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check.go
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check.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 compiler generates sys descriptions of syscalls, types and resources
// from textual descriptions.
package compiler
import (
"fmt"
"github.com/google/syzkaller/pkg/ast"
"github.com/google/syzkaller/prog"
)
func (comp *compiler) check() {
comp.checkNames()
comp.checkFields()
comp.checkTypes()
// The subsequent, more complex, checks expect basic validity of the tree,
// in particular corrent number of type arguments. If there were errors,
// don't proceed to avoid out-of-bounds references to type arguments.
if comp.errors != 0 {
return
}
comp.checkUsed()
comp.checkRecursion()
comp.checkLenTargets()
comp.checkConstructors()
comp.checkVarlens()
}
func (comp *compiler) checkNames() {
calls := make(map[string]*ast.Call)
for _, decl := range comp.desc.Nodes {
switch decl.(type) {
case *ast.Resource, *ast.Struct:
pos, typ, name := decl.Info()
if reservedName[name] {
comp.error(pos, "%v uses reserved name %v", typ, name)
continue
}
if builtinTypes[name] != nil {
comp.error(pos, "%v name %v conflicts with builtin type", typ, name)
continue
}
if prev := comp.resources[name]; prev != nil {
comp.error(pos, "type %v redeclared, previously declared as resource at %v",
name, prev.Pos)
continue
}
if prev := comp.structs[name]; prev != nil {
_, typ, _ := prev.Info()
comp.error(pos, "type %v redeclared, previously declared as %v at %v",
name, typ, prev.Pos)
continue
}
if res, ok := decl.(*ast.Resource); ok {
comp.resources[name] = res
} else if str, ok := decl.(*ast.Struct); ok {
comp.structs[name] = str
}
case *ast.IntFlags:
n := decl.(*ast.IntFlags)
name := n.Name.Name
if reservedName[name] {
comp.error(n.Pos, "flags uses reserved name %v", name)
continue
}
if prev := comp.intFlags[name]; prev != nil {
comp.error(n.Pos, "flags %v redeclared, previously declared at %v",
name, prev.Pos)
continue
}
comp.intFlags[name] = n
case *ast.StrFlags:
n := decl.(*ast.StrFlags)
name := n.Name.Name
if reservedName[name] {
comp.error(n.Pos, "string flags uses reserved name %v", name)
continue
}
if prev := comp.strFlags[name]; prev != nil {
comp.error(n.Pos, "string flags %v redeclared, previously declared at %v",
name, prev.Pos)
continue
}
comp.strFlags[name] = n
case *ast.Call:
c := decl.(*ast.Call)
name := c.Name.Name
if prev := calls[name]; prev != nil {
comp.error(c.Pos, "syscall %v redeclared, previously declared at %v",
name, prev.Pos)
}
calls[name] = c
}
}
}
func (comp *compiler) checkFields() {
const maxArgs = 9 // executor does not support more
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Struct:
_, typ, name := n.Info()
fields := make(map[string]bool)
for _, f := range n.Fields {
fn := f.Name.Name
if fn == "parent" {
comp.error(f.Pos, "reserved field name %v in %v %v", fn, typ, name)
}
if fields[fn] {
comp.error(f.Pos, "duplicate field %v in %v %v", fn, typ, name)
}
fields[fn] = true
}
if !n.IsUnion && len(n.Fields) < 1 {
comp.error(n.Pos, "struct %v has no fields, need at least 1 field", name)
}
if n.IsUnion && len(n.Fields) < 2 {
comp.error(n.Pos, "union %v has only %v field, need at least 2 fields",
name, len(n.Fields))
}
case *ast.Call:
name := n.Name.Name
args := make(map[string]bool)
for _, a := range n.Args {
an := a.Name.Name
if an == "parent" {
comp.error(a.Pos, "reserved argument name %v in syscall %v",
an, name)
}
if args[an] {
comp.error(a.Pos, "duplicate argument %v in syscall %v",
an, name)
}
args[an] = true
}
if len(n.Args) > maxArgs {
comp.error(n.Pos, "syscall %v has %v arguments, allowed maximum is %v",
name, len(n.Args), maxArgs)
}
}
}
}
func (comp *compiler) checkTypes() {
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Resource:
comp.checkType(n.Base, false, false, false, true)
case *ast.Struct:
for _, f := range n.Fields {
comp.checkType(f.Type, false, false, !n.IsUnion, false)
}
comp.checkStruct(n)
case *ast.Call:
for _, a := range n.Args {
comp.checkType(a.Type, true, false, false, false)
}
if n.Ret != nil {
comp.checkType(n.Ret, true, true, false, false)
}
}
}
}
func (comp *compiler) checkLenTargets() {
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Call:
for _, arg := range n.Args {
comp.checkLenType(arg.Type, arg.Name.Name, n.Args, nil, make(map[string]bool), true)
}
}
}
}
func (comp *compiler) checkLenType(t *ast.Type, name string, fields []*ast.Field,
parents []*ast.Struct, checked map[string]bool, isArg bool) {
desc := comp.getTypeDesc(t)
if desc == typeStruct {
s := comp.structs[t.Ident]
// Prune recursion, can happen even on correct tree via opt pointers.
if checked[s.Name.Name] {
return
}
checked[s.Name.Name] = true
parents = append(parents, s)
for _, fld := range s.Fields {
comp.checkLenType(fld.Type, fld.Name.Name, s.Fields, parents, checked, false)
}
return
}
_, args, _ := comp.getArgsBase(t, "", prog.DirIn, isArg)
for i, arg := range args {
argDesc := desc.Args[i]
if argDesc.Type == typeArgLenTarget {
comp.checkLenTarget(t, name, arg.Ident, fields, parents)
} else if argDesc.Type == typeArgType {
comp.checkLenType(arg, name, fields, parents, checked, false)
}
}
}
func (comp *compiler) checkLenTarget(t *ast.Type, name, target string, fields []*ast.Field, parents []*ast.Struct) {
if target == name {
comp.error(t.Pos, "%v target %v refer to itself", t.Ident, target)
return
}
if target == "parent" {
if len(parents) == 0 {
comp.error(t.Pos, "%v target %v does not exist", t.Ident, target)
}
return
}
for _, fld := range fields {
if target != fld.Name.Name {
continue
}
if fld.Type == t {
comp.error(t.Pos, "%v target %v refer to itself", t.Ident, target)
}
return
}
for _, parent := range parents {
if target == parent.Name.Name {
return
}
}
comp.error(t.Pos, "%v target %v does not exist", t.Ident, target)
}
func (comp *compiler) checkUsed() {
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Call:
if n.NR == ^uint64(0) {
break
}
for _, arg := range n.Args {
comp.checkUsedType(arg.Type, true)
}
if n.Ret != nil {
comp.checkUsedType(n.Ret, true)
}
}
}
}
func (comp *compiler) checkUsedType(t *ast.Type, isArg bool) {
if comp.used[t.Ident] {
return
}
desc := comp.getTypeDesc(t)
if desc == typeResource {
r := comp.resources[t.Ident]
for r != nil && !comp.used[r.Name.Name] {
comp.used[r.Name.Name] = true
r = comp.resources[r.Base.Ident]
}
return
}
if desc == typeStruct {
comp.used[t.Ident] = true
s := comp.structs[t.Ident]
for _, fld := range s.Fields {
comp.checkUsedType(fld.Type, false)
}
return
}
_, args, _ := comp.getArgsBase(t, "", prog.DirIn, isArg)
for i, arg := range args {
if desc.Args[i].Type == typeArgType {
comp.checkUsedType(arg, false)
}
}
}
type structDir struct {
Struct string
Dir prog.Dir
}
func (comp *compiler) checkConstructors() {
ctors := make(map[string]bool) // resources for which we have ctors
checked := make(map[structDir]bool)
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Call:
for _, arg := range n.Args {
comp.checkTypeCtors(arg.Type, prog.DirIn, true, ctors, checked)
}
if n.Ret != nil {
comp.checkTypeCtors(n.Ret, prog.DirOut, true, ctors, checked)
}
}
}
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Resource:
name := n.Name.Name
if !ctors[name] && comp.used[name] {
comp.error(n.Pos, "resource %v can't be created"+
" (never mentioned as a syscall return value or output argument/field)",
name)
}
}
}
}
func (comp *compiler) checkTypeCtors(t *ast.Type, dir prog.Dir, isArg bool,
ctors map[string]bool, checked map[structDir]bool) {
desc := comp.getTypeDesc(t)
if desc == typeResource {
// TODO(dvyukov): consider changing this to "dir == prog.DirOut".
// We have few questionable cases where resources can be created
// only by inout struct fields. These structs should be split
// into two different structs: one is in and second is out.
// But that will require attaching dir to individual fields.
if dir != prog.DirIn {
r := comp.resources[t.Ident]
for r != nil && !ctors[r.Name.Name] {
ctors[r.Name.Name] = true
r = comp.resources[r.Base.Ident]
}
}
return
}
if desc == typeStruct {
s := comp.structs[t.Ident]
name := s.Name.Name
key := structDir{name, dir}
if checked[key] {
return
}
checked[key] = true
for _, fld := range s.Fields {
comp.checkTypeCtors(fld.Type, dir, false, ctors, checked)
}
return
}
if desc == typePtr {
dir = genDir(t.Args[0])
}
_, args, _ := comp.getArgsBase(t, "", dir, isArg)
for i, arg := range args {
if desc.Args[i].Type == typeArgType {
comp.checkTypeCtors(arg, dir, false, ctors, checked)
}
}
}
func (comp *compiler) checkRecursion() {
checked := make(map[string]bool)
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Resource:
comp.checkResourceRecursion(n)
case *ast.Struct:
var path []pathElem
comp.checkStructRecursion(checked, n, path)
}
}
}
func (comp *compiler) checkResourceRecursion(n *ast.Resource) {
var seen []string
for n != nil {
if arrayContains(seen, n.Name.Name) {
chain := ""
for _, r := range seen {
chain += r + "->"
}
chain += n.Name.Name
comp.error(n.Pos, "recursive resource %v", chain)
return
}
seen = append(seen, n.Name.Name)
n = comp.resources[n.Base.Ident]
}
}
type pathElem struct {
Pos ast.Pos
Struct string
Field string
}
func (comp *compiler) checkStructRecursion(checked map[string]bool, n *ast.Struct, path []pathElem) {
name := n.Name.Name
if checked[name] {
return
}
for i, elem := range path {
if elem.Struct != name {
continue
}
path = path[i:]
str := ""
for _, elem := range path {
str += fmt.Sprintf("%v.%v -> ", elem.Struct, elem.Field)
}
str += name
comp.error(path[0].Pos, "recursive declaration: %v (mark some pointers as opt)", str)
checked[name] = true
return
}
for _, f := range n.Fields {
path = append(path, pathElem{
Pos: f.Pos,
Struct: name,
Field: f.Name.Name,
})
comp.recurseField(checked, f.Type, path)
path = path[:len(path)-1]
}
checked[name] = true
}
func (comp *compiler) recurseField(checked map[string]bool, t *ast.Type, path []pathElem) {
desc := comp.getTypeDesc(t)
if desc == typeStruct {
comp.checkStructRecursion(checked, comp.structs[t.Ident], path)
return
}
_, args, base := comp.getArgsBase(t, "", prog.DirIn, false)
if desc == typePtr && base.IsOptional {
return // optional pointers prune recursion
}
for i, arg := range args {
if desc.Args[i].Type == typeArgType {
comp.recurseField(checked, arg, path)
}
}
}
func (comp *compiler) checkStruct(n *ast.Struct) {
if n.IsUnion {
comp.parseUnionAttrs(n)
} else {
comp.parseStructAttrs(n)
}
}
func (comp *compiler) checkType(t *ast.Type, isArg, isRet, isStruct, isResourceBase bool) {
if unexpected, _, ok := checkTypeKind(t, kindIdent); !ok {
comp.error(t.Pos, "unexpected %v, expect type", unexpected)
return
}
desc := comp.getTypeDesc(t)
if desc == nil {
comp.error(t.Pos, "unknown type %v", t.Ident)
return
}
if t.HasColon {
if !desc.AllowColon {
comp.error(t.Pos2, "unexpected ':'")
return
}
if !isStruct {
comp.error(t.Pos2, "unexpected ':', only struct fields can be bitfields")
return
}
}
if isRet && (!desc.CanBeArg || desc.CantBeRet) {
comp.error(t.Pos, "%v can't be syscall return", t.Ident)
return
}
if isArg && !desc.CanBeArg {
comp.error(t.Pos, "%v can't be syscall argument", t.Ident)
return
}
if isResourceBase && !desc.ResourceBase {
comp.error(t.Pos, "%v can't be resource base (int types can)", t.Ident)
return
}
args, opt := removeOpt(t)
if opt && (desc.CantBeOpt || isResourceBase) {
what := "resource base"
if desc.CantBeOpt {
what = t.Ident
}
pos := t.Args[len(t.Args)-1].Pos
comp.error(pos, "%v can't be marked as opt", what)
return
}
addArgs := 0
needBase := !isArg && desc.NeedBase
if needBase {
addArgs++ // last arg must be base type, e.g. const[0, int32]
}
if len(args) > len(desc.Args)+addArgs || len(args) < len(desc.Args)-desc.OptArgs+addArgs {
comp.error(t.Pos, "wrong number of arguments for type %v, expect %v",
t.Ident, expectedTypeArgs(desc, needBase))
return
}
if needBase {
base := args[len(args)-1]
args = args[:len(args)-1]
comp.checkTypeArg(t, base, typeArgBase)
}
err0 := comp.errors
for i, arg := range args {
if desc.Args[i].Type == typeArgType {
comp.checkType(arg, false, isRet, false, false)
} else {
comp.checkTypeArg(t, arg, desc.Args[i])
}
}
if err0 != comp.errors {
return
}
if desc.Check != nil {
_, args, base := comp.getArgsBase(t, "", prog.DirIn, isArg)
desc.Check(comp, t, args, base)
}
}
func (comp *compiler) checkTypeArg(t, arg *ast.Type, argDesc namedArg) {
desc := argDesc.Type
if len(desc.Names) != 0 {
if unexpected, _, ok := checkTypeKind(arg, kindIdent); !ok {
comp.error(arg.Pos, "unexpected %v for %v argument of %v type, expect %+v",
unexpected, argDesc.Name, t.Ident, desc.Names)
return
}
if !arrayContains(desc.Names, arg.Ident) {
comp.error(arg.Pos, "unexpected value %v for %v argument of %v type, expect %+v",
arg.Ident, argDesc.Name, t.Ident, desc.Names)
return
}
} else {
if unexpected, expect, ok := checkTypeKind(arg, desc.Kind); !ok {
comp.error(arg.Pos, "unexpected %v for %v argument of %v type, expect %v",
unexpected, argDesc.Name, t.Ident, expect)
return
}
}
if !desc.AllowColon && arg.HasColon {
comp.error(arg.Pos2, "unexpected ':'")
return
}
if desc.Check != nil {
desc.Check(comp, arg)
}
}
func expectedTypeArgs(desc *typeDesc, needBase bool) string {
expect := ""
for i, arg := range desc.Args {
if expect != "" {
expect += ", "
}
opt := i >= len(desc.Args)-desc.OptArgs
if opt {
expect += "["
}
expect += arg.Name
if opt {
expect += "]"
}
}
if needBase {
if expect != "" {
expect += ", "
}
expect += typeArgBase.Name
}
if !desc.CantBeOpt {
if expect != "" {
expect += ", "
}
expect += "[opt]"
}
if expect == "" {
expect = "no arguments"
}
return expect
}
func checkTypeKind(t *ast.Type, kind int) (unexpected string, expect string, ok bool) {
switch {
case kind == kindAny:
ok = true
case t.String != "":
ok = kind == kindString
if !ok {
unexpected = fmt.Sprintf("string %q", t.String)
}
case t.Ident != "":
ok = kind == kindIdent
if !ok {
unexpected = fmt.Sprintf("identifier %v", t.Ident)
}
default:
ok = kind == kindInt
if !ok {
unexpected = fmt.Sprintf("int %v", t.Value)
}
}
if !ok {
switch kind {
case kindString:
expect = "string"
case kindIdent:
expect = "identifier"
case kindInt:
expect = "int"
}
}
return
}
func (comp *compiler) checkVarlens() {
for _, decl := range comp.desc.Nodes {
switch n := decl.(type) {
case *ast.Struct:
comp.checkVarlen(n)
}
}
}
func (comp *compiler) isVarlen(t *ast.Type) bool {
desc, args, base := comp.getArgsBase(t, "", prog.DirIn, false)
return desc.Varlen != nil && desc.Varlen(comp, t, args, base)
}
func (comp *compiler) checkVarlen(n *ast.Struct) {
// Non-varlen unions can't have varlen fields.
// Non-packed structs can't have varlen fields in the middle.
if n.IsUnion {
if varlen := comp.parseUnionAttrs(n); varlen {
return
}
} else {
if packed, _ := comp.parseStructAttrs(n); packed {
return
}
}
for i, f := range n.Fields {
if !n.IsUnion && i == len(n.Fields)-1 {
break
}
if comp.isVarlen(f.Type) {
if n.IsUnion {
comp.error(f.Pos, "variable size field %v in non-varlen union %v",
f.Name.Name, n.Name.Name)
} else {
comp.error(f.Pos, "variable size field %v in the middle of non-packed struct %v",
f.Name.Name, n.Name.Name)
}
}
}
}