RE: 0001-Part-1.-Add-generic-part-for-Intel-CET-enabling

["Tsimbalist, Igor V" <igor.v.tsimbalist@intel.com>]

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> Seems reasonable.  As a result something like
> check_missing_nocf_check_attribute is going to just go away along with the
> code in *-typeck.c which called it, right?  If so that seems like a nice cleanup.
Yes, you are right.

Updated patch is attached.

Igor

> -----Original Message-----
> From: gcc-patches-owner@gcc.gnu.org [mailto:gcc-patches-
> owner@gcc.gnu.org] On Behalf Of Jeff Law
> Sent: Thursday, October 12, 2017 8:07 AM
> To: Tsimbalist, Igor V <igor.v.tsimbalist@intel.com>; gcc-
> patches@gcc.gnu.org
> Cc: richard.guenther@gmail.com
> Subject: Re: 0001-Part-1.-Add-generic-part-for-Intel-CET-enabling
> 
> On 10/05/2017 04:20 AM, Tsimbalist, Igor V wrote:
> > I would like to implement the patch in a bit different way depending
> > on answers I will get for my following proposals:
> >
> > - I propose to make a type with 'nocf_check' attribute to be different from
> type w/o the attribute.
> >    The reason is that the type with 'nocf_check' attribute implies different
> code generation. It will be
> >    done by setting affects_type_identity field to true for the attribute. That
> in turn will trigger
> >    needed or expected type checking;
> Seems reasonable.  As a result something like
> check_missing_nocf_check_attribute is going to just go away along with the
> code in *-typeck.c which called it, right?  If so that seems like a nice cleanup.
> 
> 
> >
> > - I propose to ignore the 'nocf_check' attribute if 'fcf-protection' option is
> not specified and output
> >    the warning about this. If there is no instrumentation the type with
> attribute should not be treated
> >    differently from type w/o the attribute (see previous item) and should
> not be recorded into the
> >    type.
> Seems reasonable.
> >
> > If it's ok, please ignore my previous patch (version#3) and I will post the
> updated patch shortly.
> OK.  FWIW, I think we're ready to ACK on this.  So get it posted :-)
> 
> jeff

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From ecebc52923cddad06a2d9934996545193582bb4f Mon Sep 17 00:00:00 2001
From: Igor Tsimbalist <igor.v.tsimbalist@intel.com>
Date: Mon, 3 Jul 2017 17:11:58 +0300
Subject: [PATCH 1/6] Add generic part for Intel CET enabling: fcf-protection,
 nocf_check

The spec is available at

https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-enforcement-technology-preview.pdf

High-level design.
------------------

A proposal is to introduce a target independent flag
-fcf-protection=[none|branch|return|full] with a semantic to
instrument a code to control validness or integrity of control-flow
transfers using jump and call instructions. The main goal is to detect
and block a possible malware execution through transfer the execution
to unknown target address. Implementation could be either software or
target based. Any target platforms can provide their implementation
for instrumentation under this option.

When the -fcf-protection flag is set each implementation has
to check if a support exists for a target platform and report an error
if no support is found.

The compiler should instrument any control-flow transfer points in a
program (ex. call/jmp/ret) as well as any landing pads, which are
targets of control-flow transfers.

A new 'nocf_check' attribute is introduced to provide hand tuning
support. The attribute directs the compiler to skip a call to a
function and a function's landing pad from instrumentation. The
attribute can be used for function and pointer to function types,
otherwise it will be ignored. The attribute is saved in a type and
propagated to a GIMPLE call statement and later to a call instruction.

Currently all platforms except i386 will report the error and do no
instrumentation. i386 will provide the implementation based on a
specification published by Intel for a new technology called
Control-flow Enforcement Technology (CET).

gcc/c-family/
	* c-attribs.c (handle_nocf_check_attribute): New function.
	(c_common_attribute_table): Add 'nocf_check' handling.

gcc/c/
	* gimple-parser.c: Add second argument NULL to
	gimple_build_call_from_tree.

gcc/
	* attrib.c (comp_type_attributes): Check nocf_check attribute.
	* cfgexpand.c (expand_call_stmt): Set REG_CALL_NOCF_CHECK for
	call insn.
	* combine.c (distribute_notes): Add REG_CALL_NOCF_CHECK handling.
	* common.opt: Add fcf-protection flag.
	* emit-rtl.c (try_split): Add REG_CALL_NOCF_CHECK handling.
	* flag-types.h: Add enum cf_protection_level.
	* gimple.c (gimple_build_call_from_tree): Add second parameter.
	Add 'nocf_check' attribute propagation to gimple call.
	* gimple.h (gf_mask): Add GF_CALL_NOCF_CHECK.
	(gimple_build_call_from_tree): Update prototype.
	(gimple_call_nocf_check_p): New function.
	(gimple_call_set_nocf_check): Likewise.
	* gimplify.c: Add second argument to gimple_build_call_from_tree.
	* ipa-icf.c: Add nocf_check attribute in statement hash.
	* recog.c (peep2_attempt): Add REG_CALL_NOCF_CHECK handling.
	* reg-notes.def: Add REG_NOTE (CALL_NOCF_CHECK).
	* toplev.c (process_options): Add flag_cf_protection handling.
---
 gcc/attribs.c            |  3 +++
 gcc/c-family/c-attribs.c | 27 +++++++++++++++++++++++++++
 gcc/c/gimple-parser.c    |  4 ++--
 gcc/cfgexpand.c          | 16 ++++++++++++++++
 gcc/combine.c            |  1 +
 gcc/common.opt           | 23 +++++++++++++++++++++++
 gcc/emit-rtl.c           |  1 +
 gcc/flag-types.h         |  9 +++++++++
 gcc/gimple.c             | 19 ++++++++++++++++++-
 gcc/gimple.h             | 22 +++++++++++++++++++++-
 gcc/gimplify.c           |  6 ++----
 gcc/ipa-icf.c            |  6 ++++++
 gcc/recog.c              |  1 +
 gcc/reg-notes.def        |  7 +++++++
 gcc/toplev.c             | 26 ++++++++++++++++++++++++++
 15 files changed, 163 insertions(+), 8 deletions(-)

diff --git a/gcc/attribs.c b/gcc/attribs.c
index 4ef35b8..ed76a8d 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -1182,6 +1182,9 @@ comp_type_attributes (const_tree type1, const_tree type2)
     }
   if (lookup_attribute ("transaction_safe", CONST_CAST_TREE (a)))
     return 0;
+  if ((lookup_attribute ("nocf_check", TYPE_ATTRIBUTES (type1)) != NULL)
+      ^ (lookup_attribute ("nocf_check", TYPE_ATTRIBUTES (type2)) != NULL))
+    return 0;
   /* As some type combinations - like default calling-convention - might
      be compatible, we have to call the target hook to get the final result.  */
   return targetm.comp_type_attributes (type1, type2);
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index 0337537..4f6597a 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -65,6 +65,7 @@ static tree handle_asan_odr_indicator_attribute (tree *, tree, tree, int,
 static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noinline_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noclone_attribute (tree *, tree, tree, int, bool *);
+static tree handle_nocf_check_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noicf_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noipa_attribute (tree *, tree, tree, int, bool *);
 static tree handle_leaf_attribute (tree *, tree, tree, int, bool *);
@@ -367,6 +368,8 @@ const struct attribute_spec c_common_attribute_table[] =
   { "patchable_function_entry",	1, 2, true, false, false,
 			      handle_patchable_function_entry_attribute,
 			      false },
+  { "nocf_check",		      0, 0, false, true, true,
+			      handle_nocf_check_attribute, true },
   { NULL,                     0, 0, false, false, false, NULL, false }
 };
 
@@ -783,6 +786,30 @@ handle_noclone_attribute (tree *node, tree name,
   return NULL_TREE;
 }
 
+/* Handle a "nocf_check" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_nocf_check_attribute (tree *node, tree name,
+			  tree ARG_UNUSED (args),
+			  int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FUNCTION_TYPE
+      && TREE_CODE (*node) != METHOD_TYPE)
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+  else if (!(flag_cf_protection & CF_BRANCH))
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored. Use "
+				"-fcf-protection option to enable it", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
 /* Handle a "no_icf" attribute; arguments as in
    struct attribute_spec.handler.  */
 
diff --git a/gcc/c/gimple-parser.c b/gcc/c/gimple-parser.c
index 22f58f4..c2e31df 100644
--- a/gcc/c/gimple-parser.c
+++ b/gcc/c/gimple-parser.c
@@ -276,7 +276,7 @@ c_parser_gimple_statement (c_parser *parser, gimple_seq *seq)
       && TREE_CODE (lhs.value) == CALL_EXPR)
     {
       gimple *call;
-      call = gimple_build_call_from_tree (lhs.value);
+      call = gimple_build_call_from_tree (lhs.value, NULL);
       gimple_seq_add_stmt (seq, call);
       gimple_set_location (call, loc);
       return;
@@ -407,7 +407,7 @@ c_parser_gimple_statement (c_parser *parser, gimple_seq *seq)
       rhs = c_parser_gimple_unary_expression (parser);
       if (rhs.value != error_mark_node)
 	{
-	  gimple *call = gimple_build_call_from_tree (rhs.value);
+	  gimple *call = gimple_build_call_from_tree (rhs.value, NULL);
 	  gimple_call_set_lhs (call, lhs.value);
 	  gimple_seq_add_stmt (seq, call);
 	  gimple_set_location (call, loc);
diff --git a/gcc/cfgexpand.c b/gcc/cfgexpand.c
index 7657a65..3bcaa4c 100644
--- a/gcc/cfgexpand.c
+++ b/gcc/cfgexpand.c
@@ -2659,12 +2659,28 @@ expand_call_stmt (gcall *stmt)
 	  }
     }
 
+  rtx_insn *before_call = get_last_insn ();
   lhs = gimple_call_lhs (stmt);
   if (lhs)
     expand_assignment (lhs, exp, false);
   else
     expand_expr (exp, const0_rtx, VOIDmode, EXPAND_NORMAL);
 
+  /* If the gimple call is an indirect call and has 'nocf_check'
+     attribute find a generated CALL insn to mark it as no
+     control-flow verification is needed.  */
+  if (gimple_call_nocf_check_p (stmt)
+      && !gimple_call_fndecl (stmt))
+    {
+      rtx_insn *last = get_last_insn ();
+      while (!CALL_P (last)
+	     && last != before_call)
+	last = PREV_INSN (last);
+
+      if (last != before_call)
+	add_reg_note (last, REG_CALL_NOCF_CHECK, const0_rtx);
+    }
+
   mark_transaction_restart_calls (stmt);
 }
 
diff --git a/gcc/combine.c b/gcc/combine.c
index 1832c3c..e0315fd 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -14151,6 +14151,7 @@ distribute_notes (rtx notes, rtx_insn *from_insn, rtx_insn *i3, rtx_insn *i2,
 	case REG_SETJMP:
 	case REG_TM:
 	case REG_CALL_DECL:
+	case REG_CALL_NOCF_CHECK:
 	  /* These notes must remain with the call.  It should not be
 	     possible for both I2 and I3 to be a call.  */
 	  if (CALL_P (i3))
diff --git a/gcc/common.opt b/gcc/common.opt
index 1581ca8..b06bede 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1608,6 +1608,29 @@ finline-atomics
 Common Report Var(flag_inline_atomics) Init(1) Optimization
 Inline __atomic operations when a lock free instruction sequence is available.
 
+fcf-protection
+Common RejectNegative Alias(fcf-protection=,full)
+
+fcf-protection=
+Common Report Joined RejectNegative Enum(cf_protection_level) Var(flag_cf_protection) Init(CF_NONE)
+-fcf-protection=[full|branch|return|none]	Instrument functions with checks to verify jump/call/return control-flow transfer
+instructions have valid targets.
+
+Enum
+Name(cf_protection_level) Type(enum cf_protection_level) UnknownError(unknown Cotrol-Flow Protection Level %qs)
+
+EnumValue
+Enum(cf_protection_level) String(full) Value(CF_FULL)
+
+EnumValue
+Enum(cf_protection_level) String(branch) Value(CF_BRANCH)
+
+EnumValue
+Enum(cf_protection_level) String(return) Value(CF_RETURN)
+
+EnumValue
+Enum(cf_protection_level) String(none) Value(CF_NONE)
+
 finstrument-functions
 Common Report Var(flag_instrument_function_entry_exit)
 Instrument function entry and exit with profiling calls.
diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index e36a7dd..b68729a 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -3791,6 +3791,7 @@ try_split (rtx pat, rtx_insn *trial, int last)
 	case REG_NORETURN:
 	case REG_SETJMP:
 	case REG_TM:
+	case REG_CALL_NOCF_CHECK:
 	  for (insn = insn_last; insn != NULL_RTX; insn = PREV_INSN (insn))
 	    {
 	      if (CALL_P (insn))
diff --git a/gcc/flag-types.h b/gcc/flag-types.h
index 4938f69..c0db3c9 100644
--- a/gcc/flag-types.h
+++ b/gcc/flag-types.h
@@ -318,4 +318,13 @@ enum gfc_convert
 };
 
 
+/* Control-Flow Protection values.  */
+enum cf_protection_level
+{
+  CF_NONE = 0,
+  CF_BRANCH = 1 << 0,
+  CF_RETURN = 1 << 1,
+  CF_FULL = CF_BRANCH | CF_RETURN,
+  CF_SET = 1 << 2
+};
 #endif /* ! GCC_FLAG_TYPES_H */
diff --git a/gcc/gimple.c b/gcc/gimple.c
index c4e6f81..b01aec5 100644
--- a/gcc/gimple.c
+++ b/gcc/gimple.c
@@ -346,7 +346,7 @@ gimple_build_call_internal_vec (enum internal_fn fn, vec<tree> args)
    this fact.  */
 
 gcall *
-gimple_build_call_from_tree (tree t)
+gimple_build_call_from_tree (tree t, tree fnptrtype)
 {
   unsigned i, nargs;
   gcall *call;
@@ -380,6 +380,23 @@ gimple_build_call_from_tree (tree t)
   gimple_set_no_warning (call, TREE_NO_WARNING (t));
   gimple_call_set_with_bounds (call, CALL_WITH_BOUNDS_P (t));
 
+  if (fnptrtype)
+    {
+      gimple_call_set_fntype (call, TREE_TYPE (fnptrtype));
+
+      /* Check if it's an indirect CALL and the type has the
+ 	 nocf_check attribute. In that case propagate the information
+	 to the gimple CALL insn.  */
+      if (!fndecl)
+	{
+	  gcc_assert (POINTER_TYPE_P (fnptrtype));
+	  tree fntype = TREE_TYPE (fnptrtype);
+
+	  if (lookup_attribute ("nocf_check", TYPE_ATTRIBUTES (fntype)))
+	    gimple_call_set_nocf_check (call, TRUE);
+	}
+    }
+
   return call;
 }
 
diff --git a/gcc/gimple.h b/gcc/gimple.h
index 6213c49..334def8 100644
--- a/gcc/gimple.h
+++ b/gcc/gimple.h
@@ -148,6 +148,7 @@ enum gf_mask {
     GF_CALL_WITH_BOUNDS 	= 1 << 8,
     GF_CALL_MUST_TAIL_CALL	= 1 << 9,
     GF_CALL_BY_DESCRIPTOR	= 1 << 10,
+    GF_CALL_NOCF_CHECK		= 1 << 11,
     GF_OMP_PARALLEL_COMBINED	= 1 << 0,
     GF_OMP_PARALLEL_GRID_PHONY = 1 << 1,
     GF_OMP_TASK_TASKLOOP	= 1 << 0,
@@ -1425,7 +1426,7 @@ gcall *gimple_build_call (tree, unsigned, ...);
 gcall *gimple_build_call_valist (tree, unsigned, va_list);
 gcall *gimple_build_call_internal (enum internal_fn, unsigned, ...);
 gcall *gimple_build_call_internal_vec (enum internal_fn, vec<tree> );
-gcall *gimple_build_call_from_tree (tree);
+gcall *gimple_build_call_from_tree (tree, tree);
 gassign *gimple_build_assign (tree, tree CXX_MEM_STAT_INFO);
 gassign *gimple_build_assign (tree, enum tree_code,
 			      tree, tree, tree CXX_MEM_STAT_INFO);
@@ -2893,6 +2894,25 @@ gimple_call_set_with_bounds (gimple *gs, bool with_bounds)
 }
 
 
+/* Return true if call GS is marked as nocf_check.  */
+
+static inline bool
+gimple_call_nocf_check_p (const gcall *gs)
+{
+  return (gs->subcode & GF_CALL_NOCF_CHECK) != 0;
+}
+
+/* Mark statement GS as nocf_check call.  */
+
+static inline void
+gimple_call_set_nocf_check (gcall *gs, bool nocf_check)
+{
+  if (nocf_check)
+    gs->subcode |= GF_CALL_NOCF_CHECK;
+  else
+    gs->subcode &= ~GF_CALL_NOCF_CHECK;
+}
+
 /* Return the target of internal call GS.  */
 
 static inline enum internal_fn
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index 8b29a71..7d55625 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -3379,8 +3379,7 @@ gimplify_call_expr (tree *expr_p, gimple_seq *pre_p, bool want_value)
       /* The CALL_EXPR in *EXPR_P is already in GIMPLE form, so all we
 	 have to do is replicate it as a GIMPLE_CALL tuple.  */
       gimple_stmt_iterator gsi;
-      call = gimple_build_call_from_tree (*expr_p);
-      gimple_call_set_fntype (call, TREE_TYPE (fnptrtype));
+      call = gimple_build_call_from_tree (*expr_p, fnptrtype);
       notice_special_calls (call);
       if (EXPR_CILK_SPAWN (*expr_p))
         gimplify_cilk_detach (pre_p);
@@ -5656,8 +5655,7 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
 						    CALL_EXPR_ARG (*from_p, 2));
 	  else
 	    {
-	      call_stmt = gimple_build_call_from_tree (*from_p);
-	      gimple_call_set_fntype (call_stmt, TREE_TYPE (fnptrtype));
+	      call_stmt = gimple_build_call_from_tree (*from_p, fnptrtype);
 	    }
 	}
       notice_special_calls (call_stmt);
diff --git a/gcc/ipa-icf.c b/gcc/ipa-icf.c
index 4d152ce..e666d5a 100644
--- a/gcc/ipa-icf.c
+++ b/gcc/ipa-icf.c
@@ -1422,6 +1422,7 @@ sem_function::init (void)
 	      }
 	  }
 
+	hstate.commit_flag ();
 	gcode_hash = hstate.end ();
 	bb_sizes.safe_push (nondbg_stmt_count);
 
@@ -1644,6 +1645,11 @@ sem_function::hash_stmt (gimple *stmt, inchash::hash &hstate)
 	  if (gimple_op (stmt, i))
 	    add_type (TREE_TYPE (gimple_op (stmt, i)), hstate);
 	}
+      /* Consider nocf_check attribute in hash as it affects code
+ 	 generation.  */
+      if (code == GIMPLE_CALL
+	  && flag_cf_protection & CF_BRANCH)
+	hstate.add_flag (gimple_call_nocf_check_p (as_a <gcall *> (stmt)));
     default:
       break;
     }
diff --git a/gcc/recog.c b/gcc/recog.c
index 78c26d6..ec51cd4 100644
--- a/gcc/recog.c
+++ b/gcc/recog.c
@@ -3382,6 +3382,7 @@ peep2_attempt (basic_block bb, rtx_insn *insn, int match_len, rtx_insn *attempt)
 	  case REG_NORETURN:
 	  case REG_SETJMP:
 	  case REG_TM:
+	  case REG_CALL_NOCF_CHECK:
 	    add_reg_note (new_insn, REG_NOTE_KIND (note),
 			  XEXP (note, 0));
 	    break;
diff --git a/gcc/reg-notes.def b/gcc/reg-notes.def
index 943eff4..cc456a6 100644
--- a/gcc/reg-notes.def
+++ b/gcc/reg-notes.def
@@ -228,3 +228,10 @@ REG_NOTE (RETURNED)
    The decl might not be available in the call due to splitting of the call
    insn.  This note is a SYMBOL_REF.  */
 REG_NOTE (CALL_DECL)
+
+/* Indicate that a call should not be verified for control-flow consistency.
+   The target address of the call is assumed as a valid address and no check
+   to validate a branch to the target address is needed.  The call is marked
+   when a called function has a 'notrack' attribute.  This note is used by the
+   compiler when the option -fcf-protection=branch is specified.  */
+REG_NOTE (CALL_NOCF_CHECK)
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 7d2b8ff..3cb1124 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -1297,6 +1297,32 @@ process_options (void)
 	   "-floop-parallelize-all)");
 #endif
 
+  if (flag_cf_protection != CF_NONE
+      && !(flag_cf_protection & CF_SET))
+    {
+      if (flag_cf_protection == CF_FULL)
+	{
+	  error_at (UNKNOWN_LOCATION,
+		    "%<-fcf-protection=full%> is not supported for this "
+		    "target");
+	  flag_cf_protection = CF_NONE;
+	}
+      if (flag_cf_protection == CF_BRANCH)
+	{
+	  error_at (UNKNOWN_LOCATION,
+		    "%<-fcf-protection=branch%> is not supported for this "
+		    "target");
+	  flag_cf_protection = CF_NONE;
+	}
+      if (flag_cf_protection == CF_RETURN)
+	{
+	  error_at (UNKNOWN_LOCATION,
+		    "%<-fcf-protection=return%> is not supported for this "
+		    "target");
+	  flag_cf_protection = CF_NONE;
+	}
+    }
+
   if (flag_check_pointer_bounds)
     {
       if (targetm.chkp_bound_mode () == VOIDmode)
-- 
1.8.3.1