| // Copyright 2016 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. |
| |
| // Package dwarf generates DWARF debugging information. |
| // DWARF generation is split between the compiler and the linker, |
| // this package contains the shared code. |
| package dwarf |
| |
| import ( |
| "fmt" |
| "strings" |
| ) |
| |
| // InfoPrefix is the prefix for all the symbols containing DWARF info entries. |
| const InfoPrefix = "go.info." |
| |
| // Sym represents a symbol. |
| type Sym interface { |
| } |
| |
| // A Var represents a local variable or a function parameter. |
| type Var struct { |
| Name string |
| Abbrev int // Either DW_ABRV_AUTO or DW_ABRV_PARAM |
| Offset int32 |
| Type Sym |
| Link *Var |
| } |
| |
| // A Context specifies how to add data to a Sym. |
| type Context interface { |
| PtrSize() int |
| AddInt(s Sym, size int, i int64) |
| AddBytes(s Sym, b []byte) |
| AddAddress(s Sym, t interface{}, ofs int64) |
| AddSectionOffset(s Sym, size int, t interface{}, ofs int64) |
| AddString(s Sym, v string) |
| SymValue(s Sym) int64 |
| } |
| |
| // AppendUleb128 appends v to b using DWARF's unsigned LEB128 encoding. |
| func AppendUleb128(b []byte, v uint64) []byte { |
| for { |
| c := uint8(v & 0x7f) |
| v >>= 7 |
| if v != 0 { |
| c |= 0x80 |
| } |
| b = append(b, c) |
| if c&0x80 == 0 { |
| break |
| } |
| } |
| return b |
| } |
| |
| // AppendSleb128 appends v to b using DWARF's signed LEB128 encoding. |
| func AppendSleb128(b []byte, v int64) []byte { |
| for { |
| c := uint8(v & 0x7f) |
| s := uint8(v & 0x40) |
| v >>= 7 |
| if (v != -1 || s == 0) && (v != 0 || s != 0) { |
| c |= 0x80 |
| } |
| b = append(b, c) |
| if c&0x80 == 0 { |
| break |
| } |
| } |
| return b |
| } |
| |
| var encbuf [20]byte |
| |
| // AppendUleb128 appends v to s using DWARF's unsigned LEB128 encoding. |
| func Uleb128put(ctxt Context, s Sym, v int64) { |
| b := AppendUleb128(encbuf[:0], uint64(v)) |
| ctxt.AddBytes(s, b) |
| } |
| |
| // AppendUleb128 appends v to s using DWARF's signed LEB128 encoding. |
| func Sleb128put(ctxt Context, s Sym, v int64) { |
| b := AppendSleb128(encbuf[:0], v) |
| ctxt.AddBytes(s, b) |
| } |
| |
| /* |
| * Defining Abbrevs. This is hardcoded, and there will be |
| * only a handful of them. The DWARF spec places no restriction on |
| * the ordering of attributes in the Abbrevs and DIEs, and we will |
| * always write them out in the order of declaration in the abbrev. |
| */ |
| type dwAttrForm struct { |
| attr uint16 |
| form uint8 |
| } |
| |
| // Go-specific type attributes. |
| const ( |
| DW_AT_go_kind = 0x2900 |
| DW_AT_go_key = 0x2901 |
| DW_AT_go_elem = 0x2902 |
| |
| DW_AT_internal_location = 253 // params and locals; not emitted |
| ) |
| |
| // Index into the abbrevs table below. |
| // Keep in sync with ispubname() and ispubtype() below. |
| // ispubtype considers >= NULLTYPE public |
| const ( |
| DW_ABRV_NULL = iota |
| DW_ABRV_COMPUNIT |
| DW_ABRV_FUNCTION |
| DW_ABRV_VARIABLE |
| DW_ABRV_AUTO |
| DW_ABRV_PARAM |
| DW_ABRV_STRUCTFIELD |
| DW_ABRV_FUNCTYPEPARAM |
| DW_ABRV_DOTDOTDOT |
| DW_ABRV_ARRAYRANGE |
| DW_ABRV_NULLTYPE |
| DW_ABRV_BASETYPE |
| DW_ABRV_ARRAYTYPE |
| DW_ABRV_CHANTYPE |
| DW_ABRV_FUNCTYPE |
| DW_ABRV_IFACETYPE |
| DW_ABRV_MAPTYPE |
| DW_ABRV_PTRTYPE |
| DW_ABRV_BARE_PTRTYPE // only for void*, no DW_AT_type attr to please gdb 6. |
| DW_ABRV_SLICETYPE |
| DW_ABRV_STRINGTYPE |
| DW_ABRV_STRUCTTYPE |
| DW_ABRV_TYPEDECL |
| DW_NABRV |
| ) |
| |
| type dwAbbrev struct { |
| tag uint8 |
| children uint8 |
| attr []dwAttrForm |
| } |
| |
| var abbrevs = [DW_NABRV]dwAbbrev{ |
| /* The mandatory DW_ABRV_NULL entry. */ |
| {0, 0, []dwAttrForm{}}, |
| |
| /* COMPUNIT */ |
| { |
| DW_TAG_compile_unit, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_language, DW_FORM_data1}, |
| {DW_AT_low_pc, DW_FORM_addr}, |
| {DW_AT_high_pc, DW_FORM_addr}, |
| {DW_AT_stmt_list, DW_FORM_data4}, |
| {DW_AT_comp_dir, DW_FORM_string}, |
| }, |
| }, |
| |
| /* FUNCTION */ |
| { |
| DW_TAG_subprogram, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_low_pc, DW_FORM_addr}, |
| {DW_AT_high_pc, DW_FORM_addr}, |
| {DW_AT_external, DW_FORM_flag}, |
| }, |
| }, |
| |
| /* VARIABLE */ |
| { |
| DW_TAG_variable, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_location, DW_FORM_block1}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_external, DW_FORM_flag}, |
| }, |
| }, |
| |
| /* AUTO */ |
| { |
| DW_TAG_variable, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_location, DW_FORM_block1}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* PARAM */ |
| { |
| DW_TAG_formal_parameter, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_location, DW_FORM_block1}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* STRUCTFIELD */ |
| { |
| DW_TAG_member, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_data_member_location, DW_FORM_block1}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* FUNCTYPEPARAM */ |
| { |
| DW_TAG_formal_parameter, |
| DW_CHILDREN_no, |
| |
| // No name! |
| []dwAttrForm{ |
| {DW_AT_type, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* DOTDOTDOT */ |
| { |
| DW_TAG_unspecified_parameters, |
| DW_CHILDREN_no, |
| []dwAttrForm{}, |
| }, |
| |
| /* ARRAYRANGE */ |
| { |
| DW_TAG_subrange_type, |
| DW_CHILDREN_no, |
| |
| // No name! |
| []dwAttrForm{ |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_count, DW_FORM_udata}, |
| }, |
| }, |
| |
| // Below here are the types considered public by ispubtype |
| /* NULLTYPE */ |
| { |
| DW_TAG_unspecified_type, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| }, |
| }, |
| |
| /* BASETYPE */ |
| { |
| DW_TAG_base_type, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_encoding, DW_FORM_data1}, |
| {DW_AT_byte_size, DW_FORM_data1}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* ARRAYTYPE */ |
| // child is subrange with upper bound |
| { |
| DW_TAG_array_type, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_byte_size, DW_FORM_udata}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* CHANTYPE */ |
| { |
| DW_TAG_typedef, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| {DW_AT_go_elem, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* FUNCTYPE */ |
| { |
| DW_TAG_subroutine_type, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| // {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* IFACETYPE */ |
| { |
| DW_TAG_typedef, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* MAPTYPE */ |
| { |
| DW_TAG_typedef, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| {DW_AT_go_key, DW_FORM_ref_addr}, |
| {DW_AT_go_elem, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* PTRTYPE */ |
| { |
| DW_TAG_pointer_type, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* BARE_PTRTYPE */ |
| { |
| DW_TAG_pointer_type, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| }, |
| }, |
| |
| /* SLICETYPE */ |
| { |
| DW_TAG_structure_type, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_byte_size, DW_FORM_udata}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| {DW_AT_go_elem, DW_FORM_ref_addr}, |
| }, |
| }, |
| |
| /* STRINGTYPE */ |
| { |
| DW_TAG_structure_type, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_byte_size, DW_FORM_udata}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* STRUCTTYPE */ |
| { |
| DW_TAG_structure_type, |
| DW_CHILDREN_yes, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_byte_size, DW_FORM_udata}, |
| {DW_AT_go_kind, DW_FORM_data1}, |
| }, |
| }, |
| |
| /* TYPEDECL */ |
| { |
| DW_TAG_typedef, |
| DW_CHILDREN_no, |
| []dwAttrForm{ |
| {DW_AT_name, DW_FORM_string}, |
| {DW_AT_type, DW_FORM_ref_addr}, |
| }, |
| }, |
| } |
| |
| // GetAbbrev returns the contents of the .debug_abbrev section. |
| func GetAbbrev() []byte { |
| var buf []byte |
| for i := 1; i < DW_NABRV; i++ { |
| // See section 7.5.3 |
| buf = AppendUleb128(buf, uint64(i)) |
| |
| buf = AppendUleb128(buf, uint64(abbrevs[i].tag)) |
| buf = append(buf, byte(abbrevs[i].children)) |
| for _, f := range abbrevs[i].attr { |
| buf = AppendUleb128(buf, uint64(f.attr)) |
| buf = AppendUleb128(buf, uint64(f.form)) |
| } |
| buf = append(buf, 0, 0) |
| } |
| return append(buf, 0) |
| } |
| |
| /* |
| * Debugging Information Entries and their attributes. |
| */ |
| |
| // DWAttr represents an attribute of a DWDie. |
| // |
| // For DW_CLS_string and _block, value should contain the length, and |
| // data the data, for _reference, value is 0 and data is a DWDie* to |
| // the referenced instance, for all others, value is the whole thing |
| // and data is null. |
| type DWAttr struct { |
| Link *DWAttr |
| Atr uint16 // DW_AT_ |
| Cls uint8 // DW_CLS_ |
| Value int64 |
| Data interface{} |
| } |
| |
| // DWDie represents a DWARF debug info entry. |
| type DWDie struct { |
| Abbrev int |
| Link *DWDie |
| Child *DWDie |
| Attr *DWAttr |
| Sym Sym |
| } |
| |
| func putattr(ctxt Context, s Sym, abbrev int, form int, cls int, value int64, data interface{}) error { |
| switch form { |
| case DW_FORM_addr: // address |
| ctxt.AddAddress(s, data, value) |
| |
| case DW_FORM_block1: // block |
| if cls == DW_CLS_ADDRESS { |
| ctxt.AddInt(s, 1, int64(1+ctxt.PtrSize())) |
| ctxt.AddInt(s, 1, DW_OP_addr) |
| ctxt.AddAddress(s, data, 0) |
| break |
| } |
| |
| value &= 0xff |
| ctxt.AddInt(s, 1, value) |
| p := data.([]byte)[:value] |
| ctxt.AddBytes(s, p) |
| |
| case DW_FORM_block2: // block |
| value &= 0xffff |
| |
| ctxt.AddInt(s, 2, value) |
| p := data.([]byte)[:value] |
| ctxt.AddBytes(s, p) |
| |
| case DW_FORM_block4: // block |
| value &= 0xffffffff |
| |
| ctxt.AddInt(s, 4, value) |
| p := data.([]byte)[:value] |
| ctxt.AddBytes(s, p) |
| |
| case DW_FORM_block: // block |
| Uleb128put(ctxt, s, value) |
| |
| p := data.([]byte)[:value] |
| ctxt.AddBytes(s, p) |
| |
| case DW_FORM_data1: // constant |
| ctxt.AddInt(s, 1, value) |
| |
| case DW_FORM_data2: // constant |
| ctxt.AddInt(s, 2, value) |
| |
| case DW_FORM_data4: // constant, {line,loclist,mac,rangelist}ptr |
| if cls == DW_CLS_PTR { // DW_AT_stmt_list |
| ctxt.AddSectionOffset(s, 4, data, 0) |
| break |
| } |
| ctxt.AddInt(s, 4, value) |
| |
| case DW_FORM_data8: // constant, {line,loclist,mac,rangelist}ptr |
| ctxt.AddInt(s, 8, value) |
| |
| case DW_FORM_sdata: // constant |
| Sleb128put(ctxt, s, value) |
| |
| case DW_FORM_udata: // constant |
| Uleb128put(ctxt, s, value) |
| |
| case DW_FORM_string: // string |
| str := data.(string) |
| ctxt.AddString(s, str) |
| // TODO(ribrdb): verify padded strings are never used and remove this |
| for i := int64(len(str)); i < value; i++ { |
| ctxt.AddInt(s, 1, 0) |
| } |
| |
| case DW_FORM_flag: // flag |
| if value != 0 { |
| ctxt.AddInt(s, 1, 1) |
| } else { |
| ctxt.AddInt(s, 1, 0) |
| } |
| |
| // In DWARF 2 (which is what we claim to generate), |
| // the ref_addr is the same size as a normal address. |
| // In DWARF 3 it is always 32 bits, unless emitting a large |
| // (> 4 GB of debug info aka "64-bit") unit, which we don't implement. |
| case DW_FORM_ref_addr: // reference to a DIE in the .info section |
| if data == nil { |
| return fmt.Errorf("dwarf: null reference in %d", abbrev) |
| } else { |
| ctxt.AddSectionOffset(s, ctxt.PtrSize(), data, 0) |
| } |
| |
| case DW_FORM_ref1, // reference within the compilation unit |
| DW_FORM_ref2, // reference |
| DW_FORM_ref4, // reference |
| DW_FORM_ref8, // reference |
| DW_FORM_ref_udata, // reference |
| |
| DW_FORM_strp, // string |
| DW_FORM_indirect: // (see Section 7.5.3) |
| fallthrough |
| default: |
| return fmt.Errorf("dwarf: unsupported attribute form %d / class %d", form, cls) |
| } |
| return nil |
| } |
| |
| // PutAttrs writes the attributes for a DIE to symbol 's'. |
| // |
| // Note that we can (and do) add arbitrary attributes to a DIE, but |
| // only the ones actually listed in the Abbrev will be written out. |
| func PutAttrs(ctxt Context, s Sym, abbrev int, attr *DWAttr) { |
| Outer: |
| for _, f := range abbrevs[abbrev].attr { |
| for ap := attr; ap != nil; ap = ap.Link { |
| if ap.Atr == f.attr { |
| putattr(ctxt, s, abbrev, int(f.form), int(ap.Cls), ap.Value, ap.Data) |
| continue Outer |
| } |
| } |
| |
| putattr(ctxt, s, abbrev, int(f.form), 0, 0, nil) |
| } |
| } |
| |
| // HasChildren returns true if 'die' uses an abbrev that supports children. |
| func HasChildren(die *DWDie) bool { |
| return abbrevs[die.Abbrev].children != 0 |
| } |
| |
| // PutFunc writes a DIE for a function to s. |
| // It also writes child DIEs for each variable in vars. |
| func PutFunc(ctxt Context, s Sym, name string, external bool, startPC Sym, size int64, vars *Var) { |
| Uleb128put(ctxt, s, DW_ABRV_FUNCTION) |
| putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_string, DW_CLS_STRING, int64(len(name)), name) |
| putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, 0, startPC) |
| putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_addr, DW_CLS_ADDRESS, size+ctxt.SymValue(startPC), startPC) |
| var ev int64 |
| if external { |
| ev = 1 |
| } |
| putattr(ctxt, s, DW_ABRV_FUNCTION, DW_FORM_flag, DW_CLS_FLAG, ev, 0) |
| names := make(map[string]bool) |
| for v := vars; v != nil; v = v.Link { |
| if strings.Contains(v.Name, ".autotmp_") { |
| continue |
| } |
| var n string |
| if names[v.Name] { |
| n = fmt.Sprintf("%s#%d", v.Name, len(names)) |
| } else { |
| n = v.Name |
| } |
| names[n] = true |
| |
| Uleb128put(ctxt, s, int64(v.Abbrev)) |
| putattr(ctxt, s, v.Abbrev, DW_FORM_string, DW_CLS_STRING, int64(len(n)), n) |
| loc := append(encbuf[:0], DW_OP_call_frame_cfa) |
| if v.Offset != 0 { |
| loc = append(loc, DW_OP_consts) |
| loc = AppendSleb128(loc, int64(v.Offset)) |
| loc = append(loc, DW_OP_plus) |
| } |
| putattr(ctxt, s, v.Abbrev, DW_FORM_block1, DW_CLS_BLOCK, int64(len(loc)), loc) |
| putattr(ctxt, s, v.Abbrev, DW_FORM_ref_addr, DW_CLS_REFERENCE, 0, v.Type) |
| |
| } |
| Uleb128put(ctxt, s, 0) |
| } |
