ref: 2bbc75bddc6f2a07056ff017108e35f14061041b
dir: /third_party/boringssl/src/util/read_symbols.go/
// Copyright (c) 2018, Google Inc.
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
// read_symbols scans one or more .a files and, for each object contained in
// the .a files, reads the list of symbols in that object file.
package main
import (
"bytes"
"debug/elf"
"debug/macho"
"debug/pe"
"flag"
"fmt"
"os"
"runtime"
"sort"
"strings"
"boringssl.googlesource.com/boringssl/util/ar"
)
const (
ObjFileFormatELF = "elf"
ObjFileFormatMachO = "macho"
ObjFileFormatPE = "pe"
)
var (
outFlag = flag.String("out", "-", "File to write output symbols")
objFileFormat = flag.String("obj-file-format", defaultObjFileFormat(runtime.GOOS), "Object file format to expect (options are elf, macho, pe)")
)
func defaultObjFileFormat(goos string) string {
switch goos {
case "linux":
return ObjFileFormatELF
case "darwin":
return ObjFileFormatMachO
case "windows":
return ObjFileFormatPE
default:
// By returning a value here rather than panicking, the user can still
// cross-compile from an unsupported platform to a supported platform by
// overriding this default with a flag. If the user doesn't provide the
// flag, we will panic during flag parsing.
return "unsupported"
}
}
func printAndExit(format string, args ...interface{}) {
s := fmt.Sprintf(format, args...)
fmt.Fprintln(os.Stderr, s)
os.Exit(1)
}
func main() {
flag.Parse()
if flag.NArg() < 1 {
printAndExit("Usage: %s [-out OUT] [-obj-file-format FORMAT] ARCHIVE_FILE [ARCHIVE_FILE [...]]", os.Args[0])
}
archiveFiles := flag.Args()
out := os.Stdout
if *outFlag != "-" {
var err error
out, err = os.Create(*outFlag)
if err != nil {
printAndExit("Error opening %q: %s", *outFlag, err)
}
defer out.Close()
}
var symbols []string
// Only add first instance of any symbol; keep track of them in this map.
added := make(map[string]struct{})
for _, archive := range archiveFiles {
f, err := os.Open(archive)
if err != nil {
printAndExit("Error opening %s: %s", archive, err)
}
objectFiles, err := ar.ParseAR(f)
f.Close()
if err != nil {
printAndExit("Error parsing %s: %s", archive, err)
}
for name, contents := range objectFiles {
syms, err := listSymbols(contents)
if err != nil {
printAndExit("Error listing symbols from %q in %q: %s", name, archive, err)
}
for _, s := range syms {
if _, ok := added[s]; !ok {
added[s] = struct{}{}
symbols = append(symbols, s)
}
}
}
}
sort.Strings(symbols)
for _, s := range symbols {
var skipSymbols = []string{
// Inline functions, etc., from the compiler or language
// runtime will naturally end up in the library, to be
// deduplicated against other object files. Such symbols
// should not be prefixed. It is a limitation of this
// symbol-prefixing strategy that we cannot distinguish
// our own inline symbols (which should be prefixed)
// from the system's (which should not), so we skip known
// system symbols.
"__local_stdio_printf_options",
"__local_stdio_scanf_options",
"_vscprintf",
"_vscprintf_l",
"_vsscanf_l",
"_xmm",
"sscanf",
"vsnprintf",
// sdallocx is a weak symbol and intended to merge with
// the real one, if present.
"sdallocx",
}
var skip bool
for _, sym := range skipSymbols {
if sym == s {
skip = true
break
}
}
if skip || isCXXSymbol(s) || strings.HasPrefix(s, "__real@") || strings.HasPrefix(s, "__x86.get_pc_thunk.") {
continue
}
if _, err := fmt.Fprintln(out, s); err != nil {
printAndExit("Error writing to %s: %s", *outFlag, err)
}
}
}
func isCXXSymbol(s string) bool {
if *objFileFormat == ObjFileFormatPE {
return strings.HasPrefix(s, "?")
}
return strings.HasPrefix(s, "_Z")
}
// listSymbols lists the exported symbols from an object file.
func listSymbols(contents []byte) ([]string, error) {
switch *objFileFormat {
case ObjFileFormatELF:
return listSymbolsELF(contents)
case ObjFileFormatMachO:
return listSymbolsMachO(contents)
case ObjFileFormatPE:
return listSymbolsPE(contents)
default:
return nil, fmt.Errorf("unsupported object file format %q", *objFileFormat)
}
}
func listSymbolsELF(contents []byte) ([]string, error) {
f, err := elf.NewFile(bytes.NewReader(contents))
if err != nil {
return nil, err
}
syms, err := f.Symbols()
if err != nil {
return nil, err
}
var names []string
for _, sym := range syms {
// Only include exported, defined symbols
if elf.ST_BIND(sym.Info) != elf.STB_LOCAL && sym.Section != elf.SHN_UNDEF {
names = append(names, sym.Name)
}
}
return names, nil
}
func listSymbolsMachO(contents []byte) ([]string, error) {
f, err := macho.NewFile(bytes.NewReader(contents))
if err != nil {
return nil, err
}
if f.Symtab == nil {
return nil, nil
}
var names []string
for _, sym := range f.Symtab.Syms {
// Source: https://opensource.apple.com/source/xnu/xnu-3789.51.2/EXTERNAL_HEADERS/mach-o/nlist.h.auto.html
const (
N_PEXT uint8 = 0x10 // Private external symbol bit
N_EXT uint8 = 0x01 // External symbol bit, set for external symbols
N_TYPE uint8 = 0x0e // mask for the type bits
N_UNDF uint8 = 0x0 // undefined, n_sect == NO_SECT
N_ABS uint8 = 0x2 // absolute, n_sect == NO_SECT
N_SECT uint8 = 0xe // defined in section number n_sect
N_PBUD uint8 = 0xc // prebound undefined (defined in a dylib)
N_INDR uint8 = 0xa // indirect
)
// Only include exported, defined symbols.
if sym.Type&N_EXT != 0 && sym.Type&N_TYPE != N_UNDF {
if len(sym.Name) == 0 || sym.Name[0] != '_' {
return nil, fmt.Errorf("unexpected symbol without underscore prefix: %q", sym.Name)
}
names = append(names, sym.Name[1:])
}
}
return names, nil
}
func listSymbolsPE(contents []byte) ([]string, error) {
f, err := pe.NewFile(bytes.NewReader(contents))
if err != nil {
return nil, err
}
var ret []string
for _, sym := range f.Symbols {
const (
// https://docs.microsoft.com/en-us/windows/desktop/debug/pe-format#section-number-values
IMAGE_SYM_UNDEFINED = 0
// https://docs.microsoft.com/en-us/windows/desktop/debug/pe-format#storage-class
IMAGE_SYM_CLASS_EXTERNAL = 2
)
if sym.SectionNumber != IMAGE_SYM_UNDEFINED && sym.StorageClass == IMAGE_SYM_CLASS_EXTERNAL {
name := sym.Name
if f.Machine == pe.IMAGE_FILE_MACHINE_I386 {
// On 32-bit Windows, C symbols are decorated by calling
// convention.
// https://msdn.microsoft.com/en-us/library/56h2zst2.aspx#FormatC
if strings.HasPrefix(name, "_") || strings.HasPrefix(name, "@") {
// __cdecl, __stdcall, or __fastcall. Remove the prefix and
// suffix, if present.
name = name[1:]
if idx := strings.LastIndex(name, "@"); idx >= 0 {
name = name[:idx]
}
} else if idx := strings.LastIndex(name, "@@"); idx >= 0 {
// __vectorcall. Remove the suffix.
name = name[:idx]
}
}
ret = append(ret, name)
}
}
return ret, nil
}