Allow host-controlled avf/untrusted prop
Allow addition of properties at /avf/untrusted in the DT overlay
created by virtmgr. While I'm here, refactor reference_dt into
dt_overlay to allow this & remove confusion of reference DT which from
the pt. of view of pVM is expected from ABL.
Include (a hardcoded) instance_id of VM in the DT overlay!
Test: vm_shell start-microdroid --auto-connect
Test: Check /proc/device-tree/avf/untrusted/instance-id has value of hardcoded id in non-protected VM
Test: atest virtualizationmanager_device_test
Bug: 291213394
Revert^2: This reverts commit 655d87fc5b0a0d33baecf40165da2ec1e8f37348.
Reason for revert: Revert^1 was caused by a bug in FsFdt, fixed in
parent commit of the current one.
Change-Id: Ia79fd8dce37f5a13b95c53edef89fe99e225c439
diff --git a/virtualizationmanager/src/dt_overlay.rs b/virtualizationmanager/src/dt_overlay.rs
new file mode 100644
index 0000000..83f7734
--- /dev/null
+++ b/virtualizationmanager/src/dt_overlay.rs
@@ -0,0 +1,117 @@
+// Copyright 2024, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! This module support creating AFV related overlays, that can then be appended to DT by VM.
+
+use anyhow::{anyhow, Result};
+use cstr::cstr;
+use fsfdt::FsFdt;
+use libfdt::Fdt;
+use std::ffi::CStr;
+use std::path::Path;
+
+pub(crate) const AVF_NODE_NAME: &CStr = cstr!("avf");
+pub(crate) const UNTRUSTED_NODE_NAME: &CStr = cstr!("untrusted");
+pub(crate) const VM_DT_OVERLAY_PATH: &str = "vm_dt_overlay.dtbo";
+pub(crate) const VM_DT_OVERLAY_MAX_SIZE: usize = 2000;
+
+/// Create a Device tree overlay containing the provided proc style device tree & properties!
+/// # Arguments
+/// * `dt_path` - (Optional) Path to (proc style) device tree to be included in the overlay.
+/// * `untrusted_props` - Include a property in /avf/untrusted node. This node is used to specify
+/// host provided properties such as `instance-id`.
+///
+/// Example: with `create_device_tree_overlay(_, _, [("instance-id", _),])`
+/// ```
+/// {
+/// fragment@0 {
+/// target-path = "/";
+/// __overlay__ {
+/// avf {
+/// untrusted { instance-id = [0x01 0x23 .. ] }
+/// }
+/// };
+/// };
+/// };
+/// };
+/// ```
+pub(crate) fn create_device_tree_overlay<'a>(
+ buffer: &'a mut [u8],
+ dt_path: Option<&'a Path>,
+ untrusted_props: &[(&'a CStr, &'a [u8])],
+) -> Result<&'a mut Fdt> {
+ if dt_path.is_none() && untrusted_props.is_empty() {
+ return Err(anyhow!("Expected at least one device tree addition"));
+ }
+
+ let fdt =
+ Fdt::create_empty_tree(buffer).map_err(|e| anyhow!("Failed to create empty Fdt: {e:?}"))?;
+ let mut root = fdt.root_mut().map_err(|e| anyhow!("Failed to get root: {e:?}"))?;
+ let mut node =
+ root.add_subnode(cstr!("fragment@0")).map_err(|e| anyhow!("Failed to fragment: {e:?}"))?;
+ node.setprop(cstr!("target-path"), b"/\0")
+ .map_err(|e| anyhow!("Failed to set target-path: {e:?}"))?;
+ let mut node = node
+ .add_subnode(cstr!("__overlay__"))
+ .map_err(|e| anyhow!("Failed to __overlay__ node: {e:?}"))?;
+
+ if !untrusted_props.is_empty() {
+ let mut node = node
+ .add_subnode(AVF_NODE_NAME)
+ .map_err(|e| anyhow!("Failed to add avf node: {e:?}"))?;
+ let mut node = node
+ .add_subnode(UNTRUSTED_NODE_NAME)
+ .map_err(|e| anyhow!("Failed to add /avf/untrusted node: {e:?}"))?;
+ for (name, value) in untrusted_props {
+ node.setprop(name, value).map_err(|e| anyhow!("Failed to set property: {e:?}"))?;
+ }
+ }
+
+ if let Some(path) = dt_path {
+ fdt.overlay_onto(cstr!("/fragment@0/__overlay__"), path)?;
+ }
+ fdt.pack().map_err(|e| anyhow!("Failed to pack DT overlay, {e:?}"))?;
+
+ Ok(fdt)
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ #[test]
+ fn empty_overlays_not_allowed() {
+ let mut buffer = vec![0_u8; VM_DT_OVERLAY_MAX_SIZE];
+ let res = create_device_tree_overlay(&mut buffer, None, &[]);
+ assert!(res.is_err());
+ }
+
+ #[test]
+ fn untrusted_prop_test() {
+ let mut buffer = vec![0_u8; VM_DT_OVERLAY_MAX_SIZE];
+ let prop_name = cstr!("XOXO");
+ let prop_val_input = b"OXOX";
+ let fdt =
+ create_device_tree_overlay(&mut buffer, None, &[(prop_name, prop_val_input)]).unwrap();
+
+ let prop_value_dt = fdt
+ .node(cstr!("/fragment@0/__overlay__/avf/untrusted"))
+ .unwrap()
+ .expect("/avf/untrusted node doesn't exist")
+ .getprop(prop_name)
+ .unwrap()
+ .expect("Prop not found!");
+ assert_eq!(prop_value_dt, prop_val_input, "Unexpected property value");
+ }
+}