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/*
* Copyright (C) 2017 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 "uevent_listener.h"
#include <fcntl.h>
#include <poll.h>
#include <string.h>
#include <unistd.h>
#include <memory>
#include <android-base/logging.h>
#include <cutils/uevent.h>
namespace android {
namespace init {
static void ParseEvent(const char* msg, Uevent* uevent) {
uevent->partition_num = -1;
uevent->major = -1;
uevent->minor = -1;
uevent->action.clear();
uevent->path.clear();
uevent->subsystem.clear();
uevent->firmware.clear();
uevent->partition_name.clear();
uevent->device_name.clear();
// currently ignoring SEQNUM
while (*msg) {
if (!strncmp(msg, "ACTION=", 7)) {
msg += 7;
uevent->action = msg;
} else if (!strncmp(msg, "DEVPATH=", 8)) {
msg += 8;
uevent->path = msg;
} else if (!strncmp(msg, "SUBSYSTEM=", 10)) {
msg += 10;
uevent->subsystem = msg;
} else if (!strncmp(msg, "FIRMWARE=", 9)) {
msg += 9;
uevent->firmware = msg;
} else if (!strncmp(msg, "MAJOR=", 6)) {
msg += 6;
uevent->major = atoi(msg);
} else if (!strncmp(msg, "MINOR=", 6)) {
msg += 6;
uevent->minor = atoi(msg);
} else if (!strncmp(msg, "PARTN=", 6)) {
msg += 6;
uevent->partition_num = atoi(msg);
} else if (!strncmp(msg, "PARTNAME=", 9)) {
msg += 9;
uevent->partition_name = msg;
} else if (!strncmp(msg, "DEVNAME=", 8)) {
msg += 8;
uevent->device_name = msg;
}
// advance to after the next \0
while (*msg++)
;
}
if (LOG_UEVENTS) {
LOG(INFO) << "event { '" << uevent->action << "', '" << uevent->path << "', '"
<< uevent->subsystem << "', '" << uevent->firmware << "', " << uevent->major
<< ", " << uevent->minor << " }";
}
}
UeventListener::UeventListener() {
// is 2MB enough? udev uses 128MB!
device_fd_.reset(uevent_open_socket(2 * 1024 * 1024, true));
if (device_fd_ == -1) {
LOG(FATAL) << "Could not open uevent socket";
}
fcntl(device_fd_, F_SETFL, O_NONBLOCK);
}
bool UeventListener::ReadUevent(Uevent* uevent) const {
char msg[UEVENT_MSG_LEN + 2];
int n = uevent_kernel_multicast_recv(device_fd_, msg, UEVENT_MSG_LEN);
if (n <= 0) {
if (errno != EAGAIN && errno != EWOULDBLOCK) {
LOG(ERROR) << "Error reading from Uevent Fd";
}
return false;
}
if (n >= UEVENT_MSG_LEN) {
LOG(ERROR) << "Uevent overflowed buffer, discarding";
// Return true here even if we discard as we may have more uevents pending and we
// want to keep processing them.
return true;
}
msg[n] = '\0';
msg[n + 1] = '\0';
ParseEvent(msg, uevent);
return true;
}
// RegenerateUevents*() walks parts of the /sys tree and pokes the uevent files to cause the kernel
// to regenerate device add uevents that have already happened. This is particularly useful when
// starting ueventd, to regenerate all of the uevents that it had previously missed.
//
// We drain any pending events from the netlink socket every time we poke another uevent file to
// make sure we don't overrun the socket's buffer.
//
ListenerAction UeventListener::RegenerateUeventsForDir(DIR* d,
const ListenerCallback& callback) const {
int dfd = dirfd(d);
int fd = openat(dfd, "uevent", O_WRONLY);
if (fd >= 0) {
write(fd, "add\n", 4);
close(fd);
Uevent uevent;
while (ReadUevent(&uevent)) {
if (callback(uevent) == ListenerAction::kStop) return ListenerAction::kStop;
}
}
dirent* de;
while ((de = readdir(d)) != nullptr) {
if (de->d_type != DT_DIR || de->d_name[0] == '.') continue;
fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
if (fd < 0) continue;
std::unique_ptr<DIR, decltype(&closedir)> d2(fdopendir(fd), closedir);
if (d2 == 0) {
close(fd);
} else {
if (RegenerateUeventsForDir(d2.get(), callback) == ListenerAction::kStop) {
return ListenerAction::kStop;
}
}
}
// default is always to continue looking for uevents
return ListenerAction::kContinue;
}
ListenerAction UeventListener::RegenerateUeventsForPath(const std::string& path,
const ListenerCallback& callback) const {
std::unique_ptr<DIR, decltype(&closedir)> d(opendir(path.c_str()), closedir);
if (!d) return ListenerAction::kContinue;
return RegenerateUeventsForDir(d.get(), callback);
}
static const char* kRegenerationPaths[] = {"/sys/class", "/sys/block", "/sys/devices"};
void UeventListener::RegenerateUevents(const ListenerCallback& callback) const {
for (const auto path : kRegenerationPaths) {
if (RegenerateUeventsForPath(path, callback) == ListenerAction::kStop) return;
}
}
void UeventListener::Poll(const ListenerCallback& callback,
const std::optional<std::chrono::milliseconds> relative_timeout) const {
using namespace std::chrono;
pollfd ufd;
ufd.events = POLLIN;
ufd.fd = device_fd_;
auto start_time = steady_clock::now();
while (true) {
ufd.revents = 0;
int timeout_ms = -1;
if (relative_timeout) {
auto now = steady_clock::now();
auto time_elapsed = duration_cast<milliseconds>(now - start_time);
if (time_elapsed > *relative_timeout) return;
auto remaining_timeout = *relative_timeout - time_elapsed;
timeout_ms = remaining_timeout.count();
}
int nr = poll(&ufd, 1, timeout_ms);
if (nr == 0) return;
if (nr < 0) {
PLOG(ERROR) << "poll() of uevent socket failed, continuing";
continue;
}
if (ufd.revents & POLLIN) {
// We're non-blocking, so if we receive a poll event keep processing until
// we have exhausted all uevent messages.
Uevent uevent;
while (ReadUevent(&uevent)) {
if (callback(uevent) == ListenerAction::kStop) return;
}
}
}
}
} // namespace init
} // namespace android
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