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author | Igor Tsimbalist <igor.v.tsimbalist@intel.com> | 2017-11-17 16:21:23 +0100 |
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committer | Igor Tsimbalist <itsimbal@gcc.gnu.org> | 2017-11-17 16:21:23 +0100 |
commit | 6a10fff4e2c2fc4bc5c3f313c08698d83c2292a1 (patch) | |
tree | 714437517f3bed4370e786ffd6a22ca4d11f139f /libgcc/unwind-dw2.c | |
parent | f1b7bc164cb370b15c6e62d65120e6494729ac0c (diff) | |
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Add Intel CET support for EH in libgcc.
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
Diffstat (limited to 'libgcc/unwind-dw2.c')
-rw-r--r-- | libgcc/unwind-dw2.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c index 3f26eaf..e80ac74 100644 --- a/libgcc/unwind-dw2.c +++ b/libgcc/unwind-dw2.c @@ -1644,14 +1644,18 @@ uw_frob_return_addr (struct _Unwind_Context *current /* Install TARGET into CURRENT so that we can return to it. This is a macro because __builtin_eh_return must be invoked in the context of - our caller. */ + our caller. FRAMES is a number of frames to be unwind. + _Unwind_Frames_Extra is a macro to do additional work during unwinding + if needed, for example shadow stack pointer adjustment for Intel CET + technology. */ -#define uw_install_context(CURRENT, TARGET) \ +#define uw_install_context(CURRENT, TARGET, FRAMES) \ do \ { \ long offset = uw_install_context_1 ((CURRENT), (TARGET)); \ void *handler = uw_frob_return_addr ((CURRENT), (TARGET)); \ _Unwind_DebugHook ((TARGET)->cfa, handler); \ + _Unwind_Frames_Extra (FRAMES); \ __builtin_eh_return (offset, handler); \ } \ while (0) |