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// Copyright 2025 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 kfuzztest
import (
"debug/dwarf"
"fmt"
"strings"
"github.com/google/syzkaller/pkg/ast"
)
type Builder struct {
funcs []SyzFunc
structs []SyzStruct
constraints []SyzConstraint
annotations []SyzAnnotation
}
func NewBuilder(
funcs []SyzFunc,
structs []SyzStruct,
constraints []SyzConstraint,
annotations []SyzAnnotation,
) *Builder {
return &Builder{funcs, structs, constraints, annotations}
}
func (b *Builder) AddStruct(s SyzStruct) {
b.structs = append(b.structs, s)
}
func (b *Builder) AddFunc(f SyzFunc) {
b.funcs = append(b.funcs, f)
}
func (b *Builder) EmitSyzlangDescription() (string, error) {
constraintMap := make(map[string]map[string]SyzConstraint)
for _, constraint := range b.constraints {
if _, contains := constraintMap[constraint.InputType]; !contains {
constraintMap[constraint.InputType] = make(map[string]SyzConstraint)
}
constraintMap[constraint.InputType][constraint.FieldName] = constraint
}
annotationMap := make(map[string]map[string]SyzAnnotation)
for _, annotation := range b.annotations {
if _, contains := annotationMap[annotation.InputType]; !contains {
annotationMap[annotation.InputType] = make(map[string]SyzAnnotation)
}
annotationMap[annotation.InputType][annotation.FieldName] = annotation
}
var descBuilder strings.Builder
descBuilder.WriteString("# This description was automatically generated with tools/kfuzztest-gen\n")
for _, s := range b.structs {
structDesc, err := syzStructToSyzlang(s, constraintMap, annotationMap)
if err != nil {
return "", err
}
descBuilder.WriteString(structDesc)
descBuilder.WriteString("\n\n")
}
for i, fn := range b.funcs {
descBuilder.WriteString(syzFuncToSyzlang(fn))
if i < len(b.funcs)-1 {
descBuilder.WriteString("\n")
}
}
// Format the output syzlang descriptions for consistency.
var astError error
eh := func(pos ast.Pos, msg string) {
astError = fmt.Errorf("ast failure: %v: %v", pos, msg)
}
descAst := ast.Parse([]byte(descBuilder.String()), "", eh)
if astError != nil {
return "", astError
}
if descAst == nil {
return "", fmt.Errorf("failed to format generated syzkaller description - is it well-formed?")
}
return string(ast.Format(descAst)), nil
}
func syzStructToSyzlang(s SyzStruct, constraintMap map[string]map[string]SyzConstraint,
annotationMap map[string]map[string]SyzAnnotation) (string, error) {
var builder strings.Builder
fmt.Fprintf(&builder, "%s {\n", s.Name)
structAnnotations := annotationMap["struct "+s.Name]
structConstraints := constraintMap["struct "+s.Name]
for _, field := range s.Fields {
line, err := syzFieldToSyzLang(field, structConstraints, structAnnotations)
if err != nil {
return "", err
}
fmt.Fprintf(&builder, "\t%s\n", line)
}
fmt.Fprint(&builder, "}")
return builder.String(), nil
}
func syzFieldToSyzLang(field SyzField, constraintMap map[string]SyzConstraint,
annotationMap map[string]SyzAnnotation) (string, error) {
constraint, hasConstraint := constraintMap[field.Name]
annotation, hasAnnotation := annotationMap[field.Name]
var typeDesc string
var err error
if hasAnnotation {
// Annotations override the existing type definitions.
typeDesc, err = processAnnotation(field, annotation)
} else {
typeDesc, err = dwarfToSyzlangType(field.dwarfType)
}
if err != nil {
return "", err
}
// Process constraints only if unannotated.
// TODO: is there a situation where we would want to process both?
if hasConstraint && !hasAnnotation {
constraint, err := processConstraint(constraint)
if err != nil {
return "", err
}
typeDesc += constraint
}
return fmt.Sprintf("%s %s", field.Name, typeDesc), nil
}
func processConstraint(c SyzConstraint) (string, error) {
switch c.ConstraintType {
case ExpectEq:
return fmt.Sprintf("[%d]", c.Value1), nil
case ExpectNe:
// syzkaller does not have a built-in way to support an inequality
// constraint AFAIK.
return "", nil
case ExpectLt:
return fmt.Sprintf("[0:%d]", c.Value1-1), nil
case ExpectLe:
return fmt.Sprintf("[0:%d]", c.Value1), nil
case ExpectGt:
return fmt.Sprintf("[%d]", c.Value1+1), nil
case ExpectGe:
return fmt.Sprintf("[%d]", c.Value1), nil
case ExpectInRange:
return fmt.Sprintf("[%d:%d]", c.Value1, c.Value2), nil
default:
fmt.Printf("c = %d\n", c.ConstraintType)
return "", fmt.Errorf("unsupported constraint type")
}
}
func processAnnotation(field SyzField, annotation SyzAnnotation) (string, error) {
switch annotation.Attribute {
case AttributeLen:
underlyingType, err := dwarfToSyzlangType(field.dwarfType)
if err != nil {
return "", err
}
return fmt.Sprintf("len[%s, %s]", annotation.LinkedFieldName, underlyingType), nil
case AttributeString:
return "ptr[in, string]", nil
case AttributeArray:
pointeeType, isPtr := resolvesToPtr(field.dwarfType)
if !isPtr {
return "", fmt.Errorf("can only annotate pointer fields are arrays")
}
// TODO: discards const qualifier.
typeDesc, err := dwarfToSyzlangType(pointeeType)
if err != nil {
return "", err
}
return fmt.Sprintf("ptr[in, array[%s]]", typeDesc), nil
default:
return "", fmt.Errorf("unsupported attribute type")
}
}
// Returns true iff `dwarfType` resolved down to a pointer. For example,
// a `const *void` which isn't directly a pointer.
func resolvesToPtr(dwarfType dwarf.Type) (dwarf.Type, bool) {
switch t := dwarfType.(type) {
case *dwarf.QualType:
return resolvesToPtr(t.Type)
case *dwarf.PtrType:
return t.Type, true
}
return nil, false
}
func syzFuncToSyzlang(s SyzFunc) string {
var builder strings.Builder
typeName := strings.TrimPrefix(s.InputStructName, "struct ")
fmt.Fprintf(&builder, "syz_kfuzztest_run$%s(", s.Name)
fmt.Fprintf(&builder, "name ptr[in, string[\"%s\"]], ", s.Name)
fmt.Fprintf(&builder, "data ptr[in, %s], ", typeName)
builder.WriteString("len bytesize[data], ")
builder.WriteString("buf ptr[in, array[int8, 65536]]) ")
// TODO:(ethangraham) The only other way I can think of getting this name
// would involve using the "reflect" package and matching against the
// KFuzzTest name, which isn't much better than hardcoding this.
builder.WriteString("(kfuzz_test)")
return builder.String()
}
// Given a dwarf type, returns a syzlang string representation of this type.
func dwarfToSyzlangType(dwarfType dwarf.Type) (string, error) {
switch t := dwarfType.(type) {
case *dwarf.PtrType:
underlyingType, err := dwarfToSyzlangType(t.Type)
if err != nil {
return "", err
}
return fmt.Sprintf("ptr[in, %s]", underlyingType), nil
case *dwarf.QualType:
if t.Qual == "const" {
return dwarfToSyzlangType(t.Type)
} else {
return "", fmt.Errorf("no support for %s qualifier", t.Qual)
}
case *dwarf.ArrayType:
underlyingType, err := dwarfToSyzlangType(t.Type)
if err != nil {
return "", err
}
// If t.Count == -1 then this is a varlen array as per debug/dwarf
// documentation.
if t.Count == -1 {
return fmt.Sprintf("array[%s]", underlyingType), nil
} else {
return fmt.Sprintf("array[%s, %d]", underlyingType, t.Count), nil
}
case *dwarf.TypedefType:
return dwarfToSyzlangType(t.Type)
case *dwarf.IntType, *dwarf.UintType:
numBits := t.Size() * 8
return fmt.Sprintf("int%d", numBits), nil
case *dwarf.CharType, *dwarf.UcharType:
return "int8", nil
// `void` isn't a valid type by itself, so we know that it would have
// been wrapped in a pointer, e.g., `void *`. For this reason, we can return
// just interpret it as a byte, i.e., int8.
case *dwarf.VoidType:
return "int8", nil
case *dwarf.StructType:
return strings.TrimPrefix(t.StructName, "struct "), nil
default:
return "", fmt.Errorf("unsupported type %s", dwarfType.String())
}
}
|
