On 5/20/21 10:45 AM, Marco Elver wrote:
On Thu, 20 May 2021 at 10:33, Martin Liška <mli...@suse.cz> wrote:
Hello.

The patch implements one missing attribute which can be used for per-function
disabling of coverage sanitization.

Patch can bootstrap on x86_64-linux-gnu and survives regression tests.

Thanks for implementing this so quickly. One thing I just have to
double check, is if this works with always_inline (not instrumented if
inlined into no_sanitize),

No, in this case it's instrumented (if caller has not set the attribute).

and inline (not inlined if inline fn is
no_sanitize_coverage).

No again, it's not blocking inlining.

Just like the other no_sanitize* do. The test doesn't mention them.

It's aligned with similar issue that was discussed some time ago:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94722#c9

Martin


Thanks,
-- Marco

Ready to be installed?
Thanks,
Martin

gcc/ChangeLog:

         * asan.h (sanitize_coverage_p): New function.
         * doc/extend.texi: Document it.
         * fold-const.c (fold_range_test): Use sanitize_flags_p
         instead of flag_sanitize_coverage.
         (fold_truth_andor): Likewise.
         * sancov.c: Likewise.
         * tree-ssa-ifcombine.c (ifcombine_ifandif): Likewise.

gcc/c-family/ChangeLog:

         * c-attribs.c (handle_no_sanitize_coverage_attribute): New.

gcc/testsuite/ChangeLog:

         * gcc.dg/sancov/attribute.c: New test.
---
   gcc/asan.h                              | 10 ++++++++++
   gcc/c-family/c-attribs.c                | 20 ++++++++++++++++++++
   gcc/doc/extend.texi                     |  6 ++++++
   gcc/fold-const.c                        |  4 ++--
   gcc/sancov.c                            |  4 ++--
   gcc/testsuite/gcc.dg/sancov/attribute.c | 15 +++++++++++++++
   gcc/tree-ssa-ifcombine.c                |  4 +++-
   7 files changed, 58 insertions(+), 5 deletions(-)
   create mode 100644 gcc/testsuite/gcc.dg/sancov/attribute.c

diff --git a/gcc/asan.h b/gcc/asan.h
index f110f1db563..8c0b2baf170 100644
--- a/gcc/asan.h
+++ b/gcc/asan.h
@@ -249,4 +249,14 @@ sanitize_flags_p (unsigned int flag, const_tree fn = 
current_function_decl)
     return result_flags;
   }

+/* Return true when coverage sanitization should happend for FN function.  */
+
+static inline bool
+sanitize_coverage_p (const_tree fn = current_function_decl)
+{
+  return (flag_sanitize_coverage
+         && lookup_attribute ("no_sanitize_coverage",
+                              DECL_ATTRIBUTES (fn)) == NULL_TREE);
+}
+
   #endif /* TREE_ASAN */
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index ccf9e4ccf0b..671b27c3200 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -62,6 +62,8 @@ static tree handle_no_address_safety_analysis_attribute (tree 
*, tree, tree,
                                                          int, bool *);
   static tree handle_no_sanitize_undefined_attribute (tree *, tree, tree, int,
                                                     bool *);
+static tree handle_no_sanitize_coverage_attribute (tree *, tree, tree, int,
+                                                  bool *);
   static tree handle_asan_odr_indicator_attribute (tree *, tree, tree, int,
                                                  bool *);
   static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
@@ -449,6 +451,8 @@ const struct attribute_spec c_common_attribute_table[] =
                               handle_no_sanitize_thread_attribute, NULL },
     { "no_sanitize_undefined",  0, 0, true, false, false, false,
                               handle_no_sanitize_undefined_attribute, NULL },
+  { "no_sanitize_coverage",   0, 0, true, false, false, false,
+                             handle_no_sanitize_coverage_attribute, NULL },
     { "asan odr indicator",     0, 0, true, false, false, false,
                               handle_asan_odr_indicator_attribute, NULL },
     { "warning",                      1, 1, true,  false, false, false,
@@ -1211,6 +1215,22 @@ handle_no_sanitize_undefined_attribute (tree *node, tree 
name, tree, int,
     return NULL_TREE;
   }

+/* Handle a "no_sanitize_coverage" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_no_sanitize_coverage_attribute (tree *node, tree name, tree, int,
+                                      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 an "asan odr indicator" attribute; arguments as in
      struct attribute_spec.handler.  */

diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index 826804e6149..3ddeb0dee3a 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -3415,6 +3415,12 @@ 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 no_sanitize_coverage
+@cindex @code{no_sanitize_coverage} function attribute
+The @code{no_sanitize_coverage} attribute on functions is used
+to inform the compiler that it should not do coverage-guided
+fuzzing code instrumentation (@option{-fsanitize-coverage}).
+
   @item no_split_stack
   @cindex @code{no_split_stack} function attribute
   @opindex fsplit-stack
diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 3be9c15e6b2..d088187a057 100644
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -6016,7 +6016,7 @@ fold_range_test (location_t loc, enum tree_code code, 
tree type,
       logical_op_non_short_circuit
         = param_logical_op_non_short_circuit;
     if (logical_op_non_short_circuit
-      && !flag_sanitize_coverage
+      && !sanitize_coverage_p ()
         && lhs != 0 && rhs != 0
         && (code == TRUTH_ANDIF_EXPR || code == TRUTH_ORIF_EXPR)
         && operand_equal_p (lhs, rhs, 0))
@@ -9652,7 +9652,7 @@ fold_truth_andor (location_t loc, enum tree_code code, 
tree type,
       logical_op_non_short_circuit
         = param_logical_op_non_short_circuit;
     if (logical_op_non_short_circuit
-      && !flag_sanitize_coverage
+      && !sanitize_coverage_p ()
         && (code == TRUTH_AND_EXPR
             || code == TRUTH_ANDIF_EXPR
             || code == TRUTH_OR_EXPR
diff --git a/gcc/sancov.c b/gcc/sancov.c
index d656c37cae9..9cfbd425def 100644
--- a/gcc/sancov.c
+++ b/gcc/sancov.c
@@ -313,9 +313,9 @@ public:
       return new pass_sancov<O0> (m_ctxt);
     }
     virtual bool
-  gate (function *)
+  gate (function *fun)
     {
-    return flag_sanitize_coverage && (!O0 || !optimize);
+    return sanitize_coverage_p (fun->decl) && (!O0 || !optimize);
     }
     virtual unsigned int
     execute (function *fun)
diff --git a/gcc/testsuite/gcc.dg/sancov/attribute.c 
b/gcc/testsuite/gcc.dg/sancov/attribute.c
new file mode 100644
index 00000000000..bf6dbd4bae7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/sancov/attribute.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-fsanitize-coverage=trace-pc -fdump-tree-optimized" } */
+
+void foo(void)
+{
+}
+
+void
+__attribute__((no_sanitize_coverage))
+bar(void)
+{
+}
+
+
+/* { dg-final { scan-tree-dump-times "__builtin___sanitizer_cov_trace_pc \\(\\)" 1 
"optimized" } } */
diff --git a/gcc/tree-ssa-ifcombine.c b/gcc/tree-ssa-ifcombine.c
index 836a12d6b80..f93e04aa4df 100644
--- a/gcc/tree-ssa-ifcombine.c
+++ b/gcc/tree-ssa-ifcombine.c
@@ -40,6 +40,8 @@ along with GCC; see the file COPYING3.  If not see
   #include "gimplify-me.h"
   #include "tree-cfg.h"
   #include "tree-ssa.h"
+#include "attribs.h"
+#include "asan.h"

   #ifndef LOGICAL_OP_NON_SHORT_CIRCUIT
   #define LOGICAL_OP_NON_SHORT_CIRCUIT \
@@ -567,7 +569,7 @@ ifcombine_ifandif (basic_block inner_cond_bb, bool 
inner_inv,
           if (param_logical_op_non_short_circuit != -1)
             logical_op_non_short_circuit
               = param_logical_op_non_short_circuit;
-         if (!logical_op_non_short_circuit || flag_sanitize_coverage)
+         if (!logical_op_non_short_circuit || sanitize_coverage_p ())
             return false;
           /* Only do this optimization if the inner bb contains only the 
conditional. */
           if (!gsi_one_before_end_p (gsi_start_nondebug_after_labels_bb 
(inner_cond_bb)))
--
2.31.1


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