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// Copyright 2018 syzkaller project authors. All rights reserved.
// Use of this source code is governed by Apache 2 LICENSE that can be found in the LICENSE file.
package prog
import (
"fmt"
)
// Minimize minimizes program p into an equivalent program using the equivalence
// predicate pred. It iteratively generates simpler programs and asks pred
// whether it is equal to the original program or not. If it is equivalent then
// the simplification attempt is committed and the process continues.
func Minimize(p0 *Prog, callIndex0 int, crash bool, pred0 func(*Prog, int) bool) (*Prog, int) {
pred := func(p *Prog, callIndex int) bool {
for _, call := range p.Calls {
p.Target.SanitizeCall(call)
}
p.debugValidate()
return pred0(p, callIndex)
}
name0 := ""
if callIndex0 != -1 {
if callIndex0 < 0 || callIndex0 >= len(p0.Calls) {
panic("bad call index")
}
name0 = p0.Calls[callIndex0].Meta.Name
}
// Try to remove all calls except the last one one-by-one.
p0, callIndex0 = removeCalls(p0, callIndex0, crash, pred)
// Try to minimize individual args.
for i := 0; i < len(p0.Calls); i++ {
ctx := &minimizeArgsCtx{
target: p0.Target,
p0: &p0,
callIndex0: callIndex0,
crash: crash,
pred: pred,
triedPaths: make(map[string]bool),
}
again:
ctx.p = p0.Clone()
ctx.call = ctx.p.Calls[i]
for j, arg := range ctx.call.Args {
if ctx.do(arg, fmt.Sprintf("%v", j)) {
goto again
}
}
}
if callIndex0 != -1 {
if callIndex0 < 0 || callIndex0 >= len(p0.Calls) || name0 != p0.Calls[callIndex0].Meta.Name {
panic(fmt.Sprintf("bad call index after minimization: ncalls=%v index=%v call=%v/%v",
len(p0.Calls), callIndex0, name0, p0.Calls[callIndex0].Meta.Name))
}
}
return p0, callIndex0
}
func removeCalls(p0 *Prog, callIndex0 int, crash bool, pred func(*Prog, int) bool) (*Prog, int) {
for i := len(p0.Calls) - 1; i >= 0; i-- {
if i == callIndex0 {
continue
}
callIndex := callIndex0
if i < callIndex {
callIndex--
}
p := p0.Clone()
p.removeCall(i)
if !pred(p, callIndex) {
continue
}
p0 = p
callIndex0 = callIndex
}
return p0, callIndex0
}
type minimizeArgsCtx struct {
target *Target
p0 **Prog
p *Prog
call *Call
callIndex0 int
crash bool
pred func(*Prog, int) bool
triedPaths map[string]bool
}
func (ctx *minimizeArgsCtx) do(arg Arg, path string) bool {
path += fmt.Sprintf("-%v", arg.Type().FieldName())
if ctx.triedPaths[path] {
return false
}
if arg.Type().minimize(ctx, arg, path) {
return true
}
ctx.triedPaths[path] = true
return false
}
func (typ *TypeCommon) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
return false
}
func (typ *StructType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
a := arg.(*GroupArg)
for _, innerArg := range a.Inner {
if ctx.do(innerArg, path) {
return true
}
}
return false
}
func (typ *UnionType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
return ctx.do(arg.(*UnionArg).Option, path)
}
func (typ *PtrType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
// TODO: try to remove optional ptrs
a := arg.(*PointerArg)
if a.Res == nil {
return false
}
return ctx.do(a.Res, path)
}
func (typ *ArrayType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
a := arg.(*GroupArg)
for i := len(a.Inner) - 1; i >= 0; i-- {
elem := a.Inner[i]
elemPath := fmt.Sprintf("%v-%v", path, i)
// Try to remove individual elements one-by-one.
if !ctx.crash && !ctx.triedPaths[elemPath] &&
(typ.Kind == ArrayRandLen ||
typ.Kind == ArrayRangeLen && uint64(len(a.Inner)) > typ.RangeBegin) {
ctx.triedPaths[elemPath] = true
copy(a.Inner[i:], a.Inner[i+1:])
a.Inner = a.Inner[:len(a.Inner)-1]
removeArg(elem)
ctx.target.assignSizesCall(ctx.call)
if ctx.pred(ctx.p, ctx.callIndex0) {
*ctx.p0 = ctx.p
}
return true
}
if ctx.do(elem, elemPath) {
return true
}
}
return false
}
func (typ *IntType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
return minimizeInt(ctx, arg, path)
}
func (typ *FlagsType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
return minimizeInt(ctx, arg, path)
}
func (typ *ProcType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
return minimizeInt(ctx, arg, path)
}
func minimizeInt(ctx *minimizeArgsCtx, arg Arg, path string) bool {
// TODO: try to reset bits in ints
// TODO: try to set separate flags
if ctx.crash {
return false
}
a := arg.(*ConstArg)
def := arg.Type().makeDefaultArg().(*ConstArg)
if a.Val == def.Val {
return false
}
v0 := a.Val
a.Val = def.Val
if ctx.pred(ctx.p, ctx.callIndex0) {
*ctx.p0 = ctx.p
} else {
a.Val = v0
}
return false
}
func (typ *ResourceType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
if ctx.crash {
return false
}
a := arg.(*ResultArg)
if a.Res == nil {
return false
}
r0 := a.Res
delete(a.Res.uses, a)
a.Res, a.Val = nil, typ.Default()
if ctx.pred(ctx.p, ctx.callIndex0) {
*ctx.p0 = ctx.p
} else {
a.Res, a.Val = r0, 0
a.Res.uses[a] = true
}
return false
}
func (typ *BufferType) minimize(ctx *minimizeArgsCtx, arg Arg, path string) bool {
// TODO: try to set individual bytes to 0
if typ.Kind != BufferBlobRand && typ.Kind != BufferBlobRange || typ.Dir() == DirOut {
return false
}
a := arg.(*DataArg)
minLen := int(typ.RangeBegin)
for step := len(a.Data()) - minLen; len(a.Data()) > minLen && step > 0; {
if len(a.Data())-step >= minLen {
a.data = a.Data()[:len(a.Data())-step]
ctx.target.assignSizesCall(ctx.call)
if ctx.pred(ctx.p, ctx.callIndex0) {
continue
}
a.data = a.Data()[:len(a.Data())+step]
ctx.target.assignSizesCall(ctx.call)
}
step /= 2
if ctx.crash {
break
}
}
*ctx.p0 = ctx.p
return false
}
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