pvmfw: Clean up dangling references in __symbols__

Bug: 277993056
Test: atest libpvmfw.device_assignment.test
Change-Id: I682868d173e516a52d3e5b09dfb11e31a7aad02f

pvmfw/src/device_assignment.rs

diff --git a/pvmfw/src/device_assignment.rs b/pvmfw/src/device_assignment.rs
index e427710..2c47f9e 100644
--- a/pvmfw/src/device_assignment.rs
+++ b/pvmfw/src/device_assignment.rs
@@ -294,6 +294,26 @@
         .map_or(false, |name| name == b"__overlay__")
 }
 
+fn filter_dangling_symbols(fdt: &mut Fdt) -> Result<()> {
+    if let Some(symbols) = fdt.symbols()? {
+        let mut removed = vec![];
+        for prop in symbols.properties()? {
+            let path = CStr::from_bytes_with_nul(prop.value()?)
+                .map_err(|_| DeviceAssignmentError::Internal)?;
+            if fdt.node(path)?.is_none() {
+                let name = prop.name()?;
+                removed.push(CString::from(name));
+            }
+        }
+
+        let mut symbols = fdt.symbols_mut()?.unwrap();
+        for name in removed {
+            symbols.nop_property(&name)?;
+        }
+    }
+    Ok(())
+}
+
 impl AsRef<Fdt> for VmDtbo {
     fn as_ref(&self) -> &Fdt {
         &self.0
@@ -744,7 +764,8 @@
             device.patch(fdt, &pviommu_phandles)?;
         }
 
-        Ok(())
+        // Removes any dangling references in __symbols__ (e.g. removed pvIOMMUs)
+        filter_dangling_symbols(fdt)
     }
 }
 
@@ -1020,6 +1041,39 @@
     }
 
     #[test]
+    fn device_info_patch_no_pviommus() {
+        let mut fdt_data = fs::read(FDT_WITHOUT_IOMMUS_FILE_PATH).unwrap();
+        let mut vm_dtbo_data = fs::read(VM_DTBO_FILE_PATH).unwrap();
+        let mut data = vec![0_u8; fdt_data.len() + vm_dtbo_data.len()];
+        let fdt = Fdt::from_mut_slice(&mut fdt_data).unwrap();
+        let vm_dtbo = VmDtbo::from_mut_slice(&mut vm_dtbo_data).unwrap();
+        let platform_dt = Fdt::create_empty_tree(data.as_mut_slice()).unwrap();
+
+        let hypervisor = MockHypervisor {
+            mmio_tokens: [((0x9, 0xFF), 0x300)].into(),
+            iommu_tokens: BTreeMap::new(),
+        };
+        let device_info = DeviceAssignmentInfo::parse(fdt, vm_dtbo, &hypervisor).unwrap().unwrap();
+        device_info.filter(vm_dtbo).unwrap();
+
+        // SAFETY: Damaged VM DTBO wouldn't be used after this unsafe block.
+        unsafe {
+            platform_dt.apply_overlay(vm_dtbo.as_mut()).unwrap();
+        }
+        device_info.patch(platform_dt).unwrap();
+
+        let compatible = platform_dt.root().next_compatible(cstr!("pkvm,pviommu")).unwrap();
+        assert_eq!(None, compatible);
+
+        if let Some(symbols) = platform_dt.symbols().unwrap() {
+            for prop in symbols.properties().unwrap() {
+                let path = CStr::from_bytes_with_nul(prop.value().unwrap()).unwrap();
+                assert_ne!(None, platform_dt.node(path).unwrap());
+            }
+        }
+    }
+
+    #[test]
     fn device_info_overlay_iommu() {
         let mut fdt_data = fs::read(FDT_FILE_PATH).unwrap();
         let mut vm_dtbo_data = fs::read(VM_DTBO_FILE_PATH).unwrap();