[PATCH, Pointer Bounds Checker 5/x] Attributes

[Ilya Enkovich <enkovich dot gnu at gmail dot com>]

Hi,

This patch introduces attributes used by Pointer Bounds Checker.  Comparing to what was approved for 4.9, this one has additional attribute 'bnd_instrument' to be used for selective instrumentation.

Bootstrapped and tested on linux-x86_64.

OK for trunk?

Thanks,
Ilya
--
gcc/

2014-04-16  Ilya Enkovich  <ilya.enkovich@intel.com>

	* c-family/c-common.c (handle_bnd_variable_size_attribute): New.
	(handle_bnd_legacy): New.
	(handle_bnd_instrument): New.
	(c_common_attribute_table): Add bnd_variable_size, bnd_legacy
	and bnd_instrument.
	* doc/extend.texi: Document bnd_variable_size, bnd_legacy and
	bnd_instrument attributes.


diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 1d56bc0..babf89a 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -379,6 +379,9 @@ static tree handle_omp_declare_simd_attribute (tree *, tree, tree, int,
 					       bool *);
 static tree handle_omp_declare_target_attribute (tree *, tree, tree, int,
 						 bool *);
+static tree handle_bnd_variable_size_attribute (tree *, tree, tree, int, bool *);
+static tree handle_bnd_legacy (tree *, tree, tree, int, bool *);
+static tree handle_bnd_instrument (tree *, tree, tree, int, bool *);
 
 static void check_function_nonnull (tree, int, tree *);
 static void check_nonnull_arg (void *, tree, unsigned HOST_WIDE_INT);
@@ -772,6 +775,12 @@ const struct attribute_spec c_common_attribute_table[] =
 			      handle_alloc_align_attribute, false },
   { "assume_aligned",	      1, 2, false, true, true,
 			      handle_assume_aligned_attribute, false },
+  { "bnd_variable_size",      0, 0, true,  false, false,
+			      handle_bnd_variable_size_attribute, false },
+  { "bnd_legacy",             0, 0, true, false, false,
+			      handle_bnd_legacy, false },
+  { "bnd_instrument",         0, 0, true, false, false,
+			      handle_bnd_instrument, false },
   { NULL,                     0, 0, false, false, false, NULL, false }
 };
 
@@ -8118,6 +8127,54 @@ handle_fnspec_attribute (tree *node ATTRIBUTE_UNUSED, tree ARG_UNUSED (name),
   return NULL_TREE;
 }
 
+/* Handle a "bnd_variable_size" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_bnd_variable_size_attribute (tree *node, tree name, tree ARG_UNUSED (args),
+				    int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FIELD_DECL)
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
+/* Handle a "bnd_legacy" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_bnd_legacy (tree *node, tree name, tree ARG_UNUSED (args),
+		   int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FUNCTION_DECL)
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
+/* Handle a "bnd_instrument" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_bnd_instrument (tree *node, tree name, tree ARG_UNUSED (args),
+		       int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FUNCTION_DECL)
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
 /* Handle a "warn_unused" attribute; arguments as in
    struct attribute_spec.handler.  */
 
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 1c74990..3c18829 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -2182,7 +2182,7 @@ attributes are currently defined for functions on all targets:
 @code{returns_nonnull}, @code{gnu_inline},
 @code{externally_visible}, @code{hot}, @code{cold}, @code{artificial},
 @code{no_sanitize_address}, @code{no_address_safety_analysis},
-@code{no_sanitize_undefined},
+@code{no_sanitize_undefined}, @code{bnd_legacy}, @code{bnd_instrument},
 @code{error} and @code{warning}.
 Several other attributes are defined for functions on particular
 target systems.  Other attributes, including @code{section} are
@@ -3684,6 +3684,18 @@ The @code{no_sanitize_undefined} attribute on functions is used
 to inform the compiler that it should not check for undefined behavior
 in the function when compiling with the @option{-fsanitize=undefined} option.
 
+@item bnd_legacy
+@cindex @code{bnd_legacy} function attribute
+The @code{bnd_legacy} attribute on functions is used to inform
+compiler that function should not be instrumented when compiled
+with @option{-fcheck-pointer-bounds} option.
+
+@item bnd_instrument
+@cindex @code{bnd_instrument} function attribute
+The @code{bnd_instrument} attribute on functions is used to inform
+compiler that function should be instrumented when compiled
+with @option{-fchkp-instrument-marked-only} option.
+
 @item regparm (@var{number})
 @cindex @code{regparm} attribute
 @cindex functions that are passed arguments in registers on the 386
@@ -5501,12 +5513,12 @@ placed in either the @code{.bss_below100} section or the
 The keyword @code{__attribute__} allows you to specify special
 attributes of @code{struct} and @code{union} types when you define
 such types.  This keyword is followed by an attribute specification
-inside double parentheses.  Seven attributes are currently defined for
+inside double parentheses.  Eight attributes are currently defined for
 types: @code{aligned}, @code{packed}, @code{transparent_union},
-@code{unused}, @code{deprecated}, @code{visibility}, and
-@code{may_alias}.  Other attributes are defined for functions
-(@pxref{Function Attributes}) and for variables (@pxref{Variable
-Attributes}).
+@code{unused}, @code{deprecated}, @code{visibility}, @code{may_alias}
+and @code{bnd_variable_size}.  Other attributes are defined for
+functions (@pxref{Function Attributes}) and for variables
+(@pxref{Variable Attributes}).
 
 You may also specify any one of these attributes with @samp{__}
 preceding and following its keyword.  This allows you to use these
@@ -5798,6 +5810,35 @@ and caught in another, the class must have default visibility.
 Otherwise the two shared objects are unable to use the same
 typeinfo node and exception handling will break.
 
+@item bnd_variable_size
+When applied to a structure field, this attribute tells Pointer
+Bounds Checker that the size of this field should not be computed
+using static type information.  It may be used to mark variable
+sized static array fields placed at the end of a structure.
+
+@smallexample
+struct S
+@{
+  int size;
+  char data[1];
+@}
+S *p = (S *)malloc (sizeof(S) + 100);
+p->data[10] = 0; //Bounds violation
+@end smallexample
+
+By using an attribute for a field we may avoid bound violation
+we most probably do not want to see:
+
+@smallexample
+struct S
+@{
+  int size;
+  char data[1] __attribute__((bnd_variable_size));
+@}
+S *p = (S *)malloc (sizeof(S) + 100);
+p->data[10] = 0; //OK
+@end smallexample
+
 @end table
 
 To specify multiple attributes, separate them by commas within the