From 5f45c18a7fd77a1a9daf453c6dea9fceddf0184c Mon Sep 17 00:00:00 2001
From: Peter Collingbourne <pcc@google.com>
Date: Tue, 14 Jan 2020 17:59:41 -0800
Subject: Add an android_unsafe_frame_pointer_chase function.

This function will be used by Scudo and GWP-ASan to efficiently collect
stack traces for frames built with frame pointers.

Bug: 135634846
Bug: 135772972
Change-Id: Ic63efdbafe11dfbb1226b5b4b403d53c4dbf28f3
Merged-In: Ic63efdbafe11dfbb1226b5b4b403d53c4dbf28f3
---
 tests/android_unsafe_frame_pointer_chase_test.cpp | 98 +++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 tests/android_unsafe_frame_pointer_chase_test.cpp

(limited to 'tests/android_unsafe_frame_pointer_chase_test.cpp')

diff --git a/tests/android_unsafe_frame_pointer_chase_test.cpp b/tests/android_unsafe_frame_pointer_chase_test.cpp
new file mode 100644
index 000000000..dd04c3377
--- /dev/null
+++ b/tests/android_unsafe_frame_pointer_chase_test.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <gtest/gtest.h>
+
+#if defined(__BIONIC__)
+
+#include "platform/bionic/android_unsafe_frame_pointer_chase.h"
+
+// Prevent tail calls inside recurse.
+__attribute__((weak, noinline)) size_t nop(size_t val) {
+  return val;
+}
+
+// Call android_unsafe_frame_pointer_chase inside count recurse stack frames.
+__attribute__((weak, noinline)) int recurse(int count, uintptr_t* buf, size_t num_entries) {
+  if (count != 0) return nop(recurse(count - 1, buf, num_entries));
+  return nop(android_unsafe_frame_pointer_chase(buf, num_entries));
+}
+
+static constexpr size_t kNumFrames = 32;
+
+static bool CheckFrames(uintptr_t* frames, size_t num_frames) {
+  // We expect one recurse frame calling android_unsafe_frame_pointer_chase, followed by kNumFrames identical
+  // recurse frames calling themselves, followed by at least one frame (the first caller of
+  // recurse).
+  if (num_frames < kNumFrames + 2) {
+    printf("num_frames (0x%zu) < kNumFrames + 2", num_frames);
+    return false;
+  }
+
+  if (frames[0] == frames[1]) {
+    printf("frames[0] == frames[1] (0x%zx)", frames[0]);
+    return false;
+  }
+
+  for (size_t i = 2; i <= kNumFrames; ++i) {
+    if (frames[i] != frames[1]) {
+      printf("frames[i] (0x%zx) != frames[1] (0x%zx)", frames[i], frames[1]);
+      return false;
+    }
+  }
+
+  if (frames[kNumFrames] == frames[kNumFrames + 1]) {
+    printf("frames[kNumFrames] == frames[kNumFrames + 1] (0x%zx)", frames[kNumFrames]);
+    return false;
+  }
+
+  return true;
+}
+
+TEST(android_unsafe_frame_pointer_chase, main_thread) {
+  size_t size = recurse(kNumFrames, 0, 0);
+
+  uintptr_t frames[kNumFrames + 2];
+  size_t size2 = recurse(kNumFrames, frames, kNumFrames + 2);
+  EXPECT_EQ(size2, size);
+
+  EXPECT_TRUE(CheckFrames(frames, size));
+}
+
+static void *BacktraceThread(void *) {
+  size_t size = recurse(kNumFrames, 0, 0);
+
+  uintptr_t frames[kNumFrames + 2];
+  size_t size2 = recurse(kNumFrames, frames, kNumFrames + 2);
+  if (size2 != size) {
+    return (void*)"size2 != size";
+  }
+
+  if (!CheckFrames(frames, size)) {
+    return (void*)"CheckFrames failed";
+  }
+  return nullptr;
+}
+
+TEST(android_unsafe_frame_pointer_chase, pthread) {
+  pthread_t t;
+  ASSERT_EQ(0, pthread_create(&t, nullptr, BacktraceThread, nullptr));
+  void* retval;
+  ASSERT_EQ(0, pthread_join(t, &retval));
+  EXPECT_EQ(nullptr, reinterpret_cast<char*>(retval));
+}
+
+#endif // __BIONIC__
-- 
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