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

1 files changed, 23 insertions, 11 deletions

diff --git a/libgcc/unwind.inc b/libgcc/unwind.inc
index 658bd94f8f3..a98154b1b72 100644
--- a/libgcc/unwind.inc
+++ b/libgcc/unwind.inc
@@ -36,9 +36,11 @@
 
 static _Unwind_Reason_Code
 _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
-			      struct _Unwind_Context *context)
+			      struct _Unwind_Context *context,
+			      unsigned long *frames_p)
 {
   _Unwind_Reason_Code code;
+  unsigned long frames = 1;
 
   while (1)
     {
@@ -71,8 +73,10 @@ _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
       gcc_assert (!match_handler);
 
       uw_update_context (context, &fs);
+      frames++;
     }
 
+  *frames_p = frames;
   return code;
 }
 
@@ -83,6 +87,7 @@ _Unwind_RaiseException(struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  unsigned long frames;
 
   /* Set up this_context to describe the current stack frame.  */
   uw_init_context (&this_context);
@@ -128,11 +133,11 @@ _Unwind_RaiseException(struct _Unwind_Exception *exc)
   exc->private_2 = uw_identify_context (&cur_context);
 
   cur_context = this_context;
-  code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
+  code = _Unwind_RaiseException_Phase2 (exc, &cur_context, &frames);
   if (code != _URC_INSTALL_CONTEXT)
     return code;
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, frames);
 }
 
 
@@ -140,11 +145,13 @@ _Unwind_RaiseException(struct _Unwind_Exception *exc)
 
 static _Unwind_Reason_Code
 _Unwind_ForcedUnwind_Phase2 (struct _Unwind_Exception *exc,
-			     struct _Unwind_Context *context)
+			     struct _Unwind_Context *context,
+			     unsigned long *frames_p)
 {
   _Unwind_Stop_Fn stop = (_Unwind_Stop_Fn) (_Unwind_Ptr) exc->private_1;
   void *stop_argument = (void *) (_Unwind_Ptr) exc->private_2;
   _Unwind_Reason_Code code, stop_code;
+  unsigned long frames = 1;
 
   while (1)
     {
@@ -183,8 +190,10 @@ _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);
+      frames++;
     }
 
+  *frames_p = frames;
   return code;
 }
 
@@ -197,6 +206,7 @@ _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  unsigned long frames;
 
   uw_init_context (&this_context);
   cur_context = this_context;
@@ -204,11 +214,11 @@ _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
   exc->private_1 = (_Unwind_Ptr) stop;
   exc->private_2 = (_Unwind_Ptr) stop_argument;
 
-  code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
+  code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
   if (code != _URC_INSTALL_CONTEXT)
     return code;
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, frames);
 }
 
 
@@ -220,6 +230,7 @@ _Unwind_Resume (struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  unsigned long frames;
 
   uw_init_context (&this_context);
   cur_context = this_context;
@@ -227,13 +238,13 @@ _Unwind_Resume (struct _Unwind_Exception *exc)
   /* Choose between continuing to process _Unwind_RaiseException
      or _Unwind_ForcedUnwind.  */
   if (exc->private_1 == 0)
-    code = _Unwind_RaiseException_Phase2 (exc, &cur_context);
+    code = _Unwind_RaiseException_Phase2 (exc, &cur_context, &frames);
   else
-    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
+    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
 
   gcc_assert (code == _URC_INSTALL_CONTEXT);
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, frames);
 }
 
 
@@ -245,6 +256,7 @@ _Unwind_Resume_or_Rethrow (struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  unsigned long frames;
 
   /* Choose between continuing to process _Unwind_RaiseException
      or _Unwind_ForcedUnwind.  */
@@ -254,11 +266,11 @@ _Unwind_Resume_or_Rethrow (struct _Unwind_Exception *exc)
   uw_init_context (&this_context);
   cur_context = this_context;
 
-  code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
+  code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context, &frames);
 
   gcc_assert (code == _URC_INSTALL_CONTEXT);
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, frames);
 }