On Wed, Sep 21, 2022 at 1:42 PM H.J. Lu <hjl.to...@gmail.com> wrote: > > If shadow stack is enabled, when unwinding stack, we count how many stack > frames we pop to reach the landing pad and adjust shadow stack by the same > amount. When counting the stack frame, we compare the return address on > normal stack against the return address on shadow stack. If they don't > match, return _URC_FATAL_PHASE2_ERROR for the corrupted return address on > normal stack. Don't check the return address for > > 1. Non-catchable exception where exception_class == 0. Process will be > terminated. > 2. Zero return address which marks the outermost stack frame. > 3. Signal stack frame since kernel puts a restore token on shadow stack. > > * unwind-generic.h (_Unwind_Frames_Increment): Add the EXC > argument. > * unwind.inc (_Unwind_RaiseException_Phase2): Pass EXC to > _Unwind_Frames_Increment. > (_Unwind_ForcedUnwind_Phase2): Likewise. > * config/i386/shadow-stack-unwind.h (_Unwind_Frames_Increment): > Take the EXC argument. Return _URC_FATAL_PHASE2_ERROR if the > return address on normal stack doesn't match the return address > on shadow stack. > --- > libgcc/config/i386/shadow-stack-unwind.h | 51 ++++++++++++++++++++++-- > libgcc/unwind-generic.h | 2 +- > libgcc/unwind.inc | 4 +- > 3 files changed, 50 insertions(+), 7 deletions(-) > > diff --git a/libgcc/config/i386/shadow-stack-unwind.h > b/libgcc/config/i386/shadow-stack-unwind.h > index 2b02682bdae..89d44165000 100644 > --- a/libgcc/config/i386/shadow-stack-unwind.h > +++ b/libgcc/config/i386/shadow-stack-unwind.h > @@ -54,10 +54,39 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > If not, see > aligned. If the original shadow stack is 8 byte aligned, we just > need to pop 2 slots, one restore token, from shadow stack. Otherwise, > we need to pop 3 slots, one restore token + 4 byte padding, from > - shadow stack. */ > -#ifndef __x86_64__ > + shadow stack. > + > + When popping a stack frame, we compare the return address on normal > + stack against the return address on shadow stack. If they don't match, > + return _URC_FATAL_PHASE2_ERROR for the corrupted return address on > + normal stack. Don't check the return address for > + 1. Non-catchable exception where exception_class == 0. Process will > + be terminated. > + 2. Zero return address which marks the outermost stack frame. > + 3. Signal stack frame since kernel puts a restore token on shadow > + stack. > + */ > #undef _Unwind_Frames_Increment > -#define _Unwind_Frames_Increment(context, frames) \ > +#ifdef __x86_64__ > +#define _Unwind_Frames_Increment(exc, context, frames) \ > + { \ > + frames++; \ > + if (exc->exception_class != 0 \ > + && _Unwind_GetIP (context) != 0 \ > + && !_Unwind_IsSignalFrame (context)) \ > + { \ > + _Unwind_Word ssp = _get_ssp (); \ > + if (ssp != 0) \ > + { \ > + ssp += 8 * frames; \ > + _Unwind_Word ra = *(_Unwind_Word *) ssp; \ > + if (ra != _Unwind_GetIP (context)) \ > + return _URC_FATAL_PHASE2_ERROR; \ > + } \ > + } \ > + } > +#else > +#define _Unwind_Frames_Increment(exc, context, frames) \ > if (_Unwind_IsSignalFrame (context)) \ > do \ > { \ > @@ -83,5 +112,19 @@ see the files COPYING3 and COPYING.RUNTIME respectively. > If not, see > } \ > while (0); \ > else \ > - frames++; > + { \ > + frames++; \ > + if (exc->exception_class != 0 \ > + && _Unwind_GetIP (context) != 0) \ > + { \ > + _Unwind_Word ssp = _get_ssp (); \ > + if (ssp != 0) \ > + { \ > + ssp += 4 * frames; \ > + _Unwind_Word ra = *(_Unwind_Word *) ssp; \ > + if (ra != _Unwind_GetIP (context)) \ > + return _URC_FATAL_PHASE2_ERROR; \ > + } \ > + } \ > + } > #endif > diff --git a/libgcc/unwind-generic.h b/libgcc/unwind-generic.h > index a87c9b3ccf6..bf721282d03 100644 > --- a/libgcc/unwind-generic.h > +++ b/libgcc/unwind-generic.h > @@ -292,6 +292,6 @@ EXCEPTION_DISPOSITION _GCC_specific_handler > (PEXCEPTION_RECORD, void *, > #define _Unwind_Frames_Extra(frames) > > /* Increment frame count. */ > -#define _Unwind_Frames_Increment(context, frames) frames++ > +#define _Unwind_Frames_Increment(exc, context, frames) frames++ > > #endif /* unwind.h */ > diff --git a/libgcc/unwind.inc b/libgcc/unwind.inc > index 5efd8af1b15..a7111a7b3a8 100644 > --- a/libgcc/unwind.inc > +++ b/libgcc/unwind.inc > @@ -73,7 +73,7 @@ _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc, > gcc_assert (!match_handler); > > uw_update_context (context, &fs); > - _Unwind_Frames_Increment (context, frames); > + _Unwind_Frames_Increment (exc, context, frames); > } > > *frames_p = frames; > @@ -191,7 +191,7 @@ _Unwind_ForcedUnwind_Phase2 (struct _Unwind_Exception > *exc, > /* Update cur_context to describe the same frame as fs, and discard > the previous context if necessary. */ > uw_advance_context (context, &fs); > - _Unwind_Frames_Increment (context, frames); > + _Unwind_Frames_Increment (exc, context, frames); > } > > *frames_p = frames; > -- > 2.37.3 >
PING. Jeff has approved the generic changes. Thanks. -- H.J.