There is a configure test for assembler support for -mtune=i686. This
option was added in binutils 2.18 so the test is obsolete; this patch
removes it.
Tested for x86 (testsuite, and that installed shared libraries are
unchanged by the patch).
* sysdeps/i386/configure.ac (libc_cv_as_i686): Remove configure
test.
* sysdeps/i386/configure: Regenerated.
* sysdeps/i386/i686/Makefile [$(config-asflags-i686) = yes]: Make
code unconditional.
There is a configure test for the assembler .previous directive, and,
as a fallback, for .popsection.
glibc now only supports ELF. For ELF, the GNU assembler has supported
.previous since version 2.2 (support added by
Mon Jul 19 15:21:20 1993 Ken Raeburn (raeburn@rtl.cygnus.com)
* config/obj-elf.c (obj_elf_previous): New function.
(previous_section, previous_subsection): New vars.
(obj_elf_section): Save current place in case DWARF code wants us
to pop back to it. Handle unquoted section name as well as quoted
section name. Don't crash on invalid strings.
(obj_pseudo_table): Handle new pseudos "previous", "2byte", and
"4byte".
). Thus this configure test is obsolete, and this patch removes it
(and with it the fallback .popsection test).
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).
* configure.ac (libc_cv_asm_previous_directive): Remove configure
test.
(libc_cv_asm_popsection_directive): Likewise.
* configure: Regenerated.
* config.h.in (HAVE_ASM_PREVIOUS_DIRECTIVE): Remove #undef.
(HAVE_ASM_POPSECTION_DIRECTIVE): Likewise.
* include/libc-symbols.h [HAVE_ASM_PREVIOUS_DIRECTIVE]
(__make_section_unallocated): Make definition unconditional.
[HAVE_ASM_POPSECTION_DIRECTIVE] (__make_section_unallocated):
Remove conditional definition.
[!HAVE_ASM_PREVIOUS_DIRECTIVE && !HAVE_ASM_POPSECTION_DIRECTIVE]
(__make_section_unallocated): Likewise.
There is a configure test for -static-libgcc. GCC added this option
in version 3.0, so this test is obsolete; this patch removes it.
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).
* configure.ac (libc_cv_gcc_static_libgcc): Remove configure test.
* configure: Regenerated.
* config.make.in (static-libgcc): Remove variable.
* Makerules (build-shlib-helper): Use -static-libgcc instead of
$(static-libgcc).
(build-module-helper): Likewise.
There is a configure test "for libc-friendly stddef.h", which sets a
makefile variable stddef.h that appears to be nowhere used. It
appears the uses of this variable were removed by:
Tue Feb 21 00:10:50 1995 Roland McGrath <roland@churchy.gnu.ai.mit.edu>
* Makefile (headers): Remove $(stddef.h).
* Makeconfig (stddef.h): Variable removed; now require gcc version
>= 2.2.
* stddef.h: File removed.
(having been added by
Wed May 26 14:44:19 1993 Roland McGrath (roland@churchy.gnu.ai.mit.edu)
* configure.in (autoconf checks): Add new check for a
libc-friendly stddef.h.
so the test was of use for less than two years, before being obsolete
for over 20 years). This patch removes the test.
Tested for x86_64 and x86 (testsuite, and that installed shared
libraries are unchanged by the patch).
* configure.ac (libc_cv_friendly_stddef): Remove configure test.
* configure: Regenerated.
A custom character buffer is added in this commit, in the form of
struct char_buffer. The char_buffer_add function replaces the
ADDW macro (which has grown with each successive security fix).
The char_buffer_add slow path is moved out-of-line, reducing
code size.
* stdio-common/vfscanf.c (MEMCPY): Remove macro.
(struct char_buffer): New type.
(char_buffer_start, char_buffer_size, char_buffer_error)
(char_buffer_rewind, char_buffer_add): New functions.
(ADDW): Remove macro, replaced by the char_buffer_add function.
(_IO_vfscanf_internal): Rewrite using struct char_buffer instead
of extend_alloca. Make control flow more explicit.
Only i386 implements epoll_pwait in assembly code withot cancellation
support. All other architectures implement epoll_pwait in epoll_pwait.c
with
int epoll_pwait (int epfd, struct epoll_event *events,
int maxevents, int timeout,
const sigset_t *set)
{
return SYSCALL_CANCEL (epoll_pwait, epfd, events, maxevents,
timeout, set, _NSIG / 8);
}
Although there is no test for epoll_pwait in glibc, since SYSCALL_CANCEL
works on i386 and epoll_pwait.c works for other architectures, it is
safe to assume that epoll_pwait.c with SYSCALL_CANCEL also works on
i386.
[BZ #19137]
* sysdeps/unix/sysv/linux/i386/Makefile (CFLAGS-epoll_pwait.c):
Add -fomit-frame-pointer.
* sysdeps/unix/sysv/linux/i386/epoll_pwait.S: Remove file.
Honoring the LD_POINTER_GUARD environment variable in AT_SECURE mode
has security implications. This commit enables pointer guard
unconditionally, and the environment variable is now ignored.
[BZ #18928]
* sysdeps/generic/ldsodefs.h (struct rtld_global_ro): Remove
_dl_pointer_guard member.
* elf/rtld.c (_rtld_global_ro): Remove _dl_pointer_guard
initializer.
(security_init): Always set up pointer guard.
(process_envvars): Do not process LD_POINTER_GUARD.
The powerpc32 implementation of lround and lroundf can produce
spurious exceptions from adding 0.5 then converting to integer. This
includes "inexact" from the conversion to integer (not allowed for
integer arguments to these functions), and, for larger integer
arguments, "inexact", and "overflow" when rounding upward, from the
addition. In addition, "inexact" is not allowed together with
"invalid" and so inexact addition must be avoided when the integer
will be out of range of 32-bit long, whether or not the argument is an
integer.
This patch fixes these problems. As in the powerpc64 llround
implementation, a check is added for too-large arguments; in the
powerpc64 case that means arguments at least 2^52 in magnitude (so
that 0.5 cannot be added exactly), while in this case it means
arguments for which the result would overflow "long". In those cases
a suitable overflowing value is used for the integer conversion
without adding 0.5, while for smaller arguments it's tested whether
the argument is an integer (by adding and subtracting 2^52 to the
absolute value and comparing with the original absolute value) to
avoid adding 0.5 to integers and generating spurious "inexact".
This code is not used when the power5+ sysdeps directories are used,
as there's a separate power5+ version of these functions..
Tested for powerpc. This gets test-float (for a default powerpc32
hard-float build without any --with-cpu) back to the point where it
should pass once powerpc ulps are regenerated; test-double still needs
another problem with exceptions fixed to get back to that point (and I
haven't looked lately at what default powerpc64 results are like).
[BZ #19134]
* sysdeps/powerpc/powerpc32/fpu/s_lround.S (.LC1): New object.
(.LC2): Likewise.
(.LC3): Likewise.
(__lround): Do not add 0.5 to integer or out-of-range arguments.
_dl_tlsdesc_resolve_hold calls into a C function that clobbers r0,
but it assumes the original argument is still in r0 after the call.
This can cause crash in case of concurrent TLS access when TLSDESC
is in use (-mtls-dialect=gnu2).
Run into this while fixing BZ 18572.
Both r0 and r1 are saved/restored so the stack remains 8 byte aligned.
[BZ #19129]
* sysdeps/arm/dl-tlsdesc.S (_dl_tlsdesc_resolve_hold): Save and restore
r0 and r1.
This patch adds an internal entry for __sched_getaffinity_new so that
__sched_getaffinity_old calls __sched_getaffinity_new without going
through PLT.
[BZ #18822]
* sysdeps/unix/sysv/linux/sched_getaffinity.c
(__sched_getaffinity_new): Add libc_hidden_proto and
libc_hidden_def.
Linker in binutils 2.26 and newer generate GOT references instead
PLT references when -z now is passed to linker. We need to extend
scripts/localplt.awk to allow PLT or GOT references.
[BZ #19007]
* scripts/localplt.awk: Also allow GOT references.
* sysdeps/unix/sysv/linux/i386/localplt.data: Mark
_Unwind_Find_FDE, calloc, memalign, realloc and __libc_memalign
with "+ REL R_386_GLOB_DAT".
* sysdeps/x86_64/localplt.data: Mark calloc, memalign, realloc
and __libc_memalign with "+ RELA R_X86_64_GLOB_DAT".
This patch uses INTERNAL_SYSCALL and INLINE_SYSCALL_ERROR_RETURN_VALUE
to avoid reading and writing errno directly so that we don't need to
call __x86.get_pc_thunk.reg to load PC into reg in case there is an
error.
* sysdeps/unix/sysv/linux/i386/brk.c (__brk): Use
INLINE_SYSCALL_ERROR_RETURN_VALUE.
* sysdeps/unix/sysv/linux/i386/fxstatat.c (__fxstatat):
Likewise.
* sysdeps/unix/sysv/linux/i386/setegid.c (setegid): Likewise.
* sysdeps/unix/sysv/linux/i386/seteuid.c (seteuid): Likewise.
* sysdeps/unix/sysv/linux/i386/fxstat.c (__fxstat): Use
INTERNAL_SYSCALLINTERNAL_SYSCALL and
INLINE_SYSCALL_ERROR_RETURN_VALUE.
* sysdeps/unix/sysv/linux/i386/lockf64.c (lockf64): Likewise.
* sysdeps/unix/sysv/linux/i386/lxstat.c (__lxstat): Likewise.
* sysdeps/unix/sysv/linux/i386/sigaction.c (__libc_sigaction):
Likewise.
* sysdeps/unix/sysv/linux/i386/xstat.c (__xstat): Likewise.
The powerpc32 implementations of llroundf and llround produce spurious
and missing exceptions (some arising from such exceptions from
conversions to long long, some present even when fctidz is used).
This patch fixes those problems in a similar way to the llrint /
llrintf fixes. The spurious exceptions in the fctidz case for large
arguments arise from a converted value that saturated as LLONG_MAX
being converted back to float or double (the conversion back being
inexact, but "inexact" must not be raised together with "invalid"),
and from the subtraction x - xrf also being inexact for sufficiently
large arguments (whether the saturation was to LLONG_MAX or
LLONG_MIN); those are fixed by returning early if the argument is
large enough that no rounding is needed.
This code is not used for --with-cpu=power4 builds (I suspect the code
used in that case may also produce spurious "inexact" exceptions, but
that's something to investigate later).
Tested for powerpc.
[BZ #19125]
* sysdeps/powerpc/powerpc32/fpu/s_llround.c: Include <limits.h>,
<math_private.h> and <stdint.h>.
(__llround): Avoid conversions to and from long long int, and
subtractions, where those might raise spurious exceptions.
* sysdeps/powerpc/powerpc32/fpu/s_llroundf.c: Include
<math_private.h> and <stdint.h>.
(__llroundf): Avoid conversions to and from long long int, and
subtractions, where those might raise spurious exceptions.
When x86-64 assmebler doesn't support AVX512, we should make
_dl_runtime_resolve_avx512/_dl_runtime_profile_avx512 as aliases of
_dl_runtime_resolve_avx/_dl_runtime_profile_avx. Tested on x86-64
using GCC 5.2 with binutils 20151008 and GCC 4.8 with binutils 20130219.
There are no differences in ld.so with binutils 20151008. There are no
unexpected failures with binutils 20130219 and 20151008.
[BZ #19124]
* sysdeps/x86_64/dl-trampoline.S [!HAVE_AVX512_ASM_SUPPORT]
(_dl_runtime_resolve_avx512): Make it a hidden alias of
_dl_runtime_resolve_avx.
(_dl_runtime_profile_avx512): Make it a hidden alias of
_dl_runtime_profile_avx.
sysdeps/powerpc/fpu/ has versions of llround and llroundf that are
actually used only for powerpc32 because
sysdeps/powerpc/powerpc64/fpu/ has its own versions of those
functions. This patch moves them into sysdeps/powerpc/powerpc32/fpu
to reflect where they are actually used (in preparation for fixing
other problems with those functions).
Tested for powerpc that installed stripped shared libraries are
unchanged by this patch.
* sysdeps/powerpc/fpu/s_llround.c: Move to ....
* sysdeps/powerpc/powerpc32/fpu/s_llround.c: ...here.
* sysdeps/powerpc/fpu/s_llroundf.c: Move to ....
* sysdeps/powerpc/powerpc32/fpu/s_llroundf.c: ...here.
The versions of llrint and llrintf for older powerpc32 processors
convert the results of __rint / __rintf to long long int, resulting in
spurious exceptions from such casts in certain cases. This patch
makes glibc work around the problems with the libgcc conversions when
the compiler used to build glibc doesn't use the fctidz instruction
for them.
Tested for powerpc.
[BZ #16422]
* sysdeps/powerpc/powerpc32/fpu/configure.ac (libc_cv_ppc_fctidz):
New configure test.
* sysdeps/powerpc/powerpc32/fpu/configure: Regenerated.
* config.h.in [_LIBC] (HAVE_PPC_FCTIDZ): New macro.
* sysdeps/powerpc/powerpc32/fpu/s_llrint.c: Include <limits.h>,
<math_private.h> and <stdint.h>.
(__llrint): Avoid conversions to long long int where those might
raise spurious exceptions.
* sysdeps/powerpc/powerpc32/fpu/s_llrintf.c: Include
<math_private.h> and <stdint.h>.
(__llrintf): Avoid conversions to long long int where those might
raise spurious exceptions.
* hurd/hurd-raise.c (_hurd_raise_signal): Set errno to error returned
by __msg_sig_post.
* hurd/hurd/signal.h (_hurd_raise_signal): Add int return type.
For reasons that are slightly unclear, the ChangeLog entry added in
67ac0f74a4 contained a mangled version
of my email address. Replace that with the correct one.
Similar to the recent fix for MIPS, ARM is also missing correct
exceptions on overflow from llrint and llround functions because casts
from floating-point types to long long do not result in correct
exceptions on overflow. This patch enables the fix for this for ARM.
Tested for ARM.
[BZ #15470]
* sysdeps/arm/fix-fp-int-convert-overflow.h: New file.
For 32-bit MIPS and some other systems, various of the lrint, llrint,
lround, llround functions can be missing exceptions on overflow
because casts do not (in current GCC) result in the proper
exceptions. In the MIPS case there are two problems here: MIPS I code
generation uses an assembler macro that doesn't raise exceptions,
while the libgcc conversions of floating-point values to long long
also do not raise "invalid" on all overflow cases (and can raise
spurious "inexact").
This patch adds support in the generic code (only the functions for
which this problem has actually been seen) for forcing the "invalid"
exception in the problem cases, and enables that support for the
affected MIPS cases.
Tested for MIPS; also tested for x86_64 and x86 that installed
stripped shared libraries are unchanged by this patch.
[BZ #16399]
* sysdeps/generic/fix-fp-int-convert-overflow.h: New file.
* sysdeps/ieee754/dbl-64/s_llrint.c: Include <fenv.h>, <limits.h>
and <fix-fp-int-convert-overflow.h>.
(__llrint) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/dbl-64/s_llround.c: Include <fenv.h>, <limits.h>
and <fix-fp-int-convert-overflow.h>.
(__llround) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/dbl-64/s_lrint.c: Include
<fix-fp-int-convert-overflow.h>.
(__lrint) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/dbl-64/s_lround.c: Include
<fix-fp-int-convert-overflow.h>.
(__lround) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/flt-32/s_llrintf.c: Include <fenv.h>, <limits.h>
and <fix-fp-int-convert-overflow.h>.
(__llrintf) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/flt-32/s_llroundf.c: Include <fenv.h>,
<limits.h> and <fix-fp-int-convert-overflow.h>.
(__llroundf) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/flt-32/s_lrintf.c: Include <fenv.h>, <limits.h>
and <fix-fp-int-convert-overflow.h>.
(__lrintf) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/ieee754/flt-32/s_lroundf.c: Include <fenv.h>, <limits.h>
and <fix-fp-int-convert-overflow.h>.
(__lroundf) [FE_INVALID]: Force FE_INVALID exception as needed if
FIX_DBL_LLONG_CONVERT_OVERFLOW.
* sysdeps/mips/mips32/fpu/fix-fp-int-convert-overflow.h: New file.
Fix the copyright year and remove contributed by in the
bug-strcoll2 test. In addition add the correct dependency
on $(gen-locales) to ensure all the test locales are generated.
This patch pthread cancellation tests to check for failures cases
wherer the syscall cancel wrapper should both set the error and
the errno values.
Tested on i686, x86_64, x32, powerpc64le, and aarch64.
* nptl/Makefile (tests): Add tst-cancel26.c and tst-cancel27.c.
* nptl/tst-cancel26.c: New file.
* nptl/tst-cancel27.c: Likewise.
The x86_64 versions of lrint/lrintf/ lrintl are aliases for the long
long versions which isn't correct for x32, where exceptions must respect
overflow for 32-bit long. Separate versions of the long functions for
x32 that convert to 32-bit long and raise the right exceptions for that
conversion, while keeping the aliases in the non-x32 case.
Tested on x86_64 and x32. There are no code changes in libm.so on
x86_64.
* sysdeps/x86_64/fpu/s_llrint.S (__lrint): Add alias only if
__ILP32__ isn't defined.
(lrint): Likewise.
* sysdeps/x86_64/fpu/s_llrintf.S (__lrintf): Likewise.
(lrintf): Likewise.
* sysdeps/x86_64/fpu/s_llrintl.S (__lrintl): Likewise.
(lrintl): Likewise.
* sysdeps/x86_64/x32/fpu/s_lrint.S: New file.
* sysdeps/x86_64/x32/fpu/s_lrintf.S: Likewise.
* sysdeps/x86_64/x32/fpu/s_lrintl.S: Likewise.
This patch sets lseek/llseek for 64-bit, MIPS n32, and x86_32 as non-
cancelable. This make it consistant with 32-bit platform.
Tested on i686, x86_64, and x32.
* sysdeps/unix/sysv/linux/mips/mips64/syscalls.list (lseek): Set as
non-cancelable.
* sysdeps/unix/sysv/linux/wordsize-64/syscalls.list (llseek): Likewise.
* sysdeps/unix/sysv/linux/x86_64/x32/lseek.S (__libc_lseek64):
Likewise.
GCC added support for -mno-vzeroupper in version 4.6. Thus the
configure tests for this support are obsolete, and this patch removes
them.
Tested for x86_64 and x86 (testsuite, and that installed stripped
shared libraries are unchanged by this patch).
* sysdeps/i386/configure.ac (libc_cv_cc_novzeroupper): Remove
configure test.
* sysdeps/i386/configure: Regenerated.
* sysdeps/x86_64/configure.ac (libc_cv_cc_novzeroupper): Remove
configure test.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/Makefile [$(config-cflags-novzeroupper) = yes]:
Make code unconditional.
The dbl-64 implementation of lrint produces incorrect results for some
arguments with 64-bit long because a 32-bit (unsigned) low part of the
mantissa is shifted left, losing high bits in the process. This patch
fixes this by casting to long int before shifting, as in lround (as
this case only applies for 64-bit long, there are no issues with
sign-extension).
Tested for mips64 (n64).
[BZ #19095]
* sysdeps/ieee754/dbl-64/s_lrint.c (__lrint): Cast low part of
mantissa to long int before shifting left.
The dbl-64, ldbl-96 and ldbl-128 implementations of lrint and llrint
fail to produce "invalid" exceptions in cases where the rounded result
overflows the target type, but truncating the floating-point argument
to the next integer towards zero does not overflow it (so in
particular casts do not produce such exceptions). (This issue cannot
arise for float, or for double with 64-bit target type, or for ldbl-96
with 64-bit target type and negative arguments, because of
insufficient precision in the floating-point type for arguments with
the relevant property to exist. It also obviously cannot arise in
FE_TOWARDZERO mode.)
This patch fixes these problems by inserting checks for the special
cases that can occur in each implementation, and explicitly raising
FE_INVALID (and avoiding the cast if it might raise spurious
FE_INEXACT, while raising FE_INEXACT explicitly in the cases where it
is needed; unlike lround and llround, FE_INEXACT is required, not
optional, for these functions for a within-range inexact result).
The fixes are conditional on FE_INVALID or FE_INEXACT being defined.
If any future architecture supports one but not both of those
exceptions, the code will fail to compile and need fixing to handle
that case (this seemed better than conditioning on both macros being
defined, resulting in code that would compile but quietly miss
exceptions on such a system).
Tested for x86_64, x86 and mips64. Tested the ldbl-96 changes (only
relevant for ia64, it appears) on x86_64 by removing the x86_64
versions of lrintl / llrintl.
[BZ #19094]
* sysdeps/ieee754/dbl-64/s_lrint.c: Include <fenv.h> and
<limits.h>.
(__lrint) [FE_INVALID || FE_INEXACT]: Force FE_INVALID exception
when result overflows but exception would not result from cast.
* sysdeps/ieee754/ldbl-128/s_llrintl.c: Include <fenv.h> and
<limits.h>.
(__llrintl) [FE_INVALID || FE_INEXACT]: Force FE_INVALID exception
when result overflows but exception would not result from cast.
* sysdeps/ieee754/ldbl-128/s_lrintl.c: Include <fenv.h> and
<limits.h>.
(__lrintl) [FE_INVALID || FE_INEXACT]: Force FE_INVALID exception
when result overflows but exception would not result from cast.
* sysdeps/ieee754/ldbl-96/s_llrintl.c: Include <fenv.h> and
<limits.h>.
(__llrintl) [FE_INVALID || FE_INEXACT]: Force FE_INVALID exception
when result overflows but exception would not result from cast.
* sysdeps/ieee754/ldbl-96/s_lrintl.c: Include <fenv.h> and
<limits.h>.
(__lrintl) [FE_INVALID || FE_INEXACT]: Force FE_INVALID exception
when result overflows but exception would not result from cast.
* math/libm-test.inc (lrint_test_data): Add more tests.
(llrint_test_data): Likewise.
The optimization introduced in commit
f13c2a8dff, causes regressions in
sorting for languages that have digraphs that change sort order, like
cs_CZ which sorts ch between h and i.
My analysis shows the fast-forwarding optimization in STRCOLL advances
through a digraph while possibly stopping in the middle which results
in a subsequent skipping of the digraph and incorrect sorting. The
optimization is incorrect as implemented and because of that I'm
removing it for 2.23, and I will also commit this fix for 2.22 where
it was originally introduced.
This patch reverts the optimization, introduces a new bug-strcoll2.c
regression test that tests both cs_CZ.UTF-8 and da_DK.ISO-8859-1 and
ensures they sort one digraph each correctly. The optimization can't be
applied without regressing this test.
Checked on x86_64, bug-strcoll2.c fails without this patch and passes
after. This will also get a fix on 2.22 which has the same bug.
I noticed that some of my recently added tests of lround and llround
wrongly expected the "inexact" exception to be absent for certain
within-range non-integer arguments. (It's unspecified whether this
exception is present or not for within-range non-integer arguments; it
mustn't be present for integer arguments and out-of-range arguments.)
This patch corrects those expectations.
Tested for x86_64 and x86.
* math/libm-test.inc (lround_test_data): Do not expect the absence
of "inexact" for some tests with non-integer arguments.
(llround_test_data): Likewise.
In the per-thread arenas we apply trim_threshold-based checks
to the extra space between the pad and the top_area. This isn't
quite accurate and instead we should be harmonizing with the way
in which trim_treshold is applied everywhere else like sysrtim
and _int_free. The trimming check should be based on the size of
the top chunk and only the size of the top chunk. The following
patch harmonizes the trimming and make it consistent for the main
arena and thread arenas.
In the old code a large padding request might have meant that
trimming was not triggered. Now trimming is considered first based
on the chunk, then the pad is subtracted, and the remainder trimmed.
This is how all the other trimmings operate. I didn't measure the
performance difference of this change because it corrects what I
consider to be a behavioural anomaly. We'll need some profile driven
optimization to make this code better, and even there Ondrej and
others have better ideas on how to speedup malloc.
Tested on x86_64 with no regressions. Already reviewed by Siddhesh
Poyarekar and Mel Gorman here and discussed here:
https://sourceware.org/ml/libc-alpha/2015-05/msg00002.html
