core/asm: assembly parser label fixes (#20210)
* core/asm: Fix encoding of pushed labels EVM uses big-endian byte-order, so to pad a label value to 4 bytes, zeros must be added to the front, not the end. * core/asm: Fix PC calculations when a label is pushed Incrementing PC by 5 is only correct if the label appears after a jump, in which case there is an implicit push. When it appears after an explicit push, PC should only be incremented by 4. * core/asm: Allow JUMP with no argument This way, a label can be pushed explicitly, or loaded from memory to implement a jump table.
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@ -57,6 +57,7 @@ func NewCompiler(debug bool) *Compiler {
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// second stage to push labels and determine the right
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// position.
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func (c *Compiler) Feed(ch <-chan token) {
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var prev token
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for i := range ch {
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switch i.typ {
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case number:
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@ -73,10 +74,14 @@ func (c *Compiler) Feed(ch <-chan token) {
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c.labels[i.text] = c.pc
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c.pc++
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case label:
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c.pc += 5
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c.pc += 4
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if prev.typ == element && isJump(prev.text) {
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c.pc++
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}
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}
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c.tokens = append(c.tokens, i)
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prev = i
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}
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if c.debug {
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fmt.Fprintln(os.Stderr, "found", len(c.labels), "labels")
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@ -181,6 +186,8 @@ func (c *Compiler) compileElement(element token) error {
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pos := big.NewInt(int64(c.labels[rvalue.text])).Bytes()
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pos = append(make([]byte, 4-len(pos)), pos...)
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c.pushBin(pos)
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case lineEnd:
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c.pos--
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default:
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return compileErr(rvalue, rvalue.text, "number, string or label")
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}
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@ -201,8 +208,8 @@ func (c *Compiler) compileElement(element token) error {
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case stringValue:
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value = []byte(rvalue.text[1 : len(rvalue.text)-1])
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case label:
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value = make([]byte, 4)
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copy(value, big.NewInt(int64(c.labels[rvalue.text])).Bytes())
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value = big.NewInt(int64(c.labels[rvalue.text])).Bytes()
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value = append(make([]byte, 4-len(value)), value...)
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default:
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return compileErr(rvalue, rvalue.text, "number, string or label")
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}
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71
core/asm/compiler_test.go
Normal file
71
core/asm/compiler_test.go
Normal file
@ -0,0 +1,71 @@
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// Copyright 2019 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package asm
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import (
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"testing"
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)
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func TestCompiler(t *testing.T) {
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tests := []struct {
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input, output string
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}{
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{
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input: `
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GAS
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label:
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PUSH @label
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`,
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output: "5a5b6300000001",
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},
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{
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input: `
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PUSH @label
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label:
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`,
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output: "63000000055b",
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},
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{
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input: `
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PUSH @label
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JUMP
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label:
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`,
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output: "6300000006565b",
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},
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{
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input: `
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JUMP @label
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label:
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`,
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output: "6300000006565b",
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},
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}
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for _, test := range tests {
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ch := Lex([]byte(test.input), false)
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c := NewCompiler(false)
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c.Feed(ch)
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output, err := c.Compile()
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if len(err) != 0 {
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t.Errorf("compile error: %v\ninput: %s", err, test.input)
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continue
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}
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if output != test.output {
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t.Errorf("incorrect output\ninput: %sgot: %s\nwant: %s\n", test.input, output, test.output)
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}
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}
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}
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