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

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

> -----Original Message-----
> From: Jeff Law [mailto:law@redhat.com]
> Sent: Friday, September 29, 2017 12:44 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 09/19/2017 07:39 AM, Tsimbalist, Igor V wrote:
> > Here is an updated patch (version #2). The main differences are:
> >
> > - Change attribute and option names;
> > - Add additional parameter to gimple_build_call_from_tree by adding a
> type parameter and
> >   use it 'nocf_check' attribute propagation;
> > - Reimplement fixes in expand_call_stmt to propagate 'nocf_check'
> > attribute;
> > - Consider 'nocf_check' attribute in Identical Code Folding (ICF)
> > optimization;
> > - Add warning for type inconsistency regarding 'nocf_check' attribute;
> > - Many small fixes;
> >
> > gcc/c-family/
> > 	* c-attribs.c (handle_nocf_check_attribute): New function.
> > 	(c_common_attribute_table): Add 'nocf_check' handling.
> > 	* c-common.c (check_missing_format_attribute): New function.
> > 	* c-common.h: Likewise.
> >
> > gcc/c/
> > 	* c-typeck.c (convert_for_assignment): Add check for nocf_check
> > 	attribute.
> > 	* gimple-parser.c: Add second argument NULL to
> > 	gimple_build_call_from_tree.
> >
> > gcc/cp/
> > 	* typeck.c (convert_for_assignment): Add check for nocf_check
> > 	attribute.
> >
> > gcc/
> > 	* 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_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.
> >
> > Is it ok for trunk?
> >
> > Thanks,
> > Igor
> >
> >
> 
> 
> >
> > diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c index
> > 0337537..77d1909 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, false },
> >    { NULL,                     0, 0, false, false, false, NULL, false }
> >  };
> >
> > @@ -783,6 +786,26 @@ 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
> > +      && TREE_CODE (*node) != FIELD_DECL
> > +      && TREE_CODE (*node) != TYPE_DECL)
> So curious, is this needed for FIELD_DECL and TYPE_DECL?  ISTM the attribute
> is applied to function/method types.
> 
> If we do need to handle FIELD_DECL and TYPE_DECL here, can you add a
> quick comment why?

You are right. Probably it was left from the attribute transition from decl to type.
I removed these two lines. All CET tests passed.

> > diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c index
> > b3ec3a0..78a730e 100644
> > --- a/gcc/c-family/c-common.c
> > +++ b/gcc/c-family/c-common.c
> > @@ -7253,6 +7253,26 @@ check_missing_format_attribute (tree ltype,
> tree rtype)
> >      return false;
> >  }
> >
> > +/* Check for missing nocf_check attributes on function pointers.  LTYPE is
> > +   the new type or left-hand side type.  RTYPE is the old type or
> > +   right-hand side type.  Returns TRUE if LTYPE is missing the desired
> > +   attribute.  */
> > +
> > +bool
> > +check_missing_nocf_check_attribute (tree ltype, tree rtype) {
> > +  tree const ttr = TREE_TYPE (rtype), ttl = TREE_TYPE (ltype);
> > +  tree ra, la;
> > +
> > +  for (ra = TYPE_ATTRIBUTES (ttr); ra; ra = TREE_CHAIN (ra))
> > +    if (is_attribute_p ("nocf_check", TREE_PURPOSE (ra)))
> > +      break;
> > +  for (la = TYPE_ATTRIBUTES (ttl); la; la = TREE_CHAIN (la))
> > +    if (is_attribute_p ("nocf_check", TREE_PURPOSE (la)))
> > +      break;
> > +  return la != ra;
> ?  ISTM the only time la == ra here is when they're both NULL.  Aren't the
> TYPE_ATTRIBUTE chain members unique and thus pointer equality isn't the
> right check?
> 
> Shouldn't you be looking at the TREE_PURPOSE of ra and la and comparing
> those?

It looks I was lucky :). I see the point and re-wrote the return statement as

   if ((la && ra)		/* Both types have the attribute.  */
       || (la == ra))	/* Both types do not have the attribute.  */
     return false;
   else
     return true;		/* One of the types has the attribute.  */ 

Igor

> Not accepting or rejecting at this point as I could mis-understand how how
> this is supposed to work in my two comments above.
> 
> jeff
> 
> 
>