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core/vm: fill gaps in jump table with opUndefined #24031

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Dec 3, 2021
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core/vm: fill gaps in jump table with opUndefined #24031

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4 changes: 4 additions & 0 deletions core/vm/instructions.go
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Original file line number Diff line number Diff line change
Expand Up @@ -801,6 +801,10 @@ func opRevert(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]b
return ret, ErrExecutionReverted
}

func opUndefined(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
return nil, &ErrInvalidOpCode{opcode: OpCode(scope.Contract.Code[*pc])}
}

func opStop(pc *uint64, interpreter *EVMInterpreter, scope *ScopeContext) ([]byte, error) {
return nil, errStopToken
}
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3 changes: 0 additions & 3 deletions core/vm/interpreter.go
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Expand Up @@ -193,9 +193,6 @@ func (in *EVMInterpreter) Run(contract *Contract, input []byte, readOnly bool) (
// enough stack items available to perform the operation.
op = contract.GetOp(pc)
operation := in.cfg.JumpTable[op]
if operation == nil {
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Sorry to be constantly nagging about tracing haha but this is gonna do a lot of CaptureState(opUndefined...)

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opUndefined still aborts with ErrInvalidOpCode so there shouldn't really be a change there?

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How this is a problem?

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@s1na Well, the fix is it's basically the same as for the previous one: whenever there are two outputs for the same step of execution (same pc twice in a row), then ignore the first and only care about the second one.

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opUndefined still aborts with ErrInvalidOpCode so there shouldn't really be a change there?

@axic the change is that with this PR, it will do a capturestate prior to execute, which it didn't do previously -- erroring before it reached execute.

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Gonna do a lot of... was an exaggeration, since there aren't many txes which actually execute undefined opcodes, I think? but yeah not saying this is a show-stopper or anything. Mainly wanted to document the change.

return nil, &ErrInvalidOpCode{opcode: op}
}
// Validate stack
if sLen := stack.len(); sLen < operation.minStack {
return nil, &ErrStackUnderflow{stackLen: sLen, required: operation.minStack}
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11 changes: 10 additions & 1 deletion core/vm/jump_table.go
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Expand Up @@ -200,7 +200,7 @@ func newHomesteadInstructionSet() JumpTable {
// newFrontierInstructionSet returns the frontier instructions
// that can be executed during the frontier phase.
func newFrontierInstructionSet() JumpTable {
return JumpTable{
tbl := JumpTable{
STOP: {
execute: opStop,
constantGas: 0,
Expand Down Expand Up @@ -1002,4 +1002,13 @@ func newFrontierInstructionSet() JumpTable {
maxStack: maxStack(1, 0),
},
}

// Fill all unassigned slots with opUndefined.
for i, entry := range tbl {
if entry == nil {
tbl[i] = &operation{execute: opUndefined, maxStack: maxStack(0, 0)}
}
}

return tbl
}