forked from TrueCloudLab/neoneo-go
fc1075bf75
Same thing done in a2a8981979 for PUSHBYTES,
failing to read the amount of bytes specified should lead to FAULT. Also
makes readUint16() and readUint32() panic as this is the behavior we want in
these cases. Add some tests along the way.
128 lines
2.4 KiB
Go
128 lines
2.4 KiB
Go
package vm
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import (
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"encoding/binary"
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)
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// Context represent the current execution context of the VM.
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type Context struct {
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// Instruction pointer.
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ip int
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// The raw program script.
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prog []byte
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// Breakpoints
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breakPoints []int
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}
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// NewContext return a new Context object.
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func NewContext(b []byte) *Context {
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return &Context{
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ip: -1,
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prog: b,
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breakPoints: []int{},
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}
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}
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// Next return the next instruction to execute.
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func (c *Context) Next() Instruction {
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c.ip++
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if c.ip >= len(c.prog) {
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return RET
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}
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return Instruction(c.prog[c.ip])
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}
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// IP returns the absolute instruction without taking 0 into account.
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// If that program starts the ip = 0 but IP() will return 1, cause its
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// the first instruction.
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func (c *Context) IP() int {
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return c.ip + 1
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}
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// LenInstr returns the number of instructions loaded.
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func (c *Context) LenInstr() int {
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return len(c.prog)
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}
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// CurrInstr returns the current instruction and opcode.
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func (c *Context) CurrInstr() (int, Instruction) {
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if c.ip < 0 {
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return c.ip, NOP
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}
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return c.ip, Instruction(c.prog[c.ip])
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}
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// Copy returns an new exact copy of c.
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func (c *Context) Copy() *Context {
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return &Context{
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ip: c.ip,
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prog: c.prog,
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breakPoints: c.breakPoints,
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}
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}
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// Program returns the loaded program.
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func (c *Context) Program() []byte {
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return c.prog
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}
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// Value implements StackItem interface.
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func (c *Context) Value() interface{} {
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return c
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}
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func (c *Context) atBreakPoint() bool {
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for _, n := range c.breakPoints {
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if n == c.ip {
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return true
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}
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}
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return false
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}
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func (c *Context) String() string {
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return "execution context"
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}
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func (c *Context) readUint32() uint32 {
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start, end := c.IP(), c.IP()+4
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if end > len(c.prog) {
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panic("failed to read uint32 parameter")
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}
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val := binary.LittleEndian.Uint32(c.prog[start:end])
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c.ip += 4
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return val
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}
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func (c *Context) readUint16() uint16 {
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start, end := c.IP(), c.IP()+2
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if end > len(c.prog) {
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panic("failed to read uint16 parameter")
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}
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val := binary.LittleEndian.Uint16(c.prog[start:end])
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c.ip += 2
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return val
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}
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func (c *Context) readByte() byte {
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return c.readBytes(1)[0]
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}
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func (c *Context) readBytes(n int) []byte {
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start, end := c.IP(), c.IP()+n
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if end > len(c.prog) {
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return nil
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}
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out := make([]byte, n)
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copy(out, c.prog[start:end])
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c.ip += n
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return out
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}
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func (c *Context) readVarBytes() []byte {
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n := c.readByte()
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return c.readBytes(int(n))
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}
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