dexopt_chroot_setup

dexopt_chroot_setup is a component of ART Service. It sets up the chroot environment for Pre-reboot Dexopt, to dexopt apps on a best-effort basis before the reboot after a Mainline update or an OTA update is downloaded, to support seamless updates.

It requires elevated permissions that are not available to system_server, such as mounting filesystems. It publishes a binder interface that is internal to ART Service's Java code.

Pre-reboot Dexopt file structure

Overview

/mnt/pre_reboot_dexopt
|-- chroot
|   |-- system_ext
|   |-- vendor
|   |-- product
|   |-- data
|   |-- mnt
|   |   |-- expand
|   |   `-- artd_tmp
|   |-- dev
|   |-- proc
|   |-- sys
|   |-- metadata
|   |-- apex
|   `-- linkerconfig
`-- mount_tmp

/mnt/pre_reboot_dexopt

The root directory for Pre-reboot Dexopt, prepared by init.

/mnt/pre_reboot_dexopt/chroot

The root directory of the chroot environment for Pre-reboot Dexopt. It is the mount point of the system image. Created by dexopt_chroot_setup, and only exists for the duration of the Pre-reboot Dexopt.

/mnt/pre_reboot_dexopt/chroot/{system_ext,vendor,product}

Mount points of other readonly images.

/mnt/pre_reboot_dexopt/chroot/{data,mnt/expand,dev,proc,sys,metadata}

Same as the corresponding directories outside of chroot. These are read-write mounts.

/mnt/pre_reboot_dexopt/chroot/mnt/artd_tmp

An empty directory for storing temporary files during Pre-reboot Dexopt, managed by artd.

/mnt/pre_reboot_dexopt/chroot/apex

For holding the apex mount points used in the chroot environment, managed by apexd. Note that this is not the same as /apex outside of chroot.

/mnt/pre_reboot_dexopt/chroot/linkerconfig

For holding the linker config used in the chroot environment, managed by linkerconfig. Note that this is not the same as /linkerconfig outside of chroot.

/mnt/pre_reboot_dexopt/mount_tmp

An ephemeral directory used as a temporary mount point for bind-mounting directories “slave+shared”.