Add parent_hash to FraudProof

`parent_hash` will be used to fetch the runtime code for running the
execution.

Author: liuchengxu

crates/sp-executor/src/lib.rs

@@ -210,6 +210,10 @@ pub enum VerificationError {
 /// Fraud proof for the state computation.
 #[derive(Decode, Encode, TypeInfo, PartialEq, Eq, Clone, RuntimeDebug)]
 pub struct FraudProof {
+    /// Parent hash of the block at which the invalid execution occurred.
+    ///
+    /// Runtime code for this block's execution is retrieved on top of the parent block.
+    pub parent_hash: H256,
     /// State root before the fraudulent transaction.
     pub pre_state_root: H256,
     /// State root after the fraudulent transaction.

crates/subspace-fraud-proof/src/lib.rs

@@ -207,14 +207,17 @@ impl<
 
     fn verify(&self, proof: &FraudProof) -> Result<(), VerificationError> {
         let FraudProof {
+            parent_hash,
             pre_state_root,
             post_state_root,
             proof,
             execution_args,
         } = proof;
 
-        // TODO: we should use parent_hash.
-        let at = BlockId::Hash(Block::Hash::default());
+        let at = BlockId::Hash(
+            Block::Hash::decode(&mut parent_hash.encode().as_slice())
+                .expect("Block Hash must be H256; qed"),
+        );
 
         let state = self
             .backend

cumulus/client/cirrus-executor/src/lib.rs

@@ -626,7 +626,13 @@ where
 					None,
 				)?;
 
-				FraudProof { pre_state_root, post_state_root, proof, execution_args }
+				FraudProof {
+					parent_hash: as_h256(&parent_header.hash())?,
+					pre_state_root,
+					post_state_root,
+					proof,
+					execution_args,
+				}
 			} else if local_trace_idx == local_receipt.trace.len() - 1 {
 				// `finalize_block` execution proof.
 				let pre_state_root = as_h256(&execution_receipt.trace[local_trace_idx - 1])?;
@@ -659,7 +665,13 @@ where
 					Some((delta, post_delta_root)),
 				)?;
 
-				FraudProof { pre_state_root, post_state_root, proof, execution_args }
+				FraudProof {
+					parent_hash: as_h256(&parent_header.hash())?,
+					pre_state_root,
+					post_state_root,
+					proof,
+					execution_args,
+				}
 			} else {
 				// Regular extrinsic execution proof.
 				let pre_state_root = as_h256(&execution_receipt.trace[local_trace_idx - 1])?;
@@ -672,7 +684,13 @@ where
 				)?;
 
 				// TODO: proof should be a CompactProof.
-				FraudProof { pre_state_root, post_state_root, proof, execution_args }
+				FraudProof {
+					parent_hash: as_h256(&parent_header.hash())?,
+					pre_state_root,
+					post_state_root,
+					proof,
+					execution_args,
+				}
 			};
 
 			self.submit_fraud_proof(fraud_proof);