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 <poll.h>
21#include <stdio.h>
22#include <string.h>
23#include <sys/ioctl.h>
24#include <sys/mman.h>
25#include <sys/syscall.h>
26#include <sys/types.h>
27#include <atomic>
28#include <memory>
29
30#include <android-base/file.h>
31#include <android-base/logging.h>
32#include <android-base/stringprintf.h>
33
34#include "event_type.h"
35#include "perf_event.h"
36#include "utils.h"
37
38std::vector<char> EventFd::data_process_buffer_;
39
40static int perf_event_open(perf_event_attr* attr, pid_t pid, int cpu, int group_fd,
41                           unsigned long flags) {
42  return syscall(__NR_perf_event_open, attr, pid, cpu, group_fd, flags);
43}
44
45std::unique_ptr<EventFd> EventFd::OpenEventFile(const perf_event_attr& attr, pid_t tid, int cpu,
46                                                bool report_error) {
47  perf_event_attr perf_attr = attr;
48  std::string event_name = "unknown event";
49  const EventType* event_type = FindEventTypeByConfig(perf_attr.type, perf_attr.config);
50  if (event_type != nullptr) {
51    event_name = event_type->name;
52  }
53  int perf_event_fd = perf_event_open(&perf_attr, tid, cpu, -1, 0);
54  if (perf_event_fd == -1) {
55    if (report_error) {
56      PLOG(ERROR) << "open perf_event_file (event " << event_name << ", tid " << tid << ", cpu "
57                  << cpu << ") failed";
58    } else {
59      PLOG(DEBUG) << "open perf_event_file (event " << event_name << ", tid " << tid << ", cpu "
60                  << cpu << ") failed";
61    }
62    return nullptr;
63  }
64  if (fcntl(perf_event_fd, F_SETFD, FD_CLOEXEC) == -1) {
65    if (report_error) {
66      PLOG(ERROR) << "fcntl(FD_CLOEXEC) for perf_event_file (event " << event_name << ", tid "
67                  << tid << ", cpu " << cpu << ") failed";
68    } else {
69      PLOG(DEBUG) << "fcntl(FD_CLOEXEC) for perf_event_file (event " << event_name << ", tid "
70                  << tid << ", cpu " << cpu << ") failed";
71    }
72    return nullptr;
73  }
74  return std::unique_ptr<EventFd>(new EventFd(perf_event_fd, event_name, tid, cpu));
75}
76
77EventFd::~EventFd() {
78  if (mmap_addr_ != nullptr) {
79    munmap(mmap_addr_, mmap_len_);
80  }
81  close(perf_event_fd_);
82}
83
84std::string EventFd::Name() const {
85  return android::base::StringPrintf("perf_event_file(event %s, tid %d, cpu %d)",
86                                     event_name_.c_str(), tid_, cpu_);
87}
88
89uint64_t EventFd::Id() const {
90  if (id_ == 0) {
91    PerfCounter counter;
92    if (ReadCounter(&counter)) {
93      id_ = counter.id;
94    }
95  }
96  return id_;
97}
98
99bool EventFd::ReadCounter(PerfCounter* counter) const {
100  CHECK(counter != nullptr);
101  if (!android::base::ReadFully(perf_event_fd_, counter, sizeof(*counter))) {
102    PLOG(ERROR) << "ReadCounter from " << Name() << " failed";
103    return false;
104  }
105  return true;
106}
107
108bool EventFd::MmapContent(size_t mmap_pages) {
109  CHECK(IsPowerOfTwo(mmap_pages));
110  size_t page_size = sysconf(_SC_PAGE_SIZE);
111  size_t mmap_len = (mmap_pages + 1) * page_size;
112  void* mmap_addr = mmap(nullptr, mmap_len, PROT_READ | PROT_WRITE, MAP_SHARED, perf_event_fd_, 0);
113  if (mmap_addr == MAP_FAILED) {
114    PLOG(ERROR) << "mmap() failed for " << Name();
115    return false;
116  }
117  mmap_addr_ = mmap_addr;
118  mmap_len_ = mmap_len;
119  mmap_metadata_page_ = reinterpret_cast<perf_event_mmap_page*>(mmap_addr_);
120  mmap_data_buffer_ = reinterpret_cast<char*>(mmap_addr_) + page_size;
121  mmap_data_buffer_size_ = mmap_len_ - page_size;
122  if (data_process_buffer_.size() < mmap_data_buffer_size_) {
123    data_process_buffer_.resize(mmap_data_buffer_size_);
124  }
125  return true;
126}
127
128size_t EventFd::GetAvailableMmapData(char** pdata) {
129  // The mmap_data_buffer is used as a ring buffer like below. The kernel continuously writes
130  // records to the buffer, and the user continuously read records out.
131  //         _________________________________________
132  // buffer | can write   |   can read   |  can write |
133  //                      ^              ^
134  //                    read_head       write_head
135  //
136  // So the user can read records in [read_head, write_head), and the kernel can write records
137  // in [write_head, read_head). The kernel is responsible for updating write_head, and the user
138  // is responsible for updating read_head.
139
140  size_t buf_mask = mmap_data_buffer_size_ - 1;
141  size_t write_head = static_cast<size_t>(mmap_metadata_page_->data_head & buf_mask);
142  size_t read_head = static_cast<size_t>(mmap_metadata_page_->data_tail & buf_mask);
143
144  if (read_head == write_head) {
145    // No available data.
146    return 0;
147  }
148
149  // Make sure we can see the data after the fence.
150  std::atomic_thread_fence(std::memory_order_acquire);
151
152  // Copy records from mapped buffer to data_process_buffer. Note that records can be wrapped
153  // at the end of the mapped buffer.
154  char* to = data_process_buffer_.data();
155  if (read_head < write_head) {
156    char* from = mmap_data_buffer_ + read_head;
157    size_t n = write_head - read_head;
158    memcpy(to, from, n);
159    to += n;
160  } else {
161    char* from = mmap_data_buffer_ + read_head;
162    size_t n = mmap_data_buffer_size_ - read_head;
163    memcpy(to, from, n);
164    to += n;
165    from = mmap_data_buffer_;
166    n = write_head;
167    memcpy(to, from, n);
168    to += n;
169  }
170  size_t read_bytes = to - data_process_buffer_.data();
171  *pdata = data_process_buffer_.data();
172  DiscardMmapData(read_bytes);
173  return read_bytes;
174}
175
176void EventFd::DiscardMmapData(size_t discard_size) {
177  mmap_metadata_page_->data_tail += discard_size;
178}
179
180void EventFd::PreparePollForMmapData(pollfd* poll_fd) {
181  memset(poll_fd, 0, sizeof(pollfd));
182  poll_fd->fd = perf_event_fd_;
183  poll_fd->events = POLLIN;
184}
185
186bool IsEventAttrSupportedByKernel(perf_event_attr attr) {
187  auto event_fd = EventFd::OpenEventFile(attr, getpid(), -1, false);
188  return event_fd != nullptr;
189}
190