Transient Storage Host I/Os

arbitrator/arbutil/src/evm/api.rs

@@ -31,6 +31,8 @@ impl From<u8> for EvmApiStatus {
 pub enum EvmApiMethod {
     GetBytes32,
     SetTrieSlots,
+    GetTransientBytes32,
+    SetTransientBytes32,
     ContractCall,
     DelegateCall,
     StaticCall,
@@ -85,6 +87,14 @@ pub trait EvmApi<D: DataReader>: Send + 'static {
     /// Analogous to repeated invocations of `vm.SSTORE`.
     fn flush_storage_cache(&mut self, clear: bool, gas_left: u64) -> Result<u64>;
 
+    /// Reads the 32-byte value in the EVM's transient state trie at offset `key`.
+    /// Analogous to `vm.TLOAD`.
+    fn get_transient_bytes32(&mut self, key: Bytes32) -> Bytes32;
+
+    /// Writes the 32-byte value in the EVM's transient state trie at offset `key`.
+    /// Analogous to `vm.TSTORE`.
+    fn set_transient_bytes32(&mut self, key: Bytes32, value: Bytes32) -> Result<()>;
+
     /// Calls the contract at the given address.
     /// Returns the EVM return data's length, the gas cost, and whether the call succeeded.
     /// Analogous to `vm.CALL`.

arbitrator/arbutil/src/evm/mod.rs

@@ -20,6 +20,10 @@ pub const COLD_SLOAD_GAS: u64 = 2100;
 // params.WarmStorageReadCostEIP2929
 pub const WARM_SLOAD_GAS: u64 = 100;
 
+// params.WarmStorageReadCostEIP2929 (see enable1153 in jump_table.go)
+pub const TLOAD_GAS: u64 = WARM_SLOAD_GAS;
+pub const TSTORE_GAS: u64 = WARM_SLOAD_GAS;
+
 // params.LogGas and params.LogDataGas
 pub const LOG_TOPIC_GAS: u64 = 375;
 pub const LOG_DATA_GAS: u64 = 8;

arbitrator/arbutil/src/evm/req.rs

@@ -144,6 +144,22 @@ impl<D: DataReader, H: RequestHandler<D>> EvmApi<D> for EvmApiRequestor<D, H> {
         Ok(cost)
     }
 
+    fn get_transient_bytes32(&mut self, key: Bytes32) -> Bytes32 {
+        let (res, ..) = self.request(EvmApiMethod::GetTransientBytes32, key);
+        res.try_into().unwrap()
+    }
+
+    fn set_transient_bytes32(&mut self, key: Bytes32, value: Bytes32) -> Result<()> {
+        let mut data = Vec::with_capacity(64);
+        data.extend(key);
+        data.extend(value);
+        let (res, ..) = self.request(EvmApiMethod::SetTransientBytes32, data);
+        if res[0] != EvmApiStatus::Success.into() {
+            bail!("{}", String::from_utf8_or_hex(res));
+        }
+        Ok(())
+    }
+
     fn contract_call(
         &mut self,
         contract: Bytes20,

arbitrator/stylus/src/host.rs

@@ -141,6 +141,22 @@ pub(crate) fn storage_flush_cache<D: DataReader, E: EvmApi<D>>(
     hostio!(env, storage_flush_cache(clear != 0))
 }
 
+pub(crate) fn transient_load_bytes32<D: DataReader, E: EvmApi<D>>(
+    mut env: WasmEnvMut<D, E>,
+    key: GuestPtr,
+    dest: GuestPtr,
+) -> MaybeEscape {
+    hostio!(env, transient_load_bytes32(key, dest))
+}
+
+pub(crate) fn transient_store_bytes32<D: DataReader, E: EvmApi<D>>(
+    mut env: WasmEnvMut<D, E>,
+    key: GuestPtr,
+    value: GuestPtr,
+) -> MaybeEscape {
+    hostio!(env, transient_store_bytes32(key, value))
+}
+
 pub(crate) fn call_contract<D: DataReader, E: EvmApi<D>>(
     mut env: WasmEnvMut<D, E>,
     contract: GuestPtr,

arbitrator/stylus/src/native.rs

@@ -132,6 +132,8 @@ impl<D: DataReader, E: EvmApi<D>> NativeInstance<D, E> {
                 "storage_load_bytes32" => func!(host::storage_load_bytes32),
                 "storage_cache_bytes32" => func!(host::storage_cache_bytes32),
                 "storage_flush_cache" => func!(host::storage_flush_cache),
+                "transient_load_bytes32" => func!(host::transient_load_bytes32),
+                "transient_store_bytes32" => func!(host::transient_store_bytes32),
                 "call_contract" => func!(host::call_contract),
                 "delegate_call_contract" => func!(host::delegate_call_contract),
                 "static_call_contract" => func!(host::static_call_contract),
@@ -342,6 +344,8 @@ pub fn module(wasm: &[u8], compile: CompileConfig) -> Result<Vec<u8>> {
             "storage_load_bytes32" => stub!(|_: u32, _: u32|),
             "storage_cache_bytes32" => stub!(|_: u32, _: u32|),
             "storage_flush_cache" => stub!(|_: u32|),
+            "transient_load_bytes32" => stub!(|_: u32, _: u32|),
+            "transient_store_bytes32" => stub!(|_: u32, _: u32|),
             "call_contract" => stub!(u8 <- |_: u32, _: u32, _: u32, _: u32, _: u64, _: u32|),
             "delegate_call_contract" => stub!(u8 <- |_: u32, _: u32, _: u32, _: u64, _: u32|),
             "static_call_contract" => stub!(u8 <- |_: u32, _: u32, _: u32, _: u64, _: u32|),

arbitrator/stylus/src/test/api.rs

@@ -87,6 +87,14 @@ impl EvmApi<VecReader> for TestEvmApi {
         Ok(22100 * storage.len() as u64) // pretend worst case
     }
 
+    fn get_transient_bytes32(&mut self, _key: Bytes32) -> Bytes32 {
+        unimplemented!("tload not supported")
+    }
+
+    fn set_transient_bytes32(&mut self, _key: Bytes32, _value: Bytes32) -> Result<()> {
+        unimplemented!("tstore not supported")
+    }
+
     /// Simulates a contract call.
     /// Note: this call function is for testing purposes only and deviates from onchain behavior.
     fn contract_call(

arbitrator/stylus/tests/storage/src/main.rs

@@ -10,21 +10,39 @@ use stylus_sdk::{
     stylus_proc::entrypoint,
 };
 
+#[link(wasm_import_module = "vm_hooks")]
+extern "C" {
+    fn transient_load_bytes32(key: *const u8, dest: *mut u8);
+    fn transient_store_bytes32(key: *const u8, value: *const u8);
+}
+
 #[entrypoint]
 fn user_main(input: Vec<u8>) -> Result<Vec<u8>, Vec<u8>> {
-    let read = input[0] == 0;
     let slot = B256::try_from(&input[1..33]).unwrap();
 
-    Ok(if read {
-        console!("read {slot}");
-        let data = StorageCache::get_word(slot.into());
-        console!("value {data}");
-        data.0.into()
-    } else {
-        console!("write {slot}");
-        let data = B256::try_from(&input[33..]).unwrap();
-        unsafe { StorageCache::set_word(slot.into(), data) };
-        console!(("value {data}"));
-        vec![]
+    Ok(match input[0] {
+        0 => {
+            console!("read {slot}");
+            let data = StorageCache::get_word(slot.into());
+            console!("value {data}");
+            data.0.into()
+        }
+        1 => {
+            console!("write {slot}");
+            let data = B256::try_from(&input[33..]).unwrap();
+            unsafe { StorageCache::set_word(slot.into(), data) };
+            console!(("value {data}"));
+            vec![]
+        }
+        2 => unsafe {
+            let mut data = [0; 32];
+            transient_load_bytes32(slot.as_ptr(), data.as_mut_ptr());
+            data.into()
+        }
+        _ => unsafe {
+            let data = B256::try_from(&input[33..]).unwrap();
+            transient_store_bytes32(slot.as_ptr(), data.as_ptr());
+            vec![]
+        }
     })
 }

arbitrator/wasm-libraries/forward/src/main.rs

@@ -6,13 +6,15 @@ use std::{fs::File, io::Write, path::PathBuf};
 use structopt::StructOpt;
 
 /// order matters!
-const HOSTIOS: [[&str; 3]; 35] = [
+const HOSTIOS: [[&str; 3]; 37] = [
     ["read_args", "i32", ""],
     ["write_result", "i32 i32", ""],
     ["exit_early", "i32", ""],
     ["storage_load_bytes32", "i32 i32", ""],
     ["storage_cache_bytes32", "i32 i32", ""],
     ["storage_flush_cache", "i32", ""],
+    ["transient_load_bytes32", "i32 i32", ""],
+    ["transient_store_bytes32", "i32 i32", ""],
     ["call_contract", "i32 i32 i32 i32 i64 i32", "i32"],
     ["delegate_call_contract", "i32 i32 i32 i64 i32", "i32"],
     ["static_call_contract", "i32 i32 i32 i64 i32", "i32"],

arbitrator/wasm-libraries/host-io/src/lib.rs

@@ -3,10 +3,10 @@
 
 #![allow(clippy::missing_safety_doc)] // TODO: add safety docs
 
+use arbutil::PreimageType;
 use caller_env::{static_caller::STATIC_MEM, GuestPtr, MemAccess};
-use core::ops::{Deref, DerefMut, Index, RangeTo};
 use core::convert::TryInto;
-use arbutil::PreimageType;
+use core::ops::{Deref, DerefMut, Index, RangeTo};
 
 extern "C" {
     pub fn wavm_get_globalstate_bytes32(idx: u32, ptr: *mut u8);

arbitrator/wasm-libraries/user-host-trait/src/lib.rs

@@ -185,6 +185,38 @@ pub trait UserHost<DR: DataReader>: GasMeteredMachine {
         trace!("storage_flush_cache", self, [be!(clear as u8)], &[])
     }
 
+    /// Reads a 32-byte value from transient storage. Stylus's storage format is identical to
+    /// that of the EVM. This means that, under the hood, this hostio is accessing the 32-byte
+    /// value stored in the EVM's transient state trie at offset `key`, which will be `0` when not previously
+    /// set. The semantics, then, are equivalent to that of the EVM's [`TLOAD`] opcode.
+    ///
+    /// [`TLOAD`]: https://www.evm.codes/#5c
+    fn transient_load_bytes32(&mut self, key: GuestPtr, dest: GuestPtr) -> Result<(), Self::Err> {
+        self.buy_ink(HOSTIO_INK + 2 * PTR_INK + EVM_API_INK)?;
+        self.buy_gas(evm::TLOAD_GAS)?;
+
+        let key = self.read_bytes32(key)?;
+        let value = self.evm_api().get_transient_bytes32(key);
+        self.write_bytes32(dest, value)?;
+        trace!("transient_load_bytes32", self, key, value)
+    }
+
+    /// Writes a 32-byte value to transient storage. Stylus's storage format is identical to that
+    /// of the EVM. This means that, under the hood, this hostio represents storing a 32-byte value into
+    /// the EVM's transient state trie at offset `key`. The semantics, then, are equivalent to that of the
+    /// EVM's [`TSTORE`] opcode.
+    ///
+    /// [`TSTORE`]: https://www.evm.codes/#5d
+    fn transient_store_bytes32(&mut self, key: GuestPtr, value: GuestPtr) -> Result<(), Self::Err> {
+        self.buy_ink(HOSTIO_INK + 2 * PTR_INK + EVM_API_INK)?;
+        self.buy_gas(evm::TSTORE_GAS)?;
+
+        let key = self.read_bytes32(key)?;
+        let value = self.read_bytes32(value)?;
+        self.evm_api().set_transient_bytes32(key, value)?;
+        trace!("transient_store_bytes32", self, [key, value], &[])
+    }
+
     /// Calls the contract at the given address with options for passing value and to limit the
     /// amount of gas supplied. The return status indicates whether the call succeeded, and is
     /// nonzero on failure.

arbitrator/wasm-libraries/user-host/src/host.rs

@@ -58,6 +58,16 @@ pub unsafe extern "C" fn user_host__storage_flush_cache(clear: u32) {
     hostio!(storage_flush_cache(clear != 0))
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn user_host__transient_load_bytes32(key: GuestPtr, dest: GuestPtr) {
+    hostio!(transient_load_bytes32(key, dest))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn user_host__transient_store_bytes32(key: GuestPtr, value: GuestPtr) {
+    hostio!(transient_store_bytes32(key, value))
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn user_host__call_contract(
     contract: GuestPtr,

arbitrator/wasm-libraries/user-test/src/host.rs

@@ -44,6 +44,16 @@ pub unsafe extern "C" fn vm_hooks__storage_flush_cache(clear: u32) {
     hostio!(storage_flush_cache(clear != 0))
 }
 
+#[no_mangle]
+pub unsafe extern "C" fn vm_hooks__transient_load_bytes32(key: GuestPtr, dest: GuestPtr) {
+    hostio!(transient_load_bytes32(key, dest))
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn vm_hooks__transient_store_bytes32(key: GuestPtr, value: GuestPtr) {
+    hostio!(transient_store_bytes32(key, value))
+}
+
 #[no_mangle]
 pub unsafe extern "C" fn vm_hooks__call_contract(
     contract: GuestPtr,

arbitrator/wasm-libraries/user-test/src/program.rs

@@ -116,6 +116,14 @@ impl EvmApi<VecReader> for MockEvmApi {
         Ok(22100 * KEYS.lock().len() as u64) // pretend worst case
     }
 
+    fn get_transient_bytes32(&mut self, _key: Bytes32) -> Bytes32 {
+        unimplemented!()
+    }
+
+    fn set_transient_bytes32(&mut self, _key: Bytes32, _value: Bytes32) -> Result<()> {
+        unimplemented!()
+    }
+
     /// Simulates a contract call.
     /// Note: this call function is for testing purposes only and deviates from onchain behavior.
     fn contract_call(

arbos/programs/api.go

@@ -25,6 +25,8 @@ type RequestType int
 const (
 	GetBytes32 RequestType = iota
 	SetTrieSlots
+	GetTransientBytes32
+	SetTransientBytes32
 	ContractCall
 	DelegateCall
 	StaticCall
@@ -97,6 +99,16 @@ func newApiClosures(
 		}
 		return Success
 	}
+	getTransientBytes32 := func(key common.Hash) common.Hash {
+		return db.GetTransientState(actingAddress, key)
+	}
+	setTransientBytes32 := func(key, value common.Hash) apiStatus {
+		if readOnly {
+			return WriteProtection
+		}
+		db.SetTransientState(actingAddress, key, value)
+		return Success
+	}
 	doCall := func(
 		contract common.Address, opcode vm.OpCode, input []byte, gas uint64, value *big.Int,
 	) ([]byte, uint64, error) {
@@ -317,6 +329,15 @@ func newApiClosures(
 			gas := gasLeft
 			status := setTrieSlots(takeRest(), &gas)
 			return status.to_slice(), nil, gasLeft - gas
+		case GetTransientBytes32:
+			key := takeHash()
+			out := getTransientBytes32(key)
+			return out[:], nil, 0
+		case SetTransientBytes32:
+			key := takeHash()
+			value := takeHash()
+			status := setTransientBytes32(key, value)
+			return status.to_slice(), nil, 0
 		case ContractCall, DelegateCall, StaticCall:
 			var opcode vm.OpCode
 			switch req {