From 2433349c808fad601419d1f06275bec5b6a93ec8 Mon Sep 17 00:00:00 2001
From: gary rong <garyrong0905@gmail.com>
Date: Tue, 24 Jul 2018 23:06:40 +0800
Subject: core/vm, params: implement EXTCODEHASH opcode (#17202)

* core/vm, params: implement EXTCODEHASH opcode

* core, params: tiny fixes and polish

* core: add function description
---
 core/vm/gas_table.go    |  4 ++++
 core/vm/instructions.go | 32 ++++++++++++++++++++++++++++++++
 core/vm/jump_table.go   |  6 ++++++
 core/vm/opcodes.go      |  3 +++
 4 files changed, 45 insertions(+)

(limited to 'core')

diff --git a/core/vm/gas_table.go b/core/vm/gas_table.go
index e130406ec..f9eea319e 100644
--- a/core/vm/gas_table.go
+++ b/core/vm/gas_table.go
@@ -241,6 +241,10 @@ func gasExtCodeCopy(gt params.GasTable, evm *EVM, contract *Contract, stack *Sta
 	return gas, nil
 }
 
+func gasExtCodeHash(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
+	return gt.ExtcodeHash, nil
+}
+
 func gasMLoad(gt params.GasTable, evm *EVM, contract *Contract, stack *Stack, mem *Memory, memorySize uint64) (uint64, error) {
 	var overflow bool
 	gas, err := memoryGasCost(mem, memorySize)
diff --git a/core/vm/instructions.go b/core/vm/instructions.go
index b25c0111a..122fc21e4 100644
--- a/core/vm/instructions.go
+++ b/core/vm/instructions.go
@@ -496,6 +496,38 @@ func opExtCodeCopy(pc *uint64, evm *EVM, contract *Contract, memory *Memory, sta
 	return nil, nil
 }
 
+// opExtCodeHash returns the code hash of a specified account.
+// There are several cases when the function is called, while we can relay everything
+// to `state.GetCodeHash` function to ensure the correctness.
+//   (1) Caller tries to get the code hash of a normal contract account, state
+// should return the relative code hash and set it as the result.
+//
+//   (2) Caller tries to get the code hash of a non-existent account, state should
+// return common.Hash{} and zero will be set as the result.
+//
+//   (3) Caller tries to get the code hash for an account without contract code,
+// state should return emptyCodeHash(0xc5d246...) as the result.
+//
+//   (4) Caller tries to get the code hash of a precompiled account, the result
+// should be zero or emptyCodeHash.
+//
+// It is worth noting that in order to avoid unnecessary create and clean,
+// all precompile accounts on mainnet have been transferred 1 wei, so the return
+// here should be emptyCodeHash.
+// If the precompile account is not transferred any amount on a private or
+// customized chain, the return value will be zero.
+//
+//   (5) Caller tries to get the code hash for an account which is marked as suicided
+// in the current transaction, the code hash of this account should be returned.
+//
+//   (6) Caller tries to get the code hash for an account which is marked as deleted,
+// this account should be regarded as a non-existent account and zero should be returned.
+func opExtCodeHash(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
+	slot := stack.peek()
+	slot.SetBytes(evm.StateDB.GetCodeHash(common.BigToAddress(slot)).Bytes())
+	return nil, nil
+}
+
 func opGasprice(pc *uint64, evm *EVM, contract *Contract, memory *Memory, stack *Stack) ([]byte, error) {
 	stack.push(evm.interpreter.intPool.get().Set(evm.GasPrice))
 	return nil, nil
diff --git a/core/vm/jump_table.go b/core/vm/jump_table.go
index 014496567..f387e6133 100644
--- a/core/vm/jump_table.go
+++ b/core/vm/jump_table.go
@@ -80,6 +80,12 @@ func newConstantinopleInstructionSet() [256]operation {
 		validateStack: makeStackFunc(2, 1),
 		valid:         true,
 	}
+	instructionSet[EXTCODEHASH] = operation{
+		execute:       opExtCodeHash,
+		gasCost:       gasExtCodeHash,
+		validateStack: makeStackFunc(1, 1),
+		valid:         true,
+	}
 	instructionSet[CREATE2] = operation{
 		execute:       opCreate2,
 		gasCost:       gasCreate2,
diff --git a/core/vm/opcodes.go b/core/vm/opcodes.go
index 84426a28a..4349ffd29 100644
--- a/core/vm/opcodes.go
+++ b/core/vm/opcodes.go
@@ -90,6 +90,7 @@ const (
 	EXTCODECOPY
 	RETURNDATASIZE
 	RETURNDATACOPY
+	EXTCODEHASH
 )
 
 // 0x40 range - block operations.
@@ -267,6 +268,7 @@ var opCodeToString = map[OpCode]string{
 	EXTCODECOPY:    "EXTCODECOPY",
 	RETURNDATASIZE: "RETURNDATASIZE",
 	RETURNDATACOPY: "RETURNDATACOPY",
+	EXTCODEHASH:    "EXTCODEHASH",
 
 	// 0x40 range - block operations.
 	BLOCKHASH:  "BLOCKHASH",
@@ -435,6 +437,7 @@ var stringToOp = map[string]OpCode{
 	"EXTCODECOPY":    EXTCODECOPY,
 	"RETURNDATASIZE": RETURNDATASIZE,
 	"RETURNDATACOPY": RETURNDATACOPY,
+	"EXTCODEHASH":    EXTCODEHASH,
 	"BLOCKHASH":      BLOCKHASH,
 	"COINBASE":       COINBASE,
 	"TIMESTAMP":      TIMESTAMP,
-- 
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