Add missing 63/64 rule documentation and a test (#462)

- Prominently point out the important differences of the `pallet-revive`
runtime.
- Add a test case illustrating the problem.

See also: https://github.com/paritytech/contract-issues/issues/257

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

README.md

@@ -7,12 +7,20 @@ Yul recompiler to LLVM, targetting RISC-V on [PolkaVM](https://github.com/koute/
 
 Check the [docs](https://paritytech.github.io/revive/) or visit [contracts.polkadot.io](https://docs.polkadot.com/develop/smart-contracts/) to learn more about `revive` and contracts on Polkadot!
 
-## Status
-
-This is experimental software in active development and not ready just yet for production usage. Please do report any compiler related issues or missing features that are [not yet known to us](https://contracts.polkadot.io/known_issues/) here.
-
 Discussion around the development is hosted on the [Polkadot Forum](https://forum.polkadot.network/t/contracts-update-solidity-on-polkavm/6949#a-new-solidity-compiler-1).
 
+> [!WARNING]
+>
+> Solidity on PVM is running on the `pallet-revive` runtime. This introduces **observable semantic differences** in comparison with the EVM.
+> 
+> Study the [differences](https://paritytech.github.io/revive/user_guide/differences.html) section carefully. **Ignoring these differences may lead to defunct contracts.**
+> 
+> Notable examples:
+> - The 63/64 gas rule isn't implemented in the pallet (introduces potential DoS vector when calling other contracts)
+> - Contract instantiation works differently (by hash instead of by code)
+> - The gas model implemented by `pallet-revive` differs from Ethereum 
+> - The heap size is fixed instead of gas-metered and there's a fixed amount of stack size (contracts working fine on EVM may trap on PVM)
+
 ## Installation
 
 Building Solidity contracts for PolkaVM requires installing the following two compilers:

book/src/user_guide/differences.md

@@ -18,6 +18,10 @@ Therefore, in EVM terminology, the deploy code equals the runtime code.
 
 We are aware of the following differences in the translation of Solidity code.
 
+### The `63/64` gas rule
+
+`pallet-revive` **doesn't apply the `63/64` gas rule**. We strongly advice to change any code calling untrusted contracts to supply a limited amount of gas only!
+
 ### `address.creationCode`
 
 This returns the bytecode keccak256 hash instead.
@@ -28,7 +32,7 @@ The below list contains noteworthy differences in the translation of YUL functio
 
 > [!NOTE]
 >
-> Many functions receive memory buffer offset pointer or size arguments. Since the PVM pointer size is 32 bit, supplying memory offset or buffer size values above `2^32-1` will trap the contract immediately.
+> Many functions receive memory buffer offset pointer or size arguments. The PVM pointer size is 32 bit, supplying memory offset or buffer size values above `2^32-1` may lead to `OutOfGas` errors trap contract execution.
 
 The `solc` compiler ought to always emit valid memory references, so Solidity dApp authors don't need to worry about this unless they deal with low level `assembly` code.
 
@@ -43,6 +47,10 @@ In general, revive preserves the memory layout, meaning low level memory operati
 
 In the constructor code, the offset is ignored and this always returns `0`.
 
+> [!WARNING]
+>
+> `pallet-revive` restricts the calldata size (to 128kb at the time of writing).
+
 ### `codecopy`
 
 Only supported in constructor code.
@@ -70,6 +78,10 @@ Returns the contract hash.
 
 Returns the contract hash size (constant value of `32`).
 
+### `revert`, `return`
+
+`pallet-revive` restricts the returndata size (to 128kb at the time of writing).
+
 ### `prevrandao`, `difficulty`
 
 Translates to a constant value of `2500000000000000`.

book/src/welcome.md

@@ -2,6 +2,18 @@
 
 Hello and a warm welcome to the `revive` Solidity compiler book!
 
+> [!WARNING]
+>
+> Solidity on PVM is running on the `pallet-revive` runtime. This introduces **observable semantic differences** in comparison with the EVM.
+> 
+> Study the [differences](https://paritytech.github.io/revive/user_guide/differences.html) section carefully. **Ignoring these differences may lead to defunct contracts.**
+> 
+> Notable examples:
+> - The 63/64 gas rule isn't implemented in the pallet (introduces potential DoS vector when calling other contracts)
+> - Contract instantiation works differently (by hash instead of by code)
+> - The gas model implemented by `pallet-revive` differs from Ethereum 
+> - The heap size is fixed instead of gas-metered and there's a fixed amount of stack size (contracts working fine on EVM may trap on PVM)
+
 ## Target audience
 
 - **Solidity dApp developers** should read the [user guide](./user_guide.md). Solidity on PolkaVM introduces important differences to EVM which should be well understood.

crates/integration/contracts/RevertDataOob.sol

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.8.0;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "RevertDataOob"
+                    }
+                }
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "eb8ac921000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000ffffffff"
+            }
+        },
+        {
+            "Call": {
+                "dest": {
+                    "Instantiated": 0
+                },
+                "data": "eb8ac92100000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000100000000"
+            }
+        }
+    ]
+}
+*/
+
+contract RevertDataOob {
+    function test(uint256 offset, uint256 len) external {
+        assembly {
+            mstore(0, 0xcc572cf9)
+            mstore(32, offset)
+            mstore(64, len)
+            let stipend := mul(div(gas(), 64), 63) // On EVM this isn't necessary
+            let success := call(stipend, address(), 0, 28, 68, 0, 0)
+            mstore(0, 0xdeadbeef)
+            return(0, 32)
+        }
+    }
+
+    function main(uint256 offset, uint256 len) external pure {
+        assembly {
+            mstore(0x40, 0)
+            revert(offset, len)
+        }
+    }
+}

crates/integration/src/tests.rs

@@ -44,6 +44,7 @@ test_spec!(create, "CreateB", "Create.sol");
 test_spec!(call, "Caller", "Call.sol");
 test_spec!(balance, "Balance", "Balance.sol");
 test_spec!(return_data_oob, "ReturnDataOob", "ReturnDataOob.sol");
+test_spec!(revert_data_oob, "RevertDataOob", "RevertDataOob.sol");
 test_spec!(immutables, "Immutables", "Immutables.sol");
 test_spec!(transaction, "Transaction", "Transaction.sol");
 test_spec!(block_hash, "BlockHash", "BlockHash.sol");

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@@ -176,6 +176,18 @@
                     <main>
                         <h1 id="welcome"><a class="header" href="#welcome">Welcome</a></h1>
 <p>Hello and a warm welcome to the <code>revive</code> Solidity compiler book!</p>
+<blockquote class="blockquote-tag blockquote-tag-warning">
+<p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p>Solidity on PVM is running on the <code>pallet-revive</code> runtime. This introduces <strong>observable semantic differences</strong> in comparison with the EVM.</p>
+<p>Study the <a href="https://paritytech.github.io/revive/user_guide/differences.html">differences</a> section carefully. <strong>Ignoring these differences may lead to defunct contracts.</strong></p>
+<p>Notable examples:</p>
+<ul>
+<li>The 63/64 gas rule isn’t implemented in the pallet (introduces potential DoS vector when calling other contracts)</li>
+<li>Contract instantiation works differently (by hash instead of by code)</li>
+<li>The gas model implemented by <code>pallet-revive</code> differs from Ethereum</li>
+<li>The heap size is fixed instead of gas-metered and there’s a fixed amount of stack size (contracts working fine on EVM may trap on PVM)</li>
+</ul>
+</blockquote>
 <h2 id="target-audience"><a class="header" href="#target-audience">Target audience</a></h2>
 <ul>
 <li><strong>Solidity dApp developers</strong> should read the <a href="./user_guide.html">user guide</a>. Solidity on PolkaVM introduces important differences to EVM which should be well understood.</li>

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                     <main>
                         <h1 id="welcome"><a class="header" href="#welcome">Welcome</a></h1>
 <p>Hello and a warm welcome to the <code>revive</code> Solidity compiler book!</p>
+<blockquote class="blockquote-tag blockquote-tag-warning">
+<p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p>Solidity on PVM is running on the <code>pallet-revive</code> runtime. This introduces <strong>observable semantic differences</strong> in comparison with the EVM.</p>
+<p>Study the <a href="https://paritytech.github.io/revive/user_guide/differences.html">differences</a> section carefully. <strong>Ignoring these differences may lead to defunct contracts.</strong></p>
+<p>Notable examples:</p>
+<ul>
+<li>The 63/64 gas rule isn’t implemented in the pallet (introduces potential DoS vector when calling other contracts)</li>
+<li>Contract instantiation works differently (by hash instead of by code)</li>
+<li>The gas model implemented by <code>pallet-revive</code> differs from Ethereum</li>
+<li>The heap size is fixed instead of gas-metered and there’s a fixed amount of stack size (contracts working fine on EVM may trap on PVM)</li>
+</ul>
+</blockquote>
 <h2 id="target-audience"><a class="header" href="#target-audience">Target audience</a></h2>
 <ul>
 <li><strong>Solidity dApp developers</strong> should read the <a href="#resolc-user-guide">user guide</a>. Solidity on PolkaVM introduces important differences to EVM which should be well understood.</li>
@@ -365,13 +377,15 @@ Therefore, in EVM terminology, the deploy code equals the runtime code.</p>
 </blockquote>
 <h2 id="solidity"><a class="header" href="#solidity">Solidity</a></h2>
 <p>We are aware of the following differences in the translation of Solidity code.</p>
+<h3 id="the-6364-gas-rule"><a class="header" href="#the-6364-gas-rule">The <code>63/64</code> gas rule</a></h3>
+<p><code>pallet-revive</code> <strong>doesn’t apply the <code>63/64</code> gas rule</strong>. We strongly advice to change any code calling untrusted contracts to supply a limited amount of gas only!</p>
 <h3 id="addresscreationcode"><a class="header" href="#addresscreationcode"><code>address.creationCode</code></a></h3>
 <p>This returns the bytecode keccak256 hash instead.</p>
 <h2 id="yul-functions"><a class="header" href="#yul-functions">YUL functions</a></h2>
 <p>The below list contains noteworthy differences in the translation of YUL functions.</p>
 <blockquote class="blockquote-tag blockquote-tag-note">
 <p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
-<p>Many functions receive memory buffer offset pointer or size arguments. Since the PVM pointer size is 32 bit, supplying memory offset or buffer size values above <code>2^32-1</code> will trap the contract immediately.</p>
+<p>Many functions receive memory buffer offset pointer or size arguments. The PVM pointer size is 32 bit, supplying memory offset or buffer size values above <code>2^32-1</code> may lead to <code>OutOfGas</code> errors trap contract execution.</p>
 </blockquote>
 <p>The <code>solc</code> compiler ought to always emit valid memory references, so Solidity dApp authors don’t need to worry about this unless they deal with low level <code>assembly</code> code.</p>
 <h3 id="mload-mstore-msize-mcopy-memory-related-functions"><a class="header" href="#mload-mstore-msize-mcopy-memory-related-functions"><code>mload</code>, <code>mstore</code>, <code>msize</code>, <code>mcopy</code> (memory related functions)</a></h3>
@@ -383,6 +397,10 @@ Therefore, in EVM terminology, the deploy code equals the runtime code.</p>
 </ul>
 <h3 id="calldataload-calldatacopy"><a class="header" href="#calldataload-calldatacopy"><code>calldataload</code>, <code>calldatacopy</code></a></h3>
 <p>In the constructor code, the offset is ignored and this always returns <code>0</code>.</p>
+<blockquote class="blockquote-tag blockquote-tag-warning">
+<p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p><code>pallet-revive</code> restricts the calldata size (to 128kb at the time of writing).</p>
+</blockquote>
 <h3 id="codecopy"><a class="header" href="#codecopy"><code>codecopy</code></a></h3>
 <p>Only supported in constructor code.</p>
 <h3 id="create-create2"><a class="header" href="#create-create2"><code>create</code>, <code>create2</code></a></h3>
@@ -403,6 +421,8 @@ Thus, <code>revive</code> is able to supply the expected code hash and construct
 <p>Returns the contract hash.</p>
 <h3 id="datasize"><a class="header" href="#datasize"><code>datasize</code></a></h3>
 <p>Returns the contract hash size (constant value of <code>32</code>).</p>
+<h3 id="revert-return"><a class="header" href="#revert-return"><code>revert</code>, <code>return</code></a></h3>
+<p><code>pallet-revive</code> restricts the returndata size (to 128kb at the time of writing).</p>
 <h3 id="prevrandao-difficulty"><a class="header" href="#prevrandao-difficulty"><code>prevrandao</code>, <code>difficulty</code></a></h3>
 <p>Translates to a constant value of <code>2500000000000000</code>.</p>
 <h3 id="pc-extcodecopy"><a class="header" href="#pc-extcodecopy"><code>pc</code>, <code>extcodecopy</code></a></h3>

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@@ -187,13 +187,15 @@ Therefore, in EVM terminology, the deploy code equals the runtime code.</p>
 </blockquote>
 <h2 id="solidity"><a class="header" href="#solidity">Solidity</a></h2>
 <p>We are aware of the following differences in the translation of Solidity code.</p>
+<h3 id="the-6364-gas-rule"><a class="header" href="#the-6364-gas-rule">The <code>63/64</code> gas rule</a></h3>
+<p><code>pallet-revive</code> <strong>doesn’t apply the <code>63/64</code> gas rule</strong>. We strongly advice to change any code calling untrusted contracts to supply a limited amount of gas only!</p>
 <h3 id="addresscreationcode"><a class="header" href="#addresscreationcode"><code>address.creationCode</code></a></h3>
 <p>This returns the bytecode keccak256 hash instead.</p>
 <h2 id="yul-functions"><a class="header" href="#yul-functions">YUL functions</a></h2>
 <p>The below list contains noteworthy differences in the translation of YUL functions.</p>
 <blockquote class="blockquote-tag blockquote-tag-note">
 <p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z"></path></svg>Note</p>
-<p>Many functions receive memory buffer offset pointer or size arguments. Since the PVM pointer size is 32 bit, supplying memory offset or buffer size values above <code>2^32-1</code> will trap the contract immediately.</p>
+<p>Many functions receive memory buffer offset pointer or size arguments. The PVM pointer size is 32 bit, supplying memory offset or buffer size values above <code>2^32-1</code> may lead to <code>OutOfGas</code> errors trap contract execution.</p>
 </blockquote>
 <p>The <code>solc</code> compiler ought to always emit valid memory references, so Solidity dApp authors don’t need to worry about this unless they deal with low level <code>assembly</code> code.</p>
 <h3 id="mload-mstore-msize-mcopy-memory-related-functions"><a class="header" href="#mload-mstore-msize-mcopy-memory-related-functions"><code>mload</code>, <code>mstore</code>, <code>msize</code>, <code>mcopy</code> (memory related functions)</a></h3>
@@ -205,6 +207,10 @@ Therefore, in EVM terminology, the deploy code equals the runtime code.</p>
 </ul>
 <h3 id="calldataload-calldatacopy"><a class="header" href="#calldataload-calldatacopy"><code>calldataload</code>, <code>calldatacopy</code></a></h3>
 <p>In the constructor code, the offset is ignored and this always returns <code>0</code>.</p>
+<blockquote class="blockquote-tag blockquote-tag-warning">
+<p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p><code>pallet-revive</code> restricts the calldata size (to 128kb at the time of writing).</p>
+</blockquote>
 <h3 id="codecopy"><a class="header" href="#codecopy"><code>codecopy</code></a></h3>
 <p>Only supported in constructor code.</p>
 <h3 id="create-create2"><a class="header" href="#create-create2"><code>create</code>, <code>create2</code></a></h3>
@@ -225,6 +231,8 @@ Thus, <code>revive</code> is able to supply the expected code hash and construct
 <p>Returns the contract hash.</p>
 <h3 id="datasize"><a class="header" href="#datasize"><code>datasize</code></a></h3>
 <p>Returns the contract hash size (constant value of <code>32</code>).</p>
+<h3 id="revert-return"><a class="header" href="#revert-return"><code>revert</code>, <code>return</code></a></h3>
+<p><code>pallet-revive</code> restricts the returndata size (to 128kb at the time of writing).</p>
 <h3 id="prevrandao-difficulty"><a class="header" href="#prevrandao-difficulty"><code>prevrandao</code>, <code>difficulty</code></a></h3>
 <p>Translates to a constant value of <code>2500000000000000</code>.</p>
 <h3 id="pc-extcodecopy"><a class="header" href="#pc-extcodecopy"><code>pc</code>, <code>extcodecopy</code></a></h3>

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@@ -176,6 +176,18 @@
                     <main>
                         <h1 id="welcome"><a class="header" href="#welcome">Welcome</a></h1>
 <p>Hello and a warm welcome to the <code>revive</code> Solidity compiler book!</p>
+<blockquote class="blockquote-tag blockquote-tag-warning">
+<p class="blockquote-tag-title"><svg viewbox="0 0 16 16" width="18" height="18"><path d="M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z"></path></svg>Warning</p>
+<p>Solidity on PVM is running on the <code>pallet-revive</code> runtime. This introduces <strong>observable semantic differences</strong> in comparison with the EVM.</p>
+<p>Study the <a href="https://paritytech.github.io/revive/user_guide/differences.html">differences</a> section carefully. <strong>Ignoring these differences may lead to defunct contracts.</strong></p>
+<p>Notable examples:</p>
+<ul>
+<li>The 63/64 gas rule isn’t implemented in the pallet (introduces potential DoS vector when calling other contracts)</li>
+<li>Contract instantiation works differently (by hash instead of by code)</li>
+<li>The gas model implemented by <code>pallet-revive</code> differs from Ethereum</li>
+<li>The heap size is fixed instead of gas-metered and there’s a fixed amount of stack size (contracts working fine on EVM may trap on PVM)</li>
+</ul>
+</blockquote>
 <h2 id="target-audience"><a class="header" href="#target-audience">Target audience</a></h2>
 <ul>
 <li><strong>Solidity dApp developers</strong> should read the <a href="./user_guide.html">user guide</a>. Solidity on PolkaVM introduces important differences to EVM which should be well understood.</li>