// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// DWARF type information structures.
// The format is heavily biased toward C, but for simplicity
// the String methods use a pseudo-Go syntax.
package dwarf
import "strconv"
// A Type conventionally represents a pointer to any of the
// specific Type structures (CharType, StructType, etc.).
type Type interface {
Common() *CommonType
String() string
Size() int64
}
// A CommonType holds fields common to multiple types.
// If a field is not known or not applicable for a given type,
// the zero value is used.
type CommonType struct {
ByteSize int64 // size of value of this type, in bytes
Name string // name that can be used to refer to type
}
func (c *CommonType) Common() *CommonType { return c }
func (c *CommonType) Size() int64 { return c.ByteSize }
// Basic types
// A BasicType holds fields common to all basic types.
type BasicType struct {
CommonType
BitSize int64
BitOffset int64
}
func (b *BasicType) Basic() *BasicType { return b }
func (t *BasicType) String() string {
if t.Name != "" {
return t.Name
}
return "?"
}
// A CharType represents a signed character type.
type CharType struct {
BasicType
}
// A UcharType represents an unsigned character type.
type UcharType struct {
BasicType
}
// An IntType represents a signed integer type.
type IntType struct {
BasicType
}
// A UintType represents an unsigned integer type.
type UintType struct {
BasicType
}
// A FloatType represents a floating point type.
type FloatType struct {
BasicType
}
// A ComplexType represents a complex floating point type.
type ComplexType struct {
BasicType
}
// A BoolType represents a boolean type.
type BoolType struct {
BasicType
}
// An AddrType represents a machine address type.
type AddrType struct {
BasicType
}
// An UnspecifiedType represents an implicit, unknown, ambiguous or nonexistent type.
type UnspecifiedType struct {
BasicType
}
// qualifiers
// A QualType represents a type that has the C/C++ "const", "restrict", or "volatile" qualifier.
type QualType struct {
CommonType
Qual string
Type Type
}
func (t *QualType) String() string { return t.Qual + " " + t.Type.String() }
func (t *QualType) Size() int64 { return t.Type.Size() }
// An ArrayType represents a fixed size array type.
type ArrayType struct {
CommonType
Type Type
StrideBitSize int64 // if > 0, number of bits to hold each element
Count int64 // if == -1, an incomplete array, like char x[].
}
func (t *ArrayType) String() string {
return "[" + strconv.FormatInt(t.Count, 10) + "]" + t.Type.String()
}
func (t *ArrayType) Size() int64 {
if t.Count == -1 {
return 0
}
return t.Count * t.Type.Size()
}
// A VoidType represents the C void type.
type VoidType struct {
CommonType
}
func (t *VoidType) String() string { return "void" }
// A PtrType represents a pointer type.
type PtrType struct {
CommonType
Type Type
}
func (t *PtrType) String() string { return "*" + t.Type.String() }
// A StructType represents a struct, union, or C++ class type.
type StructType struct {
CommonType
StructName string
Kind string // "struct", "union", or "class".
Field []*StructField
Incomplete bool // if true, struct, union, class is declared but not defined
}
// A StructField represents a field in a struct, union, or C++ class type.
type StructField struct {
Name string
Type Type
ByteOffset int64
ByteSize int64 // usually zero; use Type.Size() for normal fields
BitOffset int64 // within the ByteSize bytes at ByteOffset
BitSize int64 // zero if not a bit field
}
func (t *StructType) String() string {
if t.StructName != "" {
return t.Kind + " " + t.StructName
}
return t.Defn()
}
func (t *StructType) Defn() string {
s := t.Kind
if t.StructName != "" {
s += " " + t.StructName
}
if t.Incomplete {
s += " /*incomplete*/"
return s
}
s += " {"
for i, f := range t.Field {
if i > 0 {
s += "; "
}
s += f.Name + " " + f.Type.String()
s += "@" + strconv.FormatInt(f.ByteOffset, 10)
if f.BitSize > 0 {
s += " : " + strconv.FormatInt(f.BitSize, 10)
s += "@" + strconv.FormatInt(f.BitOffset, 10)
}
}
s += "}"
return s
}
// An EnumType represents an enumerated type.
// The only indication of its native integer type is its ByteSize
// (inside CommonType).
type EnumType struct {
CommonType
EnumName string
Val []*EnumValue
}
// An EnumValue represents a single enumeration value.
type EnumValue struct {
Name string
Val int64
}
func (t *EnumType) String() string {
s := "enum"
if t.EnumName != "" {
s += " " + t.EnumName
}
s += " {"
for i, v := range t.Val {
if i > 0 {
s += "; "
}
s += v.Name + "=" + strconv.FormatInt(v.Val, 10)
}
s += "}"
return s
}
// A FuncType represents a function type.
type FuncType struct {
CommonType
ReturnType Type
ParamType []Type
}
func (t *FuncType) String() string {
s := "func("
for i, t := range t.ParamType {
if i > 0 {
s += ", "
}
s += t.String()
}
s += ")"
if t.ReturnType != nil {
s += " " + t.ReturnType.String()
}
return s
}
// A DotDotDotType represents the variadic ... function parameter.
type DotDotDotType struct {
CommonType
}
func (t *DotDotDotType) String() string { return "..." }
// A TypedefType represents a named type.
type TypedefType struct {
CommonType
Type Type
}
func (t *TypedefType) String() string { return t.Name }
func (t *TypedefType) Size() int64 { return t.Type.Size() }
// An UnsupportedType is a placeholder returned in situations where we
// encounter a type that isn't supported.
type UnsupportedType struct {
CommonType
Tag Tag
}
func (t *UnsupportedType) String() string {
if t.Name != "" {
return t.Name
}
return t.Name + "(unsupported type " + t.Tag.String() + ")"
}
// typeReader is used to read from either the info section or the
// types section.
type typeReader interface {
Seek(Offset)
Next() (*Entry, error)
clone() typeReader
offset() Offset
// AddressSize returns the size in bytes of addresses in the current
// compilation unit.
AddressSize() int
}
// Type reads the type at off in the DWARF ``info'' section.
func (d *Data) Type(off Offset) (Type, error) {
return d.readType("info", d.Reader(), off, d.typeCache, nil)
}
// readType reads a type from r at off of name. It adds types to the
// type cache, appends new typedef types to typedefs, and computes the
// sizes of types. Callers should pass nil for typedefs; this is used
// for internal recursion.
func (d *Data) readType(name string, r typeReader, off Offset, typeCache map[Offset]Type, typedefs *[]*TypedefType) (Type, error) {
if t, ok := typeCache[off]; ok {
return t, nil
}
r.Seek(off)
e, err := r.Next()
if err != nil {
return nil, err
}
addressSize := r.AddressSize()
if e == nil || e.Offset != off {
return nil, DecodeError{name, off, "no type at offset"}
}
// If this is the root of the recursion, prepare to resolve
// typedef sizes once the recursion is done. This must be done
// after the type graph is constructed because it may need to
// resolve cycles in a different order than readType
// encounters them.
if typedefs == nil {
var typedefList []*TypedefType
defer func() {
for _, t := range typedefList {
t.Common().ByteSize = t.Type.Size()
}
}()
typedefs = &typedefList
}
// Parse type from Entry.
// Must always set typeCache[off] before calling
// d.readType recursively, to handle circular types correctly.
var typ Type
nextDepth := 0
// Get next child; set err if error happens.
next := func() *Entry {
if !e.Children {
return nil
}
// Only return direct children.
// Skip over composite entries that happen to be nested
// inside this one. Most DWARF generators wouldn't generate
// such a thing, but clang does.
// See golang.org/issue/6472.
for {
kid, err1 := r.Next()
if err1 != nil {
err = err1
return nil
}
if kid == nil {
err = DecodeError{name, r.offset(), "unexpected end of DWARF entries"}
return nil
}
if kid.Tag == 0 {
if nextDepth > 0 {
nextDepth--
continue
}
return nil
}
if kid.Children {
nextDepth++
}
if nextDepth > 0 {
continue
}
return kid
}
}
// Get Type referred to by Entry's AttrType field.
// Set err if error happens. Not having a type is an error.
typeOf := func(e *Entry) Type {
tval := e.Val(AttrType)
var t Type
switch toff := tval.(type) {
case Offset:
if t, err = d.readType(name, r.clone(), toff, typeCache, typedefs); err != nil {
return nil
}
case uint64:
if t, err = d.sigToType(toff); err != nil {
return nil
}
default:
// It appears that no Type means "void".
return new(VoidType)
}
return t
}
switch e.Tag {
case TagArrayType:
// Multi-dimensional array. (DWARF v2 §5.4)
// Attributes:
// AttrType:subtype [required]
// AttrStrideSize: size in bits of each element of the array
// AttrByteSize: size of entire array
// Children:
// TagSubrangeType or TagEnumerationType giving one dimension.
// dimensions are in left to right order.
t := new(ArrayType)
typ = t
typeCache[off] = t
if t.Type = typeOf(e); err != nil {
goto Error
}
t.StrideBitSize, _ = e.Val(AttrStrideSize).(int64)
// Accumulate dimensions,
var dims []int64
for kid := next(); kid != nil; kid = next() {
// TODO(rsc): Can also be TagEnumerationType
// but haven't seen that in the wild yet.
switch kid.Tag {
case TagSubrangeType:
count, ok := kid.Val(AttrCount).(int64)
if !ok {
// Old binaries may have an upper bound instead.
count, ok = kid.Val(AttrUpperBound).(int64)
if ok {
count++ // Length is one more than upper bound.
} else if len(dims) == 0 {
count = -1 // As in x[].
}
}
dims = append(dims, count)
case TagEnumerationType:
err = DecodeError{name, kid.Offset, "cannot handle enumeration type as array bound"}
goto Error
}
}
if len(dims) == 0 {
// LLVM generates this for x[].
dims = []int64{-1}
}
t.Count = dims[0]
for i := len(dims) - 1; i >= 1; i-- {
t.Type = &ArrayType{Type: t.Type, Count: dims[i]}
}
case TagBaseType:
// Basic type. (DWARF v2 §5.1)
// Attributes:
// AttrName: name of base type in programming language of the compilation unit [required]
// AttrEncoding: encoding value for type (encFloat etc) [required]
// AttrByteSize: size of type in bytes [required]
// AttrBitOffset: for sub-byte types, size in bits
// AttrBitSize: for sub-byte types, bit offset of high order bit in the AttrByteSize bytes
name, _ := e.Val(AttrName).(string)
enc, ok := e.Val(AttrEncoding).(int64)
if !ok {
err = DecodeError{name, e.Offset, "missing encoding attribute for " + name}
goto Error
}
switch enc {
default:
err = DecodeError{name, e.Offset, "unrecognized encoding attribute value"}
goto Error
case encAddress:
typ = new(AddrType)
case encBoolean:
typ = new(BoolType)
case encComplexFloat:
typ = new(ComplexType)
if name == "complex" {
// clang writes out 'complex' instead of 'complex float' or 'complex double'.
// clang also writes out a byte size that we can use to distinguish.
// See issue 8694.
switch byteSize, _ := e.Val(AttrByteSize).(int64); byteSize {
case 8:
name = "complex float"
case 16:
name = "complex double"
}
}
case encFloat:
typ = new(FloatType)
case encSigned:
typ = new(IntType)
case encUnsigned:
typ = new(UintType)
case encSignedChar:
typ = new(CharType)
case encUnsignedChar:
typ = new(UcharType)
}
typeCache[off] = typ
t := typ.(interface {
Basic() *BasicType
}).Basic()
t.Name = name
t.BitSize, _ = e.Val(AttrBitSize).(int64)
t.BitOffset, _ = e.Val(AttrBitOffset).(int64)
case TagClassType, TagStructType, TagUnionType:
// Structure, union, or class type. (DWARF v2 §5.5)
// Attributes:
// AttrName: name of struct, union, or class
// AttrByteSize: byte size [required]
// AttrDeclaration: if true, struct/union/class is incomplete
// Children:
// TagMember to describe one member.
// AttrName: name of member [required]
// AttrType: type of member [required]
// AttrByteSize: size in bytes
// AttrBitOffset: bit offset within bytes for bit fields
// AttrBitSize: bit size for bit fields
// AttrDataMemberLoc: location within struct [required for struct, class]
// There is much more to handle C++, all ignored for now.
t := new(StructType)
typ = t
typeCache[off] = t
switch e.Tag {
case TagClassType:
t.Kind = "class"
case TagStructType:
t.Kind = "struct"
case TagUnionType:
t.Kind = "union"
}
t.StructName, _ = e.Val(AttrName).(string)
t.Incomplete = e.Val(AttrDeclaration) != nil
t.Field = make([]*StructField, 0, 8)
var lastFieldType *Type
var lastFieldBitOffset int64
for kid := next(); kid != nil; kid = next() {
if kid.Tag != TagMember {
continue
}
f := new(StructField)
if f.Type = typeOf(kid); err != nil {
goto Error
}
switch loc := kid.Val(AttrDataMemberLoc).(type) {
case []byte:
// TODO: Should have original compilation
// unit here, not unknownFormat.
b := makeBuf(d, unknownFormat{}, "location", 0, loc)
if b.uint8() != opPlusUconst {
err = DecodeError{name, kid.Offset, "unexpected opcode"}
goto Error
}
f.ByteOffset = int64(b.uint())
if b.err != nil {
err = b.err
goto Error
}
case int64:
f.ByteOffset = loc
}
haveBitOffset := false
f.Name, _ = kid.Val(AttrName).(string)
f.ByteSize, _ = kid.Val(AttrByteSize).(int64)
f.BitOffset, haveBitOffset = kid.Val(AttrBitOffset).(int64)
f.BitSize, _ = kid.Val(AttrBitSize).(int64)
t.Field = append(t.Field, f)
bito := f.BitOffset
if !haveBitOffset {
bito = f.ByteOffset * 8
}
if bito == lastFieldBitOffset && t.Kind != "union" {
// Last field was zero width. Fix array length.
// (DWARF writes out 0-length arrays as if they were 1-length arrays.)
zeroArray(lastFieldType)
}
lastFieldType = &f.Type
lastFieldBitOffset = bito
}
if t.Kind != "union" {
b, ok := e.Val(AttrByteSize).(int64)
if ok && b*8 == lastFieldBitOffset {
// Final field must be zero width. Fix array length.
zeroArray(lastFieldType)
}
}
case TagConstType, TagVolatileType, TagRestrictType:
// Type modifier (DWARF v2 §5.2)
// Attributes:
// AttrType: subtype
t := new(QualType)
typ = t
typeCache[off] = t
if t.Type = typeOf(e); err != nil {
goto Error
}
switch e.Tag {
case TagConstType:
t.Qual = "const"
case TagRestrictType:
t.Qual = "restrict"
case TagVolatileType:
t.Qual = "volatile"
}
case TagEnumerationType:
// Enumeration type (DWARF v2 §5.6)
// Attributes:
// AttrName: enum name if any
// AttrByteSize: bytes required to represent largest value
// Children:
// TagEnumerator:
// AttrName: name of constant
// AttrConstValue: value of constant
t := new(EnumType)
typ = t
typeCache[off] = t
t.EnumName, _ = e.Val(AttrName).(string)
t.Val = make([]*EnumValue, 0, 8)
for kid := next(); kid != nil; kid = next() {
if kid.Tag == TagEnumerator {
f := new(EnumValue)
f.Name, _ = kid.Val(AttrName).(string)
f.Val, _ = kid.Val(AttrConstValue).(int64)
n := len(t.Val)
if n >= cap(t.Val) {
val := make([]*EnumValue, n, n*2)
copy(val, t.Val)
t.Val = val
}
t.Val = t.Val[0 : n+1]
t.Val[n] = f
}
}
case TagPointerType:
// Type modifier (DWARF v2 §5.2)
// Attributes:
// AttrType: subtype [not required! void* has no AttrType]
// AttrAddrClass: address class [ignored]
t := new(PtrType)
typ = t
typeCache[off] = t
if e.Val(AttrType) == nil {
t.Type = &VoidType{}
break
}
t.Type = typeOf(e)
case TagSubroutineType:
// Subroutine type. (DWARF v2 §5.7)
// Attributes:
// AttrType: type of return value if any
// AttrName: possible name of type [ignored]
// AttrPrototyped: whether used ANSI C prototype [ignored]
// Children:
// TagFormalParameter: typed parameter
// AttrType: type of parameter
// TagUnspecifiedParameter: final ...
t := new(FuncType)
typ = t
typeCache[off] = t
if t.ReturnType = typeOf(e); err != nil {
goto Error
}
t.ParamType = make([]Type, 0, 8)
for kid := next(); kid != nil; kid = next() {
var tkid Type
switch kid.Tag {
default:
continue
case TagFormalParameter:
if tkid = typeOf(kid); err != nil {
goto Error
}
case TagUnspecifiedParameters:
tkid = &DotDotDotType{}
}
t.ParamType = append(t.ParamType, tkid)
}
case TagTypedef:
// Typedef (DWARF v2 §5.3)
// Attributes:
// AttrName: name [required]
// AttrType: type definition [required]
t := new(TypedefType)
typ = t
typeCache[off] = t
t.Name, _ = e.Val(AttrName).(string)
t.Type = typeOf(e)
case TagUnspecifiedType:
// Unspecified type (DWARF v3 §5.2)
// Attributes:
// AttrName: name
t := new(UnspecifiedType)
typ = t
typeCache[off] = t
t.Name, _ = e.Val(AttrName).(string)
default:
// This is some other type DIE that we're currently not
// equipped to handle. Return an abstract "unsupported type"
// object in such cases.
t := new(UnsupportedType)
typ = t
typeCache[off] = t
t.Tag = e.Tag
t.Name, _ = e.Val(AttrName).(string)
}
if err != nil {
goto Error
}
{
b, ok := e.Val(AttrByteSize).(int64)
if !ok {
b = -1
switch t := typ.(type) {
case *TypedefType:
// Record that we need to resolve this
// type's size once the type graph is
// constructed.
*typedefs = append(*typedefs, t)
case *PtrType:
b = int64(addressSize)
}
}
typ.Common().ByteSize = b
}
return typ, nil
Error:
// If the parse fails, take the type out of the cache
// so that the next call with this offset doesn't hit
// the cache and return success.
delete(typeCache, off)
return nil, err
}
func zeroArray(t *Type) {
if t == nil {
return
}
at, ok := (*t).(*ArrayType)
if !ok || at.Type.Size() == 0 {
return
}
// Make a copy to avoid invalidating typeCache.
tt := *at
tt.Count = 0
*t = &tt
}
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