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Source file src/cmd/pprof/pprof.go

Documentation: cmd/pprof

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // pprof is a tool for visualization of profile.data. It is based on
     6  // the upstream version at github.com/google/pprof, with minor
     7  // modifications specific to the Go distribution. Please consider
     8  // upstreaming any modifications to these packages.
     9  
    10  package main
    11  
    12  import (
    13  	"crypto/tls"
    14  	"debug/dwarf"
    15  	"fmt"
    16  	"io/ioutil"
    17  	"net/http"
    18  	"net/url"
    19  	"os"
    20  	"regexp"
    21  	"strconv"
    22  	"strings"
    23  	"sync"
    24  	"time"
    25  
    26  	"cmd/internal/objfile"
    27  
    28  	"github.com/google/pprof/driver"
    29  	"github.com/google/pprof/profile"
    30  )
    31  
    32  func main() {
    33  	options := &driver.Options{
    34  		Fetch: new(fetcher),
    35  		Obj:   new(objTool),
    36  	}
    37  	if err := driver.PProf(options); err != nil {
    38  		fmt.Fprintf(os.Stderr, "%v\n", err)
    39  		os.Exit(2)
    40  	}
    41  }
    42  
    43  type fetcher struct {
    44  }
    45  
    46  func (f *fetcher) Fetch(src string, duration, timeout time.Duration) (*profile.Profile, string, error) {
    47  	sourceURL, timeout := adjustURL(src, duration, timeout)
    48  	if sourceURL == "" {
    49  		// Could not recognize URL, let regular pprof attempt to fetch the profile (eg. from a file)
    50  		return nil, "", nil
    51  	}
    52  	fmt.Fprintln(os.Stderr, "Fetching profile over HTTP from", sourceURL)
    53  	if duration > 0 {
    54  		fmt.Fprintf(os.Stderr, "Please wait... (%v)\n", duration)
    55  	}
    56  	p, err := getProfile(sourceURL, timeout)
    57  	return p, sourceURL, err
    58  }
    59  
    60  func getProfile(source string, timeout time.Duration) (*profile.Profile, error) {
    61  	url, err := url.Parse(source)
    62  	if err != nil {
    63  		return nil, err
    64  	}
    65  
    66  	var tlsConfig *tls.Config
    67  	if url.Scheme == "https+insecure" {
    68  		tlsConfig = &tls.Config{
    69  			InsecureSkipVerify: true,
    70  		}
    71  		url.Scheme = "https"
    72  		source = url.String()
    73  	}
    74  
    75  	client := &http.Client{
    76  		Transport: &http.Transport{
    77  			ResponseHeaderTimeout: timeout + 5*time.Second,
    78  			Proxy:           http.ProxyFromEnvironment,
    79  			TLSClientConfig: tlsConfig,
    80  		},
    81  	}
    82  	resp, err := client.Get(source)
    83  	if err != nil {
    84  		return nil, err
    85  	}
    86  	if resp.StatusCode != http.StatusOK {
    87  		defer resp.Body.Close()
    88  		return nil, statusCodeError(resp)
    89  	}
    90  	return profile.Parse(resp.Body)
    91  }
    92  
    93  func statusCodeError(resp *http.Response) error {
    94  	if resp.Header.Get("X-Go-Pprof") != "" && strings.Contains(resp.Header.Get("Content-Type"), "text/plain") {
    95  		// error is from pprof endpoint
    96  		if body, err := ioutil.ReadAll(resp.Body); err == nil {
    97  			return fmt.Errorf("server response: %s - %s", resp.Status, body)
    98  		}
    99  	}
   100  	return fmt.Errorf("server response: %s", resp.Status)
   101  }
   102  
   103  // cpuProfileHandler is the Go pprof CPU profile handler URL.
   104  const cpuProfileHandler = "/debug/pprof/profile"
   105  
   106  // adjustURL applies the duration/timeout values and Go specific defaults
   107  func adjustURL(source string, duration, timeout time.Duration) (string, time.Duration) {
   108  	u, err := url.Parse(source)
   109  	if err != nil || (u.Host == "" && u.Scheme != "" && u.Scheme != "file") {
   110  		// Try adding http:// to catch sources of the form hostname:port/path.
   111  		// url.Parse treats "hostname" as the scheme.
   112  		u, err = url.Parse("http://" + source)
   113  	}
   114  	if err != nil || u.Host == "" {
   115  		return "", 0
   116  	}
   117  
   118  	if u.Path == "" || u.Path == "/" {
   119  		u.Path = cpuProfileHandler
   120  	}
   121  
   122  	// Apply duration/timeout overrides to URL.
   123  	values := u.Query()
   124  	if duration > 0 {
   125  		values.Set("seconds", fmt.Sprint(int(duration.Seconds())))
   126  	} else {
   127  		if urlSeconds := values.Get("seconds"); urlSeconds != "" {
   128  			if us, err := strconv.ParseInt(urlSeconds, 10, 32); err == nil {
   129  				duration = time.Duration(us) * time.Second
   130  			}
   131  		}
   132  	}
   133  	if timeout <= 0 {
   134  		if duration > 0 {
   135  			timeout = duration + duration/2
   136  		} else {
   137  			timeout = 60 * time.Second
   138  		}
   139  	}
   140  	u.RawQuery = values.Encode()
   141  	return u.String(), timeout
   142  }
   143  
   144  // objTool implements driver.ObjTool using Go libraries
   145  // (instead of invoking GNU binutils).
   146  type objTool struct {
   147  	mu          sync.Mutex
   148  	disasmCache map[string]*objfile.Disasm
   149  }
   150  
   151  func (*objTool) Open(name string, start, limit, offset uint64) (driver.ObjFile, error) {
   152  	of, err := objfile.Open(name)
   153  	if err != nil {
   154  		return nil, err
   155  	}
   156  	f := &file{
   157  		name: name,
   158  		file: of,
   159  	}
   160  	if start != 0 {
   161  		if load, err := of.LoadAddress(); err == nil {
   162  			f.offset = start - load
   163  		}
   164  	}
   165  	return f, nil
   166  }
   167  
   168  func (*objTool) Demangle(names []string) (map[string]string, error) {
   169  	// No C++, nothing to demangle.
   170  	return make(map[string]string), nil
   171  }
   172  
   173  func (t *objTool) Disasm(file string, start, end uint64) ([]driver.Inst, error) {
   174  	d, err := t.cachedDisasm(file)
   175  	if err != nil {
   176  		return nil, err
   177  	}
   178  	var asm []driver.Inst
   179  	d.Decode(start, end, nil, func(pc, size uint64, file string, line int, text string) {
   180  		asm = append(asm, driver.Inst{Addr: pc, File: file, Line: line, Text: text})
   181  	})
   182  	return asm, nil
   183  }
   184  
   185  func (t *objTool) cachedDisasm(file string) (*objfile.Disasm, error) {
   186  	t.mu.Lock()
   187  	defer t.mu.Unlock()
   188  	if t.disasmCache == nil {
   189  		t.disasmCache = make(map[string]*objfile.Disasm)
   190  	}
   191  	d := t.disasmCache[file]
   192  	if d != nil {
   193  		return d, nil
   194  	}
   195  	f, err := objfile.Open(file)
   196  	if err != nil {
   197  		return nil, err
   198  	}
   199  	d, err = f.Disasm()
   200  	f.Close()
   201  	if err != nil {
   202  		return nil, err
   203  	}
   204  	t.disasmCache[file] = d
   205  	return d, nil
   206  }
   207  
   208  func (*objTool) SetConfig(config string) {
   209  	// config is usually used to say what binaries to invoke.
   210  	// Ignore entirely.
   211  }
   212  
   213  // file implements driver.ObjFile using Go libraries
   214  // (instead of invoking GNU binutils).
   215  // A file represents a single executable being analyzed.
   216  type file struct {
   217  	name   string
   218  	offset uint64
   219  	sym    []objfile.Sym
   220  	file   *objfile.File
   221  	pcln   objfile.Liner
   222  
   223  	triedDwarf bool
   224  	dwarf      *dwarf.Data
   225  }
   226  
   227  func (f *file) Name() string {
   228  	return f.name
   229  }
   230  
   231  func (f *file) Base() uint64 {
   232  	// No support for shared libraries.
   233  	return 0
   234  }
   235  
   236  func (f *file) BuildID() string {
   237  	// No support for build ID.
   238  	return ""
   239  }
   240  
   241  func (f *file) SourceLine(addr uint64) ([]driver.Frame, error) {
   242  	if f.pcln == nil {
   243  		pcln, err := f.file.PCLineTable()
   244  		if err != nil {
   245  			return nil, err
   246  		}
   247  		f.pcln = pcln
   248  	}
   249  	addr -= f.offset
   250  	file, line, fn := f.pcln.PCToLine(addr)
   251  	if fn != nil {
   252  		frame := []driver.Frame{
   253  			{
   254  				Func: fn.Name,
   255  				File: file,
   256  				Line: line,
   257  			},
   258  		}
   259  		return frame, nil
   260  	}
   261  
   262  	frames := f.dwarfSourceLine(addr)
   263  	if frames != nil {
   264  		return frames, nil
   265  	}
   266  
   267  	return nil, fmt.Errorf("no line information for PC=%#x", addr)
   268  }
   269  
   270  // dwarfSourceLine tries to get file/line information using DWARF.
   271  // This is for C functions that appear in the profile.
   272  // Returns nil if there is no information available.
   273  func (f *file) dwarfSourceLine(addr uint64) []driver.Frame {
   274  	if f.dwarf == nil && !f.triedDwarf {
   275  		// Ignore any error--we don't care exactly why there
   276  		// is no DWARF info.
   277  		f.dwarf, _ = f.file.DWARF()
   278  		f.triedDwarf = true
   279  	}
   280  
   281  	if f.dwarf != nil {
   282  		r := f.dwarf.Reader()
   283  		unit, err := r.SeekPC(addr)
   284  		if err == nil {
   285  			if frames := f.dwarfSourceLineEntry(r, unit, addr); frames != nil {
   286  				return frames
   287  			}
   288  		}
   289  	}
   290  
   291  	return nil
   292  }
   293  
   294  // dwarfSourceLineEntry tries to get file/line information from a
   295  // DWARF compilation unit. Returns nil if it doesn't find anything.
   296  func (f *file) dwarfSourceLineEntry(r *dwarf.Reader, entry *dwarf.Entry, addr uint64) []driver.Frame {
   297  	lines, err := f.dwarf.LineReader(entry)
   298  	if err != nil {
   299  		return nil
   300  	}
   301  	var lentry dwarf.LineEntry
   302  	if err := lines.SeekPC(addr, &lentry); err != nil {
   303  		return nil
   304  	}
   305  
   306  	// Try to find the function name.
   307  	name := ""
   308  FindName:
   309  	for entry, err := r.Next(); entry != nil && err == nil; entry, err = r.Next() {
   310  		if entry.Tag == dwarf.TagSubprogram {
   311  			ranges, err := f.dwarf.Ranges(entry)
   312  			if err != nil {
   313  				return nil
   314  			}
   315  			for _, pcs := range ranges {
   316  				if pcs[0] <= addr && addr < pcs[1] {
   317  					var ok bool
   318  					// TODO: AT_linkage_name, AT_MIPS_linkage_name.
   319  					name, ok = entry.Val(dwarf.AttrName).(string)
   320  					if ok {
   321  						break FindName
   322  					}
   323  				}
   324  			}
   325  		}
   326  	}
   327  
   328  	// TODO: Report inlined functions.
   329  
   330  	frames := []driver.Frame{
   331  		{
   332  			Func: name,
   333  			File: lentry.File.Name,
   334  			Line: lentry.Line,
   335  		},
   336  	}
   337  
   338  	return frames
   339  }
   340  
   341  func (f *file) Symbols(r *regexp.Regexp, addr uint64) ([]*driver.Sym, error) {
   342  	if f.sym == nil {
   343  		sym, err := f.file.Symbols()
   344  		if err != nil {
   345  			return nil, err
   346  		}
   347  		f.sym = sym
   348  	}
   349  	var out []*driver.Sym
   350  	for _, s := range f.sym {
   351  		// Ignore a symbol with address 0 and size 0.
   352  		// An ELF STT_FILE symbol will look like that.
   353  		if s.Addr == 0 && s.Size == 0 {
   354  			continue
   355  		}
   356  		if (r == nil || r.MatchString(s.Name)) && (addr == 0 || s.Addr <= addr && addr < s.Addr+uint64(s.Size)) {
   357  			out = append(out, &driver.Sym{
   358  				Name:  []string{s.Name},
   359  				File:  f.name,
   360  				Start: s.Addr,
   361  				End:   s.Addr + uint64(s.Size) - 1,
   362  			})
   363  		}
   364  	}
   365  	return out, nil
   366  }
   367  
   368  func (f *file) Close() error {
   369  	f.file.Close()
   370  	return nil
   371  }
   372  

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