core: introduce overflow-safe num_words (#2164)

Author: yperbasis

silkworm/core/execution/call_tracer.cpp

@@ -22,6 +22,7 @@
 #include <evmone/execution_state.hpp>
 #include <evmone/instructions.hpp>
 
+#include <silkworm/core/protocol/intrinsic_gas.hpp>
 #include <silkworm/core/types/address.hpp>
 
 using namespace evmone;
@@ -72,7 +73,7 @@ inline evmc_status_code check_requirements(const CostTable& cost_table, int64_t&
 
 //! Adaptation of evmone::grow_memory: we need just to check gas requirements w/o growing memory
 inline int64_t check_memory_gas(int64_t gas_left, Memory& memory, uint64_t new_size) noexcept {
-    const auto new_words = num_words(new_size);
+    const auto new_words = static_cast<int64_t>(silkworm::num_words(new_size));
     const auto current_words = static_cast<int64_t>(memory.size() / word_size);
     const auto new_cost = 3 * new_words + new_words * new_words / 512;
     const auto current_cost = 3 * current_words + current_words * current_words / 512;
@@ -164,7 +165,7 @@ void on_create_start(const intx::uint256* stack_top, int stack_height, int64_t g
         return;  // The execution has run of out-of-gas during contract deployment, do not trace anything
     }
     const auto init_code_word_cost = 6 * (Op == Opcode::OP_CREATE2) + 2 * (state.rev >= EVMC_SHANGHAI);
-    const auto init_code_cost = num_words(init_code_size) * init_code_word_cost;
+    const auto init_code_cost = static_cast<int64_t>(silkworm::num_words(init_code_size)) * init_code_word_cost;
     if (gas - init_code_cost < 0) {
         return;  // The execution has run of out-of-gas during contract deployment, do not trace anything
     }

silkworm/core/execution/precompile.cpp

@@ -40,6 +40,7 @@
 #include <silkworm/core/crypto/rmd160.h>
 #include <silkworm/core/crypto/secp256k1n.hpp>
 #include <silkworm/core/crypto/sha256.h>
+#include <silkworm/core/protocol/intrinsic_gas.hpp>
 #include <silkworm/core/types/hash.hpp>
 
 namespace silkworm::precompile {
@@ -78,7 +79,7 @@ std::optional<Bytes> ecrec_run(ByteView input) noexcept {
 }
 
 uint64_t sha256_gas(ByteView input, evmc_revision) noexcept {
-    return 60 + 12 * ((input.length() + 31) / 32);
+    return 60 + 12 * num_words(input.length());
 }
 
 std::optional<Bytes> sha256_run(ByteView input) noexcept {
@@ -88,7 +89,7 @@ std::optional<Bytes> sha256_run(ByteView input) noexcept {
 }
 
 uint64_t rip160_gas(ByteView input, evmc_revision) noexcept {
-    return 600 + 120 * ((input.length() + 31) / 32);
+    return 600 + 120 * num_words(input.length());
 }
 
 std::optional<Bytes> rip160_run(ByteView input) noexcept {
@@ -99,7 +100,7 @@ std::optional<Bytes> rip160_run(ByteView input) noexcept {
 }
 
 uint64_t id_gas(ByteView input, evmc_revision) noexcept {
-    return 15 + 3 * ((input.length() + 31) / 32);
+    return 15 + 3 * num_words(input.length());
 }
 
 std::optional<Bytes> id_run(ByteView input) noexcept {

silkworm/core/protocol/intrinsic_gas.cpp

@@ -38,7 +38,7 @@ intx::uint128 intrinsic_gas(const UnsignedTransaction& txn, const evmc_revision
     }
     gas += total_num_of_storage_keys * fee::kAccessListStorageKeyCost;
 
-    const intx::uint128 data_len{txn.data.length()};
+    const uint64_t data_len{txn.data.length()};
     if (data_len == 0) {
         return gas;
     }
@@ -51,8 +51,7 @@ intx::uint128 intrinsic_gas(const UnsignedTransaction& txn, const evmc_revision
 
     // EIP-3860: Limit and meter initcode
     if (contract_creation && rev >= EVMC_SHANGHAI) {
-        const intx::uint128 num_words{(data_len + 31) / 32};
-        gas += num_words * fee::kInitCodeWordCost;
+        gas += num_words(data_len) * fee::kInitCodeWordCost;
     }
 
     return gas;

silkworm/core/protocol/intrinsic_gas.hpp

@@ -20,11 +20,20 @@
 
 #include <silkworm/core/types/transaction.hpp>
 
-namespace silkworm::protocol {
+namespace silkworm {
 
-// Returns the intrinsic gas of a transaction.
-// Refer to g0 in Section 6.2 "Execution" of the Yellow Paper
-// and EIP-3860 "Limit and meter initcode".
-intx::uint128 intrinsic_gas(const UnsignedTransaction& txn, evmc_revision rev) noexcept;
+// Words in EVM are 32-bytes long
+inline constexpr uint64_t num_words(uint64_t num_bytes) noexcept {
+    return num_bytes / 32 + static_cast<uint64_t>(num_bytes % 32 != 0);
+}
 
-}  // namespace silkworm::protocol
+namespace protocol {
+
+    // Returns the intrinsic gas of a transaction.
+    // Refer to g0 in Section 6.2 "Execution" of the Yellow Paper
+    // and EIP-3860 "Limit and meter initcode".
+    intx::uint128 intrinsic_gas(const UnsignedTransaction& txn, evmc_revision rev) noexcept;
+
+}  // namespace protocol
+
+}  // namespace silkworm

silkworm/core/protocol/intrinsic_gas_test.cpp

@@ -22,31 +22,48 @@
 
 #include "param.hpp"
 
-namespace silkworm::protocol {
-
-TEST_CASE("EIP-2930 intrinsic gas") {
-    std::vector<AccessListEntry> access_list{
-        {0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae_address,
-         {
-             0x0000000000000000000000000000000000000000000000000000000000000003_bytes32,
-             0x0000000000000000000000000000000000000000000000000000000000000007_bytes32,
-         }},
-        {0xbb9bc244d798123fde783fcc1c72d3bb8c189413_address, {}},
-    };
-
-    UnsignedTransaction txn{
-        .type = TransactionType::kAccessList,
-        .chain_id = kSepoliaConfig.chain_id,
-        .nonce = 7,
-        .max_priority_fee_per_gas = 30000000000,
-        .max_fee_per_gas = 30000000000,
-        .gas_limit = 5748100,
-        .to = 0x811a752c8cd697e3cb27279c330ed1ada745a8d7_address,
-        .value = 2 * kEther,
-        .access_list = access_list};
-
-    intx::uint128 g0{intrinsic_gas(txn, EVMC_ISTANBUL)};
-    CHECK(g0 == fee::kGTransaction + 2 * fee::kAccessListAddressCost + 2 * fee::kAccessListStorageKeyCost);
+namespace silkworm {
+
+TEST_CASE("num_words") {
+    CHECK(num_words(0) == 0);
+    CHECK(num_words(1) == 1);
+    CHECK(num_words(31) == 1);
+    CHECK(num_words(32) == 1);
+    CHECK(num_words(33) == 2);
+    CHECK(num_words(0xFFFFFFFFFFFFFFDF) == 0x7FFFFFFFFFFFFFF);
+    CHECK(num_words(0xFFFFFFFFFFFFFFE0) == 0x7FFFFFFFFFFFFFF);
+    CHECK(num_words(0xFFFFFFFFFFFFFFE1) == 0x800000000000000);
+    CHECK(num_words(0xFFFFFFFFFFFFFFFE) == 0x800000000000000);
+    CHECK(num_words(0xFFFFFFFFFFFFFFFF) == 0x800000000000000);
 }
 
-}  // namespace silkworm::protocol
+namespace protocol {
+
+    TEST_CASE("EIP-2930 intrinsic gas") {
+        std::vector<AccessListEntry> access_list{
+            {0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae_address,
+             {
+                 0x0000000000000000000000000000000000000000000000000000000000000003_bytes32,
+                 0x0000000000000000000000000000000000000000000000000000000000000007_bytes32,
+             }},
+            {0xbb9bc244d798123fde783fcc1c72d3bb8c189413_address, {}},
+        };
+
+        UnsignedTransaction txn{
+            .type = TransactionType::kAccessList,
+            .chain_id = kSepoliaConfig.chain_id,
+            .nonce = 7,
+            .max_priority_fee_per_gas = 30000000000,
+            .max_fee_per_gas = 30000000000,
+            .gas_limit = 5748100,
+            .to = 0x811a752c8cd697e3cb27279c330ed1ada745a8d7_address,
+            .value = 2 * kEther,
+            .access_list = access_list};
+
+        intx::uint128 g0{intrinsic_gas(txn, EVMC_ISTANBUL)};
+        CHECK(g0 == fee::kGTransaction + 2 * fee::kAccessListAddressCost + 2 * fee::kAccessListStorageKeyCost);
+    }
+
+}  // namespace protocol
+
+}  // namespace silkworm