wasm 代理跨合约调用，被调用合约 platon_caller 获取的地址应该是调用合约的caller，不应该是调用合约的地址。

[jatel]

Hi there,

wasm 代理跨合约调用，被调用合约 platon_caller 获取的地址错误。

System information

PlatON version: platon version
OS & Version: Windows/Linux/OSX
Commit hash : (if develop)

Expected behaviour

应该是调用合约的 caller

Actual behaviour

不应该是 调用合约的地址

Steps to reproduce the behaviour

1. 部署一个被调用 wasm 合约，在某一个合约方法里面通过 platon_caller函数获取被调用合约的 caller。
2. 在调用合约里面通过代理跨合约调用被调用合约里面的方法。

// callee 合约
  ACTION bool Approve(const Address &spender, u128 value) override {
    Address sender = platon_caller();
    privacy_assert(value > 0, "PlatON ARC20: approve amount illegal");
    SetAllowance(sender, spender, value);
    PLATON_EMIT_EVENT2(ApprovalEvent, sender, spender, value);
    DEBUG("approve", "sender:", sender.toString(),
          "spender:", spender.toString(), "value:", value);
    return true;
  }

// caller 合约
 function Approve_delegatecall(address wasm, address spender, uint value) internal returns (bool){
  uint64 methord = RLPEncode.hash("Approve");
  bytes memory rlpMethord = RLPEncode.encodeUint(uint(methord));
  
  bytes memory rlpPara0 = RLPEncode.encodeAddress(spender);
  bytes memory rlpPara1 = RLPEncode.encodeUint(value);
  bytes[] memory allInput = new bytes[](3);
  allInput[0] = rlpMethord;
  allInput[1] = rlpPara0;
  allInput[2] = rlpPara1;
  bytes memory payload = RLPEncode.encodeList(allInput);
  (bool success, bytes memory data) = wasm.delegatecall(payload);
  if(!success){
	  revert();
  }
  
  RLPReader.RLPItem memory rlpItem = RLPReader.toRlpItem(data);
  bool result  = RLPReader.toBoolean(rlpItem);
  return result;
 }

Backtrace

[backtrace]

[TraceBundy]

原因是caller调用时，获取地址错误。需要对此代码进行修复

PlatON-Go/core/vm/wagon_runtime.go

Line 910 in 83ac8d2

_, err := proc.WriteAt(ctx.contract.caller.Address().Bytes(), int64(dst))

[benbaley]

fixed