// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40284755): Remove this and spanify to fix the errors.
#pragma allow_unsafe_buffers
#endif
#include "base/files/file_path_watcher_kqueue.h"
#include <fcntl.h>
#include <stddef.h>
#include <sys/param.h>
#include <string>
#include <vector>
#include "base/file_descriptor_posix.h"
#include "base/files/file_util.h"
#include "base/functional/bind.h"
#include "base/logging.h"
#include "base/ranges/algorithm.h"
#include "base/strings/stringprintf.h"
#include "base/task/sequenced_task_runner.h"
#include "base/threading/scoped_blocking_call.h"
// On some platforms these are not defined.
#if !defined(EV_RECEIPT)
#define EV_RECEIPT 0
#endif
#if !defined(O_EVTONLY)
#define O_EVTONLY O_RDONLY
#endif
namespace base {
FilePathWatcherKQueue::FilePathWatcherKQueue() : kqueue_(-1) {}
FilePathWatcherKQueue::~FilePathWatcherKQueue() {
DCHECK(!task_runner() || task_runner()->RunsTasksInCurrentSequence());
}
void FilePathWatcherKQueue::ReleaseEvent(struct kevent& event) {
CloseFileDescriptor(&event.ident);
EventData* entry = EventDataForKevent(event);
delete entry;
event.udata = NULL;
}
size_t FilePathWatcherKQueue::EventsForPath(FilePath path,
EventVector* events) {
// Make sure that we are working with a clean slate.
DCHECK(events->empty());
std::vector<FilePath::StringType> components = path.GetComponents();
if (components.empty()) {
return 0;
}
size_t last_existing_entry = 0;
FilePath built_path;
bool path_still_exists = true;
for (std::vector<FilePath::StringType>::iterator i = components.begin();
i != components.end(); ++i) {
if (i == components.begin()) {
built_path = FilePath(*i);
} else {
built_path = built_path.Append(*i);
}
uintptr_t fd = kNoFileDescriptor;
if (path_still_exists) {
fd = FileDescriptorForPath(built_path);
if (fd == kNoFileDescriptor) {
path_still_exists = false;
} else {
++last_existing_entry;
}
}
FilePath::StringType subdir = (i != (components.end() - 1)) ? *(i + 1) : "";
EventData* data = new EventData(built_path, subdir);
struct kevent event;
EV_SET(&event, fd, EVFILT_VNODE, (EV_ADD | EV_CLEAR | EV_RECEIPT),
(NOTE_DELETE | NOTE_WRITE | NOTE_ATTRIB |
NOTE_RENAME | NOTE_REVOKE | NOTE_EXTEND), 0, data);
events->push_back(event);
}
return last_existing_entry;
}
// static
size_t FilePathWatcherKQueue::EventForItem(const FilePath& path,
EventVector* events) {
// Make sure that we are working with a clean slate.
DCHECK(events->empty());
events->resize(1);
auto& event = events->front();
EV_SET(&event, FileDescriptorForPath(path), EVFILT_VNODE,
(EV_ADD | EV_CLEAR | EV_RECEIPT),
(NOTE_DELETE | NOTE_WRITE | NOTE_ATTRIB | NOTE_RENAME | NOTE_REVOKE |
NOTE_EXTEND),
0, new EventData(path, /*subdir=*/FilePath::StringType()));
return event.ident != kNoFileDescriptor ? 1 : 0;
}
uintptr_t FilePathWatcherKQueue::FileDescriptorForPath(const FilePath& path) {
ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
int fd = HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY));
if (fd < 0)
return kNoFileDescriptor;
return static_cast<uintptr_t>(fd);
}
void FilePathWatcherKQueue::CloseFileDescriptor(uintptr_t* fd) {
if (*fd == kNoFileDescriptor) {
return;
}
if (IGNORE_EINTR(close(checked_cast<int>(*fd))) != 0) {
DPLOG(ERROR) << "close";
}
*fd = kNoFileDescriptor;
}
bool FilePathWatcherKQueue::AreKeventValuesValid(struct kevent* kevents,
int count) {
if (count < 0) {
DPLOG(ERROR) << "kevent";
return false;
}
bool valid = true;
for (int i = 0; i < count; ++i) {
if (kevents[i].flags & EV_ERROR && kevents[i].data) {
// Find the kevent in |events_| that matches the kevent with the error.
EventVector::iterator event = events_.begin();
for (; event != events_.end(); ++event) {
if (event->ident == kevents[i].ident) {
break;
}
}
std::string path_name;
if (event != events_.end()) {
EventData* event_data = EventDataForKevent(*event);
if (event_data != NULL) {
path_name = event_data->path_.value();
}
}
if (path_name.empty()) {
path_name = base::StringPrintf(
"fd %ld", reinterpret_cast<long>(&kevents[i].ident));
}
DLOG(ERROR) << "Error: " << kevents[i].data << " for " << path_name;
valid = false;
}
}
return valid;
}
void FilePathWatcherKQueue::HandleAttributesChange(
const EventVector::iterator& event,
bool* target_file_affected,
bool* update_watches) {
EventVector::iterator next_event = event + 1;
EventData* next_event_data = EventDataForKevent(*next_event);
// Check to see if the next item in path is still accessible.
uintptr_t have_access = FileDescriptorForPath(next_event_data->path_);
if (have_access == kNoFileDescriptor) {
*target_file_affected = true;
*update_watches = true;
EventVector::iterator local_event(event);
for (; local_event != events_.end(); ++local_event) {
// Close all nodes from the event down. This has the side effect of
// potentially rendering other events in |updates| invalid.
// There is no need to remove the events from |kqueue_| because this
// happens as a side effect of closing the file descriptor.
CloseFileDescriptor(&local_event->ident);
}
} else {
CloseFileDescriptor(&have_access);
}
}
void FilePathWatcherKQueue::HandleDeleteOrMoveChange(
const EventVector::iterator& event,
bool* target_file_affected,
bool* update_watches) {
*target_file_affected = true;
*update_watches = true;
EventVector::iterator local_event(event);
for (; local_event != events_.end(); ++local_event) {
// Close all nodes from the event down. This has the side effect of
// potentially rendering other events in |updates| invalid.
// There is no need to remove the events from |kqueue_| because this
// happens as a side effect of closing the file descriptor.
CloseFileDescriptor(&local_event->ident);
}
}
void FilePathWatcherKQueue::HandleCreateItemChange(
const EventVector::iterator& event,
bool* target_file_affected,
bool* update_watches) {
// Get the next item in the path.
EventVector::iterator next_event = event + 1;
// Check to see if it already has a valid file descriptor.
if (!IsKeventFileDescriptorOpen(*next_event)) {
EventData* next_event_data = EventDataForKevent(*next_event);
// If not, attempt to open a file descriptor for it.
next_event->ident = FileDescriptorForPath(next_event_data->path_);
if (IsKeventFileDescriptorOpen(*next_event)) {
*update_watches = true;
if (next_event_data->subdir_.empty()) {
*target_file_affected = true;
}
}
}
}
bool FilePathWatcherKQueue::UpdateWatches(bool* target_file_affected) {
// Iterate over events adding kevents for items that exist to the kqueue.
// Then check to see if new components in the path have been created.
// Repeat until no new components in the path are detected.
// This is to get around races in directory creation in a watched path.
bool update_watches = true;
while (update_watches) {
size_t valid;
for (valid = 0; valid < events_.size(); ++valid) {
if (!IsKeventFileDescriptorOpen(events_[valid])) {
break;
}
}
if (valid == 0) {
// The root of the file path is inaccessible?
return false;
}
EventVector updates(valid);
ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
const int valid_int = checked_cast<int>(valid);
int count = HANDLE_EINTR(
kevent(kqueue_, &events_[0], valid_int, &updates[0], valid_int, NULL));
if (!AreKeventValuesValid(&updates[0], count)) {
return false;
}
update_watches = false;
for (; valid < events_.size(); ++valid) {
EventData* event_data = EventDataForKevent(events_[valid]);
events_[valid].ident = FileDescriptorForPath(event_data->path_);
if (IsKeventFileDescriptorOpen(events_[valid])) {
update_watches = true;
if (event_data->subdir_.empty()) {
*target_file_affected = true;
}
} else {
break;
}
}
}
return true;
}
bool FilePathWatcherKQueue::Watch(const FilePath& path,
Type type,
const FilePathWatcher::Callback& callback) {
DCHECK(target_.value().empty()); // Can only watch one path.
DCHECK(!callback.is_null());
DCHECK_EQ(kqueue_, -1);
// Recursive watch is not supported using kqueue.
DCHECK_NE(type, Type::kRecursive);
callback_ = callback;
target_ = path;
set_task_runner(SequencedTaskRunner::GetCurrentDefault());
kqueue_ = kqueue();
if (kqueue_ == -1) {
DPLOG(ERROR) << "kqueue";
return false;
}
size_t last_entry = type == Type::kNonRecursive
? EventsForPath(target_, &events_)
: EventForItem(target_, &events_);
if (!last_entry) {
// No notifications can possibly come in, so fail fast.
Cancel();
return false;
}
EventVector responses(last_entry);
ScopedBlockingCall scoped_blocking_call(FROM_HERE, BlockingType::MAY_BLOCK);
const int last_entry_int = checked_cast<int>(last_entry);
int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], last_entry_int,
&responses[0], last_entry_int, NULL));
if (!AreKeventValuesValid(&responses[0], count)) {
// Calling Cancel() here to close any file descriptors that were opened.
// This would happen in the destructor anyways, but FilePathWatchers tend to
// be long lived, and if an error has occurred, there is no reason to waste
// the file descriptors.
Cancel();
return false;
}
// It's safe to use Unretained() because the watch is cancelled and the
// callback cannot be invoked after |kqueue_watch_controller_| (which is a
// member of |this|) has been deleted.
kqueue_watch_controller_ = FileDescriptorWatcher::WatchReadable(
kqueue_, BindRepeating(&FilePathWatcherKQueue::OnKQueueReadable,
Unretained(this)));
return true;
}
void FilePathWatcherKQueue::Cancel() {
if (!task_runner()) {
set_cancelled();
return;
}
DCHECK(task_runner()->RunsTasksInCurrentSequence());
if (!is_cancelled()) {
set_cancelled();
kqueue_watch_controller_.reset();
if (IGNORE_EINTR(close(kqueue_)) != 0) {
DPLOG(ERROR) << "close kqueue";
}
kqueue_ = -1;
base::ranges::for_each(events_, ReleaseEvent);
events_.clear();
callback_.Reset();
}
}
void FilePathWatcherKQueue::OnKQueueReadable() {
DCHECK(task_runner()->RunsTasksInCurrentSequence());
DCHECK(events_.size());
// Request the file system update notifications that have occurred and return
// them in |updates|. |count| will contain the number of updates that have
// occurred.
EventVector updates(events_.size());
struct timespec timeout = {0, 0};
int count = HANDLE_EINTR(kevent(kqueue_, NULL, 0, &updates[0],
checked_cast<int>(updates.size()), &timeout));
// Error values are stored within updates, so check to make sure that no
// errors occurred.
if (!AreKeventValuesValid(&updates[0], count)) {
callback_.Run(target_, true /* error */);
Cancel();
return;
}
bool update_watches = false;
bool send_notification = false;
// Iterate through each of the updates and react to them.
// AreKeventValuesValid() guarantees `count` is non-negative.
for (size_t i = 0; i < static_cast<size_t>(count); ++i) {
// Find our kevent record that matches the update notification.
EventVector::iterator event = events_.begin();
for (; event != events_.end(); ++event) {
if (!IsKeventFileDescriptorOpen(*event) ||
event->ident == updates[i].ident) {
break;
}
}
if (event == events_.end() || !IsKeventFileDescriptorOpen(*event)) {
// The event may no longer exist in |events_| because another event
// modified |events_| in such a way to make it invalid. For example if
// the path is /foo/bar/bam and foo is deleted, NOTE_DELETE events for
// foo, bar and bam will be sent. If foo is processed first, then
// the file descriptors for bar and bam will already be closed and set
// to -1 before they get a chance to be processed.
continue;
}
EventData* event_data = EventDataForKevent(*event);
// If the subdir is empty, this is the last item on the path and is the
// target file.
bool target_file_affected = event_data->subdir_.empty();
if ((updates[i].fflags & NOTE_ATTRIB) && !target_file_affected) {
HandleAttributesChange(event, &target_file_affected, &update_watches);
}
if (updates[i].fflags & (NOTE_DELETE | NOTE_REVOKE | NOTE_RENAME)) {
HandleDeleteOrMoveChange(event, &target_file_affected, &update_watches);
}
if ((updates[i].fflags & NOTE_WRITE) && !target_file_affected) {
HandleCreateItemChange(event, &target_file_affected, &update_watches);
}
send_notification |= target_file_affected;
}
if (update_watches) {
if (!UpdateWatches(&send_notification)) {
callback_.Run(target_, true /* error */);
Cancel();
return;
}
}
if (send_notification) {
callback_.Run(target_, false);
}
}
} // namespace base
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