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Commit 3249f9ff authored by Jooyung Han's avatar Jooyung Han Committed by Automerger Merge Worker
Browse files

Merge "Use /bootstrap-apex for bootstrap APEXes" into main am: 58ba0b44 am: 6b0c2c3c 

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2666915



Change-Id: I6f1fcda6db9affd51e5067a685e2b488665f5b30
Signed-off-by: default avatarAutomerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
parents 83a2197c 6b0c2c3c

init/builtins.cpp

+50 −0
Original line number Diff line number Diff line
@@ -1262,6 +1262,51 @@ static Result<void> MountLinkerConfigForDefaultNamespace() { 


    return {};

}



static Result<void> MountApexRootForDefaultNamespace() {

    auto mount_namespace_id = GetCurrentMountNamespace();

    if (!mount_namespace_id.ok()) {

        return mount_namespace_id.error();

    }

    // There's nothing to do if it's still in the bootstrap mount namespace.

    // This happens when we don't need to update APEXes (e.g. Microdroid)

    // where bootstrap mount namespace == default mount namespace.

    if (mount_namespace_id.value() == NS_BOOTSTRAP) {

        return {};

    }



    // Now, we're in the "default" mount namespace and need a fresh /apex for

    // the default mount namespace.

    //

    // At this point, there are two mounts at the same mount point: /apex

    // - to tmpfs (private)

    // - to /bootstrap-apex (shared)

    //

    // We need unmount the second mount so that /apex in the default mount

    // namespace becomes RW/empty and "private" (we don't want mount events to

    // propagate to the bootstrap mount namespace).

    //

    // Likewise, we don't want the unmount event itself to propagate to the

    // bootstrap mount namespace. Otherwise, /apex in the bootstrap mount

    // namespace would become empty due to the unmount.

    //

    // Hence, before unmounting, we make /apex (the second one) "private" first.

    // so that the unmouting below doesn't affect to the bootstrap mount namespace.

    if (mount(nullptr, "/apex", nullptr, MS_PRIVATE | MS_REC, nullptr) == -1) {

        return ErrnoError() << "Failed to remount /apex as private";

    }



    // Now we can unmount /apex (bind-mount to /bootstrap-apex). This only affects

    // in the default mount namespace and /apex is now seen as tmpfs mount.

    // Note that /apex in the bootstrap mount namespace is still a bind-mount to

    // /bootstrap-apex and holds the APEX mounts.

    if (umount2("/apex", MNT_DETACH) == -1) {

        return ErrnoError() << "Failed to umount /apex";

    }



    return {};

}



static Result<void> do_update_linker_config(const BuiltinArguments&) {

    return GenerateLinkerConfiguration();

}
@@ -1315,6 +1360,11 @@ static Result<void> do_enter_default_mount_ns(const BuiltinArguments& args) { 
    if (auto result = SwitchToMountNamespaceIfNeeded(NS_DEFAULT); !result.ok()) {

        return result.error();

    }



    if (auto result = MountApexRootForDefaultNamespace(); !result.ok()) {

        return result.error();

    }



    if (auto result = MountLinkerConfigForDefaultNamespace(); !result.ok()) {

        return result.error();

    }

init/init.cpp

+6 −0
Original line number Diff line number Diff line
@@ -832,6 +832,12 @@ static void MountExtraFilesystems() { 
    CHECKCALL(mount("tmpfs", "/apex", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,

                    "mode=0755,uid=0,gid=0"));



    if (NeedsTwoMountNamespaces()) {

        // /bootstrap-apex is used to mount "bootstrap" APEXes.

        CHECKCALL(mount("tmpfs", "/bootstrap-apex", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,

                        "mode=0755,uid=0,gid=0"));

    }



    // /linkerconfig is used to keep generated linker configuration

    CHECKCALL(mount("tmpfs", "/linkerconfig", "tmpfs", MS_NOEXEC | MS_NOSUID | MS_NODEV,

                    "mode=0755,uid=0,gid=0"));

init/mount_namespace.cpp

+30 −9
Original line number Diff line number Diff line
@@ -66,15 +66,6 @@ static std::string GetMountNamespaceId() { 
    return ret;

}



// In case we have two sets of APEXes (non-updatable, updatable), we need two separate mount

// namespaces.

static bool NeedsTwoMountNamespaces() {

    if (IsRecoveryMode()) return false;

    // In microdroid, there's only one set of APEXes in built-in directories include block devices.

    if (IsMicrodroid()) return false;

    return true;

}



static android::base::unique_fd bootstrap_ns_fd;

static android::base::unique_fd default_ns_fd;
@@ -83,6 +74,15 @@ static std::string default_ns_id; 


}  // namespace



// In case we have two sets of APEXes (non-updatable, updatable), we need two separate mount

// namespaces.

bool NeedsTwoMountNamespaces() {

    if (IsRecoveryMode()) return false;

    // In microdroid, there's only one set of APEXes in built-in directories include block devices.

    if (IsMicrodroid()) return false;

    return true;

}



bool SetupMountNamespaces() {

    // Set the propagation type of / as shared so that any mounting event (e.g.

    // /data) is by default visible to all processes. When private mounting is
@@ -96,6 +96,27 @@ bool SetupMountNamespaces() { 
    // the bootstrap namespace get APEXes from the read-only partition.

    if (!(ChangeMount("/apex", MS_PRIVATE))) return false;



    // However, some components (e.g. servicemanager) need to access bootstrap

    // APEXes from the default mount namespace. To achieve that, we bind-mount

    // /apex with /bootstrap-apex (not private) in the bootstrap mount namespace.

    // Bootstrap APEXes are mounted in /apex and also visible in /bootstrap-apex.

    // In the default mount namespace, we detach /bootstrap-apex from /apex and

    // bootstrap APEXes are still be visible in /bootstrap-apex.

    //

    // The end result will look like:

    //   in the bootstrap mount namespace:

    //     /apex  (== /bootstrap-apex)

    //       {bootstrap APEXes from the read-only partition}

    //

    //   in the default mount namespace:

    //     /bootstrap-apex

    //       {bootstrap APEXes from the read-only partition}

    //     /apex

    //       {APEXes, can be from /data partition}

    if (NeedsTwoMountNamespaces()) {

        if (!(BindMount("/bootstrap-apex", "/apex"))) return false;

    }



    // /linkerconfig is a private mountpoint to give a different linker configuration

    // based on the mount namespace. Subdirectory will be bind-mounted based on current mount

    // namespace

init/mount_namespace.h

+3 −0
Original line number Diff line number Diff line
@@ -24,9 +24,12 @@ namespace init { 
enum MountNamespace { NS_BOOTSTRAP, NS_DEFAULT };



bool SetupMountNamespaces();



base::Result<void> SwitchToMountNamespaceIfNeeded(MountNamespace target_mount_namespace);



base::Result<MountNamespace> GetCurrentMountNamespace();



bool NeedsTwoMountNamespaces();



}  // namespace init

}  // namespace android

init/selinux.cpp

+1 −1
Original line number Diff line number Diff line
@@ -766,7 +766,7 @@ void SelinuxRestoreContext() { 
    selinux_android_restorecon("/dev/device-mapper", 0);



    selinux_android_restorecon("/apex", 0);



    selinux_android_restorecon("/bootstrap-apex", 0);

    selinux_android_restorecon("/linkerconfig", 0);



    // adb remount, snapshot-based updates, and DSUs all create files during