Control-flow Enforcement Technology (CET), published by Intel,
introduces the Shadow Stack feature, which ensures a return from a
function is done to exactly the same location from where the function
was called. When EH is present the control-flow transfer may skip some
stack frames and the shadow stack has to be adjusted not to signal a
violation of a control-flow transfer. It's done by counting a number
of skiping frames and adjasting shadow stack pointer by this number.
Having new semantic of the 'ret' instruction if CET is supported in HW
the 'ret' instruction cannot be generated in ix86_expand_epilogue when
we are returning after EH is processed. Added a code in
ix86_expand_epilogue to adjust Shadow Stack pointer and to generate an
indirect jump instead of 'ret'. As sp register is used during this
adjustment thus the argument in pro_epilogue_adjust_stack is changed
to update cfa_reg based on whether control-flow instrumentation is set.
Without updating the cfa_reg field there is an assert later in dwarf2
pass related to mismatch the stack register and cfa_reg value.
gcc/
* config/i386/i386.c (ix86_expand_epilogue): Change simple
return to indirect jump for EH return if control-flow protection
is enabled. Change explicit 'false' argument in
pro_epilogue_adjust_stack with a value of flag_cf_protection.
* config/i386/i386.md (simple_return_indirect_internal): Remove
SImode restriction to support 64-bit.
libgcc/
* config/i386/linux-unwind.h: Include
config/i386/shadow-stack-unwind.h.
* config/i386/shadow-stack-unwind.h: New file.
* unwind-dw2.c: (uw_install_context): Add a frame parameter and
pass it to _Unwind_Frames_Extra.
* unwind-generic.h (_Unwind_Frames_Extra): New.
* unwind.inc (_Unwind_RaiseException_Phase2): Add frames_p
parameter. Add local variable frames to count number of frames.
(_Unwind_ForcedUnwind_Phase2): Likewise.
(_Unwind_RaiseException): Add local variable frames to count
number of frames, pass it to _Unwind_RaiseException_Phase2 and
uw_install_context.
(_Unwind_ForcedUnwind): Likewise.
(_Unwind_Resume): Likewise.
(_Unwind_Resume_or_Rethrow): Likewise.
From-SVN: r254876
Current glibc no longer gives the ucontext_t type the tag struct
ucontext, to conform with POSIX namespace rules. This requires
various linux-unwind.h files in libgcc, that were previously using
struct ucontext, to be fixed to use ucontext_t instead. This is
similar to the removal of the struct siginfo tag from siginfo_t some
years ago.
This patch changes those files to use ucontext_t instead. As the
standard name that should be unconditionally safe, so this is not
restricted to architectures supported by glibc, or conditioned on the
glibc version.
Tested compilation together with current glibc with glibc's
build-many-glibcs.py.
* config/aarch64/linux-unwind.h (aarch64_fallback_frame_state),
config/alpha/linux-unwind.h (alpha_fallback_frame_state),
config/bfin/linux-unwind.h (bfin_fallback_frame_state),
config/i386/linux-unwind.h (x86_64_fallback_frame_state,
x86_fallback_frame_state), config/m68k/linux-unwind.h (struct
uw_ucontext), config/nios2/linux-unwind.h (struct nios2_ucontext),
config/pa/linux-unwind.h (pa32_fallback_frame_state),
config/riscv/linux-unwind.h (riscv_fallback_frame_state),
config/sh/linux-unwind.h (sh_fallback_frame_state),
config/tilepro/linux-unwind.h (tile_fallback_frame_state),
config/xtensa/linux-unwind.h (xtensa_fallback_frame_state): Use
ucontext_t instead of struct ucontext.
From-SVN: r249731
2011-08-02 H.J. Lu <hongjiu.lu@intel.com>
* config/i386/linux-unwind.h (RT_SIGRETURN_SYSCALL): New.
(x86_64_fallback_frame_state): Use RT_SIGRETURN_SYSCALL and
long long to check rt_sigreturn syscall.
From-SVN: r177229
Jakub Jelinek