Kernel dso support for 'dl_iterate_phdr' function

Kernel provides virtual DSO for stack unwinding/exception handlind info for
signal usage case. Stack unwinding routines use 'dl_iterate_phdr' function
for additional DWARF info gathering from DSOs. Patch enables virtual DSO
enumeration via dl_iterate_phdr function.

Signed-off-by: Sergey Melnikov <sergey.melnikov@intel.com>
Change-Id: Ic2882b28f40b456a088bc1e63c50cbfda7e4a102

tests/stack_unwinding_test_impl.c

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Contributed by: Intel Corporation
+ */
+
+#include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unwind.h>
+
+#define noinline __attribute__((__noinline__))
+#define unused __attribute__((__unused__))
+
+static noinline _Unwind_Reason_Code stop_fn(int a unused,
+    _Unwind_Action action,
+    _Unwind_Exception_Class b unused, struct _Unwind_Exception* c unused,
+    struct _Unwind_Context* d unused, void* e unused) {
+  if ((action & _UA_END_OF_STACK) != 0) {
+    // We reached the end of the stack without executing foo_cleanup. Test failed.
+    abort();
+  }
+  return _URC_NO_REASON;
+}
+
+static void noinline foo_cleanup(char* param unused) {
+  exit(42);
+}
+
+static void noinline do_crash() {
+  char* ptr = NULL;
+  *ptr = 0; // Deliberately cause a SIGSEGV.
+}
+
+static void noinline foo() {
+  char c1 __attribute__((cleanup(foo_cleanup)));
+  do_crash();
+}
+
+// It's SEGSEGV handler. We start forced stack unwinding here.
+// If libgcc don't find dso for signal frame stack unwinding will be finished.
+// libgcc pass to stop_fn _UA_END_OF_STACK flag.
+// Test pass condition: stack unwinding through signal frame and foo1_handler execution.
+static void noinline sigsegv_handler(int param unused) {
+  struct _Unwind_Exception* exception = (struct _Unwind_Exception*) malloc(sizeof(*exception));
+  memset(&exception->exception_class, 0, sizeof(exception->exception_class));
+  exception->exception_cleanup = 0;
+  _Unwind_ForcedUnwind(exception, stop_fn, 0);
+}
+
+void do_test() {
+  signal(SIGSEGV, &sigsegv_handler);
+  foo();
+}