[pallet-revive] immutable data storage (#5861)

This PR introduces the concept of immutable storage data, used for
[Solidity immutable
variables](https://docs.soliditylang.org/en/latest/contracts.html#immutable).

This is a minimal implementation. Immutable data is attached to a
contract; to keep `ContractInfo` fixed in size, we only store the length
there, and store the immutable data in a dedicated storage map instead.
Which comes at the cost of requiring an additional storage read (costly)
for contracts using this feature.

We discussed more optimal solutions not requiring any additional storage
accesses internally, but they turned out to be non-trivial to implement.
Another optimization benefiting multiple calls to the same contract in a
single call stack would be to cache the immutable data in `Stack`.
However, this potential creates a DOS vulnerability (the attack vector
is to call into as many contracts in a single stack as possible, where
they all have maximum immutable data to fill the cache as efficiently as
possible). So this either has to be guaranteed to be a non-issue by
limits, or, more likely, to have some logic to bound the cache.
Eventually, we should think about introducing the concept of warm and
cold storage reads (akin to EVM). Since immutable variables are commonly
used in contracts, this change is blocking our initial launch and we
should only optimize it properly in follow-ups.

This PR also disables the `set_code_hash` API (which isn't usable for
Solidity contracts without pre-compiles anyways). With immutable storage
attached to contracts, we now want to run the constructor of the new
code hash to collect the immutable data during `set_code_hash`. This
will be implemented in a follow up PR.

---------

Signed-off-by: Cyrill Leutwiler <[email protected]>
Signed-off-by: xermicus <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: Alexander Theißen <[email protected]>
Co-authored-by: PG Herveou <[email protected]>

prdoc/pr_5861.prdoc

@@ -0,0 +1,37 @@
+title: "[pallet-revive] immutable data storage"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      This PR introduces the concept of immutable storage data, used for
+      [Solidity immutable variables](https://docs.soliditylang.org/en/latest/contracts.html#immutable).
+
+      This is a minimal implementation. Immutable data is attached to a contract; to 
+      `ContractInfo` fixed in size, we only store the length there, and store the immutable
+      data in a dedicated storage map instead. Which comes at the cost of requiring an
+      storage read (costly) for contracts using this feature.
+
+      We discussed more optimal solutions not requiring any additional storage accesses
+      internally, but they turned out to be non-trivial to implement. Another optimization
+      benefiting multiple calls to the same contract in a single call stack would be to cache
+      the immutable data in `Stack`. However, this potential creates a DOS vulnerability (the
+      attack vector is to call into as many contracts in a single stack as possible, where
+      they all have maximum immutable data to fill the cache as efficiently as possible). So
+      this either has to be guaranteed to be a non-issue by limits, or, more likely, to have
+      some logic to bound the cache. Eventually, we should think about introducing the concept
+      of warm and cold storage reads (akin to EVM). Since immutable variables are commonly
+      used in contracts, this change is blocking our initial launch and we should only
+      optimize it properly in follow-ups.
+
+      This PR also disables the `set_code_hash` API (which isn't usable for Solidity contracts
+      without pre-compiles anyways). With immutable storage attached to contracts, we now want
+      to run the constructor of the new code hash to collect the immutable data during
+      `set_code_hash`. This will be implemented in a follow up PR.
+
+crates:
+  - name: pallet-revive
+    bump: major
+  - name: pallet-revive-fixtures
+    bump: patch
+  - name: pallet-revive-uapi
+    bump: minor

substrate/frame/revive/fixtures/contracts/immutable_data.rs

@@ -0,0 +1,43 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Tests that the `get_immutable_data` and `set_immutable_data` APIs work.
+
+#![no_std]
+#![no_main]
+
+use common::input;
+use uapi::{HostFn, HostFnImpl as api};
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn deploy() {
+	input!(data: &[u8; 8],);
+
+	api::set_immutable_data(data);
+}
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn call() {
+	input!(data: &[u8; 8],);
+
+	let mut buf = [0; 8];
+	api::get_immutable_data(&mut &mut buf[..]);
+
+	assert_eq!(data, &buf);
+}

substrate/frame/revive/src/benchmarking/mod.rs

@@ -628,6 +628,53 @@ mod benchmarks {
 		assert_eq!(U256::from_little_endian(&memory[..len]), runtime.ext().balance_of(&address));
 	}
 
+	#[benchmark(pov_mode = Measured)]
+	fn seal_get_immutable_data(n: Linear<1, { limits::IMMUTABLE_BYTES }>) {
+		let len = n as usize;
+		let immutable_data = vec![1u8; len];
+
+		build_runtime!(runtime, contract, memory: [(len as u32).encode(), vec![0u8; len],]);
+
+		<ImmutableDataOf<T>>::insert::<_, BoundedVec<_, _>>(
+			contract.address(),
+			immutable_data.clone().try_into().unwrap(),
+		);
+
+		let result;
+		#[block]
+		{
+			result = runtime.bench_get_immutable_data(memory.as_mut_slice(), 4, 0 as u32);
+		}
+
+		assert_ok!(result);
+		assert_eq!(&memory[0..4], (len as u32).encode());
+		assert_eq!(&memory[4..len + 4], &immutable_data);
+	}
+
+	#[benchmark(pov_mode = Measured)]
+	fn seal_set_immutable_data(n: Linear<1, { limits::IMMUTABLE_BYTES }>) {
+		let len = n as usize;
+		let mut memory = vec![1u8; len];
+		let mut setup = CallSetup::<T>::default();
+		let input = setup.data();
+		let (mut ext, _) = setup.ext();
+		ext.override_export(crate::debug::ExportedFunction::Constructor);
+
+		let mut runtime = crate::wasm::Runtime::<_, [u8]>::new(&mut ext, input);
+
+		let result;
+		#[block]
+		{
+			result = runtime.bench_set_immutable_data(memory.as_mut_slice(), 0, n);
+		}
+
+		assert_ok!(result);
+		assert_eq!(
+			&memory[..],
+			&<ImmutableDataOf<T>>::get(setup.contract().address()).unwrap()[..]
+		);
+	}
+
 	#[benchmark(pov_mode = Measured)]
 	fn seal_value_transferred() {
 		build_runtime!(runtime, memory: [[0u8;32], ]);