imprecise mark and sweep native memory leak detector
libmemunreachable uses an imprecise mark and sweep pass over all memory
allocated by jemalloc in order to find unreachable allocations.
Change-Id: Ia70bbf31f5b40ff71dab28cfd6cd06c5ef01a2d4
diff --git a/libmemunreachable/PtracerThread.cpp b/libmemunreachable/PtracerThread.cpp
new file mode 100644
index 0000000..aa5b344
--- /dev/null
+++ b/libmemunreachable/PtracerThread.cpp
@@ -0,0 +1,153 @@
+/*
+ * 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 <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <pthread.h>
+#include <sched.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "android-base/macros.h"
+
+#include "anon_vma_naming.h"
+#include "log.h"
+#include "PtracerThread.h"
+
+class Stack {
+ public:
+ Stack(size_t size) : size_(size) {
+ int prot = PROT_READ | PROT_WRITE;
+ int flags = MAP_PRIVATE | MAP_ANONYMOUS;
+ page_size_ = sysconf(_SC_PAGE_SIZE);
+ size_ += page_size_*2; // guard pages
+ base_ = mmap(NULL, size_, prot, flags, -1, 0);
+ if (base_ == MAP_FAILED) {
+ base_ = NULL;
+ size_ = 0;
+ return;
+ }
+ prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, base_, size_, "libmemunreachable stack");
+ mprotect(base_, page_size_, PROT_NONE);
+ mprotect(top(), page_size_, PROT_NONE);
+ };
+ ~Stack() {
+ munmap(base_, size_);
+ };
+ void* top() {
+ return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(base_) + size_ - page_size_);
+ };
+ private:
+ DISALLOW_COPY_AND_ASSIGN(Stack);
+
+ void *base_;
+ size_t size_;
+ size_t page_size_;
+};
+
+PtracerThread::PtracerThread(const std::function<int()>& func) :
+ child_pid_(0) {
+ stack_ = std::make_unique<Stack>(PTHREAD_STACK_MIN);
+ if (stack_->top() == nullptr) {
+ LOG_ALWAYS_FATAL("failed to mmap child stack: %s", strerror(errno));
+ }
+
+ func_ = std::function<int()>{[&, func]() -> int {
+ // In the child thread, lock and unlock the mutex to wait for the parent
+ // to finish setting up for the child thread
+ std::unique_lock<std::mutex> lk(m_);
+ lk.unlock();
+ _exit(func());
+ }};
+}
+
+PtracerThread::~PtracerThread() {
+ Kill();
+ Join();
+ ClearTracer();
+ stack_ = nullptr;
+}
+
+bool PtracerThread::Start() {
+ std::unique_lock<std::mutex> lk(m_);
+
+ // Convert from void(*)(void*) to lambda with captures
+ auto proxy = [](void *arg) -> int {
+ prctl(PR_SET_NAME, "libmemunreachable ptrace thread");
+ return (*reinterpret_cast<std::function<int()>*>(arg))();
+ };
+
+ child_pid_ = clone(proxy, stack_->top(),
+ CLONE_VM|CLONE_FS|CLONE_FILES/*|CLONE_UNTRACED*/,
+ reinterpret_cast<void*>(&func_));
+ if (child_pid_ < 0) {
+ ALOGE("failed to clone child: %s", strerror(errno));
+ return false;
+ }
+
+ SetTracer(child_pid_);
+
+ lk.unlock();
+
+ return true;
+}
+
+int PtracerThread::Join() {
+ if (child_pid_ == -1) {
+ return -1;
+ }
+ int status;
+ int ret = TEMP_FAILURE_RETRY(waitpid(child_pid_, &status, __WALL));
+ if (ret < 0) {
+ ALOGE("waitpid %d failed: %s", child_pid_, strerror(errno));
+ return -1;
+ }
+
+ child_pid_ = -1;
+
+ if (WIFEXITED(status)) {
+ return WEXITSTATUS(status);
+ } else if (WIFSIGNALED(status)) {
+ return -WTERMSIG(status);
+ } else {
+ ALOGE("unexpected status %x", status);
+ return -1;
+ }
+}
+
+void PtracerThread::Kill() {
+ if (child_pid_ == -1) {
+ return;
+ }
+
+ syscall(SYS_tkill, child_pid_, SIGKILL);
+}
+
+void PtracerThread::SetTracer(pid_t tracer_pid) {
+ prctl(PR_SET_PTRACER, tracer_pid);
+}
+
+void PtracerThread::ClearTracer() {
+ prctl(PR_SET_PTRACER, 0);
+}