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120 lines
3.7 KiB
Go
120 lines
3.7 KiB
Go
// Copyright 2014 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dwarf
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// This file provides simple methods to access the symbol table by name and address.
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import (
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"fmt"
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"regexp"
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"sort"
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)
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// lookupEntry returns the first Entry for the name.
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// If tag is non-zero, only entries with that tag are considered.
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func (d *Data) lookupEntry(name string, tag Tag) (*Entry, error) {
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x, ok := d.nameCache[name]
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if !ok {
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return nil, fmt.Errorf("DWARF entry for %q not found", name)
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}
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for ; x != nil; x = x.link {
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if tag == 0 || x.entry.Tag == tag {
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return x.entry, nil
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}
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}
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return nil, fmt.Errorf("no DWARF entry for %q with tag %s", name, tag)
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}
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// LookupMatchingSymbols returns the names of all top-level entries matching
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// the given regular expression.
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func (d *Data) LookupMatchingSymbols(nameRE *regexp.Regexp) (result []string, err error) {
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for name := range d.nameCache {
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if nameRE.MatchString(name) {
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result = append(result, name)
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}
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}
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return result, nil
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}
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// LookupEntry returns the Entry for the named symbol.
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func (d *Data) LookupEntry(name string) (*Entry, error) {
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return d.lookupEntry(name, 0)
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}
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// LookupFunction returns the entry for a function.
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func (d *Data) LookupFunction(name string) (*Entry, error) {
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return d.lookupEntry(name, TagSubprogram)
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}
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// LookupVariable returns the entry for a (global) variable.
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func (d *Data) LookupVariable(name string) (*Entry, error) {
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return d.lookupEntry(name, TagVariable)
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}
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// EntryLocation returns the address of the object referred to by the given Entry.
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func (d *Data) EntryLocation(e *Entry) (uint64, error) {
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loc, _ := e.Val(AttrLocation).([]byte)
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if len(loc) == 0 {
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return 0, fmt.Errorf("DWARF entry has no Location attribute")
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}
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// TODO: implement the DWARF Location bytecode. What we have here only
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// recognizes a program with a single literal opAddr bytecode.
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if asize := d.unit[0].asize; loc[0] == opAddr && len(loc) == 1+asize {
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switch asize {
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case 1:
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return uint64(loc[1]), nil
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case 2:
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return uint64(d.order.Uint16(loc[1:])), nil
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case 4:
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return uint64(d.order.Uint32(loc[1:])), nil
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case 8:
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return d.order.Uint64(loc[1:]), nil
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}
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}
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return 0, fmt.Errorf("DWARF entry has an unimplemented Location op")
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}
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// EntryType returns the Type for an Entry.
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func (d *Data) EntryType(e *Entry) (Type, error) {
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off, err := d.EntryTypeOffset(e)
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if err != nil {
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return nil, err
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}
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return d.Type(off)
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}
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// EntryTypeOffset returns the offset in the given Entry's type attribute.
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func (d *Data) EntryTypeOffset(e *Entry) (Offset, error) {
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v := e.Val(AttrType)
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if v == nil {
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return 0, fmt.Errorf("DWARF entry has no Type attribute")
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}
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off, ok := v.(Offset)
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if !ok {
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return 0, fmt.Errorf("DWARF entry has an invalid Type attribute")
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}
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return off, nil
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}
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// PCToFunction returns the entry and address for the function containing the
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// specified PC.
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func (d *Data) PCToFunction(pc uint64) (entry *Entry, lowpc uint64, err error) {
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p := d.pcToFuncEntries
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if len(p) == 0 {
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return nil, 0, fmt.Errorf("no function addresses loaded")
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}
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i := sort.Search(len(p), func(i int) bool { return p[i].pc > pc }) - 1
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// The search failed if:
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// - pc was before the start of any function.
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// - The largest function bound not larger than pc was the end of a function,
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// not the start of one.
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// - The largest function bound not larger than pc was the start of a function
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// that we don't know the end of, and the PC is much larger than the start.
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if i == -1 || p[i].entry == nil || (i+1 == len(p) && pc-p[i].pc >= 1<<20) {
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return nil, 0, fmt.Errorf("no function at %x", pc)
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}
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return p[i].entry, p[i].pc, nil
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}
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