Add userdata partition to microdroid

Many programs need /data (especially /data/local/tmp) to properly work.
This change adds a basic unencrypted ext4 userdata partition to
microdroid. Eventually microdroid will support userdata encryption so
only VM can access /data.

Bug: 185767624
Test: atest MicrodroidHostTestCases
Test: log in to microdroid and test writing to /data
Change-Id: I115a8083ad6741fea9dedd61eca7194b1b5e5712
diff --git a/microdroid/Android.bp b/microdroid/Android.bp
index 2522679..5cffdb4 100644
--- a/microdroid/Android.bp
+++ b/microdroid/Android.bp
@@ -18,6 +18,7 @@
     "vendor",
     "debug_ramdisk",
     "mnt",
+    "data",
 
     "apex",
     "linkerconfig",
@@ -105,6 +106,7 @@
     name: "microdroid_vendor",
     use_avb: true,
     deps: [
+        "microdroid_fstab",
         "microdroid_plat_sepolicy_vers.txt",
         "microdroid_precompiled_sepolicy",
         "microdroid_precompiled_sepolicy.plat_sepolicy_and_mapping.sha256",
@@ -385,6 +387,11 @@
 }
 
 prebuilt_etc {
+    name: "microdroid_cdisk_userdata.json",
+    src: "microdroid_cdisk_userdata.json",
+}
+
+prebuilt_etc {
     name: "microdroid_payload.json",
     src: "microdroid_payload.json",
 }
diff --git a/microdroid/README.md b/microdroid/README.md
index 4ce74a5..4adf60d 100644
--- a/microdroid/README.md
+++ b/microdroid/README.md
@@ -34,10 +34,13 @@
 $ adb shell 'cp /apex/com.android.virt/etc/fs/*.img /data/local/tmp'
 $ adb shell 'cp /apex/com.android.virt/etc/uboot_env.img /data/local/tmp'
 $ adb shell 'dd if=/dev/zero of=/data/local/tmp/misc.img bs=4k count=256'
+$ adb shell 'dd if=/dev/zero of=/data/local/tmp/userdata.img bs=4k count=25600'
+$ adb shell 'mkfs.ext4 /data/local/tmp/userdata.img'
 $ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk.json os_composite.img'
 $ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk_env.json env_composite.img'
+$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_cdisk /apex/com.android.virt/etc/microdroid_cdisk_userdata.json userdata_composite.img'
 $ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/mk_payload /apex/com.android.virt/etc/microdroid_payload.json payload.img'
-$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/crosvm run --cid=5 --disable-sandbox --bios=bootloader --serial=type=stdout --disk=os_composite.img --disk=env_composite.img --disk=payload.img'
+$ adb shell 'cd /data/local/tmp; /apex/com.android.virt/bin/crosvm run --cid=5 --disable-sandbox --bios=bootloader --serial=type=stdout --disk=os_composite.img --disk=env_composite.img --disk=payload.img --rwdisk=userdata_composite.img'
 ```
 
 The CID in `--cid` parameter can be anything greater than 2 (`VMADDR_CID_HOST`).
diff --git a/microdroid/fstab b/microdroid/fstab
index 129718e..2f4e45f 100644
--- a/microdroid/fstab
+++ b/microdroid/fstab
@@ -1,2 +1,5 @@
 system /system ext4 noatime,ro,errors=panic wait,first_stage_mount,logical
 vendor /vendor ext4 noatime,ro,errors=panic wait,first_stage_mount,logical
+
+# TODO(b/185767624): turn on encryption
+/dev/block/by-name/userdata /data ext4 noatime,nosuid,nodev,errors=panic latemount,wait,check
diff --git a/microdroid/init.rc b/microdroid/init.rc
index 61f9ae5..721ba93 100644
--- a/microdroid/init.rc
+++ b/microdroid/init.rc
@@ -78,6 +78,8 @@
     # some services can be started.
     trigger late-fs
 
+    trigger post-fs-data
+
     # Load persist properties and override properties (if enabled) from /data.
     trigger load_persist_props_action
 
@@ -109,6 +111,10 @@
 
     start adbd
 
+on post-fs-data
+    mount_all /vendor/etc/fstab --late
+    restorecon /data
+
 service ueventd /system/bin/ueventd
     class core
     critical
diff --git a/microdroid/microdroid_cdisk_userdata.json b/microdroid/microdroid_cdisk_userdata.json
new file mode 100644
index 0000000..04af3f2
--- /dev/null
+++ b/microdroid/microdroid_cdisk_userdata.json
@@ -0,0 +1,9 @@
+{
+  "partitions": [
+    {
+      "label": "userdata",
+      "path": "userdata.img",
+      "writable": true
+    }
+  ]
+}