forked from cilium/cilium
/
elf.go
152 lines (140 loc) · 4.24 KB
/
elf.go
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// Copyright (c) 2009 The Go Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
package alignchecker
import (
"bytes"
"compress/zlib"
"debug/dwarf"
"debug/elf"
"encoding/binary"
"fmt"
"io"
"strings"
)
// Adopted from elf.File.DWARF
// https://github.com/golang/go/blob/master/src/debug/elf/file.go (go1.11.2).
//
// The former method function tries to apply relocations when extracting DWARF
// debug sections. Unfortunately, the relocations are not implemented for EM_BPF,
// so the method fails.
//
// For struct alignment checks, no relocations are needed, so we comment out
// the relocation bits.
//
// NOTE: DO NOT USE THE FUNCTION FOR ANYTHING ELSE!
func getDWARFFromELF(f *elf.File) (*dwarf.Data, error) {
dwarfSuffix := func(s *elf.Section) string {
switch {
case strings.HasPrefix(s.Name, ".debug_"):
return s.Name[7:]
case strings.HasPrefix(s.Name, ".zdebug_"):
return s.Name[8:]
default:
return ""
}
}
// sectionData gets the data for s, checks its size, and
// applies any applicable relations.
sectionData := func(i int, s *elf.Section) ([]byte, error) {
b, err := s.Data()
if err != nil && uint64(len(b)) < s.Size {
return nil, err
}
if len(b) >= 12 && string(b[:4]) == "ZLIB" {
dlen := binary.BigEndian.Uint64(b[4:12])
dbuf := make([]byte, dlen)
r, err := zlib.NewReader(bytes.NewBuffer(b[12:]))
if err != nil {
return nil, err
}
if _, err := io.ReadFull(r, dbuf); err != nil {
return nil, err
}
if err := r.Close(); err != nil {
return nil, err
}
b = dbuf
}
for _, r := range f.Sections {
if r.Type != elf.SHT_RELA && r.Type != elf.SHT_REL {
continue
}
if int(r.Info) != i {
continue
}
//rd, err := r.Data()
_, err := r.Data()
if err != nil {
return nil, err
}
// err = f.applyRelocations(b, rd)
// if err != nil {
// return nil, err
// }
}
return b, nil
}
// There are many other DWARF sections, but these
// are the ones the debug/dwarf package uses.
// Don't bother loading others.
var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil, "ranges": nil}
for i, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix == "" {
continue
}
if _, ok := dat[suffix]; !ok {
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
dat[suffix] = b
}
d, err := dwarf.New(dat["abbrev"], nil, nil, dat["info"], dat["line"], nil, dat["ranges"], dat["str"])
if err != nil {
return nil, err
}
// Look for DWARF4 .debug_types sections.
for i, s := range f.Sections {
suffix := dwarfSuffix(s)
if suffix != "types" {
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
err = d.AddTypes(fmt.Sprintf("types-%d", i), b)
if err != nil {
return nil, err
}
}
return d, nil
}