
directly to determine whether it is safe to unload the object. This
change has the added advantage of eliminating the lock taking when
calling the destructors, which could result in a deadlock. The patch
also fixes the test case tst-tls-atexit - it was making an invalid
dlclose call, which would just return an error silently.
I have also added a detailed note on concurrency which also aims to
justify why I chose the semantics I chose for accesses to
l_tls_dtor_count. Thanks to Torvald for his help in getting me
started on this and (literally) teaching my how to approach the
problem.
Change verified on x86_64; the test suite does not show any
regressions due to the patch.
ChangeLog:
[BZ #18657]
* elf/dl-close.c (_dl_close_worker): Don't unload DSO if there
are pending TLS destructor calls.
* include/link.h (struct link_map): Add concurrency note for
L_TLS_DTOR_COUNT.
* stdlib/cxa_thread_atexit_impl.c (__cxa_thread_atexit_impl):
Don't touch the link map flag. Atomically increment
l_tls_dtor_count.
(__call_tls_dtors): Atomically decrement l_tls_dtor_count.
Avoid taking the load lock and don't touch the link map flag.
* stdlib/tst-tls-atexit-nodelete.c: New test case.
* stdlib/Makefile (tests): Use it.
* stdlib/tst-tls-atexit.c (do_test): dlopen
tst-tls-atexit-lib.so again before dlclose. Add conditionals
to allow tst-tls-atexit-nodelete test case to use it.
It turns out tile suffered from the same problem as S390. However,
disabling CFI information for the __startcontext on tile was not
sufficient to fix the problem; I think the backtracer will just
blindly try to follow the link register (lr) in that case.
Instead, the change adds a cfi_undefined directive for "lr"
and then arranges to call __startcontext directly when the new
context starts, rather than just synthesizing a return to it.
In addition to being a bit easier now to understand the control
flow, this also allows the cfi_undefined directive to be placed in
a way that causes it to be in force at the address that the "lr"
from the called function points to.
Marko Myllynen [Wed, 13 May 2015 08:41:43 +0000 (11:41 +0300)]
locale: Remove obsolete repertoire map references
repertoire maps and character mnemonics were used early in the glibc
i18n/l10n effort but were quickly deprecated in favor of Unicode code
points. According to ChangeLog, the in-tree repertoire maps were
removed 2000-07-07 but some stray references remain even today. The
patch below removes them.
Mike Frysinger [Mon, 20 Jul 2015 11:29:15 +0000 (07:29 -0400)]
sparc: fix sigaction for 32bit builds [BZ #18694]
Commit a059d359d86130b5fa74e04a978c8523a0293f77 changed the sigaction
struct to pass conform tests, but it ended up also changing the ABI for
32 bit builds. For 64 bit builds, changing the long to two ints works,
but for 32 bit builds, it inserts 4 extra bytes. This leads to many
packages randomly failing like bash that spews things like:
configure: line 471: wait_for: No record of process 0
Bracket the new member by a wordsize check to fix the ABI for 32bit.
The tst-tls-atexit test case searches for its module in /proc/PID/maps
to verify that it is unloaded, which is a Linux-specific test. This
patch makes the test generic by looking for the library in the link
map list in the _r_debug structure.
Verified that the test continues to succeed on x86_64. There is a bug
in the test case where it calls dlclose once again, which is actually
incorrect but still manages to unload the DSO thanks to an existing
bug in __tls_call_dtors. This will be fixed in a later patch which
also fixes up the __cxa_thread_atexit_impl implementation. I have
added a FIXME comment to that call momentarily, which I will remove
when I fix the problem.
* stdlib/tst-tls-atexit-lib.c (do_foo): Rename to reg_dtor.
* stdlib/tst-tls-atexit.c: (is_loaded): New function.
(spawn_thread): New function.
(load): Rename to reg_dtor_and_close. Move dlopen to...
(do_test): ... here. Use IS_LOADED to test for its
availability.
mpx: Extend siginfo structure to include bound violation information
This patch adds new fields about bound violation into siginfo
structure. si_lower and si_upper are respectively lower bound
and upper bound when bound violation is caused.
This patch updates x86 struct siginfo to enable GDB with MPX support.
If 'w' mode is used with a provided buffer the fmemopen will try to find
the first null byte to set as maximum internal stream size. It should be
done only for append mode ('a').
Kudos for Stefan Liebler for finding this error on s390-32.
* libio/fmemopen.c (__fmemopen): Fix 'w' openmode with provided
buffer.
* stdio-common/tst-fmemopen2.c (do_test_with_buffer): Fix typo and
fail output information.
This patch optimizes strstr function for power >= 7 systems. Performance
gain is obtained using aligned memory access and usage of cmpb
instruction for quicker comparison. The average improvement of this
optimization is ~40%. Tested on ppc64 and ppc64le.
Mike Frysinger [Wed, 15 Jul 2015 11:40:56 +0000 (07:40 -0400)]
hppa/ia64: _dl_unmap: make it hidden
This symbol is only used by DL_UNMAP which in turn is only used by
_dl_close_worker in dl-close.c, and _dl_close_worker itself is marked
hidden as it is only used by the ldso. That means _dl_unmap should
be marked hidden. Without this, the elf/check-localplt test fails.
Mike Frysinger [Wed, 15 Jul 2015 11:37:47 +0000 (07:37 -0400)]
hppa/ia64: _dl_symbol_address: add PLT bypass for rtld
This symbol is defined in the ldso, and is used both there and libc.so.
There is no hidden symbol for it though which leads to relocations in
the ldso and the elf/check-localplt test failing. Add a hidden def for
rtld to fix all of that.
This function/file is only used by hppa & ia64, so no testing is needed
for other arches.
Set NODELETE flag when opening already open objects with RTLD_NODELETE
The DF_1_NODELETE flag is set too late when opening a DSO, due to
which, if a DSO is already open, subsequently opening it with
RTLD_NODELETE fails to set the DF_1_NODELETE flag. This patch fixes
this by setting the flag immediately after bumping the opencount.
Verified on x86_64.
[BZ #18676]
* elf/tst-nodelete-opened.c: New test case.
* elf/tst-nodelete-opened-lib.c: New test case module.
* elf/Makefile (tests, modules-names): Use them.
* elf/dl-open.c (dl_open_worker): Set DF_1_NODELETE flag
early.
These tests were skipped by the use-test-skeleton conversion done in
commit 29955b5d because they were reused in other tests via the #include
directive, and so deemed worth an inspection before they were modified.
This has now been done.
ChangeLog:
2015-07-09 Arjun Shankar <arjun.is@lostca.se>
* elf/tst-leaks1.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* localedata/tst-langinfo.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* math/test-fpucw.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* math/test-tgmath.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* math/test-tgmath2.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* setjmp/tst-setjmp.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* stdio-common/tst-sscanf.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
* sysdeps/x86_64/tst-audit6.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
This test was skipped by the use-test-skeleton conversion script
[29955b5d] because the definition of `main' did not begin according to
the GNU formatting style that the script assumed.
ChangeLog:
2015-07-09 Arjun Shankar <arjun.is@lostca.se>
* elf/tst-audit9.c (main): Converted to ...
(do_test): ... this.
(TEST_FUNCTION): New macro.
Include test-skeleton.c.
Stefan Liebler [Wed, 15 Jul 2015 07:33:15 +0000 (09:33 +0200)]
i686: Mark stdlib/tst-makecontext as XFAIL.
The testcase stdlib/tst-makecontext fails on i686 because
_Unwind_Backtrace from libgcc produces a segmentation fault if it was
called within a context created by makecontext. See Bug 18635.
ChangeLog:
* sysdeps/i386/i686/Makefile (test-xfail-tst-makecontext):
New variable.