Upgradeable validation functions (#918)

* upgrade primitives to allow changing validation function

* set up storage schema for old parachains code

* fix compilation errors

* fix test compilation

* add some tests for past code meta

* most of the runtime logic for code upgrades

* implement old-code pruning

* add a couple tests

* clean up remaining TODOs

* add a whole bunch of tests for runtime functionality

* remove unused function

* fix runtime compilation

* extract some primitives to parachain crate

* add validation-code upgrades to validation params and result

* extend validation params with code upgrade fields

* provide maximums to validation params

* port test-parachains

* add a code-upgrader test-parachain and tests

* fix collator tests

* move test-parachains to own folder to work around compilation errors

* fix test compilation

* update the Cargo.lock

* fix parachains tests

* remove dbg! invocation

* use new pool in code-upgrader

* bump lockfile

* link TODO to issue

polkadot/parachain/test-parachains/adder/src/lib.rs

@@ -0,0 +1,90 @@
+// Copyright 2017-2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Basic parachain that adds a number as part of its state.
+
+#![no_std]
+
+#![cfg_attr(not(feature = "std"), feature(core_intrinsics, lang_items, core_panic_info, alloc_error_handler))]
+
+use codec::{Encode, Decode};
+
+#[cfg(not(feature = "std"))]
+mod wasm_validation;
+
+#[cfg(not(feature = "std"))]
+#[global_allocator]
+static ALLOC: dlmalloc::GlobalDlmalloc = dlmalloc::GlobalDlmalloc;
+
+// Make the WASM binary available.
+#[cfg(feature = "std")]
+include!(concat!(env!("OUT_DIR"), "/wasm_binary.rs"));
+
+/// Head data for this parachain.
+#[derive(Default, Clone, Hash, Eq, PartialEq, Encode, Decode)]
+pub struct HeadData {
+	/// Block number
+	pub number: u64,
+	/// parent block keccak256
+	pub parent_hash: [u8; 32],
+	/// hash of post-execution state.
+	pub post_state: [u8; 32],
+}
+
+impl HeadData {
+	pub fn hash(&self) -> [u8; 32] {
+		tiny_keccak::keccak256(&self.encode())
+	}
+}
+
+/// Block data for this parachain.
+#[derive(Default, Clone, Encode, Decode)]
+pub struct BlockData {
+	/// State to begin from.
+	pub state: u64,
+	/// Amount to add (overflowing)
+	pub add: u64,
+}
+
+pub fn hash_state(state: u64) -> [u8; 32] {
+	tiny_keccak::keccak256(state.encode().as_slice())
+}
+
+/// Start state mismatched with parent header's state hash.
+#[derive(Debug)]
+pub struct StateMismatch;
+
+/// Execute a block body on top of given parent head, producing new parent head
+/// if valid.
+pub fn execute(
+	parent_hash: [u8; 32],
+	parent_head: HeadData,
+	block_data: &BlockData,
+) -> Result<HeadData, StateMismatch> {
+	debug_assert_eq!(parent_hash, parent_head.hash());
+
+	if hash_state(block_data.state) != parent_head.post_state {
+		return Err(StateMismatch);
+	}
+
+	let new_state = block_data.state.overflowing_add(block_data.add).0;
+
+	Ok(HeadData {
+		number: parent_head.number + 1,
+		parent_hash,
+		post_state: hash_state(new_state),
+	})
+}

polkadot/parachain/test-parachains/adder/src/wasm_validation.rs

@@ -0,0 +1,60 @@
+// Copyright 2019-2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! WASM validation for adder parachain.
+
+use crate::{HeadData, BlockData};
+use core::{intrinsics, panic};
+use parachain::primitives::{ValidationResult, HeadData as GenericHeadData};
+use codec::{Encode, Decode};
+
+#[panic_handler]
+#[no_mangle]
+pub fn panic(_info: &panic::PanicInfo) -> ! {
+	unsafe {
+		intrinsics::abort()
+	}
+}
+
+#[alloc_error_handler]
+#[no_mangle]
+pub fn oom(_: core::alloc::Layout) -> ! {
+	unsafe {
+		intrinsics::abort();
+	}
+}
+
+#[no_mangle]
+pub extern fn validate_block(params: *const u8, len: usize) -> u64 {
+	let params = unsafe { parachain::load_params(params, len) };
+	let parent_head = HeadData::decode(&mut &params.parent_head.0[..])
+		.expect("invalid parent head format.");
+
+	let block_data = BlockData::decode(&mut &params.block_data.0[..])
+		.expect("invalid block data format.");
+
+	let parent_hash = tiny_keccak::keccak256(&params.parent_head.0[..]);
+
+	match crate::execute(parent_hash, parent_head, &block_data) {
+		Ok(new_head) => parachain::write_result(
+			&ValidationResult {
+				head_data: GenericHeadData(new_head.encode()),
+				new_validation_code: None,
+			}
+		),
+		Err(_) => panic!("execution failure"),
+	}
+}