pprof/internal/symbolizer/symbolizer.go

// Copyright 2014 Google Inc. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package symbolizer provides a routine to populate a profile with
// symbol, file and line number information. It relies on the
// addr2liner and demangle packages to do the actual work.
package symbolizer

import (
	"fmt"
	"io/ioutil"
	"net/http"
	"path/filepath"
	"strings"

	"github.com/google/pprof/internal/binutils"
	"github.com/google/pprof/internal/plugin"
	"github.com/google/pprof/internal/symbolz"
	"github.com/google/pprof/profile"
	"github.com/ianlancetaylor/demangle"
)

// Symbolizer implements the plugin.Symbolize interface.
type Symbolizer struct {
	Obj plugin.ObjTool
	UI  plugin.UI
}

// Symbolize attempts to symbolize profile p. First uses binutils on
// local binaries; if the source is a URL it attempts to get any
// missed entries using symbolz.
func (s *Symbolizer) Symbolize(mode string, sources plugin.MappingSources, p *profile.Profile) error {
	remote, local, force, demanglerMode := true, true, false, ""
	for _, o := range strings.Split(strings.ToLower(mode), ":") {
		switch o {
		case "none", "no":
			return nil
		case "local", "fastlocal":
			remote, local = false, true
		case "remote":
			remote, local = true, false
		case "", "force":
			force = true
		default:
			switch d := strings.TrimPrefix(o, "demangle="); d {
			case "full", "none", "templates":
				demanglerMode = d
				force = true
				continue
			case "default":
				continue
			}
			s.UI.PrintErr("ignoring unrecognized symbolization option: " + mode)
			s.UI.PrintErr("expecting -symbolize=[local|fastlocal|remote|none][:force][:demangle=[none|full|templates|default]")
		}
	}

	var err error
	if local {
		// Symbolize locally using binutils.
		if err = localSymbolize(mode, p, s.Obj, s.UI); err == nil {
			remote = false // Already symbolized, no need to apply remote symbolization.
		}
	}
	if remote {
		if err = symbolz.Symbolize(sources, postURL, p, s.UI); err != nil {
			return err // Ran out of options.
		}
	}

	Demangle(p, force, demanglerMode)
	return nil
}

// postURL issues a POST to a URL over HTTP.
func postURL(source, post string) ([]byte, error) {
	resp, err := http.Post(source, "application/octet-stream", strings.NewReader(post))
	if err != nil {
		return nil, fmt.Errorf("http post %s: %v", source, err)
	}
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("server response: %s", resp.Status)
	}
	defer resp.Body.Close()
	return ioutil.ReadAll(resp.Body)
}

// localSymbolize adds symbol and line number information to all locations
// in a profile. mode enables some options to control
// symbolization.
func localSymbolize(mode string, prof *profile.Profile, obj plugin.ObjTool, ui plugin.UI) error {
	force := false
	// Disable some mechanisms based on mode string.
	for _, o := range strings.Split(strings.ToLower(mode), ":") {
		switch {
		case o == "force":
			force = true
		case o == "fastlocal":
			if bu, ok := obj.(*binutils.Binutils); ok {
				bu.SetFastSymbolization(true)
			}
		default:
		}
	}

	mt, err := newMapping(prof, obj, ui, force)
	if err != nil {
		return err
	}
	defer mt.close()

	functions := make(map[profile.Function]*profile.Function)
	for _, l := range mt.prof.Location {
		m := l.Mapping
		segment := mt.segments[m]
		if segment == nil {
			// Nothing to do.
			continue
		}

		stack, err := segment.SourceLine(l.Address)
		if err != nil || len(stack) == 0 {
			// No answers from addr2line.
			continue
		}

		l.Line = make([]profile.Line, len(stack))
		for i, frame := range stack {
			if frame.Func != "" {
				m.HasFunctions = true
			}
			if frame.File != "" {
				m.HasFilenames = true
			}
			if frame.Line != 0 {
				m.HasLineNumbers = true
			}
			f := &profile.Function{
				Name:       frame.Func,
				SystemName: frame.Func,
				Filename:   frame.File,
			}
			if fp := functions[*f]; fp != nil {
				f = fp
			} else {
				functions[*f] = f
				f.ID = uint64(len(mt.prof.Function)) + 1
				mt.prof.Function = append(mt.prof.Function, f)
			}
			l.Line[i] = profile.Line{
				Function: f,
				Line:     int64(frame.Line),
			}
		}

		if len(stack) > 0 {
			m.HasInlineFrames = true
		}
	}

	return nil
}

// Demangle updates the function names in a profile with demangled C++
// names, simplified according to demanglerMode. If force is set,
// overwrite any names that appear already demangled.
func Demangle(prof *profile.Profile, force bool, demanglerMode string) {
	if force {
		// Remove the current demangled names to force demangling
		for _, f := range prof.Function {
			if f.Name != "" && f.SystemName != "" {
				f.Name = f.SystemName
			}
		}
	}

	var options []demangle.Option
	switch demanglerMode {
	case "": // demangled, simplified: no parameters, no templates, no return type
		options = []demangle.Option{demangle.NoParams, demangle.NoTemplateParams}
	case "templates": // demangled, simplified: no parameters, no return type
		options = []demangle.Option{demangle.NoParams}
	case "full":
		options = []demangle.Option{demangle.NoClones}
	case "none": // no demangling
		return
	}

	// Copy the options because they may be updated by the call.
	o := make([]demangle.Option, len(options))
	for _, fn := range prof.Function {
		if fn.Name != "" && fn.SystemName != fn.Name {
			continue // Already demangled.
		}
		copy(o, options)
		if demangled := demangle.Filter(fn.SystemName, o...); demangled != fn.SystemName {
			fn.Name = demangled
			continue
		}
		// Could not demangle. Apply heuristics in case the name is
		// already demangled.
		name := fn.SystemName
		if looksLikeDemangledCPlusPlus(name) {
			if demanglerMode == "" || demanglerMode == "templates" {
				name = removeMatching(name, '(', ')')
			}
			if demanglerMode == "" {
				name = removeMatching(name, '<', '>')
			}
		}
		fn.Name = name
	}
}

// looksLikeDemangledCPlusPlus is a heuristic to decide if a name is
// the result of demangling C++. If so, further heuristics will be
// applied to simplify the name.
func looksLikeDemangledCPlusPlus(demangled string) bool {
	if strings.Contains(demangled, ".<") { // Skip java names of the form "class.<init>"
		return false
	}
	return strings.ContainsAny(demangled, "<>[]") || strings.Contains(demangled, "::")
}

// removeMatching removes nested instances of start..end from name.
func removeMatching(name string, start, end byte) string {
	s := string(start) + string(end)
	var nesting, first, current int
	for index := strings.IndexAny(name[current:], s); index != -1; index = strings.IndexAny(name[current:], s) {
		switch current += index; name[current] {
		case start:
			nesting++
			if nesting == 1 {
				first = current
			}
		case end:
			nesting--
			switch {
			case nesting < 0:
				return name // Mismatch, abort
			case nesting == 0:
				name = name[:first] + name[current+1:]
				current = first - 1
			}
		}
		current++
	}
	return name
}

// newMapping creates a mappingTable for a profile.
func newMapping(prof *profile.Profile, obj plugin.ObjTool, ui plugin.UI, force bool) (*mappingTable, error) {
	mt := &mappingTable{
		prof:     prof,
		segments: make(map[*profile.Mapping]plugin.ObjFile),
	}

	// Identify used mappings
	mappings := make(map[*profile.Mapping]bool)
	for _, l := range prof.Location {
		mappings[l.Mapping] = true
	}

	for _, m := range prof.Mapping {
		if !mappings[m] {
			continue
		}

		// Do not attempt to re-symbolize a mapping that has already been symbolized.
		if !force && (m.HasFunctions || m.HasFilenames || m.HasLineNumbers) {
			continue
		}

		// Skip well-known system mappings
		name := filepath.Base(m.File)
		if name == "" || name == "[vdso]" || strings.HasPrefix(name, "linux-vdso") {
			continue
		}

		f, err := obj.Open(m.File, m.Start, m.Limit, m.Offset)
		if err != nil {
			ui.PrintErr("Local symbolization failed for ", name, ": ", err)
			continue
		}
		if fid := f.BuildID(); m.BuildID != "" && fid != "" && fid != m.BuildID {
			ui.PrintErr("Local symbolization failed for ", name, ": build ID mismatch")
			f.Close()
			continue
		}

		mt.segments[m] = f
	}

	return mt, nil
}

// mappingTable contains the mechanisms for symbolization of a
// profile.
type mappingTable struct {
	prof     *profile.Profile
	segments map[*profile.Mapping]plugin.ObjFile
}

// Close releases any external processes being used for the mapping.
func (mt *mappingTable) close() {
	for _, segment := range mt.segments {
		segment.Close()
	}
}