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-rw-r--r--src/debug/dwarf/entry.go401
1 files changed, 401 insertions, 0 deletions
diff --git a/src/debug/dwarf/entry.go b/src/debug/dwarf/entry.go
new file mode 100644
index 000000000..665c6840d
--- /dev/null
+++ b/src/debug/dwarf/entry.go
@@ -0,0 +1,401 @@
+// 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 debug information entry parser.
+// An entry is a sequence of data items of a given format.
+// The first word in the entry is an index into what DWARF
+// calls the ``abbreviation table.'' An abbreviation is really
+// just a type descriptor: it's an array of attribute tag/value format pairs.
+
+package dwarf
+
+import (
+ "errors"
+ "strconv"
+)
+
+// a single entry's description: a sequence of attributes
+type abbrev struct {
+ tag Tag
+ children bool
+ field []afield
+}
+
+type afield struct {
+ attr Attr
+ fmt format
+}
+
+// a map from entry format ids to their descriptions
+type abbrevTable map[uint32]abbrev
+
+// ParseAbbrev returns the abbreviation table that starts at byte off
+// in the .debug_abbrev section.
+func (d *Data) parseAbbrev(off uint32) (abbrevTable, error) {
+ if m, ok := d.abbrevCache[off]; ok {
+ return m, nil
+ }
+
+ data := d.abbrev
+ if off > uint32(len(data)) {
+ data = nil
+ } else {
+ data = data[off:]
+ }
+ b := makeBuf(d, unknownFormat{}, "abbrev", 0, data)
+
+ // Error handling is simplified by the buf getters
+ // returning an endless stream of 0s after an error.
+ m := make(abbrevTable)
+ for {
+ // Table ends with id == 0.
+ id := uint32(b.uint())
+ if id == 0 {
+ break
+ }
+
+ // Walk over attributes, counting.
+ n := 0
+ b1 := b // Read from copy of b.
+ b1.uint()
+ b1.uint8()
+ for {
+ tag := b1.uint()
+ fmt := b1.uint()
+ if tag == 0 && fmt == 0 {
+ break
+ }
+ n++
+ }
+ if b1.err != nil {
+ return nil, b1.err
+ }
+
+ // Walk over attributes again, this time writing them down.
+ var a abbrev
+ a.tag = Tag(b.uint())
+ a.children = b.uint8() != 0
+ a.field = make([]afield, n)
+ for i := range a.field {
+ a.field[i].attr = Attr(b.uint())
+ a.field[i].fmt = format(b.uint())
+ }
+ b.uint()
+ b.uint()
+
+ m[id] = a
+ }
+ if b.err != nil {
+ return nil, b.err
+ }
+ d.abbrevCache[off] = m
+ return m, nil
+}
+
+// An entry is a sequence of attribute/value pairs.
+type Entry struct {
+ Offset Offset // offset of Entry in DWARF info
+ Tag Tag // tag (kind of Entry)
+ Children bool // whether Entry is followed by children
+ Field []Field
+}
+
+// A Field is a single attribute/value pair in an Entry.
+type Field struct {
+ Attr Attr
+ Val interface{}
+}
+
+// Val returns the value associated with attribute Attr in Entry,
+// or nil if there is no such attribute.
+//
+// A common idiom is to merge the check for nil return with
+// the check that the value has the expected dynamic type, as in:
+// v, ok := e.Val(AttrSibling).(int64);
+//
+func (e *Entry) Val(a Attr) interface{} {
+ for _, f := range e.Field {
+ if f.Attr == a {
+ return f.Val
+ }
+ }
+ return nil
+}
+
+// An Offset represents the location of an Entry within the DWARF info.
+// (See Reader.Seek.)
+type Offset uint32
+
+// Entry reads a single entry from buf, decoding
+// according to the given abbreviation table.
+func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
+ off := b.off
+ id := uint32(b.uint())
+ if id == 0 {
+ return &Entry{}
+ }
+ a, ok := atab[id]
+ if !ok {
+ b.error("unknown abbreviation table index")
+ return nil
+ }
+ e := &Entry{
+ Offset: off,
+ Tag: a.tag,
+ Children: a.children,
+ Field: make([]Field, len(a.field)),
+ }
+ for i := range e.Field {
+ e.Field[i].Attr = a.field[i].attr
+ fmt := a.field[i].fmt
+ if fmt == formIndirect {
+ fmt = format(b.uint())
+ }
+ var val interface{}
+ switch fmt {
+ default:
+ b.error("unknown entry attr format 0x" + strconv.FormatInt(int64(fmt), 16))
+
+ // address
+ case formAddr:
+ val = b.addr()
+
+ // block
+ case formDwarfBlock1:
+ val = b.bytes(int(b.uint8()))
+ case formDwarfBlock2:
+ val = b.bytes(int(b.uint16()))
+ case formDwarfBlock4:
+ val = b.bytes(int(b.uint32()))
+ case formDwarfBlock:
+ val = b.bytes(int(b.uint()))
+
+ // constant
+ case formData1:
+ val = int64(b.uint8())
+ case formData2:
+ val = int64(b.uint16())
+ case formData4:
+ val = int64(b.uint32())
+ case formData8:
+ val = int64(b.uint64())
+ case formSdata:
+ val = int64(b.int())
+ case formUdata:
+ val = int64(b.uint())
+
+ // flag
+ case formFlag:
+ val = b.uint8() == 1
+ // New in DWARF 4.
+ case formFlagPresent:
+ // The attribute is implicitly indicated as present, and no value is
+ // encoded in the debugging information entry itself.
+ val = true
+
+ // reference to other entry
+ case formRefAddr:
+ vers := b.format.version()
+ if vers == 0 {
+ b.error("unknown version for DW_FORM_ref_addr")
+ } else if vers == 2 {
+ val = Offset(b.addr())
+ } else {
+ is64, known := b.format.dwarf64()
+ if !known {
+ b.error("unknown size for DW_FORM_ref_addr")
+ } else if is64 {
+ val = Offset(b.uint64())
+ } else {
+ val = Offset(b.uint32())
+ }
+ }
+ case formRef1:
+ val = Offset(b.uint8()) + ubase
+ case formRef2:
+ val = Offset(b.uint16()) + ubase
+ case formRef4:
+ val = Offset(b.uint32()) + ubase
+ case formRef8:
+ val = Offset(b.uint64()) + ubase
+ case formRefUdata:
+ val = Offset(b.uint()) + ubase
+
+ // string
+ case formString:
+ val = b.string()
+ case formStrp:
+ off := b.uint32() // offset into .debug_str
+ if b.err != nil {
+ return nil
+ }
+ b1 := makeBuf(b.dwarf, unknownFormat{}, "str", 0, b.dwarf.str)
+ b1.skip(int(off))
+ val = b1.string()
+ if b1.err != nil {
+ b.err = b1.err
+ return nil
+ }
+
+ // lineptr, loclistptr, macptr, rangelistptr
+ // New in DWARF 4, but clang can generate them with -gdwarf-2.
+ // Section reference, replacing use of formData4 and formData8.
+ case formSecOffset, formGnuRefAlt, formGnuStrpAlt:
+ is64, known := b.format.dwarf64()
+ if !known {
+ b.error("unknown size for form 0x" + strconv.FormatInt(int64(fmt), 16))
+ } else if is64 {
+ val = int64(b.uint64())
+ } else {
+ val = int64(b.uint32())
+ }
+
+ // exprloc
+ // New in DWARF 4.
+ case formExprloc:
+ val = b.bytes(int(b.uint()))
+
+ // reference
+ // New in DWARF 4.
+ case formRefSig8:
+ // 64-bit type signature.
+ val = b.uint64()
+ }
+ e.Field[i].Val = val
+ }
+ if b.err != nil {
+ return nil
+ }
+ return e
+}
+
+// A Reader allows reading Entry structures from a DWARF ``info'' section.
+// The Entry structures are arranged in a tree. The Reader's Next function
+// return successive entries from a pre-order traversal of the tree.
+// If an entry has children, its Children field will be true, and the children
+// follow, terminated by an Entry with Tag 0.
+type Reader struct {
+ b buf
+ d *Data
+ err error
+ unit int
+ lastChildren bool // .Children of last entry returned by Next
+ lastSibling Offset // .Val(AttrSibling) of last entry returned by Next
+}
+
+// Reader returns a new Reader for Data.
+// The reader is positioned at byte offset 0 in the DWARF ``info'' section.
+func (d *Data) Reader() *Reader {
+ r := &Reader{d: d}
+ r.Seek(0)
+ return r
+}
+
+// Seek positions the Reader at offset off in the encoded entry stream.
+// Offset 0 can be used to denote the first entry.
+func (r *Reader) Seek(off Offset) {
+ d := r.d
+ r.err = nil
+ r.lastChildren = false
+ if off == 0 {
+ if len(d.unit) == 0 {
+ return
+ }
+ u := &d.unit[0]
+ r.unit = 0
+ r.b = makeBuf(r.d, u, "info", u.off, u.data)
+ return
+ }
+
+ // TODO(rsc): binary search (maybe a new package)
+ var i int
+ var u *unit
+ for i = range d.unit {
+ u = &d.unit[i]
+ if u.off <= off && off < u.off+Offset(len(u.data)) {
+ r.unit = i
+ r.b = makeBuf(r.d, u, "info", off, u.data[off-u.off:])
+ return
+ }
+ }
+ r.err = errors.New("offset out of range")
+}
+
+// maybeNextUnit advances to the next unit if this one is finished.
+func (r *Reader) maybeNextUnit() {
+ for len(r.b.data) == 0 && r.unit+1 < len(r.d.unit) {
+ r.unit++
+ u := &r.d.unit[r.unit]
+ r.b = makeBuf(r.d, u, "info", u.off, u.data)
+ }
+}
+
+// Next reads the next entry from the encoded entry stream.
+// It returns nil, nil when it reaches the end of the section.
+// It returns an error if the current offset is invalid or the data at the
+// offset cannot be decoded as a valid Entry.
+func (r *Reader) Next() (*Entry, error) {
+ if r.err != nil {
+ return nil, r.err
+ }
+ r.maybeNextUnit()
+ if len(r.b.data) == 0 {
+ return nil, nil
+ }
+ u := &r.d.unit[r.unit]
+ e := r.b.entry(u.atable, u.base)
+ if r.b.err != nil {
+ r.err = r.b.err
+ return nil, r.err
+ }
+ if e != nil {
+ r.lastChildren = e.Children
+ if r.lastChildren {
+ r.lastSibling, _ = e.Val(AttrSibling).(Offset)
+ }
+ } else {
+ r.lastChildren = false
+ }
+ return e, nil
+}
+
+// SkipChildren skips over the child entries associated with
+// the last Entry returned by Next. If that Entry did not have
+// children or Next has not been called, SkipChildren is a no-op.
+func (r *Reader) SkipChildren() {
+ if r.err != nil || !r.lastChildren {
+ return
+ }
+
+ // If the last entry had a sibling attribute,
+ // that attribute gives the offset of the next
+ // sibling, so we can avoid decoding the
+ // child subtrees.
+ if r.lastSibling >= r.b.off {
+ r.Seek(r.lastSibling)
+ return
+ }
+
+ for {
+ e, err := r.Next()
+ if err != nil || e == nil || e.Tag == 0 {
+ break
+ }
+ if e.Children {
+ r.SkipChildren()
+ }
+ }
+}
+
+// clone returns a copy of the reader. This is used by the typeReader
+// interface.
+func (r *Reader) clone() typeReader {
+ return r.d.Reader()
+}
+
+// offset returns the current buffer offset. This is used by the
+// typeReader interface.
+func (r *Reader) offset() Offset {
+ return r.b.off
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-17 22:52:22 +0000