On Wed, Oct 5, 2022 at 5:33 AM H.J. Lu <hjl.to...@gmail.com> wrote:
>
> 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.
Ok.
> >
> > * 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.
--
BR,
Hongtao
