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// 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 binutils
import (
"bufio"
"bytes"
"io"
"os/exec"
"strconv"
"strings"
"github.com/google/pprof/internal/plugin"
)
const (
defaultNM = "nm"
)
// addr2LinerNM is a connection to an nm command for obtaining address
// information from a binary.
type addr2LinerNM struct {
m []symbolInfo // Sorted list of addresses from binary.
}
type symbolInfo struct {
address uint64
name string
}
// newAddr2LinerNM starts the given nm command reporting information about the
// given executable file. If file is a shared library, base should be
// the address at which it was mapped in the program under
// consideration.
func newAddr2LinerNM(cmd, file string, base uint64) (*addr2LinerNM, error) {
if cmd == "" {
cmd = defaultNM
}
var b bytes.Buffer
c := exec.Command(cmd, "-n", file)
c.Stdout = &b
if err := c.Run(); err != nil {
return nil, err
}
return parseAddr2LinerNM(base, &b)
}
func parseAddr2LinerNM(base uint64, nm io.Reader) (*addr2LinerNM, error) {
a := &addr2LinerNM{
m: []symbolInfo{},
}
// Parse nm output and populate symbol map.
// Skip lines we fail to parse.
buf := bufio.NewReader(nm)
for {
line, err := buf.ReadString('\n')
if line == "" && err != nil {
if err == io.EOF {
break
}
return nil, err
}
line = strings.TrimSpace(line)
fields := strings.SplitN(line, " ", 3)
if len(fields) != 3 {
continue
}
address, err := strconv.ParseUint(fields[0], 16, 64)
if err != nil {
continue
}
a.m = append(a.m, symbolInfo{
address: address + base,
name: fields[2],
})
}
return a, nil
}
// addrInfo returns the stack frame information for a specific program
// address. It returns nil if the address could not be identified.
func (a *addr2LinerNM) addrInfo(addr uint64) ([]plugin.Frame, error) {
if len(a.m) == 0 || addr < a.m[0].address || addr > a.m[len(a.m)-1].address {
return nil, nil
}
// Binary search. Search until low, high are separated by 1.
low, high := 0, len(a.m)
for low+1 < high {
mid := (low + high) / 2
v := a.m[mid].address
if addr == v {
low = mid
break
} else if addr > v {
low = mid
} else {
high = mid
}
}
// Address is between a.m[low] and a.m[high].
// Pick low, as it represents [low, high).
f := []plugin.Frame{
{
Func: a.m[low].name,
},
}
return f, nil
}
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