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* [PATCH 08/22] Add Intel CET support for EH in libgcc.
@ 2017-10-12 20:01 Tsimbalist, Igor V
  2017-10-12 23:59 ` Hans-Peter Nilsson
  2017-10-31  5:09 ` Jeff Law
  0 siblings, 2 replies; 13+ messages in thread
From: Tsimbalist, Igor V @ 2017-10-12 20:01 UTC (permalink / raw)
  To: gcc-patches; +Cc: Jeff Law, ian, Tsimbalist, Igor V

[-- Attachment #1: Type: text/plain, Size: 1856 bytes --]

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 skipping frames
and adjusting shadow stack pointer by this number.

gcc/
	* config/i386/i386.c (ix86_expand_epilogue): Change simple
	return to indirect jump for EH return. 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 FRAMES argument and
	pass it to _Unwind_Frames_Extra.
	* unwind-generic.h (FRAMES_P_DECL): New.
	(FRAMES_VAR): Likewise.
	(FRAMES_VAR_P): Likewise.
	(FRAMES_VAR_DECL): Likewise.
	(FRAMES_VAR_DECL_1): Likewise.
	(FRAMES_VAR_INC): Likewise.
	(FRAMES_P_UPDATE): Likewise.
	(_Unwind_Frames_Extra): Likewise.
	* unwind.inc (_Unwind_RaiseException_Phase2): Use FRAMES_P_DECL,
	FRAMES_VAR_DECL_1, FRAMES_VAR_INC and FRAMES_P_UPDATE.
	(_Unwind_RaiseException): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_ForcedUnwind_Phase2): Use FRAMES_P_DECL,
	FRAMES_VAR_DECL_1, FRAMES_VAR_INC, FRAMES_P_UPDATE.
	(_Unwind_ForcedUnwind): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_Resume): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_Resume_or_Rethrow): Use FRAMES_VAR_DECL, FRAMES_VAR_P
	and FRAMES_VAR. 

Igor



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From 16eb1d0d9239e039fba28f1ae71762f19061b157 Mon Sep 17 00:00:00 2001
From: Igor Tsimbalist <igor.v.tsimbalist@intel.com>
Date: Wed, 19 Jul 2017 03:04:46 +0300
Subject: [PATCH 08/22] 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. 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 FRAMES argument and
	pass it to _Unwind_Frames_Extra.
	* unwind-generic.h (FRAMES_P_DECL): New.
	(FRAMES_VAR): Likewise.
	(FRAMES_VAR_P): Likewise.
	(FRAMES_VAR_DECL): Likewise.
	(FRAMES_VAR_DECL_1): Likewise.
	(FRAMES_VAR_INC): Likewise.
	(FRAMES_P_UPDATE): Likewise.
	(_Unwind_Frames_Extra): Likewise.
	* unwind.inc (_Unwind_RaiseException_Phase2): Use FRAMES_P_DECL,
	FRAMES_VAR_DECL_1, FRAMES_VAR_INC and FRAMES_P_UPDATE.
	(_Unwind_RaiseException): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_ForcedUnwind_Phase2): Use FRAMES_P_DECL,
	FRAMES_VAR_DECL_1, FRAMES_VAR_INC, FRAMES_P_UPDATE.
	(_Unwind_ForcedUnwind): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_Resume): Use FRAMES_VAR_DECL, FRAMES_VAR_P and
	FRAMES_VAR.
	(_Unwind_Resume_or_Rethrow): Use FRAMES_VAR_DECL, FRAMES_VAR_P
	and FRAMES_VAR.

---
 gcc/config/i386/i386.c                   | 34 ++++++++++++++--
 gcc/config/i386/i386.md                  |  2 +-
 libgcc/config/i386/linux-unwind.h        |  5 +++
 libgcc/config/i386/shadow-stack-unwind.h | 66 ++++++++++++++++++++++++++++++++
 libgcc/unwind-dw2.c                      |  3 +-
 libgcc/unwind-generic.h                  | 11 ++++++
 libgcc/unwind.inc                        | 34 ++++++++++------
 7 files changed, 139 insertions(+), 16 deletions(-)
 create mode 100644 libgcc/config/i386/shadow-stack-unwind.h
---
 gcc/config/i386/i386.c                   | 34 ++++++++++++++--
 gcc/config/i386/i386.md                  |  2 +-
 libgcc/config/i386/linux-unwind.h        |  5 +++
 libgcc/config/i386/shadow-stack-unwind.h | 66 ++++++++++++++++++++++++++++++++
 libgcc/unwind-dw2.c                      |  3 +-
 libgcc/unwind-generic.h                  | 11 ++++++
 libgcc/unwind.inc                        | 34 ++++++++++------
 7 files changed, 139 insertions(+), 16 deletions(-)
 create mode 100644 libgcc/config/i386/shadow-stack-unwind.h

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 384c429..1b5deb0 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -15759,7 +15759,9 @@ ix86_expand_epilogue (int style)
 		 offset relative to SA, and after this insn we have no
 		 other reasonable register to use for the CFA.  We don't
 		 bother resetting the CFA to the SP for the duration of
-		 the return insn.  */
+		 the return insn, unless we control flow instrumentation
+		 is done.  In this case the SP is used later and we have
+		 to reset CFA to SP.  */
 	      add_reg_note (insn, REG_CFA_DEF_CFA,
 			    plus_constant (Pmode, sa, UNITS_PER_WORD));
 	      ix86_add_queued_cfa_restore_notes (insn);
@@ -15771,7 +15773,8 @@ ix86_expand_epilogue (int style)
 	      m->fs.fp_valid = false;
 
 	      pro_epilogue_adjust_stack (stack_pointer_rtx, sa,
-					 const0_rtx, style, false);
+					 const0_rtx, style,
+					 flag_cf_protection);
 	    }
 	  else
 	    {
@@ -15955,7 +15958,32 @@ ix86_expand_epilogue (int style)
 	emit_jump_insn (gen_simple_return_pop_internal (popc));
     }
   else if (!m->call_ms2sysv || !restore_stub_is_tail)
-    emit_jump_insn (gen_simple_return_internal ());
+    {
+      /* In case of return from EH a simple return cannot be used
+	 as a return address will be compared with a shadow stack
+	 return address.  Use indirect jump instead.  */
+      if (style == 2 && flag_cf_protection)
+	{
+	  /* Register used in indirect jump must be in word_mode.  But
+	     Pmode may not be the same as word_mode for x32.  */
+	  rtx ecx = gen_rtx_REG (word_mode, CX_REG);
+	  rtx_insn *insn;
+
+	  insn = emit_insn (gen_pop (ecx));
+	  m->fs.cfa_offset -= UNITS_PER_WORD;
+	  m->fs.sp_offset -= UNITS_PER_WORD;
+
+	  rtx x = plus_constant (Pmode, stack_pointer_rtx, UNITS_PER_WORD);
+	  x = gen_rtx_SET (stack_pointer_rtx, x);
+	  add_reg_note (insn, REG_CFA_ADJUST_CFA, x);
+	  add_reg_note (insn, REG_CFA_REGISTER, gen_rtx_SET (ecx, pc_rtx));
+	  RTX_FRAME_RELATED_P (insn) = 1;
+
+	  emit_jump_insn (gen_simple_return_indirect_internal (ecx));
+	}
+      else
+	emit_jump_insn (gen_simple_return_internal ());
+    }
 
   /* Restore the state back to the state from the prologue,
      so that it's correct for the next epilogue.  */
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 076a48e..9c77a2b 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -12573,7 +12573,7 @@
 
 (define_insn "simple_return_indirect_internal"
   [(simple_return)
-   (use (match_operand:SI 0 "register_operand" "r"))]
+   (use (match_operand 0 "register_operand" "r"))]
   "reload_completed"
   "%!jmp\t%A0"
   [(set_attr "type" "ibr")
diff --git a/libgcc/config/i386/linux-unwind.h b/libgcc/config/i386/linux-unwind.h
index 2009ad7..c51b4d9 100644
--- a/libgcc/config/i386/linux-unwind.h
+++ b/libgcc/config/i386/linux-unwind.h
@@ -22,6 +22,11 @@ a copy of the GCC Runtime Library Exception along with this program;
 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 <http://www.gnu.org/licenses/>.  */
 
+/* Unwind shadow stack for -fcf-protection -mshstk.  */
+#if defined __SHSTK__ && defined __CET__
+# include "config/i386/shadow-stack-unwind.h"
+#endif
+
 /* Do code reading to identify a signal frame, and set the frame
    state data appropriately.  See unwind-dw2.c for the structs.
    Don't use this at all if inhibit_libc is used.  */
diff --git a/libgcc/config/i386/shadow-stack-unwind.h b/libgcc/config/i386/shadow-stack-unwind.h
new file mode 100644
index 0000000..c5d0d56
--- /dev/null
+++ b/libgcc/config/i386/shadow-stack-unwind.h
@@ -0,0 +1,66 @@
+/* _Unwind_Frames_Extra with shadow stack for x86-64 and x86.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+#ifdef __x86_64__
+# define incssp(x) __builtin_ia32_incsspq ((x))
+# define rdssp(x) __builtin_ia32_rdsspq (x)
+#else
+# define incssp(x) __builtin_ia32_incsspd ((x))
+# define rdssp(x) __builtin_ia32_rdsspd (x)
+#endif
+
+/* Unwind the shadow stack for EH.  */
+#undef _Unwind_Frames_Extra
+#define _Unwind_Frames_Extra(x)			\
+  do						\
+    {						\
+      unsigned long ssp = 0;			\
+      ssp = rdssp (ssp);			\
+      if (ssp != 0)				\
+	{					\
+	  unsigned long tmp = (x);		\
+	  while (tmp > 255)			\
+	    {					\
+	      incssp (tmp);			\
+	      tmp -= 255;			\
+	    }					\
+	  incssp (tmp);				\
+	}					\
+    }						\
+    while (0)
+
+#undef FRAMES_P_DECL
+#undef FRAMES_VAR
+#undef FRAMES_VAR_P
+#undef FRAMES_VAR_DECL
+#undef FRAMES_VAR_DECL_1
+#undef FRAMES_VAR_INC
+#undef FRAMES_P_UPDATE
+#define FRAMES_P_DECL		, unsigned long *frames_p
+#define FRAMES_VAR		frames
+#define FRAMES_VAR_P		, &frames
+#define FRAMES_VAR_DECL		unsigned long frames
+#define FRAMES_VAR_DECL_1	unsigned long frames = 1
+#define FRAMES_VAR_INC		frames++
+#define FRAMES_P_UPDATE		*frames_p = frames
diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
index 3f26eaf..7e9d26b 100644
--- a/libgcc/unwind-dw2.c
+++ b/libgcc/unwind-dw2.c
@@ -1646,12 +1646,13 @@ uw_frob_return_addr (struct _Unwind_Context *current
    macro because __builtin_eh_return must be invoked in the context of
    our caller.  */
 
-#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)
diff --git a/libgcc/unwind-generic.h b/libgcc/unwind-generic.h
index 77dd5a9..cb27587 100644
--- a/libgcc/unwind-generic.h
+++ b/libgcc/unwind-generic.h
@@ -288,4 +288,15 @@ EXCEPTION_DISPOSITION _GCC_specific_handler (PEXCEPTION_RECORD, void *,
 #pragma GCC visibility pop
 #endif
 
+#define FRAMES_P_DECL
+#define FRAMES_VAR
+#define FRAMES_VAR_P
+#define FRAMES_VAR_DECL
+#define FRAMES_VAR_DECL_1
+#define FRAMES_VAR_INC
+#define FRAMES_P_UPDATE
+
+/* Additional actions to unwind number of stack frames.  */
+#define _Unwind_Frames_Extra(frames)
+
 #endif /* unwind.h */
diff --git a/libgcc/unwind.inc b/libgcc/unwind.inc
index 658bd94..94b2d4f 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
+			      FRAMES_P_DECL)
 {
   _Unwind_Reason_Code code;
+  FRAMES_VAR_DECL_1;
 
   while (1)
     {
@@ -71,8 +73,10 @@ _Unwind_RaiseException_Phase2(struct _Unwind_Exception *exc,
       gcc_assert (!match_handler);
 
       uw_update_context (context, &fs);
+      FRAMES_VAR_INC;
     }
 
+  FRAMES_P_UPDATE;
   return code;
 }
 
@@ -83,6 +87,7 @@ _Unwind_RaiseException(struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  FRAMES_VAR_DECL;
 
   /* 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_VAR_P);
   if (code != _URC_INSTALL_CONTEXT)
     return code;
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, FRAMES_VAR);
 }
 
 
@@ -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
+			     FRAMES_P_DECL)
 {
   _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;
+  FRAMES_VAR_DECL_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_VAR_INC;
     }
 
+  FRAMES_P_UPDATE;
   return code;
 }
 
@@ -197,6 +206,7 @@ _Unwind_ForcedUnwind (struct _Unwind_Exception *exc,
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  FRAMES_VAR_DECL;
 
   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_VAR_P);
   if (code != _URC_INSTALL_CONTEXT)
     return code;
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, FRAMES_VAR);
 }
 
 
@@ -220,6 +230,7 @@ _Unwind_Resume (struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  FRAMES_VAR_DECL;
 
   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_VAR_P);
   else
-    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context);
+    code = _Unwind_ForcedUnwind_Phase2 (exc, &cur_context FRAMES_VAR_P);
 
   gcc_assert (code == _URC_INSTALL_CONTEXT);
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, FRAMES_VAR);
 }
 
 
@@ -245,6 +256,7 @@ _Unwind_Resume_or_Rethrow (struct _Unwind_Exception *exc)
 {
   struct _Unwind_Context this_context, cur_context;
   _Unwind_Reason_Code code;
+  FRAMES_VAR_DECL;
 
   /* 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_VAR_P);
 
   gcc_assert (code == _URC_INSTALL_CONTEXT);
 
-  uw_install_context (&this_context, &cur_context);
+  uw_install_context (&this_context, &cur_context, FRAMES_VAR);
 }
 
 
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 13+ messages in thread
end of thread, other threads:[~2017-11-20 11:24 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2017-10-12 20:01 [PATCH 08/22] Add Intel CET support for EH in libgcc Tsimbalist, Igor V
2017-10-12 23:59 ` Hans-Peter Nilsson
2017-10-25 17:30   ` H.J. Lu
2017-10-31  5:09 ` Jeff Law
2017-11-04 12:44   ` Tsimbalist, Igor V
2017-11-08 19:09     ` Jeff Law
2017-11-08 19:11       ` H.J. Lu
2017-11-08 22:06       ` Tsimbalist, Igor V
2017-11-13 22:16         ` Tsimbalist, Igor V
2017-11-16 19:33           ` Jeff Law
2017-11-18 15:43           ` Andreas Schwab
2017-11-19  0:10             ` Tsimbalist, Igor V
2017-11-20 11:32               ` Richard Biener

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