1/*
2 * Copyright (C) 2015 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 "event_fd.h"
18
19#include <fcntl.h>
20#include <stdio.h>
21#include <sys/ioctl.h>
22#include <sys/mman.h>
23#include <sys/syscall.h>
24#include <sys/types.h>
25#include <memory>
26
27#include <base/file.h>
28#include <base/logging.h>
29#include <base/stringprintf.h>
30
31#include "event_type.h"
32#include "perf_event.h"
33#include "utils.h"
34
35static int perf_event_open(perf_event_attr* attr, pid_t pid, int cpu, int group_fd,
36                           unsigned long flags) {
37  return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
38}
39
40std::unique_ptr<EventFd> EventFd::OpenEventFileForProcess(const perf_event_attr& attr, pid_t pid) {
41  return OpenEventFile(attr, pid, -1);
42}
43
44std::unique_ptr<EventFd> EventFd::OpenEventFileForCpu(const perf_event_attr& attr, int cpu) {
45  return OpenEventFile(attr, -1, cpu);
46}
47
48std::unique_ptr<EventFd> EventFd::OpenEventFile(const perf_event_attr& attr, pid_t pid, int cpu) {
49  perf_event_attr perf_attr = attr;
50  std::string event_name = "unknown event";
51  const EventType* event_type =
52      EventTypeFactory::FindEventTypeByConfig(perf_attr.type, perf_attr.config);
53  if (event_type != nullptr) {
54    event_name = event_type->name;
55  }
56  int perf_event_fd = perf_event_open(&perf_attr, pid, cpu, -1, 0);
57  if (perf_event_fd == -1) {
58    // It depends whether the perf_event_file configuration is supported by the kernel and the
59    // machine. So fail to open the file is not an error.
60    PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", pid " << pid << ", cpu "
61                << cpu << ") failed";
62    return nullptr;
63  }
64  if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) {
65    PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " << event_name << ", pid " << pid
66                << ", cpu " << cpu << ") failed";
67    return nullptr;
68  }
69  return std::unique_ptr<EventFd>(new EventFd(perf_event_fd, event_name, pid, cpu));
70}
71
72EventFd::~EventFd() {
73  if (mmap_addr_ != nullptr) {
74    munmap(mmap_addr_, mmap_len_);
75  }
76  close(perf_event_fd_);
77}
78
79std::string EventFd::Name() const {
80  return android::base::StringPrintf("perf_event_file(event %s, pid %d, cpu %d)",
81                                     event_name_.c_str(), pid_, cpu_);
82}
83
84uint64_t EventFd::Id() const {
85  if (id_ == 0) {
86    PerfCounter counter;
87    if (ReadCounter(&counter)) {
88      id_ = counter.id;
89    }
90  }
91  return id_;
92}
93
94bool EventFd::EnableEvent() {
95  int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_ENABLE, 0);
96  if (result < 0) {
97    PLOG(ERROR) << "ioctl(enable) " << Name() << " failed";
98    return false;
99  }
100  return true;
101}
102
103bool EventFd::DisableEvent() {
104  int result = ioctl(perf_event_fd_, PERF_EVENT_IOC_DISABLE, 0);
105  if (result < 0) {
106    PLOG(ERROR) << "ioctl(disable) " << Name() << " failed";
107    return false;
108  }
109  return true;
110}
111
112bool EventFd::ReadCounter(PerfCounter* counter) const {
113  CHECK(counter != nullptr);
114  if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) {
115    PLOG(ERROR) << "ReadCounter from " << Name() << " failed";
116    return false;
117  }
118  return true;
119}
120
121bool EventFd::MmapContent(size_t mmap_pages) {
122  CHECK(IsPowerOfTwo(mmap_pages));
123  size_t page_size = sysconf(_SC_PAGE_SIZE);
124  size_t mmap_len = (mmap_pages + 1) * page_size;
125  void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, perf_event_fd_, 0);
126  if (mmap_addr == MAP_FAILED) {
127    PLOG(ERROR) << "mmap() failed for " << Name();
128    return false;
129  }
130  mmap_addr_ = mmap_addr;
131  mmap_len_ = mmap_len;
132  mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_);
133  mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size;
134  mmap_data_buffer_size_ = mmap_len_ - page_size;
135  return true;
136}
137
138size_t EventFd::GetAvailableMmapData(char** pdata) {
139  // The mmap_data_buffer is used as a ring buffer like below. The kernel continuously writes
140  // records to the buffer, and the user continuously read records out.
141  //         _________________________________________
142  // buffer | can write   |   can read   |  can write |
143  //                      ^              ^
144  //                    read_head       write_head
145  //
146  // So the user can read records in [read_head, write_head), and the kernel can write records
147  // in [write_head, read_head). The kernel is responsible for updating write_head, and the user
148  // is responsible for updating read_head.
149
150  uint64_t buf_mask = mmap_data_buffer_size_ - 1;
151  uint64_t write_head = mmap_metadata_page_->data_head & buf_mask;
152  uint64_t read_head = mmap_metadata_page_->data_tail & buf_mask;
153
154  if (read_head == write_head) {
155    // No available data.
156    return 0;
157  }
158
159  // Make sure we can see the data after the fence.
160  std::atomic_thread_fence(std::memory_order_acquire);
161
162  *pdata = mmap_data_buffer_ + read_head;
163  if (read_head < write_head) {
164    return write_head - read_head;
165  } else {
166    return mmap_data_buffer_size_ - read_head;
167  }
168}
169
170void EventFd::DiscardMmapData(size_t discard_size) {
171  mmap_metadata_page_->data_tail += discard_size;
172}
173
174void EventFd::PreparePollForMmapData(pollfd* poll_fd) {
175  memset(poll_fd, 0, sizeof(pollfd));
176  poll_fd->fd = perf_event_fd_;
177  poll_fd->events = POLLIN;
178}
179