1/*
2 * Copyright (C) 2017 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 "uevent_listener.h"
18
19#include <fcntl.h>
20#include <poll.h>
21#include <string.h>
22#include <unistd.h>
23
24#include <memory>
25
26#include <android-base/logging.h>
27#include <cutils/uevent.h>
28
29namespace android {
30namespace init {
31
32static void ParseEvent(const char* msg, Uevent* uevent) {
33    uevent->partition_num = -1;
34    uevent->major = -1;
35    uevent->minor = -1;
36    uevent->action.clear();
37    uevent->path.clear();
38    uevent->subsystem.clear();
39    uevent->firmware.clear();
40    uevent->partition_name.clear();
41    uevent->device_name.clear();
42    // currently ignoring SEQNUM
43    while (*msg) {
44        if (!strncmp(msg, "ACTION=", 7)) {
45            msg += 7;
46            uevent->action = msg;
47        } else if (!strncmp(msg, "DEVPATH=", 8)) {
48            msg += 8;
49            uevent->path = msg;
50        } else if (!strncmp(msg, "SUBSYSTEM=", 10)) {
51            msg += 10;
52            uevent->subsystem = msg;
53        } else if (!strncmp(msg, "FIRMWARE=", 9)) {
54            msg += 9;
55            uevent->firmware = msg;
56        } else if (!strncmp(msg, "MAJOR=", 6)) {
57            msg += 6;
58            uevent->major = atoi(msg);
59        } else if (!strncmp(msg, "MINOR=", 6)) {
60            msg += 6;
61            uevent->minor = atoi(msg);
62        } else if (!strncmp(msg, "PARTN=", 6)) {
63            msg += 6;
64            uevent->partition_num = atoi(msg);
65        } else if (!strncmp(msg, "PARTNAME=", 9)) {
66            msg += 9;
67            uevent->partition_name = msg;
68        } else if (!strncmp(msg, "DEVNAME=", 8)) {
69            msg += 8;
70            uevent->device_name = msg;
71        }
72
73        // advance to after the next \0
74        while (*msg++)
75            ;
76    }
77
78    if (LOG_UEVENTS) {
79        LOG(INFO) << "event { '" << uevent->action << "', '" << uevent->path << "', '"
80                  << uevent->subsystem << "', '" << uevent->firmware << "', " << uevent->major
81                  << ", " << uevent->minor << " }";
82    }
83}
84
85UeventListener::UeventListener() {
86    // is 2MB enough? udev uses 128MB!
87    device_fd_.reset(uevent_open_socket(2 * 1024 * 1024, true));
88    if (device_fd_ == -1) {
89        LOG(FATAL) << "Could not open uevent socket";
90    }
91
92    fcntl(device_fd_, F_SETFL, O_NONBLOCK);
93}
94
95bool UeventListener::ReadUevent(Uevent* uevent) const {
96    char msg[UEVENT_MSG_LEN + 2];
97    int n = uevent_kernel_multicast_recv(device_fd_, msg, UEVENT_MSG_LEN);
98    if (n <= 0) {
99        if (errno != EAGAIN && errno != EWOULDBLOCK) {
100            LOG(ERROR) << "Error reading from Uevent Fd";
101        }
102        return false;
103    }
104    if (n >= UEVENT_MSG_LEN) {
105        LOG(ERROR) << "Uevent overflowed buffer, discarding";
106        // Return true here even if we discard as we may have more uevents pending and we
107        // want to keep processing them.
108        return true;
109    }
110
111    msg[n] = '\0';
112    msg[n + 1] = '\0';
113
114    ParseEvent(msg, uevent);
115
116    return true;
117}
118
119// RegenerateUevents*() walks parts of the /sys tree and pokes the uevent files to cause the kernel
120// to regenerate device add uevents that have already happened.  This is particularly useful when
121// starting ueventd, to regenerate all of the uevents that it had previously missed.
122//
123// We drain any pending events from the netlink socket every time we poke another uevent file to
124// make sure we don't overrun the socket's buffer.
125//
126
127ListenerAction UeventListener::RegenerateUeventsForDir(DIR* d,
128                                                       const ListenerCallback& callback) const {
129    int dfd = dirfd(d);
130
131    int fd = openat(dfd, "uevent", O_WRONLY);
132    if (fd >= 0) {
133        write(fd, "add\n", 4);
134        close(fd);
135
136        Uevent uevent;
137        while (ReadUevent(&uevent)) {
138            if (callback(uevent) == ListenerAction::kStop) return ListenerAction::kStop;
139        }
140    }
141
142    dirent* de;
143    while ((de = readdir(d)) != nullptr) {
144        if (de->d_type != DT_DIR || de->d_name[0] == '.') continue;
145
146        fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
147        if (fd < 0) continue;
148
149        std::unique_ptr<DIR, decltype(&closedir)> d2(fdopendir(fd), closedir);
150        if (d2 == 0) {
151            close(fd);
152        } else {
153            if (RegenerateUeventsForDir(d2.get(), callback) == ListenerAction::kStop) {
154                return ListenerAction::kStop;
155            }
156        }
157    }
158
159    // default is always to continue looking for uevents
160    return ListenerAction::kContinue;
161}
162
163ListenerAction UeventListener::RegenerateUeventsForPath(const std::string& path,
164                                                        const ListenerCallback& callback) const {
165    std::unique_ptr<DIR, decltype(&closedir)> d(opendir(path.c_str()), closedir);
166    if (!d) return ListenerAction::kContinue;
167
168    return RegenerateUeventsForDir(d.get(), callback);
169}
170
171static const char* kRegenerationPaths[] = {"/sys/class", "/sys/block", "/sys/devices"};
172
173void UeventListener::RegenerateUevents(const ListenerCallback& callback) const {
174    for (const auto path : kRegenerationPaths) {
175        if (RegenerateUeventsForPath(path, callback) == ListenerAction::kStop) return;
176    }
177}
178
179void UeventListener::Poll(const ListenerCallback& callback,
180                          const std::optional<std::chrono::milliseconds> relative_timeout) const {
181    using namespace std::chrono;
182
183    pollfd ufd;
184    ufd.events = POLLIN;
185    ufd.fd = device_fd_;
186
187    auto start_time = steady_clock::now();
188
189    while (true) {
190        ufd.revents = 0;
191
192        int timeout_ms = -1;
193        if (relative_timeout) {
194            auto now = steady_clock::now();
195            auto time_elapsed = duration_cast<milliseconds>(now - start_time);
196            if (time_elapsed > *relative_timeout) return;
197
198            auto remaining_timeout = *relative_timeout - time_elapsed;
199            timeout_ms = remaining_timeout.count();
200        }
201
202        int nr = poll(&ufd, 1, timeout_ms);
203        if (nr == 0) return;
204        if (nr < 0) {
205            PLOG(ERROR) << "poll() of uevent socket failed, continuing";
206            continue;
207        }
208        if (ufd.revents & POLLIN) {
209            // We're non-blocking, so if we receive a poll event keep processing until
210            // we have exhausted all uevent messages.
211            Uevent uevent;
212            while (ReadUevent(&uevent)) {
213                if (callback(uevent) == ListenerAction::kStop) return;
214            }
215        }
216    }
217}
218
219}  // namespace init
220}  // namespace android
221