eof: Return constant hash of EXTCODEHASH of EOF (#1035)

Replace runtime evaluated `keccak256("EF00")` with a constant returned
for an account with EOF code.

lib/evmone/eof.cpp

@@ -14,7 +14,6 @@
 #include <cassert>
 #include <limits>
 #include <numeric>
-#include <ostream>
 #include <queue>
 #include <unordered_set>
 #include <vector>
@@ -23,8 +22,6 @@ namespace evmone
 {
 namespace
 {
-constexpr uint8_t MAGIC_BYTES[] = {0xef, 0x00};
-constexpr bytes_view MAGIC{MAGIC_BYTES, std::size(MAGIC_BYTES)};
 constexpr uint8_t TERMINATOR = 0x00;
 constexpr uint8_t TYPE_SECTION = 0x01;
 constexpr uint8_t CODE_SECTION = 0x02;
@@ -50,7 +47,7 @@ size_t eof_header_size(const EOFSectionHeaders& headers) noexcept
     constexpr auto non_code_section_header_size = 3;  // (SECTION_ID + SIZE) per each section
     constexpr auto section_size_size = 2;
 
-    auto header_size = std::size(MAGIC) + 1 +  // 1 version byte
+    auto header_size = std::size(EOF_MAGIC) + 1 +  // 1 version byte
                        non_code_section_count * non_code_section_header_size +
                        sizeof(CODE_SECTION) + 2 + code_section_count * section_size_size +
                        sizeof(TERMINATOR);
@@ -93,7 +90,7 @@ std::variant<EOFSectionHeaders, EOFValidationError> validate_section_headers(byt
     uint16_t section_num = 0;
     EOFSectionHeaders section_headers{};
     const auto container_end = container.end();
-    auto it = container.begin() + std::size(MAGIC) + 1;  // MAGIC + VERSION
+    auto it = container.begin() + std::size(EOF_MAGIC) + 1;  // MAGIC + VERSION
     uint8_t expected_section_id = TYPE_SECTION;
     while (it != container_end && state != State::terminated)
     {
@@ -719,7 +716,7 @@ size_t EOF1Header::data_size_position() const noexcept
 {
     const auto num_code_sections = code_sizes.size();
     const auto num_container_sections = container_sizes.size();
-    return std::size(MAGIC) + 1 +       // magic + version
+    return std::size(EOF_MAGIC) + 1 +   // magic + version
            3 +                          // type section kind + size
            3 + 2 * num_code_sections +  // code sections kind + count + sizes
            // container sections kind + count + sizes
@@ -729,7 +726,7 @@ size_t EOF1Header::data_size_position() const noexcept
 
 bool is_eof_container(bytes_view container) noexcept
 {
-    return container.starts_with(MAGIC);
+    return container.starts_with(EOF_MAGIC);
 }
 
 std::variant<EOF1Header, EOFValidationError> validate_header(
@@ -806,7 +803,7 @@ std::variant<EOF1Header, EOFValidationError> validate_header(
 EOF1Header read_valid_eof1_header(bytes_view container)
 {
     EOFSectionHeaders section_headers;
-    auto it = container.begin() + std::size(MAGIC) + 1;  // MAGIC + VERSION
+    auto it = container.begin() + std::size(EOF_MAGIC) + 1;  // MAGIC + VERSION
     while (*it != TERMINATOR)
     {
         const auto section_id = *it++;

lib/evmone/eof.hpp

@@ -4,19 +4,28 @@
 #pragma once
 
 #include <evmc/bytes.hpp>
-#include <evmc/evmc.h>
+#include <evmc/evmc.hpp>
 #include <evmc/utils.h>
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
-#include <string>
+#include <string_view>
 #include <variant>
 #include <vector>
 
 namespace evmone
 {
 using evmc::bytes;
 using evmc::bytes_view;
+using namespace evmc::literals;
+
+constexpr uint8_t EOF_MAGIC_BYTES[] = {0xef, 0x00};
+constexpr bytes_view EOF_MAGIC{EOF_MAGIC_BYTES, std::size(EOF_MAGIC_BYTES)};
+
+/// The value returned by EXTCODEHASH of an address with EOF code.
+/// See EIP-3540: https://eips.ethereum.org/EIPS/eip-3540#changes-to-execution-semantics.
+static constexpr auto EOF_CODE_HASH_SENTINEL =
+    0x9dbf3648db8210552e9c4f75c6a1c3057c0ca432043bd648be15fe7be05646f5_bytes32;
 
 struct EOFCodeType
 {

test/state/host.cpp

@@ -113,9 +113,13 @@ size_t Host::get_code_size(const address& addr) const noexcept
 
 bytes32 Host::get_code_hash(const address& addr) const noexcept
 {
-    // TODO: Cache code hash. It will be needed also to compute the MPT hash.
     const auto* const acc = m_state.find(addr);
-    return (acc != nullptr && !acc->is_empty()) ? keccak256(extcode(acc->code)) : bytes32{};
+    if (acc == nullptr || acc->is_empty())
+        return {};
+    if (is_eof_container(acc->code))
+        return EOF_CODE_HASH_SENTINEL;
+    // TODO: Cache code hash. It will be needed also to compute the MPT hash.
+    return keccak256(acc->code);
 }
 
 size_t Host::copy_code(const address& addr, size_t code_offset, uint8_t* buffer_data,

test/unittests/eof_test.cpp

@@ -4,6 +4,7 @@
 
 #include <evmone/eof.hpp>
 #include <gtest/gtest.h>
+#include <test/state/hash_utils.hpp>
 #include <test/utils/bytecode.hpp>
 #include <test/utils/utils.hpp>
 
@@ -115,3 +116,8 @@ TEST(eof, get_error_message)
     // NOLINTNEXTLINE(*.EnumCastOutOfRange)
     EXPECT_EQ(evmone::get_error_message(static_cast<EOFValidationError>(-1)), "<unknown>");
 }
+
+TEST(eof, extcodehash_sentinel)
+{
+    EXPECT_EQ(keccak256(EOF_MAGIC), EOF_CODE_HASH_SENTINEL);
+}