Colin Cross | bcb4ed3 | 2016-01-14 15:35:40 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2016 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include <errno.h> |
| 18 | #include <fcntl.h> |
| 19 | #include <inttypes.h> |
| 20 | #include <pthread.h> |
| 21 | #include <sched.h> |
| 22 | #include <stddef.h> |
| 23 | #include <stdio.h> |
| 24 | #include <stdlib.h> |
| 25 | #include <string.h> |
| 26 | #include <unistd.h> |
| 27 | #include <sys/mman.h> |
| 28 | #include <sys/syscall.h> |
| 29 | #include <sys/types.h> |
| 30 | #include <sys/wait.h> |
| 31 | |
| 32 | #include "android-base/macros.h" |
| 33 | |
| 34 | #include "anon_vma_naming.h" |
| 35 | #include "log.h" |
| 36 | #include "PtracerThread.h" |
| 37 | |
| 38 | class Stack { |
| 39 | public: |
Chih-Hung Hsieh | 1c563d9 | 2016-04-29 15:44:04 -0700 | [diff] [blame] | 40 | explicit Stack(size_t size) : size_(size) { |
Colin Cross | bcb4ed3 | 2016-01-14 15:35:40 -0800 | [diff] [blame] | 41 | int prot = PROT_READ | PROT_WRITE; |
| 42 | int flags = MAP_PRIVATE | MAP_ANONYMOUS; |
| 43 | page_size_ = sysconf(_SC_PAGE_SIZE); |
| 44 | size_ += page_size_*2; // guard pages |
| 45 | base_ = mmap(NULL, size_, prot, flags, -1, 0); |
| 46 | if (base_ == MAP_FAILED) { |
| 47 | base_ = NULL; |
| 48 | size_ = 0; |
| 49 | return; |
| 50 | } |
| 51 | prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, base_, size_, "libmemunreachable stack"); |
| 52 | mprotect(base_, page_size_, PROT_NONE); |
| 53 | mprotect(top(), page_size_, PROT_NONE); |
| 54 | }; |
| 55 | ~Stack() { |
| 56 | munmap(base_, size_); |
| 57 | }; |
| 58 | void* top() { |
| 59 | return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(base_) + size_ - page_size_); |
| 60 | }; |
| 61 | private: |
| 62 | DISALLOW_COPY_AND_ASSIGN(Stack); |
| 63 | |
| 64 | void *base_; |
| 65 | size_t size_; |
| 66 | size_t page_size_; |
| 67 | }; |
| 68 | |
| 69 | PtracerThread::PtracerThread(const std::function<int()>& func) : |
| 70 | child_pid_(0) { |
| 71 | stack_ = std::make_unique<Stack>(PTHREAD_STACK_MIN); |
| 72 | if (stack_->top() == nullptr) { |
| 73 | LOG_ALWAYS_FATAL("failed to mmap child stack: %s", strerror(errno)); |
| 74 | } |
| 75 | |
| 76 | func_ = std::function<int()>{[&, func]() -> int { |
| 77 | // In the child thread, lock and unlock the mutex to wait for the parent |
| 78 | // to finish setting up for the child thread |
| 79 | std::unique_lock<std::mutex> lk(m_); |
| 80 | lk.unlock(); |
| 81 | _exit(func()); |
| 82 | }}; |
| 83 | } |
| 84 | |
| 85 | PtracerThread::~PtracerThread() { |
| 86 | Kill(); |
| 87 | Join(); |
| 88 | ClearTracer(); |
| 89 | stack_ = nullptr; |
| 90 | } |
| 91 | |
| 92 | bool PtracerThread::Start() { |
| 93 | std::unique_lock<std::mutex> lk(m_); |
| 94 | |
| 95 | // Convert from void(*)(void*) to lambda with captures |
| 96 | auto proxy = [](void *arg) -> int { |
| 97 | prctl(PR_SET_NAME, "libmemunreachable ptrace thread"); |
| 98 | return (*reinterpret_cast<std::function<int()>*>(arg))(); |
| 99 | }; |
| 100 | |
| 101 | child_pid_ = clone(proxy, stack_->top(), |
| 102 | CLONE_VM|CLONE_FS|CLONE_FILES/*|CLONE_UNTRACED*/, |
| 103 | reinterpret_cast<void*>(&func_)); |
| 104 | if (child_pid_ < 0) { |
| 105 | ALOGE("failed to clone child: %s", strerror(errno)); |
| 106 | return false; |
| 107 | } |
| 108 | |
| 109 | SetTracer(child_pid_); |
| 110 | |
| 111 | lk.unlock(); |
| 112 | |
| 113 | return true; |
| 114 | } |
| 115 | |
| 116 | int PtracerThread::Join() { |
| 117 | if (child_pid_ == -1) { |
| 118 | return -1; |
| 119 | } |
| 120 | int status; |
| 121 | int ret = TEMP_FAILURE_RETRY(waitpid(child_pid_, &status, __WALL)); |
| 122 | if (ret < 0) { |
| 123 | ALOGE("waitpid %d failed: %s", child_pid_, strerror(errno)); |
| 124 | return -1; |
| 125 | } |
| 126 | |
| 127 | child_pid_ = -1; |
| 128 | |
| 129 | if (WIFEXITED(status)) { |
| 130 | return WEXITSTATUS(status); |
| 131 | } else if (WIFSIGNALED(status)) { |
| 132 | return -WTERMSIG(status); |
| 133 | } else { |
| 134 | ALOGE("unexpected status %x", status); |
| 135 | return -1; |
| 136 | } |
| 137 | } |
| 138 | |
| 139 | void PtracerThread::Kill() { |
| 140 | if (child_pid_ == -1) { |
| 141 | return; |
| 142 | } |
| 143 | |
| 144 | syscall(SYS_tkill, child_pid_, SIGKILL); |
| 145 | } |
| 146 | |
| 147 | void PtracerThread::SetTracer(pid_t tracer_pid) { |
| 148 | prctl(PR_SET_PTRACER, tracer_pid); |
| 149 | } |
| 150 | |
| 151 | void PtracerThread::ClearTracer() { |
| 152 | prctl(PR_SET_PTRACER, 0); |
| 153 | } |