Feat/blockhash

crates/evm/src/errors.cairo

@@ -19,6 +19,7 @@ const WRITE_IN_STATIC_CONTEXT: felt252 = 'KKT: WriteInStaticContext';
 
 // STARKNET_SYSCALLS
 const READ_SYSCALL_FAILED: felt252 = 'KKT: read syscall failed';
+const BLOCK_HASH_SYSCALL_FAILED: felt252 = 'KKT: block_hash syscall failed';
 
 #[derive(Drop, Copy, PartialEq)]
 enum EVMError {

crates/evm/src/instructions/block_information.cairo

@@ -1,12 +1,13 @@
 use evm::balance::balance;
 //! Block Information.
 
-use evm::errors::EVMError;
+use evm::errors::{EVMError, BLOCK_HASH_SYSCALL_FAILED};
 use evm::machine::{Machine, MachineCurrentContextTrait};
 use evm::stack::StackTrait;
 
 // Corelib imports
-use starknet::info::{get_block_number, get_block_timestamp};
+use starknet::info::{get_block_number, get_block_timestamp, get_block_info};
+use starknet::{get_block_hash_syscall};
 use utils::constants::CHAIN_ID;
 
 #[generate_trait]
@@ -15,7 +16,27 @@ impl BlockInformation of BlockInformationTrait {
     /// Get the hash of one of the 256 most recent complete blocks.
     /// # Specification: https://www.evm.codes/#40?fork=shanghai
     fn exec_blockhash(ref self: Machine) -> Result<(), EVMError> {
-        Result::Err(EVMError::NotImplemented)
+        let block_number = self.stack.pop_u64()?;
+        let current_block = get_block_number();
+
+        // If input block number is lower than current_block - 256, return 0
+        // If input block number is higher than current_block - 10, return 0
+        // Note: in the specs, input block number can be equal - at most - to the current block number minus one.
+        // In Starknet, the `get_block_hash_syscall` is capped at current block minus ten.
+        // TODO: monitor the changes in the `get_block_hash_syscall` syscall.
+        // source: https://docs.starknet.io/documentation/architecture_and_concepts/Smart_Contracts/system-calls-cairo1/#get_block_hash
+        if block_number + 10 > current_block || block_number + 256 < current_block {
+            return self.stack.push(0);
+        }
+
+        let block_hash = get_block_hash_syscall(block_number);
+        match block_hash {
+            Result::Ok(block_hash) => self.stack.push(block_hash.into()),
+            // This syscall should not error out, as we made sure block_number =< current_block - 10
+            // In case of failed syscall, we can either return 0, or revert.
+            // Since this situation would be highly breaking, we choose to revert.
+            Result::Err(_) => Result::Err(EVMError::SyscallFailed(BLOCK_HASH_SYSCALL_FAILED)),
+        }
     }
 
     /// 0x41 - COINBASE

crates/evm/src/stack.cairo

@@ -35,6 +35,7 @@ trait StackTrait {
     fn push(ref self: Stack, item: u256) -> Result<(), EVMError>;
     fn pop(ref self: Stack) -> Result<u256, EVMError>;
     fn pop_usize(ref self: Stack) -> Result<usize, EVMError>;
+    fn pop_u64(ref self: Stack) -> Result<u64, EVMError>;
     fn pop_i256(ref self: Stack) -> Result<i256, EVMError>;
     fn pop_eth_address(ref self: Stack) -> Result<EthAddress, EVMError>;
     fn pop_n(ref self: Stack, n: usize) -> Result<Array<u256>, EVMError>;
@@ -113,11 +114,25 @@ impl StackImpl of StackTrait {
     #[inline(always)]
     fn pop_usize(ref self: Stack) -> Result<usize, EVMError> {
         let item: u256 = self.pop()?;
-        // item.try_into().ok_or(EVMError::TypeConversionError(TYPE_CONVERSION_ERROR))
         let item: usize = item.try_into_result()?;
         Result::Ok(item)
     }
 
+    /// Calls `Stack::pop` and tries to convert it to usize
+    ///
+    /// # Errors
+    ///
+    /// Returns `EVMError::StackError` with appropriate message
+    /// In case:
+    ///     - Stack is empty
+    ///     - Type conversion failed
+    #[inline(always)]
+    fn pop_u64(ref self: Stack) -> Result<u64, EVMError> {
+        let item: u256 = self.pop()?;
+        let item: u64 = item.try_into_result()?;
+        Result::Ok(item)
+    }
+
     /// Calls `Stack::pop` and convert it to i256
     ///
     /// # Errors

crates/evm/src/tests/test_instructions/test_block_information.cairo

@@ -9,6 +9,58 @@ use openzeppelin::token::erc20::interface::IERC20CamelDispatcherTrait;
 use starknet::testing::{set_block_timestamp, set_block_number, set_contract_address};
 use utils::constants::CHAIN_ID;
 
+/// 0x40 - BLOCKHASH
+#[test]
+#[available_gas(20000000)]
+fn test_block_hash_below_bounds() {
+    // Given
+    let mut machine = setup_machine();
+
+    set_block_number(500);
+
+    // When
+    machine.stack.push(243).unwrap();
+    machine.exec_blockhash();
+
+    // Then
+    assert(machine.stack.peek().unwrap() == 0, 'stack top should be 1692873993');
+}
+
+#[test]
+#[available_gas(20000000)]
+fn test_block_hash_above_bounds() {
+    // Given
+    let mut machine = setup_machine();
+
+    set_block_number(500);
+
+    // When
+    machine.stack.push(491).unwrap();
+    machine.exec_blockhash();
+
+    // Then
+    assert(machine.stack.peek().unwrap() == 0, 'stack top should be 1692873993');
+}
+
+// TODO: implement exec_blockhash testing for block number within bounds
+// https://github.com/starkware-libs/cairo/blob/77a7e7bc36aa1c317bb8dd5f6f7a7e6eef0ab4f3/crates/cairo-lang-starknet/cairo_level_tests/interoperability.cairo#L173
+#[ignore]
+#[test]
+#[available_gas(20000000)]
+fn test_block_hash_within_bounds() {
+    // Given
+    let mut machine = setup_machine();
+
+    set_block_number(500);
+
+    // When
+    machine.stack.push(244).unwrap();
+    machine.exec_blockhash();
+    // Then
+    assert(machine.stack.peek().unwrap() == 0xF, 'stack top should be 0xF');
+}
+
+
 #[test]
 #[available_gas(20000000)]
 fn test_block_timestamp_set_to_1692873993() {

crates/utils/src/traits.cairo

@@ -85,11 +85,11 @@ trait TryIntoResult<T, U> {
     fn try_into_result(self: T) -> Result<U, EVMError>;
 }
 
-impl U256TryIntoResultU32 of TryIntoResult<u256, usize> {
+impl U256TryIntoResultU32<U, +TryInto<u256, U>> of TryIntoResult<u256, U> {
     /// Converts a u256 into a Result<u32, EVMError>
     /// If the u256 is larger than MAX_U32, it returns an error.
     /// Otherwise, it returns the casted value.
-    fn try_into_result(self: u256) -> Result<usize, EVMError> {
+    fn try_into_result(self: u256) -> Result<U, EVMError> {
         match self.try_into() {
             Option::Some(value) => Result::Ok(value),
             Option::None => Result::Err(EVMError::TypeConversionError(TYPE_CONVERSION_ERROR))