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105 lines
4.1 KiB
105 lines
4.1 KiB
# Microdroid
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Microdroid is a (very) lightweight version of Android that is intended to run on
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on-device virtual machines. It is built from the same source code as the regular
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Android, but it is much smaller; no system server, no HALs, no GUI, etc. It is
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intended to host headless & native workloads only.
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## Building
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You need a VIM3L board. Instructions for building Android for the target, and
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flashing the image can be found [here](../docs/getting_started/yukawa.md).
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Then you install `com.android.virt` APEX. All files needed to run microdroid are
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included in the APEX, which is already in the `yukawa` (VIM3L) target. You can
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of course build and install the APEX manually.
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```sh
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$ source build/envsetup.sh
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$ choosecombo 1 aosp_arm64 userdebug // actually, any arm64-based target is ok
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$ m com.android.virt
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$ adb install $ANDROID_PRODUCT_OUT/system/apex/com.android.virt.apex
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$ adb reboot
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```
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## Running
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Create a config file, `microdroid.json`:
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```json
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{
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"bootloader": "/data/local/tmp/microdroid/bootloader",
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"disks": [
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{
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"image": "/data/local/tmp/microdroid/os_composite.img",
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"writable": false
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},
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{
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"image": "/data/local/tmp/microdroid/env_composite.img",
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"writable": false
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},
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{
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"image": "/data/local/tmp/microdroid/payload.img",
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"writable": false
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},
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{
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"image": "/data/local/tmp/microdroid/userdata_composite.qcow2",
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"writable": true
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}
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]
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}
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```
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Copy the artifacts to the temp directory, create the composite image using
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`mk_cdisk` and copy the VM config file. For now, some other files have to be
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manually created. In the future, you won't need these, and this shall be done
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via [`virtmanager`](../virtmanager/).
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```sh
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$ adb root
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$ adb shell 'mkdir /data/local/tmp/microdroid'
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$ adb shell 'cp /apex/com.android.virt/etc/microdroid_bootloader /data/local/tmp/microdroid/bootloader'
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$ adb shell 'cp /apex/com.android.virt/etc/fs/*.img /data/local/tmp/microdroid'
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$ adb shell 'cp /apex/com.android.virt/etc/uboot_env.img /data/local/tmp/microdroid'
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$ adb shell 'dd if=/dev/zero of=/data/local/tmp/microdroid/misc.img bs=4k count=256'
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$ adb shell 'dd if=/dev/zero of=/data/local/tmp/microdroid/userdata.img bs=1 count=0 seek=4G'
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$ adb shell 'mkfs.ext4 /data/local/tmp/microdroid/userdata.img'
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$ adb shell 'cd /data/local/tmp/microdroid; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk.json os_composite.img'
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$ adb shell 'cd /data/local/tmp/microdroid; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk_env.json env_composite.img'
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$ adb shell 'cd /data/local/tmp/microdroid; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk_userdata.json userdata_composite.img'
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$ adb shell '/apex/com.android.virt/bin/crosvm create_qcow2 --backing_file=/data/local/tmp/microdroid/userdata_composite.img /data/local/tmp/microdroid/userdata_composite.qcow2'
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$ adb shell 'cd /data/local/tmp/microdroid; /apex/com.android.virt/bin/mk_payload /apex/com.android.virt/etc/microdroid_payload.json payload.img'
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$ adb shell 'chmod go+r /data/local/tmp/microdroid/*-header.img /data/local/tmp/microdroid/*-footer.img'
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$ adb push microdroid.json /data/local/tmp/microdroid/microdroid.json
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```
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Ensure SELinux is in permissive mode to allow virtmanager and crosvm to open
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files from `/data/local/tmp`. Opening files from this directory is
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neverallow-ed and file descriptors should be passed instead but, before that is
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supported, `adb shell setenforce 0` will put the device in permissive mode.
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Now, run the VM and look for `adbd` starting in the logs.
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```sh
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$ adb shell "start virtmanager"
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$ adb shell "RUST_BACKTRACE=1 RUST_LOG=trace /apex/com.android.virt/bin/vm run /data/local/tmp/microdroid/microdroid.json"
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```
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## ADB
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```sh
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$ CID=10
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$ adb forward tcp:8000 vsock:$CID:5555
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$ adb connect localhost:8000
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```
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`CID` should be the CID that `vm` reported was assigned to the VM. You can also
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check it with `adb shell "/apex/com.android.virt/bin/vm list"`. `5555` must be
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the value. `8000` however can be any port in the development machine.
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Done. Now you can log into microdroid. Have fun!
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```sh
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$ adb -s localhost:8000 shell
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```
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