// Derived from Inferno utils/6l/obj.c and utils/6l/span.c
// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/6l/obj.c
// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/6l/span.c
//
// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
// Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
// Portions Copyright © 1997-1999 Vita Nuova Limited
// Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
// Portions Copyright © 2004,2006 Bruce Ellis
// Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
// Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
// Portions Copyright © 2009 The Go Authors. All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package ld
import (
"cmd/internal/gcprog"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/sym"
"fmt"
"log"
"os"
"sort"
"strconv"
"strings"
"sync"
)
// isRuntimeDepPkg returns whether pkg is the runtime package or its dependency
func isRuntimeDepPkg(pkg string) bool {
switch pkg {
case "runtime",
"sync/atomic": // runtime may call to sync/atomic, due to go:linkname
return true
}
return strings.HasPrefix(pkg, "runtime/internal/") && !strings.HasSuffix(pkg, "_test")
}
// Estimate the max size needed to hold any new trampolines created for this function. This
// is used to determine when the section can be split if it becomes too large, to ensure that
// the trampolines are in the same section as the function that uses them.
func maxSizeTrampolinesPPC64(s *sym.Symbol, isTramp bool) uint64 {
// If Thearch.Trampoline is nil, then trampoline support is not available on this arch.
// A trampoline does not need any dependent trampolines.
if Thearch.Trampoline == nil || isTramp {
return 0
}
n := uint64(0)
for ri := range s.R {
r := &s.R[ri]
if r.Type.IsDirectJump() {
n++
}
}
// Trampolines in ppc64 are 4 instructions.
return n * 16
}
// detect too-far jumps in function s, and add trampolines if necessary
// ARM, PPC64 & PPC64LE support trampoline insertion for internal and external linking
// On PPC64 & PPC64LE the text sections might be split but will still insert trampolines
// where necessary.
func trampoline(ctxt *Link, s *sym.Symbol) {
if Thearch.Trampoline == nil {
return // no need or no support of trampolines on this arch
}
for ri := range s.R {
r := &s.R[ri]
if !r.Type.IsDirectJump() {
continue
}
if Symaddr(r.Sym) == 0 && r.Sym.Type != sym.SDYNIMPORT {
if r.Sym.File != s.File {
if !isRuntimeDepPkg(s.File) || !isRuntimeDepPkg(r.Sym.File) {
Errorf(s, "unresolved inter-package jump to %s(%s)", r.Sym, r.Sym.File)
}
// runtime and its dependent packages may call to each other.
// they are fine, as they will be laid down together.
}
continue
}
Thearch.Trampoline(ctxt, r, s)
}
}
// resolve relocations in s.
func relocsym(ctxt *Link, s *sym.Symbol) {
for ri := int32(0); ri < int32(len(s.R)); ri++ {
r := &s.R[ri]
if r.Done {
// Relocation already processed by an earlier phase.
continue
}
r.Done = true
off := r.Off
siz := int32(r.Siz)
if off < 0 || off+siz > int32(len(s.P)) {
rname := ""
if r.Sym != nil {
rname = r.Sym.Name
}
Errorf(s, "invalid relocation %s: %d+%d not in [%d,%d)", rname, off, siz, 0, len(s.P))
continue
}
if r.Sym != nil && ((r.Sym.Type == 0 && !r.Sym.Attr.VisibilityHidden()) || r.Sym.Type == sym.SXREF) {
// When putting the runtime but not main into a shared library
// these symbols are undefined and that's OK.
if ctxt.BuildMode == BuildModeShared {
if r.Sym.Name == "main.main" || r.Sym.Name == "main.init" {
r.Sym.Type = sym.SDYNIMPORT
} else if strings.HasPrefix(r.Sym.Name, "go.info.") {
// Skip go.info symbols. They are only needed to communicate
// DWARF info between the compiler and linker.
continue
}
} else {
Errorf(s, "relocation target %s not defined", r.Sym.Name)
continue
}
}
if r.Type >= 256 {
continue
}
if r.Siz == 0 { // informational relocation - no work to do
continue
}
if r.Type == objabi.R_DWARFFILEREF {
// These should have been processed previously during
// line table writing.
Errorf(s, "orphan R_DWARFFILEREF reloc to %v", r.Sym.Name)
continue
}
// We need to be able to reference dynimport symbols when linking against
// shared libraries, and Solaris needs it always
if ctxt.HeadType != objabi.Hsolaris && r.Sym != nil && r.Sym.Type == sym.SDYNIMPORT && !ctxt.DynlinkingGo() && !r.Sym.Attr.SubSymbol() {
if !(ctxt.Arch.Family == sys.PPC64 && ctxt.LinkMode == LinkExternal && r.Sym.Name == ".TOC.") {
Errorf(s, "unhandled relocation for %s (type %d (%s) rtype %d (%s))", r.Sym.Name, r.Sym.Type, r.Sym.Type, r.Type, sym.RelocName(ctxt.Arch, r.Type))
}
}
if r.Sym != nil && r.Sym.Type != sym.STLSBSS && r.Type != objabi.R_WEAKADDROFF && !r.Sym.Attr.Reachable() {
Errorf(s, "unreachable sym in relocation: %s", r.Sym.Name)
}
// TODO(mundaym): remove this special case - see issue 14218.
if ctxt.Arch.Family == sys.S390X {
switch r.Type {
case objabi.R_PCRELDBL:
r.Type = objabi.R_PCREL
r.Variant = sym.RV_390_DBL
case objabi.R_CALL:
r.Variant = sym.RV_390_DBL
}
}
var o int64
switch r.Type {
default:
switch siz {
default:
Errorf(s, "bad reloc size %#x for %s", uint32(siz), r.Sym.Name)
case 1:
o = int64(s.P[off])
case 2:
o = int64(ctxt.Arch.ByteOrder.Uint16(s.P[off:]))
case 4:
o = int64(ctxt.Arch.ByteOrder.Uint32(s.P[off:]))
case 8:
o = int64(ctxt.Arch.ByteOrder.Uint64(s.P[off:]))
}
if !Thearch.Archreloc(ctxt, r, s, &o) {
Errorf(s, "unknown reloc to %v: %d (%s)", r.Sym.Name, r.Type, sym.RelocName(ctxt.Arch, r.Type))
}
case objabi.R_TLS_LE:
isAndroidX86 := objabi.GOOS == "android" && (ctxt.Arch.InFamily(sys.AMD64, sys.I386))
if ctxt.LinkMode == LinkExternal && ctxt.IsELF && !isAndroidX86 {
r.Done = false
if r.Sym == nil {
r.Sym = ctxt.Tlsg
}
r.Xsym = r.Sym
r.Xadd = r.Add
o = 0
if ctxt.Arch.Family != sys.AMD64 {
o = r.Add
}
break
}
if ctxt.IsELF && ctxt.Arch.Family == sys.ARM {
// On ELF ARM, the thread pointer is 8 bytes before
// the start of the thread-local data block, so add 8
// to the actual TLS offset (r->sym->value).
// This 8 seems to be a fundamental constant of
// ELF on ARM (or maybe Glibc on ARM); it is not
// related to the fact that our own TLS storage happens
// to take up 8 bytes.
o = 8 + r.Sym.Value
} else if ctxt.IsELF || ctxt.HeadType == objabi.Hplan9 || ctxt.HeadType == objabi.Hdarwin || isAndroidX86 {
o = int64(ctxt.Tlsoffset) + r.Add
} else if ctxt.HeadType == objabi.Hwindows {
o = r.Add
} else {
log.Fatalf("unexpected R_TLS_LE relocation for %v", ctxt.HeadType)
}
case objabi.R_TLS_IE:
isAndroidX86 := objabi.GOOS == "android" && (ctxt.Arch.InFamily(sys.AMD64, sys.I386))
if ctxt.LinkMode == LinkExternal && ctxt.IsELF && !isAndroidX86 {
r.Done = false
if r.Sym == nil {
r.Sym = ctxt.Tlsg
}
r.Xsym = r.Sym
r.Xadd = r.Add
o = 0
if ctxt.Arch.Family != sys.AMD64 {
o = r.Add
}
break
}
if ctxt.BuildMode == BuildModePIE && ctxt.IsELF {
// We are linking the final executable, so we
// can optimize any TLS IE relocation to LE.
if Thearch.TLSIEtoLE == nil {
log.Fatalf("internal linking of TLS IE not supported on %v", ctxt.Arch.Family)
}
Thearch.TLSIEtoLE(s, int(off), int(r.Siz))
o = int64(ctxt.Tlsoffset)
// TODO: o += r.Add when ctxt.Arch.Family != sys.AMD64?
// Why do we treat r.Add differently on AMD64?
// Is the external linker using Xadd at all?
} else {
log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", s.Name)
}
case objabi.R_ADDR:
if ctxt.LinkMode == LinkExternal && r.Sym.Type != sym.SCONST {
r.Done = false
// set up addend for eventual relocation via outer symbol.
rs := r.Sym
r.Xadd = r.Add
for rs.Outer != nil {
r.Xadd += Symaddr(rs) - Symaddr(rs.Outer)
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
Errorf(s, "missing section for relocation target %s", rs.Name)
}
r.Xsym = rs
o = r.Xadd
if ctxt.IsELF {
if ctxt.Arch.Family == sys.AMD64 {
o = 0
}
} else if ctxt.HeadType == objabi.Hdarwin {
// ld64 for arm64 has a bug where if the address pointed to by o exists in the
// symbol table (dynid >= 0), or is inside a symbol that exists in the symbol
// table, then it will add o twice into the relocated value.
// The workaround is that on arm64 don't ever add symaddr to o and always use
// extern relocation by requiring rs->dynid >= 0.
if rs.Type != sym.SHOSTOBJ {
if ctxt.Arch.Family == sys.ARM64 && rs.Dynid < 0 {
Errorf(s, "R_ADDR reloc to %s+%d is not supported on darwin/arm64", rs.Name, o)
}
if ctxt.Arch.Family != sys.ARM64 {
o += Symaddr(rs)
}
}
} else if ctxt.HeadType == objabi.Hwindows {
// nothing to do
} else {
Errorf(s, "unhandled pcrel relocation to %s on %v", rs.Name, ctxt.HeadType)
}
break
}
o = Symaddr(r.Sym) + r.Add
// On amd64, 4-byte offsets will be sign-extended, so it is impossible to
// access more than 2GB of static data; fail at link time is better than
// fail at runtime. See https://golang.org/issue/7980.
// Instead of special casing only amd64, we treat this as an error on all
// 64-bit architectures so as to be future-proof.
if int32(o) < 0 && ctxt.Arch.PtrSize > 4 && siz == 4 {
Errorf(s, "non-pc-relative relocation address for %s is too big: %#x (%#x + %#x)", r.Sym.Name, uint64(o), Symaddr(r.Sym), r.Add)
errorexit()
}
case objabi.R_DWARFSECREF:
if r.Sym.Sect == nil {
Errorf(s, "missing DWARF section for relocation target %s", r.Sym.Name)
}
if ctxt.LinkMode == LinkExternal {
r.Done = false
// On most platforms, the external linker needs to adjust DWARF references
// as it combines DWARF sections. However, on Darwin, dsymutil does the
// DWARF linking, and it understands how to follow section offsets.
// Leaving in the relocation records confuses it (see
// https://golang.org/issue/22068) so drop them for Darwin.
if ctxt.HeadType == objabi.Hdarwin {
r.Done = true
}
// PE code emits IMAGE_REL_I386_SECREL and IMAGE_REL_AMD64_SECREL
// for R_DWARFSECREF relocations, while R_ADDR is replaced with
// IMAGE_REL_I386_DIR32, IMAGE_REL_AMD64_ADDR64 and IMAGE_REL_AMD64_ADDR32.
// Do not replace R_DWARFSECREF with R_ADDR for windows -
// let PE code emit correct relocations.
if ctxt.HeadType != objabi.Hwindows {
r.Type = objabi.R_ADDR
}
r.Xsym = ctxt.Syms.ROLookup(r.Sym.Sect.Name, 0)
r.Xadd = r.Add + Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr)
o = r.Xadd
if ctxt.IsELF && ctxt.Arch.Family == sys.AMD64 {
o = 0
}
break
}
o = Symaddr(r.Sym) + r.Add - int64(r.Sym.Sect.Vaddr)
case objabi.R_WEAKADDROFF:
if !r.Sym.Attr.Reachable() {
continue
}
fallthrough
case objabi.R_ADDROFF:
// The method offset tables using this relocation expect the offset to be relative
// to the start of the first text section, even if there are multiple.
if r.Sym.Sect.Name == ".text" {
o = Symaddr(r.Sym) - int64(Segtext.Sections[0].Vaddr) + r.Add
} else {
o = Symaddr(r.Sym) - int64(r.Sym.Sect.Vaddr) + r.Add
}
case objabi.R_ADDRCUOFF:
// debug_range and debug_loc elements use this relocation type to get an
// offset from the start of the compile unit.
o = Symaddr(r.Sym) + r.Add - Symaddr(r.Sym.Lib.Textp[0])
// r->sym can be null when CALL $(constant) is transformed from absolute PC to relative PC call.
case objabi.R_GOTPCREL:
if ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin && r.Sym != nil && r.Sym.Type != sym.SCONST {
r.Done = false
r.Xadd = r.Add
r.Xadd -= int64(r.Siz) // relative to address after the relocated chunk
r.Xsym = r.Sym
o = r.Xadd
o += int64(r.Siz)
break
}
fallthrough
case objabi.R_CALL, objabi.R_PCREL:
if ctxt.LinkMode == LinkExternal && r.Sym != nil && r.Sym.Type != sym.SCONST && (r.Sym.Sect != s.Sect || r.Type == objabi.R_GOTPCREL) {
r.Done = false
// set up addend for eventual relocation via outer symbol.
rs := r.Sym
r.Xadd = r.Add
for rs.Outer != nil {
r.Xadd += Symaddr(rs) - Symaddr(rs.Outer)
rs = rs.Outer
}
r.Xadd -= int64(r.Siz) // relative to address after the relocated chunk
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Sect == nil {
Errorf(s, "missing section for relocation target %s", rs.Name)
}
r.Xsym = rs
o = r.Xadd
if ctxt.IsELF {
if ctxt.Arch.Family == sys.AMD64 {
o = 0
}
} else if ctxt.HeadType == objabi.Hdarwin {
if r.Type == objabi.R_CALL {
if rs.Type != sym.SHOSTOBJ {
o += int64(uint64(Symaddr(rs)) - rs.Sect.Vaddr)
}
o -= int64(r.Off) // relative to section offset, not symbol
} else if ctxt.Arch.Family == sys.ARM {
// see ../arm/asm.go:/machoreloc1
o += Symaddr(rs) - int64(s.Value) - int64(r.Off)
} else {
o += int64(r.Siz)
}
} else if ctxt.HeadType == objabi.Hwindows && ctxt.Arch.Family == sys.AMD64 { // only amd64 needs PCREL
// PE/COFF's PC32 relocation uses the address after the relocated
// bytes as the base. Compensate by skewing the addend.
o += int64(r.Siz)
} else {
Errorf(s, "unhandled pcrel relocation to %s on %v", rs.Name, ctxt.HeadType)
}
break
}
o = 0
if r.Sym != nil {
o += Symaddr(r.Sym)
}
o += r.Add - (s.Value + int64(r.Off) + int64(r.Siz))
case objabi.R_SIZE:
o = r.Sym.Size + r.Add
}
if r.Variant != sym.RV_NONE {
o = Thearch.Archrelocvariant(ctxt, r, s, o)
}
if false {
nam := "<nil>"
if r.Sym != nil {
nam = r.Sym.Name
}
fmt.Printf("relocate %s %#x (%#x+%#x, size %d) => %s %#x +%#x [type %d (%s)/%d, %x]\n", s.Name, s.Value+int64(off), s.Value, r.Off, r.Siz, nam, Symaddr(r.Sym), r.Add, r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Variant, o)
}
switch siz {
default:
Errorf(s, "bad reloc size %#x for %s", uint32(siz), r.Sym.Name)
fallthrough
// TODO(rsc): Remove.
case 1:
s.P[off] = byte(int8(o))
case 2:
if o != int64(int16(o)) {
Errorf(s, "relocation address for %s is too big: %#x", r.Sym.Name, o)
}
i16 := int16(o)
ctxt.Arch.ByteOrder.PutUint16(s.P[off:], uint16(i16))
case 4:
if r.Type == objabi.R_PCREL || r.Type == objabi.R_CALL {
if o != int64(int32(o)) {
Errorf(s, "pc-relative relocation address for %s is too big: %#x", r.Sym.Name, o)
}
} else {
if o != int64(int32(o)) && o != int64(uint32(o)) {
Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", r.Sym.Name, uint64(o))
}
}
fl := int32(o)
ctxt.Arch.ByteOrder.PutUint32(s.P[off:], uint32(fl))
case 8:
ctxt.Arch.ByteOrder.PutUint64(s.P[off:], uint64(o))
}
}
}
func (ctxt *Link) reloc() {
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f reloc\n", Cputime())
}
for _, s := range ctxt.Textp {
relocsym(ctxt, s)
}
for _, s := range datap {
relocsym(ctxt, s)
}
for _, s := range dwarfp {
relocsym(ctxt, s)
}
}
func windynrelocsym(ctxt *Link, s *sym.Symbol) {
rel := ctxt.Syms.Lookup(".rel", 0)
if s == rel {
return
}
for ri := 0; ri < len(s.R); ri++ {
r := &s.R[ri]
targ := r.Sym
if targ == nil {
continue
}
if !targ.Attr.Reachable() {
if r.Type == objabi.R_WEAKADDROFF {
continue
}
Errorf(s, "dynamic relocation to unreachable symbol %s", targ.Name)
}
if r.Sym.Plt == -2 && r.Sym.Got != -2 { // make dynimport JMP table for PE object files.
targ.Plt = int32(rel.Size)
r.Sym = rel
r.Add = int64(targ.Plt)
// jmp *addr
if ctxt.Arch.Family == sys.I386 {
rel.AddUint8(0xff)
rel.AddUint8(0x25)
rel.AddAddr(ctxt.Arch, targ)
rel.AddUint8(0x90)
rel.AddUint8(0x90)
} else {
rel.AddUint8(0xff)
rel.AddUint8(0x24)
rel.AddUint8(0x25)
rel.AddAddrPlus4(targ, 0)
rel.AddUint8(0x90)
}
} else if r.Sym.Plt >= 0 {
r.Sym = rel
r.Add = int64(targ.Plt)
}
}
}
func dynrelocsym(ctxt *Link, s *sym.Symbol) {
if ctxt.HeadType == objabi.Hwindows {
if ctxt.LinkMode == LinkInternal {
windynrelocsym(ctxt, s)
}
return
}
for ri := 0; ri < len(s.R); ri++ {
r := &s.R[ri]
if ctxt.BuildMode == BuildModePIE && ctxt.LinkMode == LinkInternal {
// It's expected that some relocations will be done
// later by relocsym (R_TLS_LE, R_ADDROFF), so
// don't worry if Adddynrel returns false.
Thearch.Adddynrel(ctxt, s, r)
continue
}
if r.Sym != nil && r.Sym.Type == sym.SDYNIMPORT || r.Type >= 256 {
if r.Sym != nil && !r.Sym.Attr.Reachable() {
Errorf(s, "dynamic relocation to unreachable symbol %s", r.Sym.Name)
}
if !Thearch.Adddynrel(ctxt, s, r) {
Errorf(s, "unsupported dynamic relocation for symbol %s (type=%d (%s) stype=%d (%s))", r.Sym.Name, r.Type, sym.RelocName(ctxt.Arch, r.Type), r.Sym.Type, r.Sym.Type)
}
}
}
}
func dynreloc(ctxt *Link, data *[sym.SXREF][]*sym.Symbol) {
// -d suppresses dynamic loader format, so we may as well not
// compute these sections or mark their symbols as reachable.
if *FlagD && ctxt.HeadType != objabi.Hwindows {
return
}
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f dynreloc\n", Cputime())
}
for _, s := range ctxt.Textp {
dynrelocsym(ctxt, s)
}
for _, syms := range data {
for _, s := range syms {
dynrelocsym(ctxt, s)
}
}
if ctxt.IsELF {
elfdynhash(ctxt)
}
}
func Codeblk(ctxt *Link, addr int64, size int64) {
CodeblkPad(ctxt, addr, size, zeros[:])
}
func CodeblkPad(ctxt *Link, addr int64, size int64, pad []byte) {
if *flagA {
ctxt.Logf("codeblk [%#x,%#x) at offset %#x\n", addr, addr+size, ctxt.Out.Offset())
}
blk(ctxt, ctxt.Textp, addr, size, pad)
/* again for printing */
if !*flagA {
return
}
syms := ctxt.Textp
for i, s := range syms {
if !s.Attr.Reachable() {
continue
}
if s.Value >= addr {
syms = syms[i:]
break
}
}
eaddr := addr + size
var q []byte
for _, s := range syms {
if !s.Attr.Reachable() {
continue
}
if s.Value >= eaddr {
break
}
if addr < s.Value {
ctxt.Logf("%-20s %.8x|", "_", uint64(addr))
for ; addr < s.Value; addr++ {
ctxt.Logf(" %.2x", 0)
}
ctxt.Logf("\n")
}
ctxt.Logf("%.6x\t%-20s\n", uint64(addr), s.Name)
q = s.P
for len(q) >= 16 {
ctxt.Logf("%.6x\t% x\n", uint64(addr), q[:16])
addr += 16
q = q[16:]
}
if len(q) > 0 {
ctxt.Logf("%.6x\t% x\n", uint64(addr), q)
addr += int64(len(q))
}
}
if addr < eaddr {
ctxt.Logf("%-20s %.8x|", "_", uint64(addr))
for ; addr < eaddr; addr++ {
ctxt.Logf(" %.2x", 0)
}
}
}
func blk(ctxt *Link, syms []*sym.Symbol, addr, size int64, pad []byte) {
for i, s := range syms {
if !s.Attr.SubSymbol() && s.Value >= addr {
syms = syms[i:]
break
}
}
eaddr := addr + size
for _, s := range syms {
if s.Attr.SubSymbol() {
continue
}
if s.Value >= eaddr {
break
}
if s.Value < addr {
Errorf(s, "phase error: addr=%#x but sym=%#x type=%d", addr, s.Value, s.Type)
errorexit()
}
if addr < s.Value {
ctxt.Out.WriteStringPad("", int(s.Value-addr), pad)
addr = s.Value
}
ctxt.Out.Write(s.P)
addr += int64(len(s.P))
if addr < s.Value+s.Size {
ctxt.Out.WriteStringPad("", int(s.Value+s.Size-addr), pad)
addr = s.Value + s.Size
}
if addr != s.Value+s.Size {
Errorf(s, "phase error: addr=%#x value+size=%#x", addr, s.Value+s.Size)
errorexit()
}
if s.Value+s.Size >= eaddr {
break
}
}
if addr < eaddr {
ctxt.Out.WriteStringPad("", int(eaddr-addr), pad)
}
ctxt.Out.Flush()
}
func Datblk(ctxt *Link, addr int64, size int64) {
if *flagA {
ctxt.Logf("datblk [%#x,%#x) at offset %#x\n", addr, addr+size, ctxt.Out.Offset())
}
blk(ctxt, datap, addr, size, zeros[:])
/* again for printing */
if !*flagA {
return
}
syms := datap
for i, sym := range syms {
if sym.Value >= addr {
syms = syms[i:]
break
}
}
eaddr := addr + size
for _, sym := range syms {
if sym.Value >= eaddr {
break
}
if addr < sym.Value {
ctxt.Logf("\t%.8x| 00 ...\n", uint64(addr))
addr = sym.Value
}
ctxt.Logf("%s\n\t%.8x|", sym.Name, uint64(addr))
for i, b := range sym.P {
if i > 0 && i%16 == 0 {
ctxt.Logf("\n\t%.8x|", uint64(addr)+uint64(i))
}
ctxt.Logf(" %.2x", b)
}
addr += int64(len(sym.P))
for ; addr < sym.Value+sym.Size; addr++ {
ctxt.Logf(" %.2x", 0)
}
ctxt.Logf("\n")
if ctxt.LinkMode != LinkExternal {
continue
}
for _, r := range sym.R {
rsname := ""
if r.Sym != nil {
rsname = r.Sym.Name
}
typ := "?"
switch r.Type {
case objabi.R_ADDR:
typ = "addr"
case objabi.R_PCREL:
typ = "pcrel"
case objabi.R_CALL:
typ = "call"
}
ctxt.Logf("\treloc %.8x/%d %s %s+%#x [%#x]\n", uint(sym.Value+int64(r.Off)), r.Siz, typ, rsname, r.Add, r.Sym.Value+r.Add)
}
}
if addr < eaddr {
ctxt.Logf("\t%.8x| 00 ...\n", uint(addr))
}
ctxt.Logf("\t%.8x|\n", uint(eaddr))
}
func Dwarfblk(ctxt *Link, addr int64, size int64) {
if *flagA {
ctxt.Logf("dwarfblk [%#x,%#x) at offset %#x\n", addr, addr+size, ctxt.Out.Offset())
}
blk(ctxt, dwarfp, addr, size, zeros[:])
}
var zeros [512]byte
var (
strdata = make(map[string]string)
strnames []string
)
func addstrdata1(ctxt *Link, arg string) {
eq := strings.Index(arg, "=")
dot := strings.LastIndex(arg[:eq+1], ".")
if eq < 0 || dot < 0 {
Exitf("-X flag requires argument of the form importpath.name=value")
}
pkg := arg[:dot]
if ctxt.BuildMode == BuildModePlugin && pkg == "main" {
pkg = *flagPluginPath
}
pkg = objabi.PathToPrefix(pkg)
name := pkg + arg[dot:eq]
value := arg[eq+1:]
if _, ok := strdata[name]; !ok {
strnames = append(strnames, name)
}
strdata[name] = value
}
func addstrdata(ctxt *Link, name, value string) {
s := ctxt.Syms.ROLookup(name, 0)
if s == nil || s.Gotype == nil {
// Not defined in the loaded packages.
return
}
if s.Gotype.Name != "type.string" {
Errorf(s, "cannot set with -X: not a var of type string (%s)", s.Gotype.Name)
return
}
if s.Type == sym.SBSS {
s.Type = sym.SDATA
}
p := fmt.Sprintf("%s.str", s.Name)
sp := ctxt.Syms.Lookup(p, 0)
Addstring(sp, value)
sp.Type = sym.SRODATA
s.Size = 0
s.P = s.P[:0]
s.R = s.R[:0]
reachable := s.Attr.Reachable()
s.AddAddr(ctxt.Arch, sp)
s.AddUint(ctxt.Arch, uint64(len(value)))
// addstring, addaddr, etc., mark the symbols as reachable.
// In this case that is not necessarily true, so stick to what
// we know before entering this function.
s.Attr.Set(sym.AttrReachable, reachable)
sp.Attr.Set(sym.AttrReachable, reachable)
}
func (ctxt *Link) dostrdata() {
for _, name := range strnames {
addstrdata(ctxt, name, strdata[name])
}
}
func Addstring(s *sym.Symbol, str string) int64 {
if s.Type == 0 {
s.Type = sym.SNOPTRDATA
}
s.Attr |= sym.AttrReachable
r := s.Size
if s.Name == ".shstrtab" {
elfsetstring(s, str, int(r))
}
s.P = append(s.P, str...)
s.P = append(s.P, 0)
s.Size = int64(len(s.P))
return r
}
// addgostring adds str, as a Go string value, to s. symname is the name of the
// symbol used to define the string data and must be unique per linked object.
func addgostring(ctxt *Link, s *sym.Symbol, symname, str string) {
sdata := ctxt.Syms.Lookup(symname, 0)
if sdata.Type != sym.Sxxx {
Errorf(s, "duplicate symname in addgostring: %s", symname)
}
sdata.Attr |= sym.AttrReachable
sdata.Attr |= sym.AttrLocal
sdata.Type = sym.SRODATA
sdata.Size = int64(len(str))
sdata.P = []byte(str)
s.AddAddr(ctxt.Arch, sdata)
s.AddUint(ctxt.Arch, uint64(len(str)))
}
func addinitarrdata(ctxt *Link, s *sym.Symbol) {
p := s.Name + ".ptr"
sp := ctxt.Syms.Lookup(p, 0)
sp.Type = sym.SINITARR
sp.Size = 0
sp.Attr |= sym.AttrDuplicateOK
sp.AddAddr(ctxt.Arch, s)
}
func dosymtype(ctxt *Link) {
switch ctxt.BuildMode {
case BuildModeCArchive, BuildModeCShared:
for _, s := range ctxt.Syms.Allsym {
// Create a new entry in the .init_array section that points to the
// library initializer function.
if s.Name == *flagEntrySymbol {
addinitarrdata(ctxt, s)
}
}
}
}
// symalign returns the required alignment for the given symbol s.
func symalign(s *sym.Symbol) int32 {
min := int32(Thearch.Minalign)
if s.Align >= min {
return s.Align
} else if s.Align != 0 {
return min
}
if strings.HasPrefix(s.Name, "go.string.") || strings.HasPrefix(s.Name, "type..namedata.") {
// String data is just bytes.
// If we align it, we waste a lot of space to padding.
return min
}
align := int32(Thearch.Maxalign)
for int64(align) > s.Size && align > min {
align >>= 1
}
return align
}
func aligndatsize(datsize int64, s *sym.Symbol) int64 {
return Rnd(datsize, int64(symalign(s)))
}
const debugGCProg = false
type GCProg struct {
ctxt *Link
sym *sym.Symbol
w gcprog.Writer
}
func (p *GCProg) Init(ctxt *Link, name string) {
p.ctxt = ctxt
p.sym = ctxt.Syms.Lookup(name, 0)
p.w.Init(p.writeByte(ctxt))
if debugGCProg {
fmt.Fprintf(os.Stderr, "ld: start GCProg %s\n", name)
p.w.Debug(os.Stderr)
}
}
func (p *GCProg) writeByte(ctxt *Link) func(x byte) {
return func(x byte) {
p.sym.AddUint8(x)
}
}
func (p *GCProg) End(size int64) {
p.w.ZeroUntil(size / int64(p.ctxt.Arch.PtrSize))
p.w.End()
if debugGCProg {
fmt.Fprintf(os.Stderr, "ld: end GCProg\n")
}
}
func (p *GCProg) AddSym(s *sym.Symbol) {
typ := s.Gotype
// Things without pointers should be in sym.SNOPTRDATA or sym.SNOPTRBSS;
// everything we see should have pointers and should therefore have a type.
if typ == nil {
switch s.Name {
case "runtime.data", "runtime.edata", "runtime.bss", "runtime.ebss":
// Ignore special symbols that are sometimes laid out
// as real symbols. See comment about dyld on darwin in
// the address function.
return
}
Errorf(s, "missing Go type information for global symbol: size %d", s.Size)
return
}
ptrsize := int64(p.ctxt.Arch.PtrSize)
nptr := decodetypePtrdata(p.ctxt.Arch, typ) / ptrsize
if debugGCProg {
fmt.Fprintf(os.Stderr, "gcprog sym: %s at %d (ptr=%d+%d)\n", s.Name, s.Value, s.Value/ptrsize, nptr)
}
if decodetypeUsegcprog(p.ctxt.Arch, typ) == 0 {
// Copy pointers from mask into program.
mask := decodetypeGcmask(p.ctxt, typ)
for i := int64(0); i < nptr; i++ {
if (mask[i/8]>>uint(i%8))&1 != 0 {
p.w.Ptr(s.Value/ptrsize + i)
}
}
return
}
// Copy program.
prog := decodetypeGcprog(p.ctxt, typ)
p.w.ZeroUntil(s.Value / ptrsize)
p.w.Append(prog[4:], nptr)
}
// dataSortKey is used to sort a slice of data symbol *sym.Symbol pointers.
// The sort keys are kept inline to improve cache behavior while sorting.
type dataSortKey struct {
size int64
name string
sym *sym.Symbol
}
type bySizeAndName []dataSortKey
func (d bySizeAndName) Len() int { return len(d) }
func (d bySizeAndName) Swap(i, j int) { d[i], d[j] = d[j], d[i] }
func (d bySizeAndName) Less(i, j int) bool {
s1, s2 := d[i], d[j]
if s1.size != s2.size {
return s1.size < s2.size
}
return s1.name < s2.name
}
// cutoff is the maximum data section size permitted by the linker
// (see issue #9862).
const cutoff = 2e9 // 2 GB (or so; looks better in errors than 2^31)
func checkdatsize(ctxt *Link, datsize int64, symn sym.SymKind) {
if datsize > cutoff {
Errorf(nil, "too much data in section %v (over %v bytes)", symn, cutoff)
}
}
// datap is a collection of reachable data symbols in address order.
// Generated by dodata.
var datap []*sym.Symbol
func (ctxt *Link) dodata() {
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f dodata\n", Cputime())
}
if ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin {
// The values in moduledata are filled out by relocations
// pointing to the addresses of these special symbols.
// Typically these symbols have no size and are not laid
// out with their matching section.
//
// However on darwin, dyld will find the special symbol
// in the first loaded module, even though it is local.
//
// (An hypothesis, formed without looking in the dyld sources:
// these special symbols have no size, so their address
// matches a real symbol. The dynamic linker assumes we
// want the normal symbol with the same address and finds
// it in the other module.)
//
// To work around this we lay out the symbls whose
// addresses are vital for multi-module programs to work
// as normal symbols, and give them a little size.
bss := ctxt.Syms.Lookup("runtime.bss", 0)
bss.Size = 8
bss.Attr.Set(sym.AttrSpecial, false)
ctxt.Syms.Lookup("runtime.ebss", 0).Attr.Set(sym.AttrSpecial, false)
data := ctxt.Syms.Lookup("runtime.data", 0)
data.Size = 8
data.Attr.Set(sym.AttrSpecial, false)
ctxt.Syms.Lookup("runtime.edata", 0).Attr.Set(sym.AttrSpecial, false)
types := ctxt.Syms.Lookup("runtime.types", 0)
types.Type = sym.STYPE
types.Size = 8
types.Attr.Set(sym.AttrSpecial, false)
etypes := ctxt.Syms.Lookup("runtime.etypes", 0)
etypes.Type = sym.SFUNCTAB
etypes.Attr.Set(sym.AttrSpecial, false)
}
// Collect data symbols by type into data.
var data [sym.SXREF][]*sym.Symbol
for _, s := range ctxt.Syms.Allsym {
if !s.Attr.Reachable() || s.Attr.Special() || s.Attr.SubSymbol() {
continue
}
if s.Type <= sym.STEXT || s.Type >= sym.SXREF {
continue
}
data[s.Type] = append(data[s.Type], s)
}
// Now that we have the data symbols, but before we start
// to assign addresses, record all the necessary
// dynamic relocations. These will grow the relocation
// symbol, which is itself data.
//
// On darwin, we need the symbol table numbers for dynreloc.
if ctxt.HeadType == objabi.Hdarwin {
machosymorder(ctxt)
}
dynreloc(ctxt, &data)
if ctxt.UseRelro() {
// "read only" data with relocations needs to go in its own section
// when building a shared library. We do this by boosting objects of
// type SXXX with relocations to type SXXXRELRO.
for _, symnro := range sym.ReadOnly {
symnrelro := sym.RelROMap[symnro]
ro := []*sym.Symbol{}
relro := data[symnrelro]
for _, s := range data[symnro] {
isRelro := len(s.R) > 0
switch s.Type {
case sym.STYPE, sym.STYPERELRO, sym.SGOFUNCRELRO:
// Symbols are not sorted yet, so it is possible
// that an Outer symbol has been changed to a
// relro Type before it reaches here.
isRelro = true
}
if isRelro {
s.Type = symnrelro
if s.Outer != nil {
s.Outer.Type = s.Type
}
relro = append(relro, s)
} else {
ro = append(ro, s)
}
}
// Check that we haven't made two symbols with the same .Outer into
// different types (because references two symbols with non-nil Outer
// become references to the outer symbol + offset it's vital that the
// symbol and the outer end up in the same section).
for _, s := range relro {
if s.Outer != nil && s.Outer.Type != s.Type {
Errorf(s, "inconsistent types for symbol and its Outer %s (%v != %v)",
s.Outer.Name, s.Type, s.Outer.Type)
}
}
data[symnro] = ro
data[symnrelro] = relro
}
}
// Sort symbols.
var dataMaxAlign [sym.SXREF]int32
var wg sync.WaitGroup
for symn := range data {
symn := sym.SymKind(symn)
wg.Add(1)
go func() {
data[symn], dataMaxAlign[symn] = dodataSect(ctxt, symn, data[symn])
wg.Done()
}()
}
wg.Wait()
// Allocate sections.
// Data is processed before segtext, because we need
// to see all symbols in the .data and .bss sections in order
// to generate garbage collection information.
datsize := int64(0)
// Writable data sections that do not need any specialized handling.
writable := []sym.SymKind{
sym.SELFSECT,
sym.SMACHO,
sym.SMACHOGOT,
sym.SWINDOWS,
}
for _, symn := range writable {
for _, s := range data[symn] {
sect := addsection(ctxt.Arch, &Segdata, s.Name, 06)
sect.Align = symalign(s)
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
s.Sect = sect
s.Type = sym.SDATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
sect.Length = uint64(datsize) - sect.Vaddr
}
checkdatsize(ctxt, datsize, symn)
}
// .got (and .toc on ppc64)
if len(data[sym.SELFGOT]) > 0 {
sect := addsection(ctxt.Arch, &Segdata, ".got", 06)
sect.Align = dataMaxAlign[sym.SELFGOT]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
var toc *sym.Symbol
for _, s := range data[sym.SELFGOT] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SDATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
// Resolve .TOC. symbol for this object file (ppc64)
toc = ctxt.Syms.ROLookup(".TOC.", int(s.Version))
if toc != nil {
toc.Sect = sect
toc.Outer = s
toc.Sub = s.Sub
s.Sub = toc
toc.Value = 0x8000
}
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SELFGOT)
sect.Length = uint64(datsize) - sect.Vaddr
}
/* pointer-free data */
sect := addsection(ctxt.Arch, &Segdata, ".noptrdata", 06)
sect.Align = dataMaxAlign[sym.SNOPTRDATA]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.noptrdata", 0).Sect = sect
ctxt.Syms.Lookup("runtime.enoptrdata", 0).Sect = sect
for _, s := range data[sym.SNOPTRDATA] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SDATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SNOPTRDATA)
sect.Length = uint64(datsize) - sect.Vaddr
hasinitarr := ctxt.linkShared
/* shared library initializer */
switch ctxt.BuildMode {
case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePlugin:
hasinitarr = true
}
if hasinitarr {
sect := addsection(ctxt.Arch, &Segdata, ".init_array", 06)
sect.Align = dataMaxAlign[sym.SINITARR]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
for _, s := range data[sym.SINITARR] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
sect.Length = uint64(datsize) - sect.Vaddr
checkdatsize(ctxt, datsize, sym.SINITARR)
}
/* data */
sect = addsection(ctxt.Arch, &Segdata, ".data", 06)
sect.Align = dataMaxAlign[sym.SDATA]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.data", 0).Sect = sect
ctxt.Syms.Lookup("runtime.edata", 0).Sect = sect
var gc GCProg
gc.Init(ctxt, "runtime.gcdata")
for _, s := range data[sym.SDATA] {
s.Sect = sect
s.Type = sym.SDATA
datsize = aligndatsize(datsize, s)
s.Value = int64(uint64(datsize) - sect.Vaddr)
gc.AddSym(s)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SDATA)
sect.Length = uint64(datsize) - sect.Vaddr
gc.End(int64(sect.Length))
/* bss */
sect = addsection(ctxt.Arch, &Segdata, ".bss", 06)
sect.Align = dataMaxAlign[sym.SBSS]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.bss", 0).Sect = sect
ctxt.Syms.Lookup("runtime.ebss", 0).Sect = sect
gc = GCProg{}
gc.Init(ctxt, "runtime.gcbss")
for _, s := range data[sym.SBSS] {
s.Sect = sect
datsize = aligndatsize(datsize, s)
s.Value = int64(uint64(datsize) - sect.Vaddr)
gc.AddSym(s)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SBSS)
sect.Length = uint64(datsize) - sect.Vaddr
gc.End(int64(sect.Length))
/* pointer-free bss */
sect = addsection(ctxt.Arch, &Segdata, ".noptrbss", 06)
sect.Align = dataMaxAlign[sym.SNOPTRBSS]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.noptrbss", 0).Sect = sect
ctxt.Syms.Lookup("runtime.enoptrbss", 0).Sect = sect
for _, s := range data[sym.SNOPTRBSS] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
sect.Length = uint64(datsize) - sect.Vaddr
ctxt.Syms.Lookup("runtime.end", 0).Sect = sect
checkdatsize(ctxt, datsize, sym.SNOPTRBSS)
if len(data[sym.STLSBSS]) > 0 {
var sect *sym.Section
if ctxt.IsELF && (ctxt.LinkMode == LinkExternal || !*FlagD) {
sect = addsection(ctxt.Arch, &Segdata, ".tbss", 06)
sect.Align = int32(ctxt.Arch.PtrSize)
sect.Vaddr = 0
}
datsize = 0
for _, s := range data[sym.STLSBSS] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Value = datsize
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.STLSBSS)
if sect != nil {
sect.Length = uint64(datsize)
}
}
/*
* We finished data, begin read-only data.
* Not all systems support a separate read-only non-executable data section.
* ELF systems do.
* OS X and Plan 9 do not.
* Windows PE may, but if so we have not implemented it.
* And if we're using external linking mode, the point is moot,
* since it's not our decision; that code expects the sections in
* segtext.
*/
var segro *sym.Segment
if ctxt.IsELF && ctxt.LinkMode == LinkInternal {
segro = &Segrodata
} else {
segro = &Segtext
}
datsize = 0
/* read-only executable ELF, Mach-O sections */
if len(data[sym.STEXT]) != 0 {
Errorf(nil, "dodata found an sym.STEXT symbol: %s", data[sym.STEXT][0].Name)
}
for _, s := range data[sym.SELFRXSECT] {
sect := addsection(ctxt.Arch, &Segtext, s.Name, 04)
sect.Align = symalign(s)
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
sect.Length = uint64(datsize) - sect.Vaddr
checkdatsize(ctxt, datsize, sym.SELFRXSECT)
}
/* read-only data */
sect = addsection(ctxt.Arch, segro, ".rodata", 04)
sect.Vaddr = 0
ctxt.Syms.Lookup("runtime.rodata", 0).Sect = sect
ctxt.Syms.Lookup("runtime.erodata", 0).Sect = sect
if !ctxt.UseRelro() {
ctxt.Syms.Lookup("runtime.types", 0).Sect = sect
ctxt.Syms.Lookup("runtime.etypes", 0).Sect = sect
}
for _, symn := range sym.ReadOnly {
align := dataMaxAlign[symn]
if sect.Align < align {
sect.Align = align
}
}
datsize = Rnd(datsize, int64(sect.Align))
for _, symn := range sym.ReadOnly {
for _, s := range data[symn] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, symn)
}
sect.Length = uint64(datsize) - sect.Vaddr
/* read-only ELF, Mach-O sections */
for _, s := range data[sym.SELFROSECT] {
sect = addsection(ctxt.Arch, segro, s.Name, 04)
sect.Align = symalign(s)
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
sect.Length = uint64(datsize) - sect.Vaddr
}
checkdatsize(ctxt, datsize, sym.SELFROSECT)
for _, s := range data[sym.SMACHOPLT] {
sect = addsection(ctxt.Arch, segro, s.Name, 04)
sect.Align = symalign(s)
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
sect.Length = uint64(datsize) - sect.Vaddr
}
checkdatsize(ctxt, datsize, sym.SMACHOPLT)
// There is some data that are conceptually read-only but are written to by
// relocations. On GNU systems, we can arrange for the dynamic linker to
// mprotect sections after relocations are applied by giving them write
// permissions in the object file and calling them ".data.rel.ro.FOO". We
// divide the .rodata section between actual .rodata and .data.rel.ro.rodata,
// but for the other sections that this applies to, we just write a read-only
// .FOO section or a read-write .data.rel.ro.FOO section depending on the
// situation.
// TODO(mwhudson): It would make sense to do this more widely, but it makes
// the system linker segfault on darwin.
addrelrosection := func(suffix string) *sym.Section {
return addsection(ctxt.Arch, segro, suffix, 04)
}
if ctxt.UseRelro() {
addrelrosection = func(suffix string) *sym.Section {
seg := &Segrelrodata
if ctxt.LinkMode == LinkExternal {
// Using a separate segment with an external
// linker results in some programs moving
// their data sections unexpectedly, which
// corrupts the moduledata. So we use the
// rodata segment and let the external linker
// sort out a rel.ro segment.
seg = &Segrodata
}
return addsection(ctxt.Arch, seg, ".data.rel.ro"+suffix, 06)
}
/* data only written by relocations */
sect = addrelrosection("")
sect.Vaddr = 0
ctxt.Syms.Lookup("runtime.types", 0).Sect = sect
ctxt.Syms.Lookup("runtime.etypes", 0).Sect = sect
for _, symnro := range sym.ReadOnly {
symn := sym.RelROMap[symnro]
align := dataMaxAlign[symn]
if sect.Align < align {
sect.Align = align
}
}
datsize = Rnd(datsize, int64(sect.Align))
for _, symnro := range sym.ReadOnly {
symn := sym.RelROMap[symnro]
for _, s := range data[symn] {
datsize = aligndatsize(datsize, s)
if s.Outer != nil && s.Outer.Sect != nil && s.Outer.Sect != sect {
Errorf(s, "s.Outer (%s) in different section from s, %s != %s", s.Outer.Name, s.Outer.Sect.Name, sect.Name)
}
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, symn)
}
sect.Length = uint64(datsize) - sect.Vaddr
}
/* typelink */
sect = addrelrosection(".typelink")
sect.Align = dataMaxAlign[sym.STYPELINK]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
typelink := ctxt.Syms.Lookup("runtime.typelink", 0)
typelink.Sect = sect
typelink.Type = sym.SRODATA
datsize += typelink.Size
checkdatsize(ctxt, datsize, sym.STYPELINK)
sect.Length = uint64(datsize) - sect.Vaddr
/* itablink */
sect = addrelrosection(".itablink")
sect.Align = dataMaxAlign[sym.SITABLINK]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.itablink", 0).Sect = sect
ctxt.Syms.Lookup("runtime.eitablink", 0).Sect = sect
for _, s := range data[sym.SITABLINK] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SITABLINK)
sect.Length = uint64(datsize) - sect.Vaddr
/* gosymtab */
sect = addrelrosection(".gosymtab")
sect.Align = dataMaxAlign[sym.SSYMTAB]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.symtab", 0).Sect = sect
ctxt.Syms.Lookup("runtime.esymtab", 0).Sect = sect
for _, s := range data[sym.SSYMTAB] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SSYMTAB)
sect.Length = uint64(datsize) - sect.Vaddr
/* gopclntab */
sect = addrelrosection(".gopclntab")
sect.Align = dataMaxAlign[sym.SPCLNTAB]
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
ctxt.Syms.Lookup("runtime.pclntab", 0).Sect = sect
ctxt.Syms.Lookup("runtime.epclntab", 0).Sect = sect
for _, s := range data[sym.SPCLNTAB] {
datsize = aligndatsize(datsize, s)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
}
checkdatsize(ctxt, datsize, sym.SRODATA)
sect.Length = uint64(datsize) - sect.Vaddr
// 6g uses 4-byte relocation offsets, so the entire segment must fit in 32 bits.
if datsize != int64(uint32(datsize)) {
Errorf(nil, "read-only data segment too large: %d", datsize)
}
for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ {
datap = append(datap, data[symn]...)
}
dwarfgeneratedebugsyms(ctxt)
var i int
for ; i < len(dwarfp); i++ {
s := dwarfp[i]
if s.Type != sym.SDWARFSECT {
break
}
sect = addsection(ctxt.Arch, &Segdwarf, s.Name, 04)
sect.Align = 1
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
datsize += s.Size
sect.Length = uint64(datsize) - sect.Vaddr
}
checkdatsize(ctxt, datsize, sym.SDWARFSECT)
for i < len(dwarfp) {
curType := dwarfp[i].Type
var sect *sym.Section
switch curType {
case sym.SDWARFINFO:
sect = addsection(ctxt.Arch, &Segdwarf, ".debug_info", 04)
case sym.SDWARFRANGE:
sect = addsection(ctxt.Arch, &Segdwarf, ".debug_ranges", 04)
case sym.SDWARFLOC:
sect = addsection(ctxt.Arch, &Segdwarf, ".debug_loc", 04)
default:
Errorf(dwarfp[i], "unknown DWARF section %v", curType)
}
sect.Align = 1
datsize = Rnd(datsize, int64(sect.Align))
sect.Vaddr = uint64(datsize)
for ; i < len(dwarfp); i++ {
s := dwarfp[i]
if s.Type != curType {
break
}
s.Sect = sect
s.Type = sym.SRODATA
s.Value = int64(uint64(datsize) - sect.Vaddr)
s.Attr |= sym.AttrLocal
datsize += s.Size
}
sect.Length = uint64(datsize) - sect.Vaddr
checkdatsize(ctxt, datsize, curType)
}
/* number the sections */
n := int32(1)
for _, sect := range Segtext.Sections {
sect.Extnum = int16(n)
n++
}
for _, sect := range Segrodata.Sections {
sect.Extnum = int16(n)
n++
}
for _, sect := range Segrelrodata.Sections {
sect.Extnum = int16(n)
n++
}
for _, sect := range Segdata.Sections {
sect.Extnum = int16(n)
n++
}
for _, sect := range Segdwarf.Sections {
sect.Extnum = int16(n)
n++
}
}
func dodataSect(ctxt *Link, symn sym.SymKind, syms []*sym.Symbol) (result []*sym.Symbol, maxAlign int32) {
if ctxt.HeadType == objabi.Hdarwin {
// Some symbols may no longer belong in syms
// due to movement in machosymorder.
newSyms := make([]*sym.Symbol, 0, len(syms))
for _, s := range syms {
if s.Type == symn {
newSyms = append(newSyms, s)
}
}
syms = newSyms
}
var head, tail *sym.Symbol
symsSort := make([]dataSortKey, 0, len(syms))
for _, s := range syms {
if s.Attr.OnList() {
log.Fatalf("symbol %s listed multiple times", s.Name)
}
s.Attr |= sym.AttrOnList
switch {
case s.Size < int64(len(s.P)):
Errorf(s, "initialize bounds (%d < %d)", s.Size, len(s.P))
case s.Size < 0:
Errorf(s, "negative size (%d bytes)", s.Size)
case s.Size > cutoff:
Errorf(s, "symbol too large (%d bytes)", s.Size)
}
// If the usually-special section-marker symbols are being laid
// out as regular symbols, put them either at the beginning or
// end of their section.
if ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin {
switch s.Name {
case "runtime.text", "runtime.bss", "runtime.data", "runtime.types":
head = s
continue
case "runtime.etext", "runtime.ebss", "runtime.edata", "runtime.etypes":
tail = s
continue
}
}
key := dataSortKey{
size: s.Size,
name: s.Name,
sym: s,
}
switch s.Type {
case sym.SELFGOT:
// For ppc64, we want to interleave the .got and .toc sections
// from input files. Both are type sym.SELFGOT, so in that case
// we skip size comparison and fall through to the name
// comparison (conveniently, .got sorts before .toc).
key.size = 0
}
symsSort = append(symsSort, key)
}
sort.Sort(bySizeAndName(symsSort))
off := 0
if head != nil {
syms[0] = head
off++
}
for i, symSort := range symsSort {
syms[i+off] = symSort.sym
align := symalign(symSort.sym)
if maxAlign < align {
maxAlign = align
}
}
if tail != nil {
syms[len(syms)-1] = tail
}
if ctxt.IsELF && symn == sym.SELFROSECT {
// Make .rela and .rela.plt contiguous, the ELF ABI requires this
// and Solaris actually cares.
reli, plti := -1, -1
for i, s := range syms {
switch s.Name {
case ".rel.plt", ".rela.plt":
plti = i
case ".rel", ".rela":
reli = i
}
}
if reli >= 0 && plti >= 0 && plti != reli+1 {
var first, second int
if plti > reli {
first, second = reli, plti
} else {
first, second = plti, reli
}
rel, plt := syms[reli], syms[plti]
copy(syms[first+2:], syms[first+1:second])
syms[first+0] = rel
syms[first+1] = plt
// Make sure alignment doesn't introduce a gap.
// Setting the alignment explicitly prevents
// symalign from basing it on the size and
// getting it wrong.
rel.Align = int32(ctxt.Arch.RegSize)
plt.Align = int32(ctxt.Arch.RegSize)
}
}
return syms, maxAlign
}
// Add buildid to beginning of text segment, on non-ELF systems.
// Non-ELF binary formats are not always flexible enough to
// give us a place to put the Go build ID. On those systems, we put it
// at the very beginning of the text segment.
// This ``header'' is read by cmd/go.
func (ctxt *Link) textbuildid() {
if ctxt.IsELF || ctxt.BuildMode == BuildModePlugin || *flagBuildid == "" {
return
}
s := ctxt.Syms.Lookup("go.buildid", 0)
s.Attr |= sym.AttrReachable
// The \xff is invalid UTF-8, meant to make it less likely
// to find one of these accidentally.
data := "\xff Go build ID: " + strconv.Quote(*flagBuildid) + "\n \xff"
s.Type = sym.STEXT
s.P = []byte(data)
s.Size = int64(len(s.P))
ctxt.Textp = append(ctxt.Textp, nil)
copy(ctxt.Textp[1:], ctxt.Textp)
ctxt.Textp[0] = s
}
// assign addresses to text
func (ctxt *Link) textaddress() {
addsection(ctxt.Arch, &Segtext, ".text", 05)
// Assign PCs in text segment.
// Could parallelize, by assigning to text
// and then letting threads copy down, but probably not worth it.
sect := Segtext.Sections[0]
sect.Align = int32(Funcalign)
text := ctxt.Syms.Lookup("runtime.text", 0)
text.Sect = sect
if ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin {
etext := ctxt.Syms.Lookup("runtime.etext", 0)
etext.Sect = sect
ctxt.Textp = append(ctxt.Textp, etext, nil)
copy(ctxt.Textp[1:], ctxt.Textp)
ctxt.Textp[0] = text
}
va := uint64(*FlagTextAddr)
n := 1
sect.Vaddr = va
ntramps := 0
for _, s := range ctxt.Textp {
sect, n, va = assignAddress(ctxt, sect, n, s, va, false)
trampoline(ctxt, s) // resolve jumps, may add trampolines if jump too far
// lay down trampolines after each function
for ; ntramps < len(ctxt.tramps); ntramps++ {
tramp := ctxt.tramps[ntramps]
sect, n, va = assignAddress(ctxt, sect, n, tramp, va, true)
}
}
sect.Length = va - sect.Vaddr
ctxt.Syms.Lookup("runtime.etext", 0).Sect = sect
// merge tramps into Textp, keeping Textp in address order
if ntramps != 0 {
newtextp := make([]*sym.Symbol, 0, len(ctxt.Textp)+ntramps)
i := 0
for _, s := range ctxt.Textp {
for ; i < ntramps && ctxt.tramps[i].Value < s.Value; i++ {
newtextp = append(newtextp, ctxt.tramps[i])
}
newtextp = append(newtextp, s)
}
newtextp = append(newtextp, ctxt.tramps[i:ntramps]...)
ctxt.Textp = newtextp
}
}
// assigns address for a text symbol, returns (possibly new) section, its number, and the address
// Note: once we have trampoline insertion support for external linking, this function
// will not need to create new text sections, and so no need to return sect and n.
func assignAddress(ctxt *Link, sect *sym.Section, n int, s *sym.Symbol, va uint64, isTramp bool) (*sym.Section, int, uint64) {
s.Sect = sect
if s.Attr.SubSymbol() {
return sect, n, va
}
if s.Align != 0 {
va = uint64(Rnd(int64(va), int64(s.Align)))
} else {
va = uint64(Rnd(int64(va), int64(Funcalign)))
}
s.Value = 0
for sub := s; sub != nil; sub = sub.Sub {
sub.Value += int64(va)
}
funcsize := uint64(MINFUNC) // spacing required for findfunctab
if s.Size > MINFUNC {
funcsize = uint64(s.Size)
}
// On ppc64x a text section should not be larger than 2^26 bytes due to the size of
// call target offset field in the bl instruction. Splitting into smaller text
// sections smaller than this limit allows the GNU linker to modify the long calls
// appropriately. The limit allows for the space needed for tables inserted by the linker.
// If this function doesn't fit in the current text section, then create a new one.
// Only break at outermost syms.
if ctxt.Arch.InFamily(sys.PPC64) && s.Outer == nil && ctxt.IsELF && ctxt.LinkMode == LinkExternal && va-sect.Vaddr+funcsize+maxSizeTrampolinesPPC64(s, isTramp) > 0x1c00000 {
// Set the length for the previous text section
sect.Length = va - sect.Vaddr
// Create new section, set the starting Vaddr
sect = addsection(ctxt.Arch, &Segtext, ".text", 05)
sect.Vaddr = va
s.Sect = sect
// Create a symbol for the start of the secondary text sections
ctxt.Syms.Lookup(fmt.Sprintf("runtime.text.%d", n), 0).Sect = sect
n++
}
va += funcsize
return sect, n, va
}
// assign addresses
func (ctxt *Link) address() {
va := uint64(*FlagTextAddr)
Segtext.Rwx = 05
Segtext.Vaddr = va
Segtext.Fileoff = uint64(HEADR)
for _, s := range Segtext.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segtext.Length = va - uint64(*FlagTextAddr)
Segtext.Filelen = Segtext.Length
if ctxt.HeadType == objabi.Hnacl {
va += 32 // room for the "halt sled"
}
if len(Segrodata.Sections) > 0 {
// align to page boundary so as not to mix
// rodata and executable text.
//
// Note: gold or GNU ld will reduce the size of the executable
// file by arranging for the relro segment to end at a page
// boundary, and overlap the end of the text segment with the
// start of the relro segment in the file. The PT_LOAD segments
// will be such that the last page of the text segment will be
// mapped twice, once r-x and once starting out rw- and, after
// relocation processing, changed to r--.
//
// Ideally the last page of the text segment would not be
// writable even for this short period.
va = uint64(Rnd(int64(va), int64(*FlagRound)))
Segrodata.Rwx = 04
Segrodata.Vaddr = va
Segrodata.Fileoff = va - Segtext.Vaddr + Segtext.Fileoff
Segrodata.Filelen = 0
for _, s := range Segrodata.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segrodata.Length = va - Segrodata.Vaddr
Segrodata.Filelen = Segrodata.Length
}
if len(Segrelrodata.Sections) > 0 {
// align to page boundary so as not to mix
// rodata, rel-ro data, and executable text.
va = uint64(Rnd(int64(va), int64(*FlagRound)))
Segrelrodata.Rwx = 06
Segrelrodata.Vaddr = va
Segrelrodata.Fileoff = va - Segrodata.Vaddr + Segrodata.Fileoff
Segrelrodata.Filelen = 0
for _, s := range Segrelrodata.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segrelrodata.Length = va - Segrelrodata.Vaddr
Segrelrodata.Filelen = Segrelrodata.Length
}
va = uint64(Rnd(int64(va), int64(*FlagRound)))
Segdata.Rwx = 06
Segdata.Vaddr = va
Segdata.Fileoff = va - Segtext.Vaddr + Segtext.Fileoff
Segdata.Filelen = 0
if ctxt.HeadType == objabi.Hwindows {
Segdata.Fileoff = Segtext.Fileoff + uint64(Rnd(int64(Segtext.Length), PEFILEALIGN))
}
if ctxt.HeadType == objabi.Hplan9 {
Segdata.Fileoff = Segtext.Fileoff + Segtext.Filelen
}
var data *sym.Section
var noptr *sym.Section
var bss *sym.Section
var noptrbss *sym.Section
for i, s := range Segdata.Sections {
if ctxt.IsELF && s.Name == ".tbss" {
continue
}
vlen := int64(s.Length)
if i+1 < len(Segdata.Sections) && !(ctxt.IsELF && Segdata.Sections[i+1].Name == ".tbss") {
vlen = int64(Segdata.Sections[i+1].Vaddr - s.Vaddr)
}
s.Vaddr = va
va += uint64(vlen)
Segdata.Length = va - Segdata.Vaddr
if s.Name == ".data" {
data = s
}
if s.Name == ".noptrdata" {
noptr = s
}
if s.Name == ".bss" {
bss = s
}
if s.Name == ".noptrbss" {
noptrbss = s
}
}
Segdata.Filelen = bss.Vaddr - Segdata.Vaddr
va = uint64(Rnd(int64(va), int64(*FlagRound)))
Segdwarf.Rwx = 06
Segdwarf.Vaddr = va
Segdwarf.Fileoff = Segdata.Fileoff + uint64(Rnd(int64(Segdata.Filelen), int64(*FlagRound)))
Segdwarf.Filelen = 0
if ctxt.HeadType == objabi.Hwindows {
Segdwarf.Fileoff = Segdata.Fileoff + uint64(Rnd(int64(Segdata.Filelen), int64(PEFILEALIGN)))
}
for i, s := range Segdwarf.Sections {
vlen := int64(s.Length)
if i+1 < len(Segdwarf.Sections) {
vlen = int64(Segdwarf.Sections[i+1].Vaddr - s.Vaddr)
}
s.Vaddr = va
va += uint64(vlen)
if ctxt.HeadType == objabi.Hwindows {
va = uint64(Rnd(int64(va), PEFILEALIGN))
}
Segdwarf.Length = va - Segdwarf.Vaddr
}
Segdwarf.Filelen = va - Segdwarf.Vaddr
var (
text = Segtext.Sections[0]
rodata = ctxt.Syms.Lookup("runtime.rodata", 0).Sect
itablink = ctxt.Syms.Lookup("runtime.itablink", 0).Sect
symtab = ctxt.Syms.Lookup("runtime.symtab", 0).Sect
pclntab = ctxt.Syms.Lookup("runtime.pclntab", 0).Sect
types = ctxt.Syms.Lookup("runtime.types", 0).Sect
)
lasttext := text
// Could be multiple .text sections
for _, sect := range Segtext.Sections {
if sect.Name == ".text" {
lasttext = sect
}
}
for _, s := range datap {
if s.Sect != nil {
s.Value += int64(s.Sect.Vaddr)
}
for sub := s.Sub; sub != nil; sub = sub.Sub {
sub.Value += s.Value
}
}
for _, s := range dwarfp {
if s.Sect != nil {
s.Value += int64(s.Sect.Vaddr)
}
for sub := s.Sub; sub != nil; sub = sub.Sub {
sub.Value += s.Value
}
}
if ctxt.BuildMode == BuildModeShared {
s := ctxt.Syms.Lookup("go.link.abihashbytes", 0)
sectSym := ctxt.Syms.Lookup(".note.go.abihash", 0)
s.Sect = sectSym.Sect
s.Value = int64(sectSym.Sect.Vaddr + 16)
}
ctxt.xdefine("runtime.text", sym.STEXT, int64(text.Vaddr))
ctxt.xdefine("runtime.etext", sym.STEXT, int64(lasttext.Vaddr+lasttext.Length))
// If there are multiple text sections, create runtime.text.n for
// their section Vaddr, using n for index
n := 1
for _, sect := range Segtext.Sections[1:] {
if sect.Name != ".text" {
break
}
symname := fmt.Sprintf("runtime.text.%d", n)
ctxt.xdefine(symname, sym.STEXT, int64(sect.Vaddr))
n++
}
ctxt.xdefine("runtime.rodata", sym.SRODATA, int64(rodata.Vaddr))
ctxt.xdefine("runtime.erodata", sym.SRODATA, int64(rodata.Vaddr+rodata.Length))
ctxt.xdefine("runtime.types", sym.SRODATA, int64(types.Vaddr))
ctxt.xdefine("runtime.etypes", sym.SRODATA, int64(types.Vaddr+types.Length))
ctxt.xdefine("runtime.itablink", sym.SRODATA, int64(itablink.Vaddr))
ctxt.xdefine("runtime.eitablink", sym.SRODATA, int64(itablink.Vaddr+itablink.Length))
s := ctxt.Syms.Lookup("runtime.gcdata", 0)
s.Attr |= sym.AttrLocal
ctxt.xdefine("runtime.egcdata", sym.SRODATA, Symaddr(s)+s.Size)
ctxt.Syms.Lookup("runtime.egcdata", 0).Sect = s.Sect
s = ctxt.Syms.Lookup("runtime.gcbss", 0)
s.Attr |= sym.AttrLocal
ctxt.xdefine("runtime.egcbss", sym.SRODATA, Symaddr(s)+s.Size)
ctxt.Syms.Lookup("runtime.egcbss", 0).Sect = s.Sect
ctxt.xdefine("runtime.symtab", sym.SRODATA, int64(symtab.Vaddr))
ctxt.xdefine("runtime.esymtab", sym.SRODATA, int64(symtab.Vaddr+symtab.Length))
ctxt.xdefine("runtime.pclntab", sym.SRODATA, int64(pclntab.Vaddr))
ctxt.xdefine("runtime.epclntab", sym.SRODATA, int64(pclntab.Vaddr+pclntab.Length))
ctxt.xdefine("runtime.noptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr))
ctxt.xdefine("runtime.enoptrdata", sym.SNOPTRDATA, int64(noptr.Vaddr+noptr.Length))
ctxt.xdefine("runtime.bss", sym.SBSS, int64(bss.Vaddr))
ctxt.xdefine("runtime.ebss", sym.SBSS, int64(bss.Vaddr+bss.Length))
ctxt.xdefine("runtime.data", sym.SDATA, int64(data.Vaddr))
ctxt.xdefine("runtime.edata", sym.SDATA, int64(data.Vaddr+data.Length))
ctxt.xdefine("runtime.noptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr))
ctxt.xdefine("runtime.enoptrbss", sym.SNOPTRBSS, int64(noptrbss.Vaddr+noptrbss.Length))
ctxt.xdefine("runtime.end", sym.SBSS, int64(Segdata.Vaddr+Segdata.Length))
}
// add a trampoline with symbol s (to be laid down after the current function)
func (ctxt *Link) AddTramp(s *sym.Symbol) {
s.Type = sym.STEXT
s.Attr |= sym.AttrReachable
s.Attr |= sym.AttrOnList
ctxt.tramps = append(ctxt.tramps, s)
if *FlagDebugTramp > 0 && ctxt.Debugvlog > 0 {
ctxt.Logf("trampoline %s inserted\n", s)
}
}