[pallet-revive] last call return data API

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

@@ -0,0 +1,166 @@
+// 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.
+
+//! This tests that the `return_data_size` and `return_data_copy` APIs work.
+//! 
+//! It does so by calling and instantiating the "return_with_data" fixture,
+//! which always echoes back the input[4..] regardless of the call outcome.
+//! 
+//! We also check that the saved return data is properly reset after a trap
+//! and unaffected by plain transfers.
+
+#![no_std]
+#![no_main]
+
+use common::{input, u256_bytes};
+use uapi::{HostFn, HostFnImpl as api};
+
+const INPUT_BUF_SIZE: usize = 128;
+static INPUT_DATA: [u8; INPUT_BUF_SIZE] = [0xFF; INPUT_BUF_SIZE];
+/// The "return_with_data" fixture echoes back 4 bytes less than the input
+const OUTPUT_BUF_SIZE: usize = INPUT_BUF_SIZE - 4;
+static OUTPUT_DATA: [u8; OUTPUT_BUF_SIZE] = [0xEE; OUTPUT_BUF_SIZE];
+
+fn assert_return_data_after_call(input: &[u8]) {
+	assert_return_data_size_of(OUTPUT_BUF_SIZE as u64);
+	assert_plain_transfer_does_not_reset(OUTPUT_BUF_SIZE as u64);
+	assert_return_data_copy(&input[4..]);
+	reset_return_data();
+}
+
+/// Assert that what we get from [api::return_data_copy] matches `whole_return_data`,
+/// either fully or partially with an offset and limited size.
+fn assert_return_data_copy(whole_return_data: &[u8]) {
+	// The full return data should match
+	let mut buf = OUTPUT_DATA;
+	let mut full = &mut buf[..whole_return_data.len()];
+	api::return_data_copy(&mut full, 0);
+	assert_eq!(whole_return_data, full);
+
+	// Partial return data should match
+	let mut buf = OUTPUT_DATA;
+	let offset = 5; // we just pick some offset
+	let size = 32; // we just pick some size
+	let mut partial = &mut buf[offset..offset + size];
+	api::return_data_copy(&mut partial, offset as u32);
+	assert_eq!(*partial, whole_return_data[offset..offset + size]);
+}
+
+/// This function panics in a recursive contract call context.
+fn recursion_guard() -> [u8; 20] {
+	let mut caller_address = [0u8; 20];
+	api::caller(&mut caller_address);
+
+	let mut own_address = [0u8; 20];
+	api::address(&mut own_address);
+
+	assert_ne!(caller_address, own_address);
+
+	own_address
+}
+
+/// Call ourselves recursively, which panics the callee and thus resets the return data.
+fn reset_return_data() {
+	api::call(
+		uapi::CallFlags::ALLOW_REENTRY,
+		&recursion_guard(),
+		0u64,
+		0u64,
+		None,
+		&[0u8; 32],
+		&[0u8; 32],
+		None,
+	)
+	.unwrap_err();
+	assert_return_data_size_of(0);
+}
+
+/// Assert [api::return_data_size] to match the `expected` value.
+fn assert_return_data_size_of(expected: u64) {
+	let mut return_data_size = [0xff; 32];
+	api::return_data_size(&mut return_data_size);
+	assert_eq!(return_data_size, u256_bytes(expected));
+}
+
+/// Assert [api::return_data_size] to match the `expected` value after a plain transfer
+/// (plain transfers don't issue a call and so should not reset the return data)
+fn assert_plain_transfer_does_not_reset(expected: u64) {
+	api::transfer(&[0; 20], &u256_bytes(128)).unwrap();
+	assert_return_data_size_of(expected);
+}
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn deploy() {}
+
+#[no_mangle]
+#[polkavm_derive::polkavm_export]
+pub extern "C" fn call() {
+	input!(code_hash: &[u8; 32],);
+
+	recursion_guard();
+
+	// we didn't do anything yet; return data size should be 0
+	assert_return_data_size_of(0);
+
+	let mut address_buf = [0; 20];
+	let construct_input = |exit_flag| {
+		let mut input = INPUT_DATA;
+		input[0] = exit_flag;
+		input[9] = 7;
+		input[17 / 2] = 127;
+		input[89 / 2] = 127;
+		input
+	};
+	let mut instantiate = |exit_flag| {
+		api::instantiate(
+			code_hash,
+			0u64,
+			0u64,
+			None,
+			&[0; 32],
+			&construct_input(exit_flag),
+			Some(&mut address_buf),
+			None,
+			None,
+		)
+	};
+	let call = |exit_flag, address_buf| {
+		api::call(
+			uapi::CallFlags::empty(),
+			address_buf,
+			0u64,
+			0u64,
+			None,
+			&[0; 32],
+			&construct_input(exit_flag),
+			None,
+		)
+	};
+
+	instantiate(0).unwrap();
+	assert_return_data_after_call(&construct_input(0)[..]);
+
+	instantiate(1).unwrap_err();
+	assert_return_data_after_call(&construct_input(1)[..]);
+
+	call(0, &address_buf).unwrap();
+	assert_return_data_after_call(&construct_input(0)[..]);
+
+	call(1, &address_buf).unwrap_err();
+	assert_return_data_after_call(&construct_input(1)[..]);
+}

substrate/frame/revive/src/exec.rs

@@ -427,6 +427,12 @@ pub trait Ext: sealing::Sealed {
 
 	/// Check if running in read-only context.
 	fn is_read_only(&self) -> bool;
+
+	/// Returns an immutable reference to saved output of the last executed call frame.
+	fn last_frame_output(&self) -> &[u8];
+
+	/// Returns a mutable reference to saved output of the last executed call frame.
+	fn last_frame_output_mut(&mut self) -> &mut Vec<u8>;
 }
 
 /// Describes the different functions that can be exported by an [`Executable`].
@@ -547,6 +553,8 @@ struct Frame<T: Config> {
 	read_only: bool,
 	/// The caller of the currently executing frame which was spawned by `delegate_call`.
 	delegate_caller: Option<Origin<T>>,
+	/// The output of the last call frame
+	last_frame_output: Vec<u8>,
 }
 
 /// Used in a delegate call frame arguments in order to override the executable and caller.
@@ -911,6 +919,7 @@ where
 			nested_storage: storage_meter.nested(deposit_limit),
 			allows_reentry: true,
 			read_only,
+			last_frame_output: Vec::new(),
 		};
 
 		Ok(Some((frame, executable)))
@@ -971,6 +980,9 @@ where
 		let delegated_code_hash =
 			if frame.delegate_caller.is_some() { Some(*executable.code_hash()) } else { None };
 
+		if let Some(previous) = self.caller_output_mut() {
+			*previous = Vec::new();
+		}
 		self.transient_storage.start_transaction();
 
 		let do_transaction = || {
@@ -1265,6 +1277,15 @@ where
 	fn account_balance(&self, who: &T::AccountId) -> U256 {
 		T::Currency::reducible_balance(who, Preservation::Preserve, Fortitude::Polite).into()
 	}
+
+	/// Returns a mutable reference to saved output of the caller frame.
+	fn caller_output_mut(&mut self) -> Option<&mut Vec<u8>> {
+		match self.frames.len() {
+			0 => None,
+			1 => Some(&mut self.first_frame.last_frame_output),
+			_ => self.frames.get_mut(self.frames.len() - 2).map(|frame| &mut frame.last_frame_output),
+		}
+	}
 }
 
 impl<'a, T, E> Ext for Stack<'a, T, E>
@@ -1690,6 +1711,14 @@ where
 	fn is_read_only(&self) -> bool {
 		self.top_frame().read_only
 	}
+
+	fn last_frame_output(&self) -> &[u8] {
+		&self.top_frame().last_frame_output
+	}
+
+	fn last_frame_output_mut(&mut self) -> &mut Vec<u8> {
+		&mut self.top_frame_mut().last_frame_output
+	}
 }
 
 mod sealing {

substrate/frame/revive/src/tests.rs

@@ -4310,4 +4310,32 @@ mod run_tests {
 			assert_ok!(builder::call(addr).build());
 		});
 	}
+
+	#[test]
+	fn return_data_api_works() {
+		let (code_return_data_api, _) = compile_module("return_data_api").unwrap();
+		let (code_return_with_data, hash_return_with_data) = compile_module("return_with_data").unwrap();
+
+		ExtBuilder::default().existential_deposit(100).build().execute_with(|| {
+			let _ = <Test as Config>::Currency::set_balance(&ALICE, 1_000_000);
+
+			// Upload the io echoing fixture for later use
+			assert_ok!(Contracts::upload_code(
+				RuntimeOrigin::signed(ALICE),
+				code_return_with_data,
+				deposit_limit::<Test>(),
+			));
+
+			// Create fixture: Constructor does nothing
+			let Contract { addr, .. } =
+				builder::bare_instantiate(Code::Upload(code_return_data_api))
+					.build_and_unwrap_contract();
+
+			// Call the contract: It will issue calls and deploys, asserting on
+			assert_ok!(builder::call(addr)
+				.value(10 * 1024)
+				.data(hash_return_with_data.encode())
+				.build());
+		});
+	}
 }