1. Remove _dl_runtime_resolve_shstk and _dl_runtime_profile_shstk.
2. Move CET offsets from x86 cpu-features-offsets.sym to x86-64
features-offsets.sym.
3. Rename x86 cet-control.h to x86-64 feature-control.h since it is only
for x86-64 and also used for PLT rewrite.
4. Add x86-64 ldsodefs.h to include feature-control.h.
5. Change TUNABLE_CALLBACK (set_plt_rewrite) to x86-64 only.
6. Move x86 dl-procruntime.c to x86-64.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Previously, CET was enabled by kernel before passing control to user
space and the startup code must disable CET if applications or shared
libraries aren't CET enabled. Since the current kernel only supports
shadow stack and won't enable shadow stack before passing control to
user space, we need to enable shadow stack during startup if the
application and all shared library are shadow stack enabled. There
is no need to disable shadow stack at startup. Shadow stack can only
be enabled in a function which will never return. Otherwise, shadow
stack will underflow at the function return.
1. GL(dl_x86_feature_1) is set to the CET features which are supported
by the processor and are not disabled by the tunable. Only non-zero
features in GL(dl_x86_feature_1) should be enabled. After enabling
shadow stack with ARCH_SHSTK_ENABLE, ARCH_SHSTK_STATUS is used to check
if shadow stack is really enabled.
2. Use ARCH_SHSTK_ENABLE in RTLD_START in dynamic executable. It is
safe since RTLD_START never returns.
3. Call arch_prctl (ARCH_SHSTK_ENABLE) from ARCH_SETUP_TLS in static
executable. Since the start function using ARCH_SETUP_TLS never returns,
it is safe to enable shadow stack in ARCH_SETUP_TLS.
In _dl_runtime_resolve, use fxsave/xsave/xsavec to preserve all vector,
mask and bound registers. It simplifies _dl_runtime_resolve and supports
different calling conventions. ld.so code size is reduced by more than
1 KB. However, use fxsave/xsave/xsavec takes a little bit more cycles
than saving and restoring vector and bound registers individually.
Latency for _dl_runtime_resolve to lookup the function, foo, from one
shared library plus libc.so:
Before After Change
Westmere (SSE)/fxsave 345 866 151%
IvyBridge (AVX)/xsave 420 643 53%
Haswell (AVX)/xsave 713 1252 75%
Skylake (AVX+MPX)/xsavec 559 719 28%
Skylake (AVX512+MPX)/xsavec 145 272 87%
Ryzen (AVX)/xsavec 280 553 97%
This is the worst case where portion of time spent for saving and
restoring registers is bigger than majority of cases. With smaller
_dl_runtime_resolve code size, overall performance impact is negligible.
On IvyBridge, differences in build and test time of binutils with lazy
binding GCC and binutils are noises. On Westmere, differences in
bootstrap and "makc check" time of GCC 7 with lazy binding GCC and
binutils are also noises.
[BZ #21265]
* sysdeps/x86/cpu-features-offsets.sym (XSAVE_STATE_SIZE_OFFSET):
New.
* sysdeps/x86/cpu-features.c: Include <libc-pointer-arith.h>.
(get_common_indeces): Set xsave_state_size, xsave_state_full_size
and bit_arch_XSAVEC_Usable if needed.
(init_cpu_features): Remove bit_arch_Use_dl_runtime_resolve_slow
and bit_arch_Use_dl_runtime_resolve_opt.
* sysdeps/x86/cpu-features.h (bit_arch_Use_dl_runtime_resolve_opt):
Removed.
(bit_arch_Use_dl_runtime_resolve_slow): Likewise.
(bit_arch_Prefer_No_AVX512): Updated.
(bit_arch_MathVec_Prefer_No_AVX512): Likewise.
(bit_arch_XSAVEC_Usable): New.
(STATE_SAVE_OFFSET): Likewise.
(STATE_SAVE_MASK): Likewise.
[__ASSEMBLER__]: Include <cpu-features-offsets.h>.
(cpu_features): Add xsave_state_size and xsave_state_full_size.
(index_arch_Use_dl_runtime_resolve_opt): Removed.
(index_arch_Use_dl_runtime_resolve_slow): Likewise.
(index_arch_XSAVEC_Usable): New.
* sysdeps/x86/cpu-tunables.c (TUNABLE_CALLBACK (set_hwcaps)):
Support XSAVEC_Usable. Remove Use_dl_runtime_resolve_slow.
* sysdeps/x86_64/Makefile (tst-x86_64-1-ENV): New if tunables
is enabled.
* sysdeps/x86_64/dl-machine.h (elf_machine_runtime_setup):
Replace _dl_runtime_resolve_sse, _dl_runtime_resolve_avx,
_dl_runtime_resolve_avx_slow, _dl_runtime_resolve_avx_opt,
_dl_runtime_resolve_avx512 and _dl_runtime_resolve_avx512_opt
with _dl_runtime_resolve_fxsave, _dl_runtime_resolve_xsave and
_dl_runtime_resolve_xsavec.
* sysdeps/x86_64/dl-trampoline.S (DL_RUNTIME_UNALIGNED_VEC_SIZE):
Removed.
(DL_RUNTIME_RESOLVE_REALIGN_STACK): Check STATE_SAVE_ALIGNMENT
instead of VEC_SIZE.
(REGISTER_SAVE_BND0): Removed.
(REGISTER_SAVE_BND1): Likewise.
(REGISTER_SAVE_BND3): Likewise.
(REGISTER_SAVE_RAX): Always defined to 0.
(VMOV): Removed.
(_dl_runtime_resolve_avx): Likewise.
(_dl_runtime_resolve_avx_slow): Likewise.
(_dl_runtime_resolve_avx_opt): Likewise.
(_dl_runtime_resolve_avx512): Likewise.
(_dl_runtime_resolve_avx512_opt): Likewise.
(_dl_runtime_resolve_sse): Likewise.
(_dl_runtime_resolve_sse_vex): Likewise.
(USE_FXSAVE): New.
(_dl_runtime_resolve_fxsave): Likewise.
(USE_XSAVE): Likewise.
(_dl_runtime_resolve_xsave): Likewise.
(USE_XSAVEC): Likewise.
(_dl_runtime_resolve_xsavec): Likewise.
* sysdeps/x86_64/dl-trampoline.h (_dl_runtime_resolve_avx512):
Removed.
(_dl_runtime_resolve_avx512_opt): Likewise.
(_dl_runtime_resolve_avx): Likewise.
(_dl_runtime_resolve_avx_opt): Likewise.
(_dl_runtime_resolve_sse): Likewise.
(_dl_runtime_resolve_sse_vex): Likewise.
(_dl_runtime_resolve_fxsave): New.
(_dl_runtime_resolve_xsave): Likewise.
(_dl_runtime_resolve_xsavec): Likewise.
Merge x86 ifunc-defines.sym with x86 cpu-features-offsets.sym. Remove
x86 ifunc-defines.sym and rtld-global-offsets.sym. No code changes on
i686 and x86-64.
* sysdeps/i386/i686/multiarch/Makefile (gen-as-const-headers):
Remove ifunc-defines.sym.
* sysdeps/x86_64/multiarch/Makefile (gen-as-const-headers):
Likewise.
* sysdeps/i386/i686/multiarch/ifunc-defines.sym: Removed.
* sysdeps/x86/rtld-global-offsets.sym: Likewise.
* sysdeps/x86_64/multiarch/ifunc-defines.sym: Likewise.
* sysdeps/x86/Makefile (gen-as-const-headers): Remove
rtld-global-offsets.sym.
* sysdeps/x86_64/multiarch/ifunc-defines.sym: Merged with ...
* sysdeps/x86/cpu-features-offsets.sym: This.
* sysdeps/x86/cpu-features.h: Include <cpu-features-offsets.h>
instead of <ifunc-defines.h> and <rtld-global-offsets.h>.
