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/*
* Copyright (C) 2019 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 "mount_handler.h"
#include <ctype.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/types.h>
#include <unistd.h>
#include <algorithm>
#include <filesystem>
#include <string>
#include <utility>
#include <vector>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <fs_mgr.h>
#include <fstab/fstab.h>
#include <libdm/dm.h>
#include "epoll.h"
using android::base::Basename;
using android::base::StringPrintf;
namespace android {
namespace init {
namespace {
MountHandlerEntry ParseMount(const std::string& line) {
auto fields = android::base::Split(line, " ");
while (fields.size() < 3) fields.emplace_back("");
if (fields[0] == "/dev/root") {
auto& dm = dm::DeviceMapper::Instance();
std::string path;
if (dm.GetDmDevicePathByName("system", &path) || dm.GetDmDevicePathByName("vroot", &path)) {
fields[0] = path;
} else if (android::fs_mgr::Fstab fstab; android::fs_mgr::ReadDefaultFstab(&fstab)) {
auto entry = GetEntryForMountPoint(&fstab, "/");
if (entry || (entry = GetEntryForMountPoint(&fstab, "/system"))) {
fields[0] = entry->blk_device;
}
}
}
if (android::base::StartsWith(fields[0], "/dev/")) {
if (std::string link; android::base::Readlink(fields[0], &link)) {
fields[0] = link;
}
}
return MountHandlerEntry(fields[0], fields[1], fields[2]);
}
// return sda25 for dm-4, sda25 for sda25, or mmcblk0p24 for mmcblk0p24
std::string GetDiskPart(std::string blockdev) {
if (blockdev.find('/') != std::string::npos) return {};
while (android::base::StartsWith(blockdev, "dm-")) {
auto& dm = dm::DeviceMapper::Instance();
std::optional<std::string> parent = dm.GetParentBlockDeviceByPath("/dev/block/" + blockdev);
if (parent) {
blockdev = android::base::Basename(*parent);
} else {
return {};
}
}
return blockdev;
}
// return sda for sda25, or mmcblk0 for mmcblk0p24
std::string GetRootDisk(std::string blockdev) {
if (blockdev.empty()) return {};
if (blockdev.find('/') != std::string::npos) return {};
std::error_code ec;
for (const auto& entry : std::filesystem::directory_iterator("/sys/block", ec)) {
const std::string path = entry.path().string();
if (std::filesystem::exists(StringPrintf("%s/%s", path.c_str(), blockdev.c_str()))) {
return Basename(path);
}
}
return {};
}
void SetMountProperty(const MountHandlerEntry& entry, bool add) {
static constexpr char devblock[] = "/dev/block/";
if (!android::base::StartsWith(entry.blk_device, devblock)) return;
auto target = entry.blk_device.substr(strlen(devblock));
std::string diskpart, rootdisk;
if (add) {
diskpart = GetDiskPart(target);
rootdisk = GetRootDisk(diskpart);
struct stat sb;
if (stat(entry.mount_point.c_str(), &sb) || !S_ISDIR(sb.st_mode)) rootdisk = "";
// Clear the noise associated with loopback and APEX.
if (android::base::StartsWith(target, "loop")) rootdisk = "";
if (android::base::StartsWith(entry.mount_point, "/apex/")) rootdisk = "";
}
auto mount_prop = entry.mount_point;
if (mount_prop == "/") mount_prop = "/root";
std::replace(mount_prop.begin(), mount_prop.end(), '/', '.');
auto blk_mount_prop = "dev.mnt.blk" + mount_prop;
auto dev_mount_prop = "dev.mnt.dev" + mount_prop;
auto rootdisk_mount_prop = "dev.mnt.rootdisk" + mount_prop;
// Set property even if its rootdisk does not change to trigger 'on property:'
// handling, except for clearing non-existent or already clear property.
// Goal is reduction of empty properties and associated triggers.
if (rootdisk.empty() && android::base::GetProperty(blk_mount_prop, "").empty()) return;
if (rootdisk.empty()) {
android::base::SetProperty(blk_mount_prop, "");
android::base::SetProperty(dev_mount_prop, "");
android::base::SetProperty(rootdisk_mount_prop, "");
return;
}
// 1. dm-N
// dev.mnt.dev.data = dm-N
// dev.mnt.blk.data = sdaN or mmcblk0pN
// dev.mnt.rootdisk.data = sda or mmcblk0
//
// 2. sdaN or mmcblk0pN
// dev.mnt.dev.data = sdaN or mmcblk0pN
// dev.mnt.blk.data = sdaN or mmcblk0pN
// dev.mnt.rootdisk.data = sda or mmcblk0
android::base::SetProperty(dev_mount_prop, target);
android::base::SetProperty(blk_mount_prop, diskpart);
android::base::SetProperty(rootdisk_mount_prop, rootdisk);
}
} // namespace
MountHandlerEntry::MountHandlerEntry(const std::string& blk_device, const std::string& mount_point,
const std::string& fs_type)
: blk_device(blk_device), mount_point(mount_point), fs_type(fs_type) {}
bool MountHandlerEntry::operator<(const MountHandlerEntry& r) const {
if (blk_device < r.blk_device) return true;
if (blk_device > r.blk_device) return false;
if (mount_point < r.mount_point) return true;
if (mount_point > r.mount_point) return false;
return fs_type < r.fs_type;
}
MountHandler::MountHandler(Epoll* epoll) : epoll_(epoll), fp_(fopen("/proc/mounts", "re"), fclose) {
if (!fp_) PLOG(FATAL) << "Could not open /proc/mounts";
auto result = epoll->RegisterHandler(
fileno(fp_.get()), [this]() { this->MountHandlerFunction(); }, EPOLLERR | EPOLLPRI);
if (!result.ok()) LOG(FATAL) << result.error();
}
MountHandler::~MountHandler() {
if (fp_) epoll_->UnregisterHandler(fileno(fp_.get()));
}
void MountHandler::MountHandlerFunction() {
rewind(fp_.get());
std::vector<MountHandlerEntry> touched;
auto untouched = mounts_;
char* buf = nullptr;
size_t len = 0;
while (getline(&buf, &len, fp_.get()) != -1) {
auto buf_string = std::string(buf);
if (buf_string.find("/emulated") != std::string::npos) {
continue;
}
auto entry = ParseMount(buf_string);
auto match = untouched.find(entry);
if (match == untouched.end()) {
touched.emplace_back(std::move(entry));
} else {
untouched.erase(match);
}
}
free(buf);
for (auto& entry : untouched) {
SetMountProperty(entry, false);
mounts_.erase(entry);
}
for (auto& entry : touched) {
SetMountProperty(entry, true);
mounts_.emplace(std::move(entry));
}
}
} // namespace init
} // namespace android
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