866c08c0ac
When using the recovery image as a trampoline to boot the system, first chroot from the recovery image to /first_stage_ramdisk, to minimize differences between these two boot paths. Primary motivation is due to the fact that the basename of each mount point is used by device-manager to name its nodes, and the previous code that created used /system_recovery_mount as the mount point for system.img broke AVB. Instead of hacking around that issue, this change unified mounting for the recovery trampoline and true first stage ramdisk paths. Change when relanding: the original change skipped the move mount from /first_stage_ramdisk to / and only did a chroot instead. This was a mistake that resulted in the subsequent move mount of /system to / to mount over the '/' directory instead of moving that mount. This change uses a bind mount of /first_stage_ramdisk to itself instead of skipping the first move mount. Bug: 114062208 Test: AVB works with blueline_mainline Change-Id: I65207edfe98531892da2eafcbff19b438c9c64fe
99 lines
2.9 KiB
C++
99 lines
2.9 KiB
C++
/*
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* Copyright (C) 2018 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "switch_root.h"
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#include <fcntl.h>
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#include <mntent.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <android-base/logging.h>
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#include <android-base/strings.h>
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using android::base::StartsWith;
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using namespace std::literals;
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namespace android {
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namespace init {
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namespace {
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std::vector<std::string> GetMounts(const std::string& new_root) {
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auto fp = std::unique_ptr<std::FILE, decltype(&endmntent)>{setmntent("/proc/mounts", "re"),
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endmntent};
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if (fp == nullptr) {
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PLOG(FATAL) << "Failed to open /proc/mounts";
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}
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std::vector<std::string> result;
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mntent* mentry;
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while ((mentry = getmntent(fp.get())) != nullptr) {
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// We won't try to move rootfs.
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if (mentry->mnt_dir == "/"s) {
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continue;
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}
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// The new root mount is handled separately.
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if (mentry->mnt_dir == new_root) {
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continue;
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}
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// Move operates on subtrees, so do not try to move children of other mounts.
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if (std::find_if(result.begin(), result.end(), [&mentry](const auto& older_mount) {
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return StartsWith(mentry->mnt_dir, older_mount);
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}) != result.end()) {
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continue;
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}
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result.emplace_back(mentry->mnt_dir);
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}
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return result;
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}
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} // namespace
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void SwitchRoot(const std::string& new_root) {
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auto mounts = GetMounts(new_root);
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LOG(INFO) << "Switching root to '" << new_root << "'";
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for (const auto& mount_path : mounts) {
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auto new_mount_path = new_root + mount_path;
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mkdir(new_mount_path.c_str(), 0755);
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if (mount(mount_path.c_str(), new_mount_path.c_str(), nullptr, MS_MOVE, nullptr) != 0) {
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PLOG(FATAL) << "Unable to move mount at '" << mount_path << "'";
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}
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}
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if (chdir(new_root.c_str()) != 0) {
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PLOG(FATAL) << "Could not chdir to new_root, '" << new_root << "'";
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}
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if (mount(new_root.c_str(), "/", nullptr, MS_MOVE, nullptr) != 0) {
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PLOG(FATAL) << "Unable to move root mount to new_root, '" << new_root << "'";
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}
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if (chroot(".") != 0) {
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PLOG(FATAL) << "Unable to chroot to new root";
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}
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}
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} // namespace init
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} // namespace android
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