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// 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/objabi"
"cmd/internal/sys"
"fmt"
"log"
)
// 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, objabi.GOOS, objabi.GOARCH)
}
switch s {
default:
return fmt.Errorf("invalid buildmode: %q", s)
case "exe":
switch objabi.GOOS + "/" + objabi.GOARCH {
case "darwin/arm64", "windows/arm": // On these platforms, everything is PIE
*mode = BuildModePIE
default:
*mode = BuildModeExe
}
case "pie":
switch objabi.GOOS {
case "aix", "android", "linux", "windows", "darwin", "ios":
case "freebsd":
switch objabi.GOARCH {
case "amd64":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildModePIE
case "c-archive":
switch objabi.GOOS {
case "aix", "darwin", "ios", "linux":
case "freebsd":
switch objabi.GOARCH {
case "amd64":
default:
return badmode()
}
case "windows":
switch objabi.GOARCH {
case "amd64", "386", "arm":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildModeCArchive
case "c-shared":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64", "ppc64le", "s390x":
default:
return badmode()
}
*mode = BuildModeCShared
case "shared":
switch objabi.GOOS {
case "linux":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64", "ppc64le", "s390x":
default:
return badmode()
}
default:
return badmode()
}
*mode = BuildModeShared
case "plugin":
switch objabi.GOOS {
case "linux":
switch objabi.GOARCH {
case "386", "amd64", "arm", "arm64", "s390x", "ppc64le":
default:
return badmode()
}
case "darwin":
switch objabi.GOARCH {
case "amd64", "arm64":
default:
return badmode()
}
case "freebsd":
switch objabi.GOARCH {
case "amd64":
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)
}
}()
}
if sys.MustLinkExternal(objabi.GOOS, objabi.GOARCH) {
return true, fmt.Sprintf("%s/%s requires external linking", objabi.GOOS, objabi.GOARCH)
}
if *flagMsan {
return true, "msan"
}
// Internally linking cgo is incomplete on some architectures.
// https://golang.org/issue/14449
// https://golang.org/issue/21961
if iscgo && ctxt.Arch.InFamily(sys.MIPS64, sys.MIPS, sys.PPC64, sys.RISCV64) {
return true, objabi.GOARCH + " does not support internal cgo"
}
if iscgo && objabi.GOOS == "android" {
return true, objabi.GOOS + " does not support internal cgo"
}
// When the race flag is set, the LLVM tsan relocatable file is linked
// into the final binary, which means external linking is required because
// internal linking does not support it.
if *flagRace && ctxt.Arch.InFamily(sys.PPC64) {
return true, "race on " + objabi.GOARCH
}
// Some build modes require work the internal linker cannot do (yet).
switch ctxt.BuildMode {
case BuildModeCArchive:
return true, "buildmode=c-archive"
case BuildModeCShared:
return true, "buildmode=c-shared"
case BuildModePIE:
switch objabi.GOOS + "/" + objabi.GOARCH {
case "linux/amd64", "linux/arm64", "android/arm64":
case "windows/386", "windows/amd64", "windows/arm":
case "darwin/amd64", "darwin/arm64":
default:
// Internal linking does not support TLS_IE.
return true, "buildmode=pie"
}
case BuildModePlugin:
return true, "buildmode=plugin"
case BuildModeShared:
return true, "buildmode=shared"
}
if ctxt.linkShared {
return true, "dynamically linking with a shared library"
}
return false, ""
}
// determineLinkMode sets ctxt.LinkMode.
//
// It is called after flags are processed and inputs are processed,
// so the ctxt.LinkMode variable has an initial value from the -linkmode
// flag and the iscgo externalobj variables are set.
func determineLinkMode(ctxt *Link) {
extNeeded, extReason := mustLinkExternal(ctxt)
via := ""
if ctxt.LinkMode == 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 objabi.Getgoextlinkenabled() {
case "0":
ctxt.LinkMode = LinkInternal
via = "via GO_EXTLINK_ENABLED "
case "1":
ctxt.LinkMode = LinkExternal
via = "via GO_EXTLINK_ENABLED "
default:
if extNeeded || (iscgo && externalobj) {
ctxt.LinkMode = LinkExternal
} else {
ctxt.LinkMode = LinkInternal
}
}
}
switch ctxt.LinkMode {
case LinkInternal:
if extNeeded {
Exitf("internal linking requested %sbut external linking required: %s", via, extReason)
}
case LinkExternal:
switch {
case objabi.GOARCH == "ppc64" && objabi.GOOS != "aix":
Exitf("external linking not supported for %s/ppc64", objabi.GOOS)
}
}
}