addr2liner_llvm.go

     1  // Copyright 2014 Google Inc. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package binutils
    16  
    17  import (
    18  	"bufio"
    19  	"fmt"
    20  	"io"
    21  	"os/exec"
    22  	"strconv"
    23  	"strings"
    24  	"sync"
    25  
    26  	"github.com/google/pprof/internal/plugin"
    27  )
    28  
    29  const (
    30  	defaultLLVMSymbolizer = "llvm-symbolizer"
    31  )
    32  
    33  // llvmSymbolizer is a connection to an llvm-symbolizer command for
    34  // obtaining address and line number information from a binary.
    35  type llvmSymbolizer struct {
    36  	sync.Mutex
    37  	filename string
    38  	rw       lineReaderWriter
    39  	base     uint64
    40  }
    41  
    42  type llvmSymbolizerJob struct {
    43  	cmd *exec.Cmd
    44  	in  io.WriteCloser
    45  	out *bufio.Reader
    46  	// llvm-symbolizer requires the symbol type, CODE or DATA, for symbolization.
    47  	symType string
    48  }
    49  
    50  func (a *llvmSymbolizerJob) write(s string) error {
    51  	_, err := fmt.Fprintln(a.in, a.symType, s)
    52  	return err
    53  }
    54  
    55  func (a *llvmSymbolizerJob) readLine() (string, error) {
    56  	s, err := a.out.ReadString('\n')
    57  	if err != nil {
    58  		return "", err
    59  	}
    60  	return strings.TrimSpace(s), nil
    61  }
    62  
    63  // close releases any resources used by the llvmSymbolizer object.
    64  func (a *llvmSymbolizerJob) close() {
    65  	a.in.Close()
    66  	a.cmd.Wait()
    67  }
    68  
    69  // newLLVMSymbolizer starts the given llvmSymbolizer command reporting
    70  // information about the given executable file. If file is a shared
    71  // library, base should be the address at which it was mapped in the
    72  // program under consideration.
    73  func newLLVMSymbolizer(cmd, file string, base uint64, isData bool) (*llvmSymbolizer, error) {
    74  	if cmd == "" {
    75  		cmd = defaultLLVMSymbolizer
    76  	}
    77  
    78  	j := &llvmSymbolizerJob{
    79  		cmd:     exec.Command(cmd, "--inlining", "-demangle=false"),
    80  		symType: "CODE",
    81  	}
    82  	if isData {
    83  		j.symType = "DATA"
    84  	}
    85  
    86  	var err error
    87  	if j.in, err = j.cmd.StdinPipe(); err != nil {
    88  		return nil, err
    89  	}
    90  
    91  	outPipe, err := j.cmd.StdoutPipe()
    92  	if err != nil {
    93  		return nil, err
    94  	}
    95  
    96  	j.out = bufio.NewReader(outPipe)
    97  	if err := j.cmd.Start(); err != nil {
    98  		return nil, err
    99  	}
   100  
   101  	a := &llvmSymbolizer{
   102  		filename: file,
   103  		rw:       j,
   104  		base:     base,
   105  	}
   106  
   107  	return a, nil
   108  }
   109  
   110  // readFrame parses the llvm-symbolizer output for a single address. It
   111  // returns a populated plugin.Frame and whether it has reached the end of the
   112  // data.
   113  func (d *llvmSymbolizer) readFrame() (plugin.Frame, bool) {
   114  	funcname, err := d.rw.readLine()
   115  	if err != nil {
   116  		return plugin.Frame{}, true
   117  	}
   118  
   119  	switch funcname {
   120  	case "":
   121  		return plugin.Frame{}, true
   122  	case "??":
   123  		funcname = ""
   124  	}
   125  
   126  	fileline, err := d.rw.readLine()
   127  	if err != nil {
   128  		return plugin.Frame{Func: funcname}, true
   129  	}
   130  
   131  	linenumber := 0
   132  	// The llvm-symbolizer outputs the <file_name>:<line_number>:<column_number>.
   133  	// When it cannot identify the source code location, it outputs "??:0:0".
   134  	// Older versions output just the filename and line number, so we check for
   135  	// both conditions here.
   136  	if fileline == "??:0" || fileline == "??:0:0" {
   137  		fileline = ""
   138  	} else {
   139  		switch split := strings.Split(fileline, ":"); len(split) {
   140  		case 1:
   141  			// filename
   142  			fileline = split[0]
   143  		case 2, 3:
   144  			// filename:line , or
   145  			// filename:line:disc , or
   146  			fileline = split[0]
   147  			if line, err := strconv.Atoi(split[1]); err == nil {
   148  				linenumber = line
   149  			}
   150  		default:
   151  			// Unrecognized, ignore
   152  		}
   153  	}
   154  
   155  	return plugin.Frame{Func: funcname, File: fileline, Line: linenumber}, false
   156  }
   157  
   158  // addrInfo returns the stack frame information for a specific program
   159  // address. It returns nil if the address could not be identified.
   160  func (d *llvmSymbolizer) addrInfo(addr uint64) ([]plugin.Frame, error) {
   161  	d.Lock()
   162  	defer d.Unlock()
   163  
   164  	if err := d.rw.write(fmt.Sprintf("%s 0x%x", d.filename, addr-d.base)); err != nil {
   165  		return nil, err
   166  	}
   167  
   168  	var stack []plugin.Frame
   169  	for {
   170  		frame, end := d.readFrame()
   171  		if end {
   172  			break
   173  		}
   174  
   175  		if frame != (plugin.Frame{}) {
   176  			stack = append(stack, frame)
   177  		}
   178  	}
   179  
   180  	return stack, nil
   181  }
   182
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