build(blockifier): add get class hash at syscall

crates/blockifier/resources/versioned_constants_0_13_0.json

@@ -122,6 +122,10 @@
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 50
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "emit_event_gas_cost": {
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 10
@@ -397,6 +401,11 @@
                 "builtin_instance_counter": {},
                 "n_memory_holes": 0,
                 "n_steps": 46
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_1.json

@@ -122,6 +122,10 @@
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 50
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "emit_event_gas_cost": {
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 10
@@ -421,6 +425,11 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_1_1.json

@@ -122,6 +122,10 @@
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 50
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "emit_event_gas_cost": {
             "syscall_base_gas_cost": 1,
             "step_gas_cost": 10
@@ -421,6 +425,11 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_2.json

@@ -185,6 +185,10 @@
             "step_gas_cost": 50,
             "syscall_base_gas_cost": 1
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "stored_block_hash_buffer": 10,
         "syscall_base_gas_cost": {
             "step_gas_cost": 100
@@ -425,6 +429,11 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_2_1.json

@@ -185,6 +185,10 @@
             "step_gas_cost": 50,
             "syscall_base_gas_cost": 1
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "stored_block_hash_buffer": 10,
         "syscall_base_gas_cost": {
             "step_gas_cost": 100
@@ -425,6 +429,11 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_3.json

@@ -185,6 +185,10 @@
             "step_gas_cost": 50,
             "syscall_base_gas_cost": 1
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 0,
+            "syscall_base_gas_cost": 0
+        },
         "stored_block_hash_buffer": 10,
         "syscall_base_gas_cost": {
             "step_gas_cost": 100
@@ -425,6 +429,11 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 0,
+                "builtin_instance_counter": {},
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/resources/versioned_constants_0_13_4.json

@@ -186,6 +186,10 @@
             "step_gas_cost": 100,
             "range_check_gas_cost": 1
         },
+        "get_class_hash_at_gas_cost": {
+            "step_gas_cost": 100,
+            "range_check_gas_cost": 1
+        },
         "stored_block_hash_buffer": 10,
         "syscall_base_gas_cost": {
             "step_gas_cost": 100
@@ -427,6 +431,13 @@
                     "range_check_builtin": 1
                 },
                 "n_memory_holes": 0
+            },
+            "GetClassHashAt": {
+                "n_steps": 100,
+                "builtin_instance_counter": {
+                    "range_check_builtin": 1
+                },
+                "n_memory_holes": 0
             }
         },
         "execute_txs_inner": {

crates/blockifier/src/execution/call_info.rs

@@ -4,7 +4,7 @@ use std::ops::Add;
 
 use cairo_vm::vm::runners::cairo_runner::ExecutionResources;
 use serde::Serialize;
-use starknet_api::core::{ClassHash, EthAddress};
+use starknet_api::core::{ClassHash, ContractAddress, EthAddress};
 use starknet_api::execution_resources::GasAmount;
 use starknet_api::state::StorageKey;
 use starknet_api::transaction::{EventContent, L2ToL1Payload};
@@ -126,6 +126,8 @@ pub struct CallInfo {
     // Additional information gathered during execution.
     pub storage_read_values: Vec<Felt>,
     pub accessed_storage_keys: HashSet<StorageKey>,
+    pub read_class_hash_values: Vec<ClassHash>,
+    pub accessed_contract_addresses: HashSet<ContractAddress>,
 }
 
 impl CallInfo {

crates/blockifier/src/execution/deprecated_entry_point_execution.rs

@@ -285,6 +285,7 @@ pub fn finalize_execution(
         ),
         storage_read_values: syscall_handler.read_values,
         accessed_storage_keys: syscall_handler.accessed_keys,
+        ..Default::default()
     })
 }
 

crates/blockifier/src/execution/deprecated_syscalls/mod.rs

@@ -57,6 +57,7 @@ pub enum DeprecatedSyscallSelector {
     GetBlockNumber,
     GetBlockTimestamp,
     GetCallerAddress,
+    GetClassHashAt,
     GetContractAddress,
     GetExecutionInfo,
     GetSequencerAddress,
@@ -99,6 +100,7 @@ impl TryFrom<Felt> for DeprecatedSyscallSelector {
             b"GetBlockNumber" => Ok(Self::GetBlockNumber),
             b"GetBlockTimestamp" => Ok(Self::GetBlockTimestamp),
             b"GetCallerAddress" => Ok(Self::GetCallerAddress),
+            b"GetClassHashAt" => Ok(Self::GetClassHashAt),
             b"GetContractAddress" => Ok(Self::GetContractAddress),
             b"GetExecutionInfo" => Ok(Self::GetExecutionInfo),
             b"GetSequencerAddress" => Ok(Self::GetSequencerAddress),

crates/blockifier/src/execution/entry_point_execution.rs

@@ -458,6 +458,8 @@ pub fn finalize_execution(
         charged_resources,
         storage_read_values: syscall_handler.read_values,
         accessed_storage_keys: syscall_handler.accessed_keys,
+        read_class_hash_values: syscall_handler.read_class_hash_values,
+        accessed_contract_addresses: syscall_handler.accessed_contract_addresses,
     })
 }
 

crates/blockifier/src/execution/native/entry_point_execution.rs

@@ -38,6 +38,7 @@ pub fn execute_entry_point_call(
     create_callinfo(call_result, syscall_handler)
 }
 
+#[allow(unreachable_code)]
 fn create_callinfo(
     call_result: ContractExecutionResult,
     syscall_handler: NativeSyscallHandler<'_>,
@@ -78,6 +79,11 @@ fn create_callinfo(
         inner_calls: syscall_handler.inner_calls,
         storage_read_values: syscall_handler.read_values,
         accessed_storage_keys: syscall_handler.accessed_keys,
+        // TODO(Aviv): The syscall is not supported here yet.
+        // Currently, `accessed_contract_addresses` and `read_class_hash_values` are initialized
+        // as empty. Support for handling accessed storage keys via syscalls should be implemented.
+        accessed_contract_addresses: Default::default(),
+        read_class_hash_values: Default::default(),
         tracked_resource: TrackedResource::SierraGas,
     })
 }

crates/blockifier/src/execution/syscalls/hint_processor.rs

@@ -57,6 +57,7 @@ use crate::execution::syscalls::{
     deploy,
     emit_event,
     get_block_hash,
+    get_class_hash_at,
     get_execution_info,
     keccak,
     library_call,
@@ -233,6 +234,9 @@ pub struct SyscallHintProcessor<'a> {
     // Additional information gathered during execution.
     pub read_values: Vec<Felt>,
     pub accessed_keys: HashSet<StorageKey>,
+    pub read_class_hash_values: Vec<ClassHash>,
+    // Accessed addresses by the `get_class_hash_at` syscall.
+    pub accessed_contract_addresses: HashSet<ContractAddress>,
 
     // The original storage value of the executed contract.
     // Should be moved back `context.revert_info` before executing an inner call.
@@ -282,6 +286,8 @@ impl<'a> SyscallHintProcessor<'a> {
             syscall_ptr: initial_syscall_ptr,
             read_values: vec![],
             accessed_keys: HashSet::new(),
+            read_class_hash_values: vec![],
+            accessed_contract_addresses: HashSet::new(),
             original_values,
             hints,
             execution_info_ptr: None,
@@ -349,6 +355,11 @@ impl<'a> SyscallHintProcessor<'a> {
                 get_block_hash,
                 self.context.gas_costs().get_block_hash_gas_cost,
             ),
+            SyscallSelector::GetClassHashAt => self.execute_syscall(
+                vm,
+                get_class_hash_at,
+                self.context.gas_costs().get_class_hash_at_gas_cost,
+            ),
             SyscallSelector::GetExecutionInfo => self.execute_syscall(
                 vm,
                 get_execution_info,

crates/blockifier/src/execution/syscalls/mod.rs

@@ -786,3 +786,34 @@ pub fn sha_256_process_block(
 
     Ok(Sha256ProcessBlockResponse { state_ptr: response })
 }
+
+// GetClassHashAt syscall.
+
+pub(crate) type GetClassHashAtRequest = ContractAddress;
+pub(crate) type GetClassHashAtResponse = ClassHash;
+
+impl SyscallRequest for GetClassHashAtRequest {
+    fn read(vm: &VirtualMachine, ptr: &mut Relocatable) -> SyscallResult<GetClassHashAtRequest> {
+        let address = ContractAddress::try_from(felt_from_ptr(vm, ptr)?)?;
+        Ok(address)
+    }
+}
+
+impl SyscallResponse for GetClassHashAtResponse {
+    fn write(self, vm: &mut VirtualMachine, ptr: &mut Relocatable) -> WriteResponseResult {
+        write_felt(vm, ptr, *self)?;
+        Ok(())
+    }
+}
+
+pub(crate) fn get_class_hash_at(
+    request: GetClassHashAtRequest,
+    _vm: &mut VirtualMachine,
+    syscall_handler: &mut SyscallHintProcessor<'_>,
+    _remaining_gas: &mut u64,
+) -> SyscallResult<GetClassHashAtResponse> {
+    syscall_handler.accessed_contract_addresses.insert(request);
+    let class_hash = syscall_handler.state.get_class_hash_at(request)?;
+    syscall_handler.read_class_hash_values.push(class_hash);
+    Ok(class_hash)
+}

crates/blockifier/src/execution/syscalls/syscall_tests/constants.rs

@@ -1,3 +1,4 @@
 pub const REQUIRED_GAS_CALL_CONTRACT_TEST: u64 = 170370;
 pub const REQUIRED_GAS_STORAGE_READ_WRITE_TEST: u64 = 16990;
+pub const REQUIRED_GAS_GET_CLASS_HASH_AT_TEST: u64 = 7830;
 pub const REQUIRED_GAS_LIBRARY_CALL_TEST: u64 = 167970;

crates/blockifier/src/execution/syscalls/syscall_tests/get_class_hash_at.rs

@@ -0,0 +1,71 @@
+use starknet_api::{calldata, class_hash, contract_address, felt};
+use test_case::test_case;
+
+use crate::abi::abi_utils::selector_from_name;
+use crate::context::ChainInfo;
+use crate::execution::call_info::CallExecution;
+use crate::execution::entry_point::CallEntryPoint;
+use crate::execution::syscalls::syscall_tests::constants::REQUIRED_GAS_GET_CLASS_HASH_AT_TEST;
+use crate::retdata;
+use crate::test_utils::contracts::FeatureContract;
+use crate::test_utils::initial_test_state::test_state;
+use crate::test_utils::{trivial_external_entry_point_new, CairoVersion, BALANCE};
+
+/// Tests the `get_class_hash_at` syscall, ensuring that:
+/// 1. `accessed_contract_addresses` contains `address` for a valid entry.
+/// 2. `read_class_hash_values` includes `class_hash`.
+/// 3. Execution succeeds with expected gas for valid cases.
+/// 4. Execution fails if `address` has a different `class_hash`.
+/// 5. Execution succeeds and returns `class_hash` = 0 if `address` is absent.
+#[test_case(FeatureContract::TestContract(CairoVersion::Cairo1), REQUIRED_GAS_GET_CLASS_HASH_AT_TEST; "VM")]
+fn test_get_class_hash_at(test_contract: FeatureContract, expected_gas: u64) {
+    let chain_info = &ChainInfo::create_for_testing();
+    let mut state = test_state(chain_info, BALANCE, &[(test_contract, 1)]);
+    let address = contract_address!("0x111");
+    let class_hash = class_hash!("0x222");
+    state.state.address_to_class_hash.insert(address, class_hash);
+
+    // Test deployed contract.
+    let positive_entry_point_call = CallEntryPoint {
+        calldata: calldata![address.into(), class_hash.0],
+        entry_point_selector: selector_from_name("test_get_class_hash_at"),
+        ..trivial_external_entry_point_new(test_contract)
+    };
+    let positive_call_info = positive_entry_point_call.execute_directly(&mut state).unwrap();
+    assert!(positive_call_info.accessed_contract_addresses.contains(&address));
+    assert!(positive_call_info.read_class_hash_values[0] == class_hash);
+    assert_eq!(
+        positive_call_info.execution,
+        CallExecution {
+            retdata: retdata!(),
+            gas_consumed: expected_gas,
+            failed: false,
+            ..CallExecution::default()
+        }
+    );
+    // Test undeployed contract - should return class_hash = 0 and succeed.
+    let non_existing_address = felt!("0x333");
+    let class_hash_of_undeployed_contract = felt!("0x0");
+
+    let negative_entry_point_call = CallEntryPoint {
+        calldata: calldata![non_existing_address, class_hash_of_undeployed_contract],
+        entry_point_selector: selector_from_name("test_get_class_hash_at"),
+        ..trivial_external_entry_point_new(test_contract)
+    };
+    assert!(!negative_entry_point_call.execute_directly(&mut state).unwrap().execution.failed);
+
+    // Sanity check: giving the wrong expected class hash to the test should make it fail.
+    let different_class_hash = class_hash!("0x444");
+    let different_class_hash_entry_point_call = CallEntryPoint {
+        calldata: calldata![address.into(), different_class_hash.0],
+        entry_point_selector: selector_from_name("test_get_class_hash_at"),
+        ..trivial_external_entry_point_new(test_contract)
+    };
+    assert!(
+        different_class_hash_entry_point_call
+            .execute_directly(&mut state)
+            .unwrap()
+            .execution
+            .failed
+    );
+}

crates/blockifier/src/execution/syscalls/syscall_tests/mod.rs

@@ -4,6 +4,7 @@ mod deploy;
 mod emit_event;
 mod failure_format;
 mod get_block_hash;
+mod get_class_hash_at;
 mod get_execution_info;
 mod keccak;
 mod library_call;