fix: do not charge data fee for system tx

src/handler.rs

@@ -60,7 +60,7 @@ where
     #[inline]
     fn pre_execution(&self, evm: &mut Self::Evm) -> Result<u64, Self::Error> {
         // only load the L1BlockInfo for txs that are not l1 messages.
-        if !evm.ctx().tx().is_l1_msg() {
+        if !evm.ctx().tx().is_l1_msg() && !evm.ctx().tx().is_system_tx() {
             let spec = evm.ctx().cfg().spec();
             let l1_block_info = L1BlockInfo::try_fetch(&mut evm.ctx().db(), spec)?;
             *evm.ctx().chain() = l1_block_info;
@@ -84,16 +84,21 @@ where
         let ctx = evm.ctx();
         let caller = ctx.tx().caller();
         let is_l1_msg = ctx.tx().is_l1_msg();
+        let is_system_tx = ctx.tx().is_system_tx();
         let kind = ctx.tx().kind();
         let spec = ctx.cfg().spec();
         let is_eip3607_disabled = ctx.cfg().is_eip3607_disabled();
         let is_nonce_check_disabled = ctx.cfg().is_nonce_check_disabled();
 
+        // execute normal checks and transaction processing logic for non-l1-msgs
         if !is_l1_msg {
             // We deduct caller max balance after minting and before deducing the
             // l1 cost, max values is already checked in pre_validate but l1 cost wasn't.
             pre_execution::validate_against_state_and_deduct_caller::<_, ERROR>(ctx)?;
+        }
 
+        // process rollup fee
+        if !is_l1_msg && !is_system_tx {
             let l1_block_info = ctx.chain().clone();
             let Some(rlp_bytes) = ctx.tx().rlp_bytes() else {
                 return Err(ERROR::from_string(
@@ -112,7 +117,10 @@ where
             }
             caller_account.data.info.balance =
                 caller_account.data.info.balance.saturating_sub(tx_l1_cost);
-        } else {
+        }
+
+        // execute l1 msg checks
+        if is_l1_msg {
             // Load caller's account.
             let (tx, journal) = ctx.tx_journal();
             let mut caller_account = journal.load_account(caller)?;

src/tests/fees.rs

@@ -2,6 +2,7 @@ use crate::{
     builder::ScrollBuilder,
     handler::ScrollHandler,
     test_utils::{context_with_funds, CALLER},
+    transaction::SYSTEM_ADDRESS,
     ScrollSpecId,
 };
 use std::boxed::Box;
@@ -45,3 +46,25 @@ fn test_should_deduct_correct_fees_curie() -> Result<(), Box<dyn core::error::Er
 
     Ok(())
 }
+
+#[test]
+fn test_no_rollup_fee_for_system_tx() -> Result<(), Box<dyn core::error::Error>> {
+    let ctx = context_with_funds(U256::from(70_000))
+        .modify_cfg_chained(|cfg| cfg.spec = ScrollSpecId::CURIE)
+        .modify_tx_chained(|tx| {
+            tx.base.caller = SYSTEM_ADDRESS;
+            tx.base.gas_price = 0
+        });
+
+    let mut evm = ctx.clone().build_scroll();
+    let handler = ScrollHandler::<_, EVMError<_>, EthFrame<_, _, _>>::new();
+
+    handler.pre_execution(&mut evm).unwrap();
+
+    let caller_account = evm.ctx().journal().load_account(CALLER)?;
+
+    // gas price is 0, no data fee => balance is unchanged.
+    assert_eq!(caller_account.data.info.balance, U256::from(70_000));
+
+    Ok(())
+}

src/transaction.rs

@@ -1,14 +1,20 @@
 use revm::context::{Transaction, TxEnv};
-use revm_primitives::{Address, Bytes, TxKind, B256, U256};
+use revm_primitives::{address, Address, Bytes, TxKind, B256, U256};
 
 /// The type for a l1 message transaction.
 pub const L1_MESSAGE_TYPE: u8 = 0x7E;
 
+/// The caller address of EIP-2935 system transactions.
+pub const SYSTEM_ADDRESS: Address = address!("0xfffffffffffffffffffffffffffffffffffffffe");
+
 #[auto_impl::auto_impl(&, Arc, Box)]
 pub trait ScrollTxTr: Transaction {
     /// Whether the transaction is an L1 message.
     fn is_l1_msg(&self) -> bool;
 
+    /// Whether the transaction is a system transaction (e.g. EIP-2935).
+    fn is_system_tx(&self) -> bool;
+
     /// The RLP encoded transaction bytes which are used to calculate the cost associated with
     /// posting the transaction on L1.
     fn rlp_bytes(&self) -> Option<&Bytes>;
@@ -111,6 +117,10 @@ impl<T: Transaction> ScrollTxTr for ScrollTransaction<T> {
         self.tx_type() == L1_MESSAGE_TYPE
     }
 
+    fn is_system_tx(&self) -> bool {
+        self.caller() == SYSTEM_ADDRESS
+    }
+
     fn rlp_bytes(&self) -> Option<&Bytes> {
         self.rlp_bytes.as_ref()
     }