On Skylake server, _dl_runtime_resolve_avx512_opt is used to preserve
the first 8 vector registers. The code layout is
if only %xmm0 - %xmm7 registers are used
preserve %xmm0 - %xmm7 registers
if only %ymm0 - %ymm7 registers are used
preserve %ymm0 - %ymm7 registers
preserve %zmm0 - %zmm7 registers
Branch predication always executes the fallthrough code path to preserve
%zmm0 - %zmm7 registers speculatively, even though only %xmm0 - %xmm7
registers are used. This leads to lower CPU frequency on Skylake
server. This patch changes the fallthrough code path to preserve
%xmm0 - %xmm7 registers instead:
if whole %zmm0 - %zmm7 registers are used
preserve %zmm0 - %zmm7 registers
if only %ymm0 - %ymm7 registers are used
preserve %ymm0 - %ymm7 registers
preserve %xmm0 - %xmm7 registers
Tested on Skylake server.
[BZ #21258]
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_resolve_opt):
Define only if _dl_runtime_resolve is defined to
_dl_runtime_resolve_sse_vex.
* sysdeps/x86_64/dl-trampoline.h (_dl_runtime_resolve_opt):
Fallthrough to _dl_runtime_resolve_sse_vex.
There is transition penalty when SSE instructions are mixed with 256-bit
AVX or 512-bit AVX512 load instructions. Since _dl_runtime_resolve_avx
and _dl_runtime_profile_avx512 save/restore 256-bit YMM/512-bit ZMM
registers, there is transition penalty when SSE instructions are used
with lazy binding on AVX and AVX512 processors.
To avoid SSE transition penalty, if only the lower 128 bits of the first
8 vector registers are non-zero, we can preserve %xmm0 - %xmm7 registers
with the zero upper bits.
For AVX and AVX512 processors which support XGETBV with ECX == 1, we can
use XGETBV with ECX == 1 to check if the upper 128 bits of YMM registers
or the upper 256 bits of ZMM registers are zero. We can restore only the
non-zero portion of vector registers with AVX/AVX512 load instructions
which will zero-extend upper bits of vector registers.
This patch adds _dl_runtime_resolve_sse_vex which saves and restores
XMM registers with 128-bit AVX store/load instructions. It is used to
preserve YMM/ZMM registers when only the lower 128 bits are non-zero.
_dl_runtime_resolve_avx_opt and _dl_runtime_resolve_avx512_opt are added
and used on AVX/AVX512 processors supporting XGETBV with ECX == 1 so
that we store and load only the non-zero portion of vector registers.
This avoids SSE transition penalty caused by _dl_runtime_resolve_avx and
_dl_runtime_profile_avx512 when only the lower 128 bits of vector
registers are used.
_dl_runtime_resolve_avx_slow is added and used for AVX processors which
don't support XGETBV with ECX == 1. Since there is no SSE transition
penalty on AVX512 processors which don't support XGETBV with ECX == 1,
_dl_runtime_resolve_avx512_slow isn't provided.
[BZ #20495]
[BZ #20508]
* sysdeps/x86/cpu-features.c (init_cpu_features): For Intel
processors, set Use_dl_runtime_resolve_slow and set
Use_dl_runtime_resolve_opt if XGETBV suports ECX == 1.
* sysdeps/x86/cpu-features.h (bit_arch_Use_dl_runtime_resolve_opt):
New.
(bit_arch_Use_dl_runtime_resolve_slow): Likewise.
(index_arch_Use_dl_runtime_resolve_opt): Likewise.
(index_arch_Use_dl_runtime_resolve_slow): Likewise.
* sysdeps/x86_64/dl-machine.h (elf_machine_runtime_setup): Use
_dl_runtime_resolve_avx512_opt and _dl_runtime_resolve_avx_opt
if Use_dl_runtime_resolve_opt is set. Use
_dl_runtime_resolve_slow if Use_dl_runtime_resolve_slow is set.
* sysdeps/x86_64/dl-trampoline.S: Include <cpu-features.h>.
(_dl_runtime_resolve_opt): New. Defined for AVX and AVX512.
(_dl_runtime_resolve): Add one for _dl_runtime_resolve_sse_vex.
* sysdeps/x86_64/dl-trampoline.h (_dl_runtime_resolve_avx_slow):
New.
(_dl_runtime_resolve_opt): Likewise.
(_dl_runtime_profile): Define only if _dl_runtime_profile is
defined.
If assembler doesn't support AVX512DQ, _dl_runtime_resolve_avx is used
to save the first 8 vector registers, which only saves the lower 256
bits of vector register, for lazy binding. When it is called on AVX512
platform, the upper 256 bits of ZMM registers are clobbered. Parameters
passed in ZMM registers will be wrong when the function is called the
first time. This patch requires binutils 2.24, whose assembler can store
and load ZMM registers, to build x86-64 glibc. Since mathvec library
needs assembler support for AVX512DQ, we disable mathvec if assembler
doesn't support AVX512DQ.
[BZ #20139]
* config.h.in (HAVE_AVX512_ASM_SUPPORT): Renamed to ...
(HAVE_AVX512DQ_ASM_SUPPORT): This.
* sysdeps/x86_64/configure.ac: Require assembler from binutils
2.24 or above.
(HAVE_AVX512_ASM_SUPPORT): Removed.
(HAVE_AVX512DQ_ASM_SUPPORT): New.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/dl-trampoline.S: Make HAVE_AVX512_ASM_SUPPORT
check unconditional.
* sysdeps/x86_64/multiarch/ifunc-impl-list.c: Likewise.
* sysdeps/x86_64/multiarch/memcpy.S: Likewise.
* sysdeps/x86_64/multiarch/memcpy_chk.S: Likewise.
* sysdeps/x86_64/multiarch/memmove-avx512-no-vzeroupper.S:
Likewise.
* sysdeps/x86_64/multiarch/memmove-avx512-unaligned-erms.S:
Likewise.
* sysdeps/x86_64/multiarch/memmove.S: Likewise.
* sysdeps/x86_64/multiarch/memmove_chk.S: Likewise.
* sysdeps/x86_64/multiarch/mempcpy.S: Likewise.
* sysdeps/x86_64/multiarch/mempcpy_chk.S: Likewise.
* sysdeps/x86_64/multiarch/memset-avx512-no-vzeroupper.S:
Likewise.
* sysdeps/x86_64/multiarch/memset-avx512-unaligned-erms.S:
Likewise.
* sysdeps/x86_64/multiarch/memset.S: Likewise.
* sysdeps/x86_64/multiarch/memset_chk.S: Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_d_cos8_core_avx512.S: Check
HAVE_AVX512DQ_ASM_SUPPORT instead of HAVE_AVX512_ASM_SUPPORT.
* sysdeps/x86_64/fpu/multiarch/svml_d_exp8_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_d_log8_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_d_pow8_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_d_sin8_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_d_sincos8_core_avx512.:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_cosf16_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_expf16_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_logf16_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_powf16_core_avx512.S:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_sincosf16_core_avx51:
Likewise.
* sysdeps/x86_64/fpu/multiarch/svml_s_sinf16_core_avx512.S:
Likewise.
Due to GCC bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58066
__tls_get_addr may be called with 8-byte stack alignment. Although
this bug has been fixed in GCC 4.9.4, 5.3 and 6, we can't assume
that stack will be always aligned at 16 bytes. Since SSE optimized
memory/string functions with aligned SSE register load and store are
used in the dynamic linker, we must set DL_RUNTIME_UNALIGNED_VEC_SIZE
to 8 so that _dl_runtime_resolve_sse will align the stack before
calling _dl_fixup:
Dump of assembler code for function _dl_runtime_resolve_sse:
0x00007ffff7deea90 <+0>: push %rbx
0x00007ffff7deea91 <+1>: mov %rsp,%rbx
0x00007ffff7deea94 <+4>: and $0xfffffffffffffff0,%rsp
^^^^^^^^^^^ Align stack to 16 bytes
0x00007ffff7deea98 <+8>: sub $0x100,%rsp
0x00007ffff7deea9f <+15>: mov %rax,0xc0(%rsp)
0x00007ffff7deeaa7 <+23>: mov %rcx,0xc8(%rsp)
0x00007ffff7deeaaf <+31>: mov %rdx,0xd0(%rsp)
0x00007ffff7deeab7 <+39>: mov %rsi,0xd8(%rsp)
0x00007ffff7deeabf <+47>: mov %rdi,0xe0(%rsp)
0x00007ffff7deeac7 <+55>: mov %r8,0xe8(%rsp)
0x00007ffff7deeacf <+63>: mov %r9,0xf0(%rsp)
0x00007ffff7deead7 <+71>: movaps %xmm0,(%rsp)
0x00007ffff7deeadb <+75>: movaps %xmm1,0x10(%rsp)
0x00007ffff7deeae0 <+80>: movaps %xmm2,0x20(%rsp)
0x00007ffff7deeae5 <+85>: movaps %xmm3,0x30(%rsp)
0x00007ffff7deeaea <+90>: movaps %xmm4,0x40(%rsp)
0x00007ffff7deeaef <+95>: movaps %xmm5,0x50(%rsp)
0x00007ffff7deeaf4 <+100>: movaps %xmm6,0x60(%rsp)
0x00007ffff7deeaf9 <+105>: movaps %xmm7,0x70(%rsp)
[BZ #19679]
* sysdeps/x86_64/dl-trampoline.S (DL_RUNIME_UNALIGNED_VEC_SIZE):
Renamed to ...
(DL_RUNTIME_UNALIGNED_VEC_SIZE): This. Set to 8.
(DL_RUNIME_RESOLVE_REALIGN_STACK): Renamed to ...
(DL_RUNTIME_RESOLVE_REALIGN_STACK): This. Updated.
(DL_RUNIME_RESOLVE_REALIGN_STACK): Renamed to ...
(DL_RUNTIME_RESOLVE_REALIGN_STACK): This.
* sysdeps/x86_64/dl-trampoline.h
(DL_RUNIME_RESOLVE_REALIGN_STACK): Renamed to ...
(DL_RUNTIME_RESOLVE_REALIGN_STACK): This.
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.
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.
If x86-64 assembler doesn't support MPX, we encode bndmov instruction by
hand. When displacement is zero, assembler generates shorter encoding.
This patch improves bndmov encoding with zero displacement so that ld.so
is identical when using assemblers with and without MPX support.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_resolve): Improve
bndmov encoding with zero displacement.
We need to save/restore bound registers and add a BND prefix before
branches in _dl_runtime_profile so that bound registers for pointer
pass and return are preserved when LD_AUDIT is used.
[BZ #18134]
* sysdeps/i386/configure.ac: Set HAVE_MPX_SUPPORT.
* sysdeps/i386/configure: Regenerated.
* sysdeps/i386/dl-trampoline.S (PRESERVE_BND_REGS_PREFIX): New.
(_dl_runtime_profile): Save and restore Intel MPX return bound
registers when calling _dl_call_pltexit. Add
PRESERVE_BND_REGS_PREFIX before return.
* sysdeps/i386/link-defines.sym (LRV_BND0_OFFSET): New.
(LRV_BND1_OFFSET): Likewise.
* sysdeps/x86/bits/link.h (La_i86_retval): Add lrv_bnd0 and
lrv_bnd1.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_profile): Fix
typo in bndmov encoding.
* sysdeps/x86_64/dl-trampoline.h: Properly save and restore
Intel MPX bound registers. Add PRESERVE_BND_REGS_PREFIX before
branch instructions to preserve bounds.
We need to add a BND prefix before indirect branch at the end of
_dl_runtime_resolve to preserve bound registers.
[BZ #18134]
* sysdeps/x86_64/dl-trampoline.S (PRESERVE_BND_REGS_PREFIX): New.
(_dl_runtime_resolve): Add a BND prefix before indirect branch.
This patch saves and restores bound registers in symbol lookup for x86-64:
1. Branches without BND prefix clear bound registers.
2. x86-64 pass bounds in bound registers as specified in MPX psABI
extension on hjl/mpx/master branch at
https://github.com/hjl-tools/x86-64-psABIhttps://groups.google.com/forum/#!topic/x86-64-abi/KFsB0XTgWYc
Binutils has been updated to create an alternate PLT to add BND prefix
when branching to ld.so.
* config.h.in (HAVE_MPX_SUPPORT): New #undef.
* sysdeps/x86_64/configure.ac: Set HAVE_MPX_SUPPORT.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/dl-trampoline.S (REGISTER_SAVE_AREA): New
macro.
(REGISTER_SAVE_RAX): Likewise.
(REGISTER_SAVE_RCX): Likewise.
(REGISTER_SAVE_RDX): Likewise.
(REGISTER_SAVE_RSI): Likewise.
(REGISTER_SAVE_RDI): Likewise.
(REGISTER_SAVE_R8): Likewise.
(REGISTER_SAVE_R9): Likewise.
(REGISTER_SAVE_BND0): Likewise.
(REGISTER_SAVE_BND1): Likewise.
(REGISTER_SAVE_BND2): Likewise.
(_dl_runtime_resolve): Use them. Save and restore Intel MPX
bound registers when calling _dl_fixup.
AVX-512 ISA adds 512-bit zmm registers. This patch updates
_dl_runtime_profile to pass zmm registers to run-time audit. It also
changes _dl_x86_64_save_sse and _dl_x86_64_restore_sse to upport zmm
registers, which are called when only when RTLD_PREPARE_FOREIGN_CALL
is used. Its performance impact is minimum.
* config.h.in (HAVE_AVX512_SUPPORT): New #undef.
(HAVE_AVX512_ASM_SUPPORT): Likewise.
* sysdeps/x86_64/bits/link.h (La_x86_64_zmm): New.
(La_x86_64_vector): Add zmm.
* sysdeps/x86_64/Makefile (tests): Add tst-audit10.
(modules-names): Add tst-auditmod10a and tst-auditmod10b.
($(objpfx)tst-audit10): New target.
($(objpfx)tst-audit10.out): Likewise.
(tst-audit10-ENV): New.
(AVX512-CFLAGS): Likewise.
(CFLAGS-tst-audit10.c): Likewise.
(CFLAGS-tst-auditmod10a.c): Likewise.
(CFLAGS-tst-auditmod10b.c): Likewise.
* sysdeps/x86_64/configure.ac: Set config-cflags-avx512,
HAVE_AVX512_SUPPORT and HAVE_AVX512_ASM_SUPPORT.
* sysdeps/x86_64/configure: Regenerated.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_profile): Add
AVX-512 zmm register support.
(_dl_x86_64_save_sse): Likewise.
(_dl_x86_64_restore_sse): Likewise.
* sysdeps/x86_64/dl-trampoline.h: Updated to support different
size vector registers.
* sysdeps/x86_64/link-defines.sym (YMM_SIZE): New.
(ZMM_SIZE): Likewise.
* sysdeps/x86_64/tst-audit10.c: New file.
* sysdeps/x86_64/tst-auditmod10a.c: Likewise.
* sysdeps/x86_64/tst-auditmod10b.c: Likewise.
If a signal arrived during a symbol lookup and the signal handler also
required a symbol lookup, the end of the lookup in the signal handler reset
the flag whether restoring AVX/SSE registers is needed. Resetting means
in this case that the tail part of the outer lookup code will try to
restore the registers and this can fail miserably. We now restore to the
previous value which makes nesting calls possible.
This patch fixes mixed SSE/AVX audit and checks AVX only once in
_dl_runtime_profile. When an AVX or SSE register value in pltenter is
modified, we have to make sure that the SSE part value is the same in both
lr_xmm and lr_vector fields so that pltexit will get the correct value
from either lr_xmm or lr_vector fields. AVX-enabled pltenter should
update both lr_xmm and lr_vector fields to support stacked AVX/SSE
pltenter functions.
SSE registers are used for passing parameters and must be preserved
in runtime relocations. This is inside ld.so enforced through the
tests in tst-xmmymm.sh. But the malloc routines used after startup
come from libc.so and can be arbitrarily complex. It's overkill
to save the SSE registers all the time because of that. These calls
are rare. Instead we save them on demand. The new infrastructure
put in place in this patch makes this possible and efficient.
The original AVX patch used a function pointer to handle the difference
between machines with and without AVX support. This is insecure. A
well-placed memory exploit could lead to redirection of the execution.
Using a variable and several tests is a bit slower but cannot be
exploited in this way.
* inet/inet6_rth.c (inet6_rth_add): Add some error checking.
Patch mostly by Yang Hongyang <yanghy@cn.fujitsu.com>.
* inet/Makefile (tests): Add tst-inet6_rth.
* inet/tst-inet6_rth.c: New file.
alignment of La_x86_64_regs. Store xmm parameters.
(reloc_index): Define.
(_dl_fixup): Rename reloc_offset parameter to reloc_arg.
(_dl_fixup_profile): Likewise. Use reloc_index instead of
computing index from reloc_offset.
(_dl_call_pltexit): Likewise.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_resolve): Just pass
the relocation index to _dl_fixup.
(_dl_runtime_profile): Likewise for _dl_fixup_profile and
_dl_call_pltexit.
* sysdeps/x86_64/dl-runtime.c: New file.
* sysdeps/x86_64/dl-trampoline.S (_dl_runtime_profile): Fix
alignement of La_x86_64_regs. Store xmm parameters.
Patch mostly by Jiri Olsa <olsajiri@gmail.com>.
H.J. Lu
Joseph Myers
Igor Zamyatin
Allan McRae
Ondřej Bílka
Paul Eggert
H.J. Lu
Ulrich Drepper
Andreas Schwab
Ulrich Drepper
Jakub Jelinek