Merge pull request #456 from ethereum/mocked_host

Add mocked_host library

CHANGELOG.md

@@ -5,6 +5,15 @@ Documentation of all notable changes to the **EVMC** project.
 The format is based on [Keep a Changelog],
 and this project adheres to [Semantic Versioning].
 
+## [7.1.0] — unreleased
+
+### Added
+
+- Added `MockedHost` C++ class (in form of header-only `evmc::mocked_host` library)
+  which can be used to emulate Host behavior when testing VM implementations.
+  [#456](https://github.com/ethereum/evmc/pull/456)
+
+
 ## [7.0.0] „Istanbul Ready” — 2019-11-11
 
 This version of EVMC delivers compatibility with Istanbul EVM revision.
@@ -401,6 +410,7 @@ removed.
   [#52](https://github.com/ethereum/evmc/pull/52)
 
 
+[7.1.0]: https://github.com/ethereum/evmc/compare/v7.0.0...master
 [7.0.0]: https://github.com/ethereum/evmc/releases/tag/v7.0.0
 [6.3.1]: https://github.com/ethereum/evmc/releases/tag/v6.3.1
 [6.3.0]: https://github.com/ethereum/evmc/releases/tag/v6.3.0

include/evmc/mocked_host.hpp

@@ -0,0 +1,312 @@
+// EVMC: Ethereum Client-VM Connector API.
+// Copyright 2019 The EVMC Authors.
+// Licensed under the Apache License, Version 2.0.
+#pragma once
+
+#include <evmc/evmc.hpp>
+#include <algorithm>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+namespace evmc
+{
+/// The string of bytes.
+using bytes = std::basic_string<uint8_t>;
+
+/// Mocked account.
+struct MockedAccount
+{
+    /// Extended value (by dirty flag) for account storage.
+    struct storage_value
+    {
+        /// The storage value.
+        bytes32 value;
+
+        /// True means this value has been modified already by the current transaction.
+        bool dirty{false};
+
+        /// Default constructor.
+        storage_value() noexcept = default;
+
+        /// Constructor.
+        storage_value(const bytes32& _value, bool _dirty = false) noexcept  // NOLINT
+          : value{_value}, dirty{_dirty}
+        {}
+    };
+
+    /// The account code.
+    bytes code;
+
+    /// The code hash. Can be a value not related to the actual code.
+    bytes32 codehash;
+
+    /// The account balance.
+    uint256be balance;
+
+    /// The account storage map.
+    std::unordered_map<bytes32, storage_value> storage;
+
+    /// Helper method for setting balance by numeric type.
+    void set_balance(uint64_t x) noexcept
+    {
+        balance = uint256be{};
+        for (std::size_t i = 0; i < sizeof(x); ++i)
+            balance.bytes[sizeof(balance) - 1 - i] = static_cast<uint8_t>(x >> (8 * i));
+    }
+};
+
+/// Mocked EVMC Host implementation.
+class MockedHost : public Host
+{
+public:
+    /// LOG record.
+    struct log_record
+    {
+        /// The address of the account which created the log.
+        address creator;
+
+        /// The data attached to the log.
+        bytes data;
+
+        /// The log topics.
+        std::vector<bytes32> topics;
+
+        /// Equal operator.
+        bool operator==(const log_record& other) const noexcept
+        {
+            return creator == other.creator && data == other.data && topics == other.topics;
+        }
+    };
+
+    /// SELFDESTRUCT record.
+    struct selfdestuct_record
+    {
+        /// The address of the account which has self-destructed.
+        address selfdestructed;
+
+        /// The address of the beneficiary account.
+        address beneficiary;
+
+        /// Equal operator.
+        bool operator==(const selfdestuct_record& other) const noexcept
+        {
+            return selfdestructed == other.selfdestructed && beneficiary == other.beneficiary;
+        }
+    };
+
+    /// The set of all accounts in the Host, organized by their addresses.
+    std::unordered_map<address, MockedAccount> accounts;
+
+    /// The EVMC transaction context to be returned by get_tx_context().
+    evmc_tx_context tx_context = {};
+
+    /// The block header hash value to be returned by get_block_hash().
+    bytes32 block_hash = {};
+
+    /// The call result to be returned by the call() method.
+    evmc_result call_result = {};
+
+    /// The record of all block numbers for which get_block_hash() was called.
+    std::vector<int64_t> recorded_blockhashes;
+
+    /// The record of all account accesses.
+    std::vector<address> recorded_account_accesses;
+
+    /// The maximum number of entries in recorded_account_accesses record.
+    /// This is arbitrary value useful in fuzzing when we don't want the record to explode.
+    static constexpr auto max_recorded_account_accesses = 200;
+
+    /// The record of all call messages requested in the call() method.
+    std::vector<evmc_message> recorded_calls;
+
+    /// The maximum number of entries in recorded_calls record.
+    /// This is arbitrary value useful in fuzzing when we don't want the record to explode.
+    static constexpr auto max_recorded_calls = 100;
+
+    /// The record of all LOGs passed to the emit_log() method.
+    std::vector<log_record> recorded_logs;
+
+    /// The record of all SELFDESTRUCTs from the selfdestruct() method.
+    std::vector<selfdestuct_record> recorded_selfdestructs;
+
+protected:
+    /// The copy of call inputs for the recorded_calls record.
+    std::vector<bytes> m_recorded_calls_inputs;
+
+    /// Record an account access.
+    /// @param addr  The address of the accessed account.
+    void record_account_access(const address& addr)
+    {
+        if (recorded_account_accesses.empty())
+            recorded_account_accesses.reserve(max_recorded_account_accesses);
+
+        if (recorded_account_accesses.size() < max_recorded_account_accesses)
+            recorded_account_accesses.emplace_back(addr);
+    }
+
+    /// Returns true if an account exists (EVMC Host method).
+    bool account_exists(const address& addr) noexcept override
+    {
+        record_account_access(addr);
+        return accounts.count(addr) != 0;
+    }
+
+    /// Get the account's storage value at the given key (EVMC Host method).
+    bytes32 get_storage(const address& addr, const bytes32& key) noexcept override
+    {
+        record_account_access(addr);
+
+        const auto account_iter = accounts.find(addr);
+        if (account_iter == accounts.end())
+            return {};
+
+        const auto storage_iter = account_iter->second.storage.find(key);
+        if (storage_iter != account_iter->second.storage.end())
+            return storage_iter->second.value;
+        return {};
+    }
+
+    /// Set the account's storage value (EVMC Host method).
+    evmc_storage_status set_storage(const address& addr,
+                                    const bytes32& key,
+                                    const bytes32& value) noexcept override
+    {
+        record_account_access(addr);
+        const auto it = accounts.find(addr);
+        if (it == accounts.end())
+            return EVMC_STORAGE_UNCHANGED;
+
+        auto& old = it->second.storage[key];
+
+        // Follow https://eips.ethereum.org/EIPS/eip-1283 specification.
+        // WARNING! This is not complete implementation as refund is not handled here.
+
+        if (old.value == value)
+            return EVMC_STORAGE_UNCHANGED;
+
+        evmc_storage_status status{};
+        if (!old.dirty)
+        {
+            old.dirty = true;
+            if (!old.value)
+                status = EVMC_STORAGE_ADDED;
+            else if (value)
+                status = EVMC_STORAGE_MODIFIED;
+            else
+                status = EVMC_STORAGE_DELETED;
+        }
+        else
+            status = EVMC_STORAGE_MODIFIED_AGAIN;
+
+        old.value = value;
+        return status;
+    }
+
+    /// Get the account's balance (EVMC Host method).
+    uint256be get_balance(const address& addr) noexcept override
+    {
+        record_account_access(addr);
+        const auto it = accounts.find(addr);
+        if (it == accounts.end())
+            return {};
+
+        return it->second.balance;
+    }
+
+    /// Get the account's code size (EVMC host method).
+    size_t get_code_size(const address& addr) noexcept override
+    {
+        record_account_access(addr);
+        const auto it = accounts.find(addr);
+        if (it == accounts.end())
+            return 0;
+        return it->second.code.size();
+    }
+
+    /// Get the account's code hash (EVMC host method).
+    bytes32 get_code_hash(const address& addr) noexcept override
+    {
+        record_account_access(addr);
+        const auto it = accounts.find(addr);
+        if (it == accounts.end())
+            return {};
+        return it->second.codehash;
+    }
+
+    /// Copy the account's code to the given buffer (EVMC host method).
+    size_t copy_code(const address& addr,
+                     size_t code_offset,
+                     uint8_t* buffer_data,
+                     size_t buffer_size) noexcept override
+    {
+        record_account_access(addr);
+        const auto it = accounts.find(addr);
+        if (it == accounts.end())
+            return 0;
+
+        const auto& code = it->second.code;
+
+        if (code_offset >= code.size())
+            return 0;
+
+        const auto n = std::min(buffer_size, code.size() - code_offset);
+
+        if (n > 0)
+            std::copy_n(&code[code_offset], n, buffer_data);
+        return n;
+    }
+
+    /// Selfdestruct the account (EVMC host method).
+    void selfdestruct(const address& addr, const address& beneficiary) noexcept override
+    {
+        record_account_access(addr);
+        recorded_selfdestructs.push_back({addr, beneficiary});
+    }
+
+    /// Call/create other contract (EVMC host method).
+    result call(const evmc_message& msg) noexcept override
+    {
+        record_account_access(msg.destination);
+
+        if (recorded_calls.empty())
+        {
+            recorded_calls.reserve(max_recorded_calls);
+            m_recorded_calls_inputs.reserve(max_recorded_calls);  // Iterators will not invalidate.
+        }
+
+        if (recorded_calls.size() < max_recorded_calls)
+        {
+            recorded_calls.emplace_back(msg);
+            auto& call_msg = recorded_calls.back();
+            if (call_msg.input_size > 0)
+            {
+                m_recorded_calls_inputs.emplace_back(call_msg.input_data, call_msg.input_size);
+                const auto& input_copy = m_recorded_calls_inputs.back();
+                call_msg.input_data = input_copy.data();
+            }
+        }
+        return result{call_result};
+    }
+
+    /// Get transaction context (EVMC host method).
+    evmc_tx_context get_tx_context() noexcept override { return tx_context; }
+
+    /// Get the block header hash (EVMC host method).
+    bytes32 get_block_hash(int64_t block_number) noexcept override
+    {
+        recorded_blockhashes.emplace_back(block_number);
+        return block_hash;
+    }
+
+    /// Emit LOG (EVMC host method).
+    void emit_log(const address& addr,
+                  const uint8_t* data,
+                  size_t data_size,
+                  const bytes32 topics[],
+                  size_t topics_count) noexcept override
+    {
+        recorded_logs.push_back({addr, {data, data_size}, {topics, topics + topics_count}});
+    }
+};
+}  // namespace evmc

lib/CMakeLists.txt

@@ -4,3 +4,4 @@
 
 add_subdirectory(instructions)
 add_subdirectory(loader)
+add_subdirectory(mocked_host)

lib/mocked_host/CMakeLists.txt

@@ -0,0 +1,15 @@
+# EVMC: Ethereum Client-VM Connector API.
+# Copyright 2019 The EVMC Authors.
+# Licensed under the Apache License, Version 2.0.
+
+add_library(mocked_host INTERFACE)
+target_sources(mocked_host INTERFACE $<BUILD_INTERFACE:${include_dir}/evmc/mocked_host.hpp>)
+
+add_library(evmc::mocked_host ALIAS mocked_host)
+target_include_directories(mocked_host INTERFACE
+    $<BUILD_INTERFACE:${include_dir}>$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+
+if(EVMC_INSTALL)
+    install(TARGETS mocked_host EXPORT evmcTargets)
+endif()

test/integration/compilation/compilation_test.cxx

@@ -10,6 +10,7 @@
 #include <evmc/helpers.h>
 #include <evmc/instructions.h>
 #include <evmc/loader.h>
+#include <evmc/mocked_host.hpp>
 #include <evmc/utils.h>
 
 // Include again to check if headers have proper include guards.
@@ -18,4 +19,5 @@
 #include <evmc/helpers.h>
 #include <evmc/instructions.h>
 #include <evmc/loader.h>
+#include <evmc/mocked_host.hpp>
 #include <evmc/utils.h>

test/unittests/test_cpp.cpp

@@ -6,14 +6,12 @@
 // previously related to using explicit template argument (SFINAE disabled).
 #include <vector>
 
-#include "../../examples/example_host.h"
 #include "../../examples/example_precompiles_vm/example_precompiles_vm.h"
 #include "../../examples/example_vm/example_vm.h"
 
 #include <evmc/evmc.hpp>
-
+#include <evmc/mocked_host.hpp>
 #include <gtest/gtest.h>
-
 #include <array>
 #include <cstring>
 #include <map>
@@ -438,18 +436,21 @@ TEST(cpp, vm_execute_with_null_host)
 
 TEST(cpp, host)
 {
-    // Use example host to execute all methods from the C++ host wrapper.
+    // Use MockedHost to execute all methods from the C++ host wrapper.
+    evmc::MockedHost mockedHost;
+    const auto& host_interface = evmc::MockedHost::get_interface();
+    auto* host_context = mockedHost.to_context();
 
-    const auto* host_interface = example_host_get_interface();
-    ASSERT_NE(host_interface, nullptr);
-    auto* host_context = example_host_create_context(evmc_tx_context{});
-    auto host = evmc::HostContext{*host_interface, host_context};
+    auto host = evmc::HostContext{host_interface, host_context};
 
     const auto a = evmc::address{{{1}}};
     const auto v = evmc::bytes32{{{7, 7, 7}}};
 
     EXPECT_FALSE(host.account_exists(a));
 
+    mockedHost.accounts[a].storage[{}].value.bytes[0] = 1;
+    EXPECT_TRUE(host.account_exists(a));
+
     EXPECT_EQ(host.set_storage(a, {}, v), EVMC_STORAGE_MODIFIED);
     EXPECT_EQ(host.set_storage(a, {}, v), EVMC_STORAGE_UNCHANGED);
     EXPECT_EQ(host.get_storage(a, {}), v);
@@ -468,34 +469,53 @@ TEST(cpp, host)
     EXPECT_EQ(host.get_block_hash(0), evmc::bytes32{});
 
     host.emit_log(a, nullptr, 0, nullptr, 0);
-
-    example_host_destroy_context(host_context);
 }
 
 TEST(cpp, host_call)
 {
     // Use example host to test Host::call() method.
+    evmc::MockedHost mockedHost;
+    const auto& host_interface = evmc::MockedHost::get_interface();
+    auto* host_context = mockedHost.to_context();
 
     auto host = evmc::HostContext{};  // Use default constructor.
-    const auto* host_interface = example_host_get_interface();
-    ASSERT_NE(host_interface, nullptr);
-    auto* host_context = example_host_create_context(evmc_tx_context{});
-    host = evmc::HostContext{*host_interface, host_context};
+    host = evmc::HostContext{host_interface, host_context};
 
     EXPECT_EQ(host.call({}).gas_left, 0);
+    ASSERT_EQ(mockedHost.recorded_calls.size(), 1u);
+    const auto& recorded_msg1 = mockedHost.recorded_calls.back();
+    EXPECT_EQ(recorded_msg1.kind, EVMC_CALL);
+    EXPECT_EQ(recorded_msg1.gas, 0);
+    EXPECT_EQ(recorded_msg1.flags, 0u);
+    EXPECT_EQ(recorded_msg1.depth, 0);
+    EXPECT_EQ(recorded_msg1.input_data, nullptr);
+    EXPECT_EQ(recorded_msg1.input_size, 0u);
 
     auto msg = evmc_message{};
     msg.gas = 1;
-    uint8_t input[] = {0xa, 0xb, 0xc};
-    msg.input_data = input;
-    msg.input_size = sizeof(input);
+    evmc::bytes input{0xa, 0xb, 0xc};
+    msg.input_data = input.data();
+    msg.input_size = input.size();
+
+    mockedHost.call_result.status_code = EVMC_REVERT;
+    mockedHost.call_result.gas_left = 4321;
+    mockedHost.call_result.output_data = &input[2];
+    mockedHost.call_result.output_size = 1;
 
     auto res = host.call(msg);
-    EXPECT_EQ(res.status_code, EVMC_REVERT);
-    EXPECT_EQ(res.output_size, msg.input_size);
-    EXPECT_TRUE(std::equal(&res.output_data[0], &res.output_data[res.output_size], msg.input_data));
+    ASSERT_EQ(mockedHost.recorded_calls.size(), 2u);
+    const auto& recorded_msg2 = mockedHost.recorded_calls.back();
+    EXPECT_EQ(recorded_msg2.kind, EVMC_CALL);
+    EXPECT_EQ(recorded_msg2.gas, 1);
+    EXPECT_EQ(recorded_msg2.flags, 0u);
+    EXPECT_EQ(recorded_msg2.depth, 0);
+    ASSERT_EQ(recorded_msg2.input_size, 3u);
+    EXPECT_EQ(evmc::bytes(recorded_msg2.input_data, recorded_msg2.input_size), input);
 
-    example_host_destroy_context(host_context);
+    EXPECT_EQ(res.status_code, EVMC_REVERT);
+    EXPECT_EQ(res.gas_left, 4321);
+    ASSERT_EQ(res.output_size, 1u);
+    EXPECT_EQ(*res.output_data, input[2]);
 }
 
 TEST(cpp, result_raii)