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  	"flag"
    16  	"fmt"
    17  	"io"
    18  	"net/http"
    19  	"net/url"
    20  	"os"
    21  	"regexp"
    22  	"strconv"
    23  	"strings"
    24  	"sync"
    25  	"time"
    26  
    27  	"cmd/internal/objfile"
    28  	"cmd/internal/telemetry/counter"
    29  
    30  	"github.com/google/pprof/driver"
    31  	"github.com/google/pprof/profile"
    32  )
    33  
    34  func main() {
    35  	counter.Open()
    36  	counter.Inc("pprof/invocations")
    37  	options := &driver.Options{
    38  		Fetch: new(fetcher),
    39  		Obj:   new(objTool),
    40  		UI:    newUI(),
    41  	}
    42  	err := driver.PProf(options)
    43  	counter.CountFlags("pprof/flag:", *flag.CommandLine) // pprof will use the flag package as its default
    44  	if err != nil {
    45  		fmt.Fprintf(os.Stderr, "%v\n", err)
    46  		os.Exit(2)
    47  	}
    48  }
    49  
    50  type fetcher struct {
    51  }
    52  
    53  func (f *fetcher) Fetch(src string, duration, timeout time.Duration) (*profile.Profile, string, error) {
    54  	// Firstly, determine if the src is an existing file on the disk.
    55  	// If it is a file, let regular pprof open it.
    56  	// If it is not a file, when the src contains `:`
    57  	// (e.g. mem_2023-11-02_03:55:24 or abc:123/mem_2023-11-02_03:55:24),
    58  	// url.Parse will recognize it as a link and ultimately report an error,
    59  	// similar to `abc:123/mem_2023-11-02_03:55:24:
    60  	// Get "http://abc:123/mem_2023-11-02_03:55:24": dial tcp: lookup abc: no such host`
    61  	if _, openErr := os.Stat(src); openErr == nil {
    62  		return nil, "", nil
    63  	}
    64  	sourceURL, timeout := adjustURL(src, duration, timeout)
    65  	if sourceURL == "" {
    66  		// Could not recognize URL, let regular pprof attempt to fetch the profile (eg. from a file)
    67  		return nil, "", nil
    68  	}
    69  	fmt.Fprintln(os.Stderr, "Fetching profile over HTTP from", sourceURL)
    70  	if duration > 0 {
    71  		fmt.Fprintf(os.Stderr, "Please wait... (%v)\n", duration)
    72  	}
    73  	p, err := getProfile(sourceURL, timeout)
    74  	return p, sourceURL, err
    75  }
    76  
    77  func getProfile(source string, timeout time.Duration) (*profile.Profile, error) {
    78  	url, err := url.Parse(source)
    79  	if err != nil {
    80  		return nil, err
    81  	}
    82  
    83  	var tlsConfig *tls.Config
    84  	if url.Scheme == "https+insecure" {
    85  		tlsConfig = &tls.Config{
    86  			InsecureSkipVerify: true,
    87  		}
    88  		url.Scheme = "https"
    89  		source = url.String()
    90  	}
    91  
    92  	client := &http.Client{
    93  		Transport: &http.Transport{
    94  			ResponseHeaderTimeout: timeout + 5*time.Second,
    95  			Proxy:                 http.ProxyFromEnvironment,
    96  			TLSClientConfig:       tlsConfig,
    97  		},
    98  	}
    99  	resp, err := client.Get(source)
   100  	if err != nil {
   101  		return nil, err
   102  	}
   103  	defer resp.Body.Close()
   104  	if resp.StatusCode != http.StatusOK {
   105  		return nil, statusCodeError(resp)
   106  	}
   107  	return profile.Parse(resp.Body)
   108  }
   109  
   110  func statusCodeError(resp *http.Response) error {
   111  	if resp.Header.Get("X-Go-Pprof") != "" && strings.Contains(resp.Header.Get("Content-Type"), "text/plain") {
   112  		// error is from pprof endpoint
   113  		if body, err := io.ReadAll(resp.Body); err == nil {
   114  			return fmt.Errorf("server response: %s - %s", resp.Status, body)
   115  		}
   116  	}
   117  	return fmt.Errorf("server response: %s", resp.Status)
   118  }
   119  
   120  // cpuProfileHandler is the Go pprof CPU profile handler URL.
   121  const cpuProfileHandler = "/debug/pprof/profile"
   122  
   123  // adjustURL applies the duration/timeout values and Go specific defaults.
   124  func adjustURL(source string, duration, timeout time.Duration) (string, time.Duration) {
   125  	u, err := url.Parse(source)
   126  	if err != nil || (u.Host == "" && u.Scheme != "" && u.Scheme != "file") {
   127  		// Try adding http:// to catch sources of the form hostname:port/path.
   128  		// url.Parse treats "hostname" as the scheme.
   129  		u, err = url.Parse("http://" + source)
   130  	}
   131  	if err != nil || u.Host == "" {
   132  		return "", 0
   133  	}
   134  
   135  	if u.Path == "" || u.Path == "/" {
   136  		u.Path = cpuProfileHandler
   137  	}
   138  
   139  	// Apply duration/timeout overrides to URL.
   140  	values := u.Query()
   141  	if duration > 0 {
   142  		values.Set("seconds", fmt.Sprint(int(duration.Seconds())))
   143  	} else {
   144  		if urlSeconds := values.Get("seconds"); urlSeconds != "" {
   145  			if us, err := strconv.ParseInt(urlSeconds, 10, 32); err == nil {
   146  				duration = time.Duration(us) * time.Second
   147  			}
   148  		}
   149  	}
   150  	if timeout <= 0 {
   151  		if duration > 0 {
   152  			timeout = duration + duration/2
   153  		} else {
   154  			timeout = 60 * time.Second
   155  		}
   156  	}
   157  	u.RawQuery = values.Encode()
   158  	return u.String(), timeout
   159  }
   160  
   161  // objTool implements driver.ObjTool using Go libraries
   162  // (instead of invoking GNU binutils).
   163  type objTool struct {
   164  	mu          sync.Mutex
   165  	disasmCache map[string]*objfile.Disasm
   166  }
   167  
   168  func (*objTool) Open(name string, start, limit, offset uint64, relocationSymbol string) (driver.ObjFile, error) {
   169  	of, err := objfile.Open(name)
   170  	if err != nil {
   171  		return nil, err
   172  	}
   173  	f := &file{
   174  		name: name,
   175  		file: of,
   176  	}
   177  	if start != 0 {
   178  		if load, err := of.LoadAddress(); err == nil {
   179  			f.offset = start - load
   180  		}
   181  	}
   182  	return f, nil
   183  }
   184  
   185  func (*objTool) Demangle(names []string) (map[string]string, error) {
   186  	// No C++, nothing to demangle.
   187  	return make(map[string]string), nil
   188  }
   189  
   190  func (t *objTool) Disasm(file string, start, end uint64, intelSyntax bool) ([]driver.Inst, error) {
   191  	if intelSyntax {
   192  		return nil, fmt.Errorf("printing assembly in Intel syntax is not supported")
   193  	}
   194  	d, err := t.cachedDisasm(file)
   195  	if err != nil {
   196  		return nil, err
   197  	}
   198  	var asm []driver.Inst
   199  	d.Decode(start, end, nil, false, func(pc, size uint64, file string, line int, text string) {
   200  		asm = append(asm, driver.Inst{Addr: pc, File: file, Line: line, Text: text})
   201  	})
   202  	return asm, nil
   203  }
   204  
   205  func (t *objTool) cachedDisasm(file string) (*objfile.Disasm, error) {
   206  	t.mu.Lock()
   207  	defer t.mu.Unlock()
   208  	if t.disasmCache == nil {
   209  		t.disasmCache = make(map[string]*objfile.Disasm)
   210  	}
   211  	d := t.disasmCache[file]
   212  	if d != nil {
   213  		return d, nil
   214  	}
   215  	f, err := objfile.Open(file)
   216  	if err != nil {
   217  		return nil, err
   218  	}
   219  	d, err = f.Disasm()
   220  	f.Close()
   221  	if err != nil {
   222  		return nil, err
   223  	}
   224  	t.disasmCache[file] = d
   225  	return d, nil
   226  }
   227  
   228  func (*objTool) SetConfig(config string) {
   229  	// config is usually used to say what binaries to invoke.
   230  	// Ignore entirely.
   231  }
   232  
   233  // file implements driver.ObjFile using Go libraries
   234  // (instead of invoking GNU binutils).
   235  // A file represents a single executable being analyzed.
   236  type file struct {
   237  	name   string
   238  	offset uint64
   239  	sym    []objfile.Sym
   240  	file   *objfile.File
   241  	pcln   objfile.Liner
   242  
   243  	triedDwarf bool
   244  	dwarf      *dwarf.Data
   245  }
   246  
   247  func (f *file) Name() string {
   248  	return f.name
   249  }
   250  
   251  func (f *file) ObjAddr(addr uint64) (uint64, error) {
   252  	return addr - f.offset, nil
   253  }
   254  
   255  func (f *file) BuildID() string {
   256  	// No support for build ID.
   257  	return ""
   258  }
   259  
   260  func (f *file) SourceLine(addr uint64) ([]driver.Frame, error) {
   261  	if f.pcln == nil {
   262  		pcln, err := f.file.PCLineTable()
   263  		if err != nil {
   264  			return nil, err
   265  		}
   266  		f.pcln = pcln
   267  	}
   268  	addr -= f.offset
   269  	file, line, fn := f.pcln.PCToLine(addr)
   270  	if fn != nil {
   271  		frame := []driver.Frame{
   272  			{
   273  				Func: fn.Name,
   274  				File: file,
   275  				Line: line,
   276  			},
   277  		}
   278  		return frame, nil
   279  	}
   280  
   281  	frames := f.dwarfSourceLine(addr)
   282  	if frames != nil {
   283  		return frames, nil
   284  	}
   285  
   286  	return nil, fmt.Errorf("no line information for PC=%#x", addr)
   287  }
   288  
   289  // dwarfSourceLine tries to get file/line information using DWARF.
   290  // This is for C functions that appear in the profile.
   291  // Returns nil if there is no information available.
   292  func (f *file) dwarfSourceLine(addr uint64) []driver.Frame {
   293  	if f.dwarf == nil && !f.triedDwarf {
   294  		// Ignore any error--we don't care exactly why there
   295  		// is no DWARF info.
   296  		f.dwarf, _ = f.file.DWARF()
   297  		f.triedDwarf = true
   298  	}
   299  
   300  	if f.dwarf != nil {
   301  		r := f.dwarf.Reader()
   302  		unit, err := r.SeekPC(addr)
   303  		if err == nil {
   304  			if frames := f.dwarfSourceLineEntry(r, unit, addr); frames != nil {
   305  				return frames
   306  			}
   307  		}
   308  	}
   309  
   310  	return nil
   311  }
   312  
   313  // dwarfSourceLineEntry tries to get file/line information from a
   314  // DWARF compilation unit. Returns nil if it doesn't find anything.
   315  func (f *file) dwarfSourceLineEntry(r *dwarf.Reader, entry *dwarf.Entry, addr uint64) []driver.Frame {
   316  	lines, err := f.dwarf.LineReader(entry)
   317  	if err != nil {
   318  		return nil
   319  	}
   320  	var lentry dwarf.LineEntry
   321  	if err := lines.SeekPC(addr, &lentry); err != nil {
   322  		return nil
   323  	}
   324  
   325  	// Try to find the function name.
   326  	name := ""
   327  FindName:
   328  	for entry, err := r.Next(); entry != nil && err == nil; entry, err = r.Next() {
   329  		if entry.Tag == dwarf.TagSubprogram {
   330  			ranges, err := f.dwarf.Ranges(entry)
   331  			if err != nil {
   332  				return nil
   333  			}
   334  			for _, pcs := range ranges {
   335  				if pcs[0] <= addr && addr < pcs[1] {
   336  					var ok bool
   337  					// TODO: AT_linkage_name, AT_MIPS_linkage_name.
   338  					name, ok = entry.Val(dwarf.AttrName).(string)
   339  					if ok {
   340  						break FindName
   341  					}
   342  				}
   343  			}
   344  		}
   345  	}
   346  
   347  	// TODO: Report inlined functions.
   348  
   349  	frames := []driver.Frame{
   350  		{
   351  			Func: name,
   352  			File: lentry.File.Name,
   353  			Line: lentry.Line,
   354  		},
   355  	}
   356  
   357  	return frames
   358  }
   359  
   360  func (f *file) Symbols(r *regexp.Regexp, addr uint64) ([]*driver.Sym, error) {
   361  	if f.sym == nil {
   362  		sym, err := f.file.Symbols()
   363  		if err != nil {
   364  			return nil, err
   365  		}
   366  		f.sym = sym
   367  	}
   368  	var out []*driver.Sym
   369  	for _, s := range f.sym {
   370  		// Ignore a symbol with address 0 and size 0.
   371  		// An ELF STT_FILE symbol will look like that.
   372  		if s.Addr == 0 && s.Size == 0 {
   373  			continue
   374  		}
   375  		if (r == nil || r.MatchString(s.Name)) && (addr == 0 || s.Addr <= addr && addr < s.Addr+uint64(s.Size)) {
   376  			out = append(out, &driver.Sym{
   377  				Name:  []string{s.Name},
   378  				File:  f.name,
   379  				Start: s.Addr,
   380  				End:   s.Addr + uint64(s.Size) - 1,
   381  			})
   382  		}
   383  	}
   384  	return out, nil
   385  }
   386  
   387  func (f *file) Close() error {
   388  	f.file.Close()
   389  	return nil
   390  }
   391  
   392  // newUI will be set in readlineui.go in some platforms
   393  // for interactive readline functionality.
   394  var newUI = func() driver.UI { return nil }
   395
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