disasm.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  	"bytes"
    19  	"io"
    20  	"regexp"
    21  	"strconv"
    22  	"strings"
    23  
    24  	"github.com/google/pprof/internal/plugin"
    25  	"github.com/ianlancetaylor/demangle"
    26  )
    27  
    28  var (
    29  	nmOutputRE                = regexp.MustCompile(`^\s*([[:xdigit:]]+)\s+(.)\s+(.*)`)
    30  	objdumpAsmOutputRE        = regexp.MustCompile(`^\s*([[:xdigit:]]+):\s+(.*)`)
    31  	objdumpOutputFileLine     = regexp.MustCompile(`^;?\s?(.*):([0-9]+)`)
    32  	objdumpOutputFunction     = regexp.MustCompile(`^;?\s?(\S.*)\(\):`)
    33  	objdumpOutputFunctionLLVM = regexp.MustCompile(`^([[:xdigit:]]+)?\s?(.*):`)
    34  )
    35  
    36  func findSymbols(syms []byte, file string, r *regexp.Regexp, address uint64) ([]*plugin.Sym, error) {
    37  	// Collect all symbols from the nm output, grouping names mapped to
    38  	// the same address into a single symbol.
    39  
    40  	// The symbols to return.
    41  	var symbols []*plugin.Sym
    42  
    43  	// The current group of symbol names, and the address they are all at.
    44  	names, start := []string{}, uint64(0)
    45  
    46  	buf := bytes.NewBuffer(syms)
    47  
    48  	for {
    49  		symAddr, name, err := nextSymbol(buf)
    50  		if err == io.EOF {
    51  			// Done. If there was an unfinished group, append it.
    52  			if len(names) != 0 {
    53  				if match := matchSymbol(names, start, symAddr-1, r, address); match != nil {
    54  					symbols = append(symbols, &plugin.Sym{Name: match, File: file, Start: start, End: symAddr - 1})
    55  				}
    56  			}
    57  
    58  			// And return the symbols.
    59  			return symbols, nil
    60  		}
    61  
    62  		if err != nil {
    63  			// There was some kind of serious error reading nm's output.
    64  			return nil, err
    65  		}
    66  
    67  		// If this symbol is at the same address as the current group, add it to the group.
    68  		if symAddr == start {
    69  			names = append(names, name)
    70  			continue
    71  		}
    72  
    73  		// Otherwise append the current group to the list of symbols.
    74  		if match := matchSymbol(names, start, symAddr-1, r, address); match != nil {
    75  			symbols = append(symbols, &plugin.Sym{Name: match, File: file, Start: start, End: symAddr - 1})
    76  		}
    77  
    78  		// And start a new group.
    79  		names, start = []string{name}, symAddr
    80  	}
    81  }
    82  
    83  // matchSymbol checks if a symbol is to be selected by checking its
    84  // name to the regexp and optionally its address. It returns the name(s)
    85  // to be used for the matched symbol, or nil if no match
    86  func matchSymbol(names []string, start, end uint64, r *regexp.Regexp, address uint64) []string {
    87  	if address != 0 && address >= start && address <= end {
    88  		return names
    89  	}
    90  	for _, name := range names {
    91  		if r == nil || r.MatchString(name) {
    92  			return []string{name}
    93  		}
    94  
    95  		// Match all possible demangled versions of the name.
    96  		for _, o := range [][]demangle.Option{
    97  			{demangle.NoClones},
    98  			{demangle.NoParams},
    99  			{demangle.NoParams, demangle.NoTemplateParams},
   100  		} {
   101  			if demangled, err := demangle.ToString(name, o...); err == nil && r.MatchString(demangled) {
   102  				return []string{demangled}
   103  			}
   104  		}
   105  	}
   106  	return nil
   107  }
   108  
   109  // disassemble parses the output of the objdump command and returns
   110  // the assembly instructions in a slice.
   111  func disassemble(asm []byte) ([]plugin.Inst, error) {
   112  	buf := bytes.NewBuffer(asm)
   113  	function, file, line := "", "", 0
   114  	var assembly []plugin.Inst
   115  	for {
   116  		input, err := buf.ReadString('\n')
   117  		if err != nil {
   118  			if err != io.EOF {
   119  				return nil, err
   120  			}
   121  			if input == "" {
   122  				break
   123  			}
   124  		}
   125  		input = strings.TrimSpace(input)
   126  
   127  		if fields := objdumpAsmOutputRE.FindStringSubmatch(input); len(fields) == 3 {
   128  			if address, err := strconv.ParseUint(fields[1], 16, 64); err == nil {
   129  				assembly = append(assembly,
   130  					plugin.Inst{
   131  						Addr:     address,
   132  						Text:     fields[2],
   133  						Function: function,
   134  						File:     file,
   135  						Line:     line,
   136  					})
   137  				continue
   138  			}
   139  		}
   140  		if fields := objdumpOutputFileLine.FindStringSubmatch(input); len(fields) == 3 {
   141  			if l, err := strconv.ParseUint(fields[2], 10, 32); err == nil {
   142  				file, line = fields[1], int(l)
   143  			}
   144  			continue
   145  		}
   146  		if fields := objdumpOutputFunction.FindStringSubmatch(input); len(fields) == 2 {
   147  			function = fields[1]
   148  			continue
   149  		} else {
   150  			if fields := objdumpOutputFunctionLLVM.FindStringSubmatch(input); len(fields) == 3 {
   151  				function = fields[2]
   152  				continue
   153  			}
   154  		}
   155  		// Reset on unrecognized lines.
   156  		function, file, line = "", "", 0
   157  	}
   158  
   159  	return assembly, nil
   160  }
   161  
   162  // nextSymbol parses the nm output to find the next symbol listed.
   163  // Skips over any output it cannot recognize.
   164  func nextSymbol(buf *bytes.Buffer) (uint64, string, error) {
   165  	for {
   166  		line, err := buf.ReadString('\n')
   167  		if err != nil {
   168  			if err != io.EOF || line == "" {
   169  				return 0, "", err
   170  			}
   171  		}
   172  		line = strings.TrimSpace(line)
   173  
   174  		if fields := nmOutputRE.FindStringSubmatch(line); len(fields) == 4 {
   175  			if address, err := strconv.ParseUint(fields[1], 16, 64); err == nil {
   176  				return address, fields[3], nil
   177  			}
   178  		}
   179  	}
   180  }
   181
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