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Reland: "init: chroot from recovery to /first_stage_ramdisk"

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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
This commit is contained in:
Tom Cherry 2018-11-06 10:32:53 -08:00
parent 223114008c
commit 866c08c0ac
3 changed files with 91 additions and 71 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

18
init/first_stage_mount.cpp
View file

@ -17,6 +17,7 @@
#include "first_stage_mount.h"
#include <stdlib.h>
#include <sys/mount.h>
#include <unistd.h>
#include <chrono>
@ -123,18 +124,8 @@ static inline bool IsDtVbmetaCompatible() {
return is_android_dt_value_expected("vbmeta/compatible", "android,vbmeta");
}
static bool ForceNormalBoot() {
static bool force_normal_boot = []() {
std::string cmdline;
android::base::ReadFileToString("/proc/cmdline", &cmdline);
return cmdline.find("androidboot.force_normal_boot=1") != std::string::npos;
}();
return force_normal_boot;
}
static bool IsRecoveryMode() {
return !ForceNormalBoot() && access("/system/bin/recovery", F_OK) == 0;
return access("/system/bin/recovery", F_OK) == 0;
}
// Class Definitions
@ -403,11 +394,6 @@ bool FirstStageMount::MountPartitions() {
[](const auto& rec) { return rec->mount_point == "/system"s; });
if (system_partition != mount_fstab_recs_.end()) {
if (ForceNormalBoot()) {
free((*system_partition)->mount_point);
(*system_partition)->mount_point = strdup("/system_recovery_mount");
}
if (!MountPartition(*system_partition)) {
return false;
}

86
init/init_first_stage.cpp
View file

@ -14,6 +14,8 @@
* limitations under the License.
*/
#include <dirent.h>
#include <fcntl.h>
#include <paths.h>
#include <stdlib.h>
#include <sys/mount.h>
@ -26,19 +28,72 @@
#include <vector>
#include <android-base/chrono_utils.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <cutils/android_reboot.h>
#include <private/android_filesystem_config.h>
#include "first_stage_mount.h"
#include "reboot_utils.h"
#include "switch_root.h"
#include "util.h"
using android::base::boot_clock;
using namespace std::literals;
namespace android {
namespace init {
namespace {
void FreeRamdisk(DIR* dir, dev_t dev) {
int dfd = dirfd(dir);
dirent* de;
while ((de = readdir(dir)) != nullptr) {
if (de->d_name == "."s || de->d_name == ".."s) {
continue;
}
bool is_dir = false;
if (de->d_type == DT_DIR || de->d_type == DT_UNKNOWN) {
struct stat info;
if (fstatat(dfd, de->d_name, &info, AT_SYMLINK_NOFOLLOW) != 0) {
continue;
}
if (info.st_dev != dev) {
continue;
}
if (S_ISDIR(info.st_mode)) {
is_dir = true;
auto fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
if (fd >= 0) {
auto subdir =
std::unique_ptr<DIR, decltype(&closedir)>{fdopendir(fd), closedir};
if (subdir) {
FreeRamdisk(subdir.get(), dev);
} else {
close(fd);
}
}
}
}
unlinkat(dfd, de->d_name, is_dir ? AT_REMOVEDIR : 0);
}
}
bool ForceNormalBoot() {
std::string cmdline;
android::base::ReadFileToString("/proc/cmdline", &cmdline);
return cmdline.find("androidboot.force_normal_boot=1") != std::string::npos;
}
} // namespace
int main(int argc, char** argv) {
if (REBOOT_BOOTLOADER_ON_PANIC) {
InstallRebootSignalHandlers();
@ -117,10 +172,41 @@ int main(int argc, char** argv) {
LOG(INFO) << "init first stage started!";
auto old_root_dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/"), closedir};
if (!old_root_dir) {
PLOG(ERROR) << "Could not opendir(\"/\"), not freeing ramdisk";
}
struct stat old_root_info;
if (stat("/", &old_root_info) != 0) {
PLOG(ERROR) << "Could not stat(\"/\"), not freeing ramdisk";
old_root_dir.reset();
}
if (ForceNormalBoot()) {
mkdir("/first_stage_ramdisk", 0755);
// SwitchRoot() must be called with a mount point as the target, so we bind mount the
// target directory to itself here.
if (mount("/first_stage_ramdisk", "/first_stage_ramdisk", nullptr, MS_BIND, nullptr) != 0) {
LOG(FATAL) << "Could not bind mount /first_stage_ramdisk to itself";
}
SwitchRoot("/first_stage_ramdisk");
}
if (!DoFirstStageMount()) {
LOG(FATAL) << "Failed to mount required partitions early ...";
}
struct stat new_root_info;
if (stat("/", &new_root_info) != 0) {
PLOG(ERROR) << "Could not stat(\"/\"), not freeing ramdisk";
old_root_dir.reset();
}
if (old_root_dir && old_root_info.st_dev != new_root_info.st_dev) {
FreeRamdisk(old_root_dir.get(), old_root_info.st_dev);
}
SetInitAvbVersionInRecovery();
static constexpr uint32_t kNanosecondsPerMillisecond = 1e6;

58
init/switch_root.cpp
View file

@ -16,7 +16,6 @@
#include "switch_root.h"
#include <dirent.h>
#include <fcntl.h>
#include <mntent.h>
#include <sys/mount.h>
@ -35,45 +34,6 @@ namespace init {
namespace {
void FreeRamdisk(DIR* dir, dev_t dev) {
int dfd = dirfd(dir);
dirent* de;
while ((de = readdir(dir)) != nullptr) {
if (de->d_name == "."s || de->d_name == ".."s) {
continue;
}
bool is_dir = false;
if (de->d_type == DT_DIR || de->d_type == DT_UNKNOWN) {
struct stat info;
if (fstatat(dfd, de->d_name, &info, AT_SYMLINK_NOFOLLOW) != 0) {
continue;
}
if (info.st_dev != dev) {
continue;
}
if (S_ISDIR(info.st_mode)) {
is_dir = true;
auto fd = openat(dfd, de->d_name, O_RDONLY | O_DIRECTORY);
if (fd >= 0) {
auto subdir =
std::unique_ptr<DIR, decltype(&closedir)>{fdopendir(fd), closedir};
if (subdir) {
FreeRamdisk(subdir.get(), dev);
} else {
close(fd);
}
}
}
}
unlinkat(dfd, de->d_name, is_dir ? AT_REMOVEDIR : 0);
}
}
std::vector<std::string> GetMounts(const std::string& new_root) {
auto fp = std::unique_ptr<std::FILE, decltype(&endmntent)>{setmntent("/proc/mounts", "re"),
endmntent};
@ -112,24 +72,16 @@ std::vector<std::string> GetMounts(const std::string& new_root) {
void SwitchRoot(const std::string& new_root) {
auto mounts = GetMounts(new_root);
LOG(INFO) << "Switching root to '" << new_root << "'";
for (const auto& mount_path : mounts) {
auto new_mount_path = new_root + mount_path;
mkdir(new_mount_path.c_str(), 0755);
if (mount(mount_path.c_str(), new_mount_path.c_str(), nullptr, MS_MOVE, nullptr) != 0) {
PLOG(FATAL) << "Unable to move mount at '" << mount_path << "'";
}
}
auto old_root_dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/"), closedir};
if (!old_root_dir) {
PLOG(ERROR) << "Could not opendir(\"/\"), not freeing ramdisk";
}
struct stat old_root_info;
if (stat("/", &old_root_info) != 0) {
PLOG(ERROR) << "Could not stat(\"/\"), not freeing ramdisk";
old_root_dir.reset();
}
if (chdir(new_root.c_str()) != 0) {
PLOG(FATAL) << "Could not chdir to new_root, '" << new_root << "'";
}
@ -141,10 +93,6 @@ void SwitchRoot(const std::string& new_root) {
if (chroot(".") != 0) {
PLOG(FATAL) << "Unable to chroot to new root";
}
if (old_root_dir) {
FreeRamdisk(old_root_dir.get(), old_root_info.st_dev);
}
}
} // namespace init