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Commit 56999b41 authored by Tom Cherry's avatar Tom Cherry
Browse files

init: chroot from recovery to /first_stage_ramdisk 

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.

Bug: 114062208
Test: AVB works with blueline_mainline
Change-Id: Iffb154962b6e160150917e068f1e7d0bf7cb84e7
parent 166ae693

init/first_stage_mount.cpp

+3 −17
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include "first_stage_mount.h"



#include <stdlib.h>

#include <sys/mount.h>

#include <unistd.h>



#include <chrono>
@@ -122,18 +123,8 @@ 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
@@ -371,16 +362,11 @@ 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;

        }



        SwitchRoot((*system_partition)->mount_point);

        SwitchRoot((*system_partition)->mount_point, true);



        mount_fstab_recs_.erase(system_partition);

    }

init/init_first_stage.cpp

+81 −0
Original line number Diff line number Diff line
@@ -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 +172,36 @@ 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("/first_stage_ramdisk", false);

    }



    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;

init/switch_root.cpp

+8 −58
Original line number Diff line number Diff line
@@ -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};
@@ -109,42 +69,32 @@ std::vector<std::string> GetMounts(const std::string& new_root) { 


}  // namespace



void SwitchRoot(const std::string& new_root) {

void SwitchRoot(const std::string& new_root, bool move_root_mount) {

    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 << "'";

    }



    if (move_root_mount) {

        if (mount(new_root.c_str(), "/", nullptr, MS_MOVE, nullptr) != 0) {

            PLOG(FATAL) << "Unable to move root mount to new_root, '" << 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

init/switch_root.h

+1 −1
Original line number Diff line number Diff line
@@ -21,7 +21,7 @@ 
namespace android {

namespace init {



void SwitchRoot(const std::string& new_root);

void SwitchRoot(const std::string& new_root, bool move_root_mount);



}  // namespace init

}  // namespace android