libmemunreachable: track kernel binder references

The kernel can hold references to binder objects that have no userspace
references.  Allow libmemunreachable to call into libbinder and
libhwbinder to get lists of kernel references.  Use undefined weak
symbols so that libmemunreachable will continue to work in processes
that do not have libbinder.

Test: memunreachable_binder_test
Bug: 28275695
Change-Id: I9eae73f2a51a49a7025ffe6309ccdc2693a2391b

5 files changed, 294 insertions, 3 deletions

diff --git a/libmemunreachable/Android.bp b/libmemunreachable/Android.bp
index cdac76bab..826a576e6 100644
--- a/libmemunreachable/Android.bp
+++ b/libmemunreachable/Android.bp
@@ -26,6 +26,7 @@ cc_library_shared {
     defaults: ["libmemunreachable_defaults"],
     srcs: [
         "Allocator.cpp",
+        "Binder.cpp",
         "HeapWalker.cpp",
         "LeakFolding.cpp",
         "LeakPipe.cpp",
@@ -84,3 +85,18 @@ cc_test {
         },
     },
 }
+
+cc_test {
+    name: "memunreachable_binder_test",
+    defaults: ["libmemunreachable_defaults"],
+    srcs: [
+        "tests/Binder_test.cpp",
+        "tests/MemUnreachable_test.cpp",
+    ],
+    shared_libs: [
+        "libbinder",
+        "libhwbinder",
+        "libmemunreachable",
+        "libutils",
+    ],
+}
diff --git a/libmemunreachable/Binder.cpp b/libmemunreachable/Binder.cpp
new file mode 100644
index 000000000..60512a3f8
--- /dev/null
+++ b/libmemunreachable/Binder.cpp
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2017 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 <sys/cdefs.h>
+#include <unistd.h>
+
+#include <functional>
+
+#include "Binder.h"
+#include "log.h"
+
+__BEGIN_DECLS
+
+// Weak undefined references to the symbols in libbinder and libhwbinder
+// so that libmemunreachable can call them in processes that have them
+// loaded without requiring libmemunreachable to have dependencies on them.
+ssize_t __attribute__((weak)) getBinderKernelReferences(size_t, uintptr_t*);
+ssize_t __attribute__((weak)) getHWBinderKernelReferences(size_t, uintptr_t*);
+
+__END_DECLS
+
+namespace android {
+
+static bool BinderReferencesToVector(allocator::vector<uintptr_t>& refs,
+                                     std::function<ssize_t(size_t, uintptr_t*)> fn) {
+  if (fn == nullptr) {
+    return true;
+  }
+
+  size_t size = refs.size();
+
+  do {
+    refs.resize(size);
+
+    ssize_t ret = fn(refs.size(), refs.data());
+    if (ret < 0) {
+      return false;
+    }
+
+    size = ret;
+  } while (size > refs.size());
+
+  refs.resize(size);
+  return true;
+}
+
+bool BinderReferences(allocator::vector<uintptr_t>& refs) {
+  refs.clear();
+
+  allocator::vector<uintptr_t> binder_refs{refs.get_allocator()};
+  if (BinderReferencesToVector(refs, getBinderKernelReferences)) {
+    refs.insert(refs.end(), binder_refs.begin(), binder_refs.end());
+  } else {
+    MEM_ALOGE("getBinderKernelReferences failed");
+  }
+
+  allocator::vector<uintptr_t> hwbinder_refs{refs.get_allocator()};
+  if (BinderReferencesToVector(hwbinder_refs, getHWBinderKernelReferences)) {
+    refs.insert(refs.end(), hwbinder_refs.begin(), hwbinder_refs.end());
+  } else {
+    MEM_ALOGE("getHWBinderKernelReferences failed");
+  }
+
+  return true;
+}
+
+}  // namespace android
diff --git a/libmemunreachable/Binder.h b/libmemunreachable/Binder.h
new file mode 100644
index 000000000..bf4fd3e18
--- /dev/null
+++ b/libmemunreachable/Binder.h
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#ifndef LIBMEMUNREACHABLE_BINDER_H_
+#define LIBMEMUNREACHABLE_BINDER_H_
+
+#include "Allocator.h"
+
+namespace android {
+
+bool BinderReferences(allocator::vector<uintptr_t>& refs);
+
+}  // namespace android
+
+#endif  // LIBMEMUNREACHABLE_BINDER_H_
diff --git a/libmemunreachable/MemUnreachable.cpp b/libmemunreachable/MemUnreachable.cpp
index a1f74c333..5e062fde7 100644
--- a/libmemunreachable/MemUnreachable.cpp
+++ b/libmemunreachable/MemUnreachable.cpp
@@ -28,6 +28,7 @@
 #include <backtrace.h>
 
 #include "Allocator.h"
+#include "Binder.h"
 #include "HeapWalker.h"
 #include "Leak.h"
 #include "LeakFolding.h"
@@ -53,7 +54,8 @@ class MemUnreachable {
   MemUnreachable(pid_t pid, Allocator<void> allocator)
       : pid_(pid), allocator_(allocator), heap_walker_(allocator_) {}
   bool CollectAllocations(const allocator::vector<ThreadInfo>& threads,
-                          const allocator::vector<Mapping>& mappings);
+                          const allocator::vector<Mapping>& mappings,
+                          const allocator::vector<uintptr_t>& refs);
   bool GetUnreachableMemory(allocator::vector<Leak>& leaks, size_t limit, size_t* num_leaks,
                             size_t* leak_bytes);
   size_t Allocations() { return heap_walker_.Allocations(); }
@@ -82,7 +84,8 @@ static void HeapIterate(const Mapping& heap_mapping,
 }
 
 bool MemUnreachable::CollectAllocations(const allocator::vector<ThreadInfo>& threads,
-                                        const allocator::vector<Mapping>& mappings) {
+                                        const allocator::vector<Mapping>& mappings,
+                                        const allocator::vector<uintptr_t>& refs) {
   MEM_ALOGI("searching process %d for allocations", pid_);
   allocator::vector<Mapping> heap_mappings{mappings};
   allocator::vector<Mapping> anon_mappings{mappings};
@@ -118,6 +121,8 @@ bool MemUnreachable::CollectAllocations(const allocator::vector<ThreadInfo>& thr
     heap_walker_.Root(thread_it->regs);
   }
 
+  heap_walker_.Root(refs);
+
   MEM_ALOGI("searching done");
 
   return true;
@@ -282,6 +287,7 @@ bool GetUnreachableMemory(UnreachableMemoryInfo& info, size_t limit) {
     ThreadCapture thread_capture(parent_pid, heap);
     allocator::vector<ThreadInfo> thread_info(heap);
     allocator::vector<Mapping> mappings(heap);
+    allocator::vector<uintptr_t> refs(heap);
 
     // ptrace all the threads
     if (!thread_capture.CaptureThreads()) {
@@ -301,6 +307,11 @@ bool GetUnreachableMemory(UnreachableMemoryInfo& info, size_t limit) {
       return 1;
     }
 
+    if (!BinderReferences(refs)) {
+      continue_parent_sem.Post();
+      return 1;
+    }
+
     // malloc must be enabled to call fork, at_fork handlers take the same
     // locks as ScopedDisableMalloc.  All threads are paused in ptrace, so
     // memory state is still consistent.  Unfreeze the original thread so it
@@ -326,7 +337,7 @@ bool GetUnreachableMemory(UnreachableMemoryInfo& info, size_t limit) {
 
       MemUnreachable unreachable{parent_pid, heap};
 
-      if (!unreachable.CollectAllocations(thread_info, mappings)) {
+      if (!unreachable.CollectAllocations(thread_info, mappings, refs)) {
         _exit(2);
       }
       size_t num_allocations = unreachable.Allocations();
diff --git a/libmemunreachable/tests/Binder_test.cpp b/libmemunreachable/tests/Binder_test.cpp
new file mode 100644
index 000000000..6e85d5ab3
--- /dev/null
+++ b/libmemunreachable/tests/Binder_test.cpp
@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2016 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 <signal.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <binder/Binder.h>
+#include <binder/IBinder.h>
+#include <binder/IServiceManager.h>
+#include <binder/Parcel.h>
+#include <binder/ProcessState.h>
+
+#include <gtest/gtest.h>
+
+#include "Allocator.h"
+#include "Binder.h"
+
+namespace android {
+
+static const String16 service_name("test.libmemunreachable_binder");
+
+class BinderService : public BBinder {
+ public:
+  BinderService() = default;
+  virtual ~BinderService() = default;
+
+  virtual status_t onTransact(uint32_t /*code*/, const Parcel& data, Parcel* reply,
+                              uint32_t /*flags*/ = 0) {
+    reply->writeStrongBinder(ref);
+    ref = data.readStrongBinder();
+    return 0;
+  }
+
+ private:
+  sp<IBinder> ref;
+};
+
+class BinderObject : public BBinder {
+ public:
+  BinderObject() = default;
+  ~BinderObject() = default;
+};
+
+class ServiceProcess {
+ public:
+  ServiceProcess() : child_(0) {}
+  ~ServiceProcess() { Stop(); }
+
+  bool Run() {
+    pid_t ret = fork();
+    if (ret < 0) {
+      return false;
+    } else if (ret == 0) {
+      // child
+      _exit(Service());
+    } else {
+      // parent
+      child_ = ret;
+      return true;
+    }
+  }
+
+  bool Stop() {
+    if (child_ > 0) {
+      if (kill(child_, SIGTERM)) {
+        return false;
+      }
+      int status = 0;
+      if (TEMP_FAILURE_RETRY(waitpid(child_, &status, 0)) != child_) {
+        return false;
+      }
+      child_ = 0;
+      return WIFEXITED(status) && WEXITSTATUS(status) == 0;
+    }
+
+    return true;
+  }
+
+  int Service() {
+    sp<ProcessState> proc{ProcessState::self()};
+    sp<IServiceManager> sm = defaultServiceManager();
+    if (sm == nullptr) {
+      fprintf(stderr, "Failed to get service manager\n");
+      return 1;
+    }
+    if (sm->addService(service_name, new BinderService()) != OK) {
+      fprintf(stderr, "Failed to add test service\n");
+      return 1;
+    }
+    proc->startThreadPool();
+    pause();
+    return 0;
+  }
+
+ private:
+  pid_t child_;
+};
+
+class BinderTest : public ::testing::Test {
+ protected:
+  ServiceProcess service_process_;
+};
+
+TEST_F(BinderTest, binder) {
+  ServiceProcess service_process;
+  ASSERT_TRUE(service_process.Run());
+
+  sp<IServiceManager> sm = defaultServiceManager();
+  ASSERT_TRUE(sm != nullptr);
+
+  // A small sleep allows the service to start, which
+  // prevents a longer sleep in getService.
+  usleep(100000);
+
+  sp<IBinder> service = sm->getService(service_name);
+  ASSERT_TRUE(service != nullptr);
+
+  sp<IBinder> binder{new BinderObject()};
+
+  Parcel send;
+  Parcel reply;
+
+  send.writeStrongBinder(binder);
+  status_t rv = service->transact(0, send, &reply);
+  ASSERT_EQ(static_cast<status_t>(OK), rv);
+
+  Heap heap;
+  allocator::vector<uintptr_t> refs{heap};
+
+  ASSERT_TRUE(BinderReferences(refs));
+
+  bool found_ref = false;
+  for (auto ref : refs) {
+    if (ref == reinterpret_cast<uintptr_t>(binder.get())) {
+      found_ref = true;
+    }
+  }
+
+  ASSERT_TRUE(found_ref);
+}
+
+}  // namespace android