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Handle multiple compile units in DWARF data #65

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2b47603
detect compile units and apply entry prefixing
Abyss-W4tcher Aug 29, 2024
1c6137c
split if-branch on baseType detection
Abyss-W4tcher Aug 30, 2024
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91 changes: 61 additions & 30 deletions main.go
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,11 @@ const (
SystemMap Extract = 16
)

// DW_AT_language bindings
const (
DW_LANG_Rust = 0x1c
)

// FileToProcess defines the file that needs to be processed and
// information that should be extracted from that file
type FileToProcess struct {
Expand Down Expand Up @@ -194,7 +199,7 @@ type vtypeJson struct {
Symbols map[string]*vtypeSymbol `json:"symbols"`
}

func (doc *vtypeJson) addStruct(structType *dwarf.StructType, name, endian string, off dwarf.Offset) error {
func (doc *vtypeJson) addStruct(structType *dwarf.StructType, name, endian string, off dwarf.Offset, codeNs string) error {
if structType.Incomplete {
return nil
}
Expand All @@ -212,7 +217,7 @@ func (doc *vtypeJson) addStruct(structType *dwarf.StructType, name, endian strin
continue
}

fieldType := typeName(field.Type)
fieldType := typeName(field.Type, codeNs)

// skip fields for which type cannot be obtained
if fieldType == nil {
Expand Down Expand Up @@ -289,7 +294,7 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)

doc.BaseTypes["void"] = &vtypeBaseType{Size: 0, Signed: false, Kind: "void", Endian: endian}

symbolsCb := func(entry *dwarf.Entry, addressSize int) error {
symbolsCb := func(entry *dwarf.Entry, addressSize int, codeNs string) error {
switch entry.Tag {
case dwarf.TagVariable:
name, _ := entry.Val(dwarf.AttrName).(string)
Expand All @@ -316,20 +321,20 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
sym := &vtypeSymbol{Address: address}
genericType, err := data.Type(typOff)
if err == nil {
sym.SymbolType = typeName(genericType)
sym.SymbolType = typeName(genericType, codeNs)
} else {
voidType := make(map[string]interface{}, 0)
voidType["kind"] = "base"
voidType["name"] = "void"
sym.SymbolType = voidType
}
doc.Symbols[name] = sym
doc.Symbols[codeNs+name] = sym
}
return nil

}

typesCb := func(entry *dwarf.Entry, addressSize int) error {
typesCb := func(entry *dwarf.Entry, addressSize int, codeNs string) error {
switch entry.Tag {
case dwarf.TagUnionType:
fallthrough
Expand All @@ -342,8 +347,7 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
if ok != true {
return fmt.Errorf("%s is not a StructType?", genericType.String())
}

err = doc.addStruct(structType, structName(structType), endian, entry.Offset)
err = doc.addStruct(structType, structName(structType, codeNs), endian, entry.Offset, codeNs)
if err != nil {
return fmt.Errorf("could not parse struct: %s", err)
}
Expand Down Expand Up @@ -378,7 +382,15 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
// Sort keys to make map enum type selection deterministic
keys := make([]string, 0, len(doc.BaseTypes))
for k := range doc.BaseTypes {
keys = append(keys, k)
// Avoid inserting language typed baseTypes in the (default) non-typed
// C baseTypes pool.
if codeNs == "" {
if !strings.Contains(k, ".") {
keys = append(keys, k)
}
} else if strings.HasPrefix(k, codeNs) {
keys = append(keys, k)
}
}
sort.Strings(keys)
// Now match type using sorted keys
Expand All @@ -390,14 +402,14 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
}
}

doc.Enums[enumName(enumType)] = et
doc.Enums[enumName(enumType, codeNs)] = et
case dwarf.TagPointerType:
if _, present := doc.BaseTypes["pointer"]; !present {
if _, present := doc.BaseTypes[codeNs+"pointer"]; !present {
genericType, err := data.Type(entry.Offset)
if err != nil {
break
}
doc.BaseTypes["pointer"] =
doc.BaseTypes[codeNs+"pointer"] =
&vtypeBaseType{Size: genericType.Size(), Signed: false, Kind: "int", Endian: endian}
}
case dwarf.TagBaseType:
Expand All @@ -406,8 +418,8 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
break
}
common := genericType.Common()
if _, present := doc.BaseTypes[common.Name]; !present {
doc.BaseTypes[common.Name] = newBasetype(genericType, endian)
if _, present := doc.BaseTypes[codeNs+common.Name]; !present {
doc.BaseTypes[codeNs+common.Name] = newBasetype(genericType, endian)
}
case dwarf.TagTypedef:
genericType, err := data.Type(entry.Offset)
Expand All @@ -421,7 +433,7 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
}

if structType, ok := typedefType.Type.(*dwarf.StructType); ok && structType.Name == "" {
err := doc.addStruct(structType, typedefType.Name, endian, entry.Offset)
err := doc.addStruct(structType, codeNs+typedefType.Name, endian, entry.Offset, codeNs)
if err != nil {
return fmt.Errorf("could not parse struct: %s", err)
}
Expand All @@ -431,7 +443,7 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
return nil
}

callBacks := []func(entry *dwarf.Entry, addressSize int) error{}
callBacks := []func(entry *dwarf.Entry, addressSize int, codeNs string) error{}

if extract&DwarfTypes != 0 {
callBacks = append(callBacks, typesCb)
Expand All @@ -440,6 +452,8 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
callBacks = append(callBacks, symbolsCb)
}

// Initialize namespace prefix to an empty string
codeNs := ""
// go through the DWARF
reader := data.Reader()
for {
Expand All @@ -453,8 +467,25 @@ func (doc *vtypeJson) addDwarf(data *dwarf.Data, endian string, extract Extract)
return err
}

/* Check if this entry is a compile unit.
This will mark all children of this CU with
the corresponding prefix ("<language>.").
The goal is to avoid conflicts between common names (structs, symbols...)
accross multiple languages, by prefixing objects with a namespace. */
if entry.Tag == dwarf.TagCompileUnit {
// Detect RUST language, needed for Linux kernel 6.5+
if entry.Val(dwarf.AttrLanguage).(int64) == DW_LANG_Rust {
codeNs = "rust."
} else {
// Default to an empty string for other languages (C mostly).
// Avoid trying to specifically detect C language
// to prevent edge cases.
codeNs = ""
}
}

for _, cb := range callBacks {
err = cb(entry, reader.AddressSize())
err = cb(entry, reader.AddressSize(), codeNs)
if err != nil {
return err
}
Expand Down Expand Up @@ -517,57 +548,57 @@ func locationToUint64(loc *dwarf.Field, addressSize int) uint64 {
return result
}

func structName(dwarfStruct *dwarf.StructType) string {
func structName(dwarfStruct *dwarf.StructType, codeNs string) string {
if dwarfStruct.StructName != "" {
return dwarfStruct.StructName
return codeNs + dwarfStruct.StructName
}

data := sha1.Sum([]byte(dwarfStruct.Defn()))
return fmt.Sprintf("unnamed_%8x", data[0:8])
}

func enumName(dwarfEnum *dwarf.EnumType) string {
func enumName(dwarfEnum *dwarf.EnumType, codeNs string) string {
if dwarfEnum.EnumName != "" {
return dwarfEnum.EnumName
return codeNs + dwarfEnum.EnumName
}

data := sha1.Sum([]byte(dwarfEnum.String()))
return fmt.Sprintf("unnamed_%8x", data[0:8])
}

func typeName(dwarfType dwarf.Type) map[string]interface{} {
func typeName(dwarfType dwarf.Type, codeNs string) map[string]interface{} {
result := make(map[string]interface{}, 0)

switch t := dwarfType.(type) {
case *dwarf.StructType:
result["kind"] = t.Kind
result["name"] = structName(t)
result["name"] = structName(t, codeNs)
case *dwarf.ArrayType:
result["kind"] = "array"
if t.Count < 0 {
result["count"] = 0
} else {
result["count"] = t.Count
}
result["subtype"] = typeName(t.Type)
result["subtype"] = typeName(t.Type, codeNs)
case *dwarf.PtrType:
result["kind"] = "pointer"
result["subtype"] = typeName(t.Type)
result["subtype"] = typeName(t.Type, codeNs)
case *dwarf.EnumType:
result["kind"] = "enum"
result["name"] = enumName(t)
result["name"] = enumName(t, codeNs)
case *dwarf.BoolType, *dwarf.CharType, *dwarf.ComplexType, *dwarf.IntType, *dwarf.FloatType, *dwarf.UcharType, *dwarf.UintType:
result["kind"] = "base"
result["name"] = t.Common().Name
result["name"] = codeNs + t.Common().Name
case *dwarf.TypedefType:
if structType, ok := t.Type.(*dwarf.StructType); ok && structType.Name == "" {
result["kind"] = structType.Kind
result["name"] = t.Name
result["name"] = codeNs + t.Name
} else {
result = typeName(t.Type)
result = typeName(t.Type, codeNs)
}
case *dwarf.QualType:
result = typeName(t.Type)
result = typeName(t.Type, codeNs)
case *dwarf.VoidType, *dwarf.UnspecifiedType:
result["kind"] = "base"
result["name"] = "void"
Expand Down