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resources.go
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resources.go
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// Copyright 2017 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"
)
var (
// We need to support structs as resources,
// but for now we just special-case timespec/timeval.
timespecRes = &ResourceDesc{
Name: "timespec",
Kind: []string{"timespec"},
}
// On one hand these are resources, but they don't have constructors.
// It can make sense to provide generic support for such things,
// but for now we just special-case them.
filenameRes = &ResourceDesc{
Name: "filename",
Kind: []string{"filename"},
}
vmaRes = &ResourceDesc{
Name: "vma",
Kind: []string{"vma"},
}
)
func (target *Target) calcResourceCtors(res *ResourceDesc, precise bool) []*Syscall {
var metas []*Syscall
for _, ctor := range res.Ctors {
if !precise || ctor.Precise {
metas = append(metas, target.Syscalls[ctor.Call])
}
}
if res.Kind[0] == timespecRes.Name {
if c := target.SyscallMap["clock_gettime"]; c != nil {
metas = append(metas, c)
}
}
return metas
}
func (target *Target) populateResourceCtors() {
// Find resources that are created by each call.
callsResources := make([][]*ResourceDesc, len(target.Syscalls))
ForeachType(target.Syscalls, func(typ Type, ctx TypeCtx) {
switch typ1 := typ.(type) {
case *ResourceType:
if ctx.Dir != DirIn {
callsResources[ctx.Meta.ID] = append(callsResources[ctx.Meta.ID], typ1.Desc)
}
}
})
// Populate resource ctors accounting for resource compatibility.
for _, res := range target.Resources {
for call, callResources := range callsResources {
preciseOk := false
impreciseOk := false
for _, callRes := range callResources {
if preciseOk && impreciseOk {
break
}
if isCompatibleResourceImpl(res.Kind, callRes.Kind, true) {
preciseOk = true
}
if isCompatibleResourceImpl(res.Kind, callRes.Kind, false) {
impreciseOk = true
}
}
if preciseOk {
res.Ctors = append(res.Ctors, ResourceCtor{call, true})
}
if impreciseOk {
res.Ctors = append(res.Ctors, ResourceCtor{call, false})
}
}
}
}
// isCompatibleResource returns true if resource of kind src can be passed as an argument of kind dst.
func (target *Target) isCompatibleResource(dst, src string) bool {
if target.isAnyRes(dst) {
return true
}
if target.isAnyRes(src) {
return false
}
dstRes := target.resourceMap[dst]
if dstRes == nil {
panic(fmt.Sprintf("unknown resource %q", dst))
}
srcRes := target.resourceMap[src]
if srcRes == nil {
panic(fmt.Sprintf("unknown resource %q", src))
}
return isCompatibleResourceImpl(dstRes.Kind, srcRes.Kind, false)
}
// isCompatibleResourceImpl returns true if resource of kind src can be passed as an argument of kind dst.
// If precise is true, then it does not allow passing a less specialized resource (e.g. fd)
// as a more specialized resource (e.g. socket). Otherwise it does.
func isCompatibleResourceImpl(dst, src []string, precise bool) bool {
if len(dst) > len(src) {
// dst is more specialized, e.g dst=socket, src=fd.
if precise {
return false
}
dst = dst[:len(src)]
}
if len(src) > len(dst) {
// src is more specialized, e.g dst=fd, src=socket.
src = src[:len(dst)]
}
for i, k := range dst {
if k != src[i] {
return false
}
}
return true
}
func (target *Target) getInputResources(c *Syscall) []*ResourceDesc {
var resources []*ResourceDesc
ForeachCallType(c, func(typ Type, ctx TypeCtx) {
if ctx.Dir == DirOut {
return
}
switch typ1 := typ.(type) {
case *ResourceType:
if !typ1.IsOptional {
resources = append(resources, typ1.Desc)
}
case *StructType:
if target.OS == "linux" && (typ1.Name() == "timespec" || typ1.Name() == "timeval") {
resources = append(resources, timespecRes)
}
}
})
return resources
}
func (target *Target) getOutputResources(c *Syscall) []*ResourceDesc {
var resources []*ResourceDesc
ForeachCallType(c, func(typ Type, ctx TypeCtx) {
switch typ1 := typ.(type) {
case *ResourceType:
if ctx.Dir != DirIn {
resources = append(resources, typ1.Desc)
}
}
})
if c.CallName == "clock_gettime" {
resources = append(resources, timespecRes)
}
return resources
}
func (target *Target) transitivelyEnabled(enabled map[*Syscall]bool) (map[*Syscall]bool, map[string]bool) {
supported := make(map[*Syscall]bool, len(enabled))
canCreate := make(map[string]bool, len(enabled))
for {
n := len(supported)
for c := range enabled {
if supported[c] {
continue
}
ready := true
for _, res := range c.inputResources {
if !canCreate[res.Name] {
ready = false
break
}
}
if ready {
supported[c] = true
for _, res := range c.outputResources {
for _, kind := range res.Kind {
canCreate[kind] = true
}
}
}
}
if n == len(supported) {
break
}
}
return supported, canCreate
}
func (target *Target) TransitivelyEnabledCalls(enabled map[*Syscall]bool) (map[*Syscall]bool, map[*Syscall]string) {
supported, canCreate := target.transitivelyEnabled(enabled)
disabled := make(map[*Syscall]string)
ctors := make(map[string][]string)
for c := range enabled {
if supported[c] {
continue
}
for _, res := range c.inputResources {
if canCreate[res.Name] {
continue
}
if ctors[res.Name] == nil {
var names []string
for _, call := range target.calcResourceCtors(res, true) {
names = append(names, call.Name)
}
ctors[res.Name] = names
}
disabled[c] = fmt.Sprintf("no syscalls can create resource %v,"+
" enable some syscalls that can create it %v",
res.Name, ctors[res.Name])
break
}
}
if len(enabled) != len(supported)+len(disabled) {
panic("lost syscalls")
}
return supported, disabled
}