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cmd/link: attempt to rationalize linkmode init

Browse Source 
This CL gives Linkmode a type, switches it to the standard flag
handling mechanism, and deduplicates some logic.

There is a semantic change in this CL. Previously if a link was
invoked explicitly with -linkmode=internal, any condition that forced
external linking would silently override this and use external
linking. Instead it now fails with a reason why. I believe this is an
improvement, but will change it back if there's disagreement.

Fixes #12848

Change-Id: Ic80e341fff65ecfdd2b6fdd6079674cc7210fc5f
Reviewed-on: https://go-review.googlesource.com/28971
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
David Crawshaw 2016-09-09 17:34:07 -04:00
parent 1df438f79c
commit 6007c8c76b
13 changed files with 250 additions and 338 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
src/cmd/link/internal/amd64/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -84,34 +83,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hdarwin,
obj.Hdragonfly,
obj.Hfreebsd,
obj.Hlinux,
obj.Hnacl,
obj.Hnetbsd,
obj.Hopenbsd,
obj.Hsolaris,
obj.Hwindows,
obj.Hwindowsgui:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

23
src/cmd/link/internal/arm/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -79,28 +78,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hlinux,
obj.Hfreebsd,
obj.Hnacl,
obj.Hdarwin:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

24
src/cmd/link/internal/arm64/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -80,29 +79,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
// Darwin/arm64 only supports external linking
if ld.Headtype == obj.Hdarwin {
ld.Linkmode = ld.LinkExternal
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hlinux, obj.Hdarwin:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

242
src/cmd/link/internal/ld/config.go Normal file
View File

@ -0,0 +1,242 @@
// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package ld
import (
"cmd/internal/obj"
"cmd/internal/sys"
"fmt"
"log"
)
var (
Linkmode LinkMode
Buildmode BuildMode
)
// A BuildMode indicates the sort of object we are building.
//
// Possible build modes are the same as those for the -buildmode flag
// in cmd/go, and are documented in 'go help buildmode'.
type BuildMode uint8
const (
BuildmodeUnset BuildMode = iota
BuildmodeExe
BuildmodePIE
BuildmodeCArchive
BuildmodeCShared
BuildmodeShared
BuildmodePlugin
)
func (mode *BuildMode) Set(s string) error {
badmode := func() error {
return fmt.Errorf("buildmode %s not supported on %s/%s", s, obj.GOOS, obj.GOARCH)
}
switch s {
default:
return fmt.Errorf("invalid buildmode: %q", s)
case "exe":
*mode = BuildmodeExe
case "pie":
switch obj.GOOS {
case "android", "linux":
default:
return badmode()
}
*mode = BuildmodePIE
case "c-archive":
switch obj.GOOS {
case "darwin", "linux":
case "windows":
switch obj.GOARCH {
case "amd64", "386":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeCArchive
case "c-shared":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64":
default:
return badmode()
}
*mode = BuildmodeCShared
case "shared":
switch obj.GOOS {
case "linux":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64", "ppc64le", "s390x":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeShared
case "plugin":
switch obj.GOOS {
case "linux":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodePlugin
}
return nil
}
func (mode *BuildMode) String() string {
switch *mode {
case BuildmodeUnset:
return "" // avoid showing a default in usage message
case BuildmodeExe:
return "exe"
case BuildmodePIE:
return "pie"
case BuildmodeCArchive:
return "c-archive"
case BuildmodeCShared:
return "c-shared"
case BuildmodeShared:
return "shared"
case BuildmodePlugin:
return "plugin"
}
return fmt.Sprintf("BuildMode(%d)", uint8(*mode))
}
// LinkMode indicates whether an external linker is used for the final link.
type LinkMode uint8
const (
LinkAuto LinkMode = iota
LinkInternal
LinkExternal
)
func (mode *LinkMode) Set(s string) error {
switch s {
default:
return fmt.Errorf("invalid linkmode: %q", s)
case "auto":
*mode = LinkAuto
case "internal":
*mode = LinkInternal
case "external":
*mode = LinkExternal
}
return nil
}
func (mode *LinkMode) String() string {
switch *mode {
case LinkAuto:
return "auto"
case LinkInternal:
return "internal"
case LinkExternal:
return "external"
}
return fmt.Sprintf("LinkMode(%d)", uint8(*mode))
}
// mustLinkExternal reports whether the program being linked requires
// the external linker be used to complete the link.
func mustLinkExternal(ctxt *Link) (res bool, reason string) {
if ctxt.Debugvlog > 1 {
defer func() {
if res {
log.Printf("external linking is forced by: %s\n", reason)
}
}()
}
switch obj.GOOS {
case "android":
return true, "android"
case "darwin":
if SysArch.InFamily(sys.ARM, sys.ARM64) {
return true, "iOS"
}
}
if *flagMsan {
return true, "msan"
}
// Internally linking cgo is incomplete on some architectures.
// https://golang.org/issue/10373
// https://golang.org/issue/14449
if iscgo && SysArch.InFamily(sys.ARM64, sys.MIPS64) {
return true, obj.GOARCH + " does not support internal cgo"
}
// Some build modes require work the internal linker cannot do (yet).
switch Buildmode {
case BuildmodeCArchive:
return true, "buildmode=c-archive"
case BuildmodeCShared:
return true, "buildmode=c-shared"
case BuildmodePIE:
switch obj.GOOS + "/" + obj.GOARCH {
case "linux/amd64":
default:
// Internal linking does not support TLS_IE.
return true, "buildmode=pie"
}
case BuildmodeShared:
return true, "buildmode=shared"
}
if *FlagLinkshared {
return true, "dynamically linking with a shared library"
}
return false, ""
}
// determineLinkMode sets Linkmode.
//
// It is called after flags are processed and inputs are processed,
// so the Linkmode variable has an initial value from the -linkmode
// flag and the iscgo externalobj variables are set.
func determineLinkMode(ctxt *Link) {
switch Linkmode {
case LinkAuto:
// The environment variable GO_EXTLINK_ENABLED controls the
// default value of -linkmode. If it is not set when the
// linker is called we take the value it was set to when
// cmd/link was compiled. (See make.bash.)
switch obj.Getgoextlinkenabled() {
case "0":
if needed, reason := mustLinkExternal(ctxt); needed {
Exitf("internal linking requested via GO_EXTLINK_ENABLED, but external linking required: %s", reason)
}
Linkmode = LinkInternal
case "1":
Linkmode = LinkExternal
default:
if needed, _ := mustLinkExternal(ctxt); needed {
Linkmode = LinkExternal
} else if iscgo && externalobj {
Linkmode = LinkExternal
} else {
Linkmode = LinkInternal
}
}
case LinkInternal:
if needed, reason := mustLinkExternal(ctxt); needed {
Exitf("internal linking requested but external linking required: %s", reason)
}
}
}

12
src/cmd/link/internal/ld/go.go
View File

@ -419,15 +419,3 @@ func importcycles() {
p.cycle()
}
}
func setlinkmode(arg string) {
if arg == "internal" {
Linkmode = LinkInternal
} else if arg == "external" {
Linkmode = LinkExternal
} else if arg == "auto" {
Linkmode = LinkAuto
} else {
Exitf("unknown link mode -linkmode %s", arg)
}
}

48
src/cmd/link/internal/ld/lib.go
View File

@ -198,7 +198,6 @@ var (
Headtype obj.HeadType
nerrors int
Linkmode int
liveness int64
)
@ -441,49 +440,12 @@ func (ctxt *Link) loadlib() {
}
}
if Linkmode == LinkAuto {
if iscgo && externalobj {
Linkmode = LinkExternal
} else {
Linkmode = LinkInternal
}
// We now have enough information to determine the link mode.
determineLinkMode(ctxt)
// Force external linking for android.
if obj.GOOS == "android" {
Linkmode = LinkExternal
}
// These build modes depend on the external linker
// to handle some relocations (such as TLS IE) not
// yet supported by the internal linker.
switch Buildmode {
case BuildmodeCArchive, BuildmodeCShared, BuildmodePIE, BuildmodePlugin, BuildmodeShared:
Linkmode = LinkExternal
}
if *FlagLinkshared {
Linkmode = LinkExternal
}
// cgo on Darwin must use external linking
// we can always use external linking, but then there will be circular
// dependency problems when compiling natively (external linking requires
// runtime/cgo, runtime/cgo requires cmd/cgo, but cmd/cgo needs to be
// compiled using external linking.)
if SysArch.InFamily(sys.ARM, sys.ARM64) && Headtype == obj.Hdarwin && iscgo {
Linkmode = LinkExternal
}
// Force external linking for msan.
if *flagMsan {
Linkmode = LinkExternal
}
}
// cmd/7l doesn't support cgo internal linking
// This is https://golang.org/issue/10373.
// mips64x doesn't support cgo internal linking either (golang.org/issue/14449)
if iscgo && (obj.GOARCH == "arm64" || obj.GOARCH == "mips64" || obj.GOARCH == "mips64le") {
Linkmode = LinkExternal
if Linkmode == LinkExternal && SysArch.Family == sys.PPC64 {
toc := Linklookup(ctxt, ".TOC.", 0)
toc.Type = obj.SDYNIMPORT
}
if Linkmode == LinkExternal && !iscgo {

16
src/cmd/link/internal/ld/link.go
View File

@ -159,6 +159,8 @@ type Shlib struct {
gcdataAddresses map[*Symbol]uint64
}
// Link holds the context for writing object code from a compiler
// or for reading that input into the linker.
type Link struct {
Arch *sys.Arch
Debugvlog int
@ -265,17 +267,3 @@ const (
RV_CHECK_OVERFLOW = 1 << 8
RV_TYPE_MASK = RV_CHECK_OVERFLOW - 1
)
// Pcdata iterator.
// for(pciterinit(ctxt, &it, &pcd); !it.done; pciternext(&it)) { it.value holds in [it.pc, it.nextpc) }
// Link holds the context for writing object code from a compiler
// to be linker input or for reading that input into the linker.
// LinkArch is the definition of a single architecture.
const (
LinkAuto = 0 + iota
LinkInternal
LinkExternal
)

3
src/cmd/link/internal/ld/main.go
View File

@ -48,6 +48,7 @@ var (
)
func init() {
flag.Var(&Linkmode, "linkmode", "set link `mode`")
flag.Var(&Buildmode, "buildmode", "set build `mode`")
flag.Var(&Headtype, "H", "set header `type`")
flag.Var(&rpath, "r", "set the ELF dynamic linker search `path` to dir1:dir2:...")
@ -59,7 +60,6 @@ var (
flagOutfile = flag.String("o", "", "write output to `file`")
FlagLinkshared = flag.Bool("linkshared", false, "link against installed Go shared libraries")
Buildmode BuildMode
flagInstallSuffix = flag.String("installsuffix", "", "set package directory `suffix`")
flagDumpDep = flag.Bool("dumpdep", false, "dump symbol dependency graph")
@ -120,7 +120,6 @@ func Main() {
obj.Flagfn0("V", "print version and exit", doversion)
obj.Flagfn1("X", "add string value `definition` of the form importpath.name=value", func(s string) { addstrdata1(ctxt, s) })
obj.Flagcount("v", "print link trace", &ctxt.Debugvlog)
obj.Flagfn1("linkmode", "set link `mode` (internal, external, auto)", setlinkmode)
obj.Flagparse(usage)

105
src/cmd/link/internal/ld/sym.go
View File

@ -34,7 +34,6 @@ package ld
import (
"cmd/internal/obj"
"cmd/internal/sys"
"fmt"
"log"
)
@ -166,107 +165,3 @@ func Linklookup(ctxt *Link, name string, v int) *Symbol {
func Linkrlookup(ctxt *Link, name string, v int) *Symbol {
return ctxt.Hash[v][name]
}
// A BuildMode indicates the sort of object we are building:
// "exe": build a main package and everything it imports into an executable.
// "c-shared": build a main package, plus all packages that it imports, into a
// single C shared library. The only callable symbols will be those functions
// marked as exported.
// "shared": combine all packages passed on the command line, and their
// dependencies, into a single shared library that will be used when
// building with the -linkshared option.
type BuildMode uint8
const (
BuildmodeUnset BuildMode = iota
BuildmodeExe
BuildmodePIE
BuildmodeCArchive
BuildmodeCShared
BuildmodeShared
BuildmodePlugin
)
func (mode *BuildMode) Set(s string) error {
badmode := func() error {
return fmt.Errorf("buildmode %s not supported on %s/%s", s, obj.GOOS, obj.GOARCH)
}
switch s {
default:
return fmt.Errorf("invalid buildmode: %q", s)
case "exe":
*mode = BuildmodeExe
case "pie":
switch obj.GOOS {
case "android", "linux":
default:
return badmode()
}
*mode = BuildmodePIE
case "c-archive":
switch obj.GOOS {
case "darwin", "linux":
case "windows":
switch obj.GOARCH {
case "amd64", "386":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeCArchive
case "c-shared":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64":
default:
return badmode()
}
*mode = BuildmodeCShared
case "shared":
switch obj.GOOS {
case "linux":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64", "ppc64le", "s390x":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodeShared
case "plugin":
switch obj.GOOS {
case "linux":
switch obj.GOARCH {
case "386", "amd64", "arm", "arm64":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildmodePlugin
}
return nil
}
func (mode *BuildMode) String() string {
switch *mode {
case BuildmodeUnset:
return "" // avoid showing a default in usage message
case BuildmodeExe:
return "exe"
case BuildmodePIE:
return "pie"
case BuildmodeCArchive:
return "c-archive"
case BuildmodeCShared:
return "c-shared"
case BuildmodeShared:
return "shared"
case BuildmodePlugin:
return "plugin"
}
return fmt.Sprintf("BuildMode(%d)", uint8(*mode))
}

20
src/cmd/link/internal/mips64/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -93,25 +92,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hlinux:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

34
src/cmd/link/internal/ppc64/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -94,39 +93,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Buildmode {
case ld.BuildmodePIE, ld.BuildmodeShared:
ld.Linkmode = ld.LinkExternal
}
if *ld.FlagLinkshared {
ld.Linkmode = ld.LinkExternal
}
if ld.Linkmode == ld.LinkExternal {
toc := ld.Linklookup(ctxt, ".TOC.", 0)
toc.Type = obj.SDYNIMPORT
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hlinux:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

6
src/cmd/link/internal/s390x/obj.go
View File

@ -80,12 +80,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)

26
src/cmd/link/internal/x86/obj.go
View File

@ -35,7 +35,6 @@ import (
"cmd/internal/sys"
"cmd/link/internal/ld"
"fmt"
"log"
)
// Reading object files.
@ -79,31 +78,6 @@ func linkarchinit() {
}
func archinit(ctxt *ld.Link) {
// getgoextlinkenabled is based on GO_EXTLINK_ENABLED when
// Go was built; see ../../make.bash.
if ld.Linkmode == ld.LinkAuto && obj.Getgoextlinkenabled() == "0" {
ld.Linkmode = ld.LinkInternal
}
switch ld.Headtype {
default:
if ld.Linkmode == ld.LinkAuto {
ld.Linkmode = ld.LinkInternal
}
if ld.Linkmode == ld.LinkExternal && obj.Getgoextlinkenabled() != "1" {
log.Fatalf("cannot use -linkmode=external with -H %v", ld.Headtype)
}
case obj.Hdarwin,
obj.Hfreebsd,
obj.Hlinux,
obj.Hnetbsd,
obj.Hopenbsd,
obj.Hwindows,
obj.Hwindowsgui:
break
}
switch ld.Headtype {
default:
ld.Exitf("unknown -H option: %v", ld.Headtype)