EVM gasCall values always stay on positive side (#2459)

* EVM gasCall values always stay on positive side

This is also another part of preparations before
converting GasInt to uint64

* Fix test_evm_support

nimbus/evm/interpreter/gas_costs.nim

@@ -67,7 +67,8 @@ type
 
     kind*: Op
     isNewAccount*: bool
-    gasBalance*: GasInt
+    gasLeft*: GasInt
+    gasCallEIP2929*: GasInt
     contractGas*: UInt256
     currentMemSize*: GasNatural
     memOffset*: GasNatural
@@ -348,7 +349,6 @@ template gasCosts(fork: EVMFork, prefix, ResultGasCostsName: untyped) =
       static(4 * FeeSchedule[GasLogTopic])
 
   func `prefix gasCall`(value: UInt256, params: GasParams): EvmResult[CallGasResult] {.nimcall.} =
-
     # From the Yellow Paper, going through the equation from bottom to top
     # https://ethereum.github.io/yellowpaper/paper.pdf#appendix.H
     #
@@ -369,15 +369,18 @@ template gasCosts(fork: EVMFork, prefix, ResultGasCostsName: untyped) =
     # The discussion for the draft EIP-5, which proposes to change the CALL opcode also goes over
     # the current implementation - https://github.com/ethereum/EIPs/issues/8
 
-    # Both gasCost and childGasLimit can go below zero
-    # but that is an OOG condition. Leaving this function
-    # both of them are positive integers.
+    # Both gasCost and childGasLimit are always on positive side
 
-    var gasCost: int64 =  `prefix gasMemoryExpansion`(
+    var gasLeft = params.gasLeft
+    if gasLeft < params.gasCallEIP2929:
+      return err(opErr(OutOfGas))
+    gasLeft -= params.gasCallEIP2929
+
+    var gasCost: GasInt = `prefix gasMemoryExpansion`(
                              params.currentMemSize,
                              params.memOffset,
                              params.memLength)
-    var childGasLimit: int64
+    var childGasLimit: GasInt
 
     # Cnew_account
     if params.isNewAccount and params.kind == Call:
@@ -398,33 +401,34 @@ template gasCosts(fork: EVMFork, prefix, ResultGasCostsName: untyped) =
     # Cextra
     gasCost += static(FeeSchedule[GasCall])
 
+    if gasLeft < gasCost:
+      return err(opErr(OutOfGas))
+    gasLeft -= gasCost
+
     # Cgascap
     when fork >= FkTangerine:
       # https://github.com/ethereum/EIPs/blob/master/EIPS/eip-150.md
-      let gas = `prefix all_but_one_64th`(params.gasBalance - gasCost)
-      if params.contractGas > high(int64).u256 or
-        gas < params.contractGas.truncate(int64):
+      let gas = `prefix all_but_one_64th`(gasLeft)
+      if params.contractGas > high(GasInt).u256 or
+        gas < params.contractGas.truncate(GasInt):
         childGasLimit = gas
       else:
-        childGasLimit = params.contractGas.truncate(int64)
+        childGasLimit = params.contractGas.truncate(GasInt)
     else:
-      if params.contractGas > high(int64).u256:
+      if params.contractGas > high(GasInt).u256:
         return err(gasErr(GasIntOverflow))
-      childGasLimit = params.contractGas.truncate(int64)
+      childGasLimit = params.contractGas.truncate(GasInt)
 
-    if childGasLimit > 0: # skip check if childGasLimit is negative
-      if gasCost.u256 + childGasLimit.u256 > high(int64).u256:
-        return err(gasErr(GasIntOverflow))
+    if gasCost.u256 + childGasLimit.u256 + params.gasCallEIP2929.u256 > high(GasInt).u256:
+      return err(gasErr(GasIntOverflow))
 
     gasCost += childGasLimit
+    gasCost += params.gasCallEIP2929
 
     # Ccallgas - Gas sent to the child message
     if not value.isZero and params.kind in {Call, CallCode}:
       childGasLimit += static(FeeSchedule[GasCallStipend])
 
-    if gasCost <= 0 and childGasLimit <= 0:
-      return err(opErr(OutOfGas))
-
     # at this point gasCost and childGasLimit is always > 0
     ok( (gasCost, childGasLimit) )
 

nimbus/evm/interpreter/op_handlers/oph_call.nim

@@ -210,21 +210,18 @@ proc callOp(k: var VmCtx): EvmResultVoid =
 
   let
     p = ? cpt.callParams
-
-  var
     (gasCost, childGasLimit) = ? cpt.gasCosts[Call].c_handler(
       p.value,
       GasParams(
         kind:           Call,
         isNewAccount:   not cpt.accountExists(p.contractAddress),
-        gasBalance:     cpt.gasMeter.gasRemaining - p.gasCallEIP2929,
+        gasLeft:        cpt.gasMeter.gasRemaining,
+        gasCallEIP2929: p.gasCallEIP2929,
         contractGas:    p.gas,
         currentMemSize: cpt.memory.len,
         memOffset:      p.memOffset,
         memLength:      p.memLength))
 
-  # at this point gasCost is always > 0
-  gasCost += p.gasCallEIP2929
   ? cpt.opcodeGastCost(Call, gasCost, reason = $Call)
 
   cpt.returnData.setLen(0)
@@ -285,21 +282,18 @@ proc callCodeOp(k: var VmCtx): EvmResultVoid =
   let
     cpt = k.cpt
     p = ? cpt.callCodeParams
-
-  var
     (gasCost, childGasLimit) = ? cpt.gasCosts[CallCode].c_handler(
       p.value,
       GasParams(
         kind:           CallCode,
         isNewAccount:   not cpt.accountExists(p.contractAddress),
-        gasBalance:     cpt.gasMeter.gasRemaining - p.gasCallEIP2929,
+        gasLeft:        cpt.gasMeter.gasRemaining,
+        gasCallEIP2929: p.gasCallEIP2929,
         contractGas:    p.gas,
         currentMemSize: cpt.memory.len,
         memOffset:      p.memOffset,
         memLength:      p.memLength))
 
-  # at this point gasCost is always > 0
-  gasCost += p.gasCallEIP2929
   ? cpt.opcodeGastCost(CallCode, gasCost, reason = $CallCode)
 
   cpt.returnData.setLen(0)
@@ -361,21 +355,18 @@ proc delegateCallOp(k: var VmCtx): EvmResultVoid =
   let
     cpt = k.cpt
     p = ? cpt.delegateCallParams
-
-  var
     (gasCost, childGasLimit) = ? cpt.gasCosts[DelegateCall].c_handler(
       p.value,
       GasParams(
         kind:           DelegateCall,
         isNewAccount:   not cpt.accountExists(p.contractAddress),
-        gasBalance:     cpt.gasMeter.gasRemaining - p.gasCallEIP2929,
+        gasLeft:        cpt.gasMeter.gasRemaining,
+        gasCallEIP2929: p.gasCallEIP2929,
         contractGas:    p.gas,
         currentMemSize: cpt.memory.len,
         memOffset:      p.memOffset,
         memLength:      p.memLength))
 
-  # at this point gasCost is always > 0
-  gasCost += p.gasCallEIP2929
   ? cpt.opcodeGastCost(DelegateCall, gasCost, reason = $DelegateCall)
 
   cpt.returnData.setLen(0)
@@ -431,21 +422,18 @@ proc staticCallOp(k: var VmCtx): EvmResultVoid =
   let
     cpt = k.cpt
     p = ? cpt.staticCallParams
-
-  var
     (gasCost, childGasLimit) = ? cpt.gasCosts[StaticCall].c_handler(
       p.value,
       GasParams(
         kind:           StaticCall,
         isNewAccount:   not cpt.accountExists(p.contractAddress),
-        gasBalance:     cpt.gasMeter.gasRemaining - p.gasCallEIP2929,
+        gasLeft:        cpt.gasMeter.gasRemaining,
+        gasCallEIP2929: p.gasCallEIP2929,
         contractGas:    p.gas,
         currentMemSize: cpt.memory.len,
         memOffset:      p.memOffset,
         memLength:      p.memLength))
 
-  # at this point gasCost is always > 0
-  gasCost += p.gasCallEIP2929
   ? cpt.opcodeGastCost(StaticCall, gasCost, reason = $StaticCall)
 
   cpt.returnData.setLen(0)

tests/test_evm_support.nim

@@ -381,7 +381,8 @@ proc runTestOverflow() =
     when defined(evmc_enabled):
       check res.error == "EVMC_FAILURE"
     else:
-      check res.error == "Opcode Dispatch Error: GasIntOverflow, depth=1"
+      # After gasCall values always on positive, this test become OOG
+      check res.error == "Opcode Dispatch Error: OutOfGas, depth=1"
 
 proc evmSupportMain*() =
   runStackTests()

tools/t8n/testdata/00-521/exp.txt

@@ -12,6 +12,6 @@
 {"pc":8,"op":96,"gas":"0xf","gasCost":"0x3","memSize":0,"stack":["0x0","0x0","0x0","0x0"],"depth":2,"refund":0,"opName":"PUSH1"}
 {"pc":10,"op":96,"gas":"0xc","gasCost":"0x3","memSize":0,"stack":["0x0","0x0","0x0","0x0","0x0"],"depth":2,"refund":0,"opName":"PUSH1"}
 {"pc":12,"op":90,"gas":"0x9","gasCost":"0x2","memSize":0,"stack":["0x0","0x0","0x0","0x0","0x0","0xfa"],"depth":2,"refund":0,"opName":"GAS"}
-{"pc":13,"op":241,"gas":"0x7","gasCost":"0x9","memSize":0,"stack":["0x0","0x0","0x0","0x0","0x0","0xfa","0x7"],"depth":2,"refund":0,"opName":"CALL","error":"Opcode Dispatch Error: OutOfGas, depth=2"}
+{"pc":13,"op":241,"gas":"0x7","gasCost":"0x7","memSize":0,"stack":["0x0","0x0","0x0","0x0","0x0","0xfa","0x7"],"depth":2,"refund":0,"opName":"CALL","error":"Opcode Dispatch Error: OutOfGas, depth=2"}
 {"pc":12,"op":80,"gas":"0x0","gasCost":"0x2","memSize":0,"stack":["0x0"],"depth":1,"refund":0,"opName":"POP","error":"Opcode Dispatch Error: OutOfGas, depth=1"}
 {"output":"","gasUsed":"0xa54","error":"Opcode Dispatch Error: OutOfGas, depth=1"}