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// Derived from Inferno utils/6l/obj.c and utils/6l/span.c
// https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/obj.c
// https://bitbucket.org/inferno-os/inferno-os/src/master/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 (
"bytes"
"cmd/internal/gcprog"
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"compress/zlib"
"debug/elf"
"encoding/binary"
"fmt"
"log"
"os"
"sort"
"strconv"
"strings"
"sync"
"sync/atomic"
)
// isRuntimeDepPkg reports 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
"internal/abi", // used by reflectcall (and maybe more)
"internal/bytealg", // for IndexByte
"internal/cpu": // for cpu features
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 maxSizeTrampolines(ctxt *Link, ldr *loader.Loader, s loader.Sym, 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)
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if r.Type().IsDirectCallOrJump() {
n++
}
}
if ctxt.IsPPC64() {
return n * 16 // Trampolines in PPC64 are 4 instructions.
}
if ctxt.IsARM64() {
return n * 12 // Trampolines in ARM64 are 3 instructions.
}
panic("unreachable")
}
// Detect too-far jumps in function s, and add trampolines if necessary.
// ARM, PPC64, PPC64LE and RISCV64 support trampoline insertion for internal
// and external linking. On PPC64 and PPC64LE the text sections might be split
// but will still insert trampolines where necessary.
func trampoline(ctxt *Link, s loader.Sym) {
if thearch.Trampoline == nil {
return // no need or no support of trampolines on this arch
}
ldr := ctxt.loader
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
rt := r.Type()
if !rt.IsDirectCallOrJump() && !isPLTCall(rt) {
continue
}
rs := r.Sym()
if !ldr.AttrReachable(rs) || ldr.SymType(rs) == sym.Sxxx {
continue // something is wrong. skip it here and we'll emit a better error later
}
// RISC-V is only able to reach +/-1MiB via a JAL instruction,
// which we can readily exceed in the same package. As such, we
// need to generate trampolines when the address is unknown.
if ldr.SymValue(rs) == 0 && !ctxt.Target.IsRISCV64() && ldr.SymType(rs) != sym.SDYNIMPORT && ldr.SymType(rs) != sym.SUNDEFEXT {
if ldr.SymPkg(s) != "" && ldr.SymPkg(rs) == ldr.SymPkg(s) {
// Symbols in the same package are laid out together.
// Except that if SymPkg(s) == "", it is a host object symbol
// which may call an external symbol via PLT.
continue
}
if isRuntimeDepPkg(ldr.SymPkg(s)) && isRuntimeDepPkg(ldr.SymPkg(rs)) {
continue // runtime packages are laid out together
}
}
thearch.Trampoline(ctxt, ldr, ri, rs, s)
}
}
// whether rt is a (host object) relocation that will be turned into
// a call to PLT.
func isPLTCall(rt objabi.RelocType) bool {
const pcrel = 1
switch rt {
// ARM64
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_CALL26),
objabi.ElfRelocOffset + objabi.RelocType(elf.R_AARCH64_JUMP26),
objabi.MachoRelocOffset + MACHO_ARM64_RELOC_BRANCH26*2 + pcrel:
return true
// ARM
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_CALL),
objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_PC24),
objabi.ElfRelocOffset + objabi.RelocType(elf.R_ARM_JUMP24):
return true
}
// TODO: other architectures.
return false
}
// FoldSubSymbolOffset computes the offset of symbol s to its top-level outer
// symbol. Returns the top-level symbol and the offset.
// This is used in generating external relocations.
func FoldSubSymbolOffset(ldr *loader.Loader, s loader.Sym) (loader.Sym, int64) {
outer := ldr.OuterSym(s)
off := int64(0)
if outer != 0 {
off += ldr.SymValue(s) - ldr.SymValue(outer)
s = outer
}
return s, off
}
// relocsym resolve relocations in "s", updating the symbol's content
// in "P".
// The main loop walks through the list of relocations attached to "s"
// and resolves them where applicable. Relocations are often
// architecture-specific, requiring calls into the 'archreloc' and/or
// 'archrelocvariant' functions for the architecture. When external
// linking is in effect, it may not be possible to completely resolve
// the address/offset for a symbol, in which case the goal is to lay
// the groundwork for turning a given relocation into an external reloc
// (to be applied by the external linker). For more on how relocations
// work in general, see
//
// "Linkers and Loaders", by John R. Levine (Morgan Kaufmann, 1999), ch. 7
//
// This is a performance-critical function for the linker; be careful
// to avoid introducing unnecessary allocations in the main loop.
func (st *relocSymState) relocsym(s loader.Sym, P []byte) {
ldr := st.ldr
relocs := ldr.Relocs(s)
if relocs.Count() == 0 {
return
}
target := st.target
syms := st.syms
nExtReloc := 0 // number of external relocations
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
off := r.Off()
siz := int32(r.Siz())
rs := r.Sym()
rt := r.Type()
weak := r.Weak()
if off < 0 || off+siz > int32(len(P)) {
rname := ""
if rs != 0 {
rname = ldr.SymName(rs)
}
st.err.Errorf(s, "invalid relocation %s: %d+%d not in [%d,%d)", rname, off, siz, 0, len(P))
continue
}
if siz == 0 { // informational relocation - no work to do
continue
}
var rst sym.SymKind
if rs != 0 {
rst = ldr.SymType(rs)
}
if rs != 0 && ((rst == sym.Sxxx && !ldr.AttrVisibilityHidden(rs)) || rst == sym.SXREF) {
// When putting the runtime but not main into a shared library
// these symbols are undefined and that's OK.
if target.IsShared() || target.IsPlugin() {
if ldr.SymName(rs) == "main.main" || (!target.IsPlugin() && ldr.SymName(rs) == "main..inittask") {
sb := ldr.MakeSymbolUpdater(rs)
sb.SetType(sym.SDYNIMPORT)
} else if strings.HasPrefix(ldr.SymName(rs), "go.info.") {
// Skip go.info symbols. They are only needed to communicate
// DWARF info between the compiler and linker.
continue
}
} else {
st.err.errorUnresolved(ldr, s, rs)
continue
}
}
if rt >= objabi.ElfRelocOffset {
continue
}
// We need to be able to reference dynimport symbols when linking against
// shared libraries, and AIX, Darwin, OpenBSD and Solaris always need it.
if !target.IsAIX() && !target.IsDarwin() && !target.IsSolaris() && !target.IsOpenbsd() && rs != 0 && rst == sym.SDYNIMPORT && !target.IsDynlinkingGo() && !ldr.AttrSubSymbol(rs) {
if !(target.IsPPC64() && target.IsExternal() && ldr.SymName(rs) == ".TOC.") {
st.err.Errorf(s, "unhandled relocation for %s (type %d (%s) rtype %d (%s))", ldr.SymName(rs), rst, rst, rt, sym.RelocName(target.Arch, rt))
}
}
if rs != 0 && rst != sym.STLSBSS && !weak && rt != objabi.R_METHODOFF && !ldr.AttrReachable(rs) {
st.err.Errorf(s, "unreachable sym in relocation: %s", ldr.SymName(rs))
}
var rv sym.RelocVariant
if target.IsPPC64() || target.IsS390X() {
rv = ldr.RelocVariant(s, ri)
}
// TODO(mundaym): remove this special case - see issue 14218.
if target.IsS390X() {
switch rt {
case objabi.R_PCRELDBL:
rt = objabi.R_PCREL
rv = sym.RV_390_DBL
case objabi.R_CALL:
rv = sym.RV_390_DBL
}
}
var o int64
switch rt {
default:
switch siz {
default:
st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs))
case 1:
o = int64(P[off])
case 2:
o = int64(target.Arch.ByteOrder.Uint16(P[off:]))
case 4:
o = int64(target.Arch.ByteOrder.Uint32(P[off:]))
case 8:
o = int64(target.Arch.ByteOrder.Uint64(P[off:]))
}
out, n, ok := thearch.Archreloc(target, ldr, syms, r, s, o)
if target.IsExternal() {
nExtReloc += n
}
if ok {
o = out
} else {
st.err.Errorf(s, "unknown reloc to %v: %d (%s)", ldr.SymName(rs), rt, sym.RelocName(target.Arch, rt))
}
case objabi.R_TLS_LE:
if target.IsExternal() && target.IsElf() {
nExtReloc++
o = 0
if !target.IsAMD64() {
o = r.Add()
}
break
}
if target.IsElf() && target.IsARM() {
// 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 + ldr.SymValue(rs)
} else if target.IsElf() || target.IsPlan9() || target.IsDarwin() {
o = int64(syms.Tlsoffset) + r.Add()
} else if target.IsWindows() {
o = r.Add()
} else {
log.Fatalf("unexpected R_TLS_LE relocation for %v", target.HeadType)
}
case objabi.R_TLS_IE:
if target.IsExternal() && target.IsElf() {
nExtReloc++
o = 0
if !target.IsAMD64() {
o = r.Add()
}
if target.Is386() {
nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1
}
break
}
if target.IsPIE() && target.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", target.Arch.Family)
}
thearch.TLSIEtoLE(P, int(off), int(siz))
o = int64(syms.Tlsoffset)
} else {
log.Fatalf("cannot handle R_TLS_IE (sym %s) when linking internally", ldr.SymName(s))
}
case objabi.R_ADDR:
if weak && !ldr.AttrReachable(rs) {
// Redirect it to runtime.unreachableMethod, which will throw if called.
rs = syms.unreachableMethod
}
if target.IsExternal() {
nExtReloc++
// set up addend for eventual relocation via outer symbol.
rs := rs
rs, off := FoldSubSymbolOffset(ldr, rs)
xadd := r.Add() + off
rst := ldr.SymType(rs)
if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs))
}
o = xadd
if target.IsElf() {
if target.IsAMD64() {
o = 0
}
} else if target.IsDarwin() {
if ldr.SymType(rs) != sym.SHOSTOBJ {
o += ldr.SymValue(rs)
}
} else if target.IsWindows() {
// nothing to do
} else if target.IsAIX() {
o = ldr.SymValue(rs) + xadd
} else {
st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType)
}
break
}
// On AIX, a second relocation must be done by the loader,
// as section addresses can change once loaded.
// The "default" symbol address is still needed by the loader so
// the current relocation can't be skipped.
if target.IsAIX() && rst != sym.SDYNIMPORT {
// It's not possible to make a loader relocation in a
// symbol which is not inside .data section.
// FIXME: It should be forbidden to have R_ADDR from a
// symbol which isn't in .data. However, as .text has the
// same address once loaded, this is possible.
if ldr.SymSect(s).Seg == &Segdata {
Xcoffadddynrel(target, ldr, syms, s, r, ri)
}
}
o = ldr.SymValue(rs) + 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 && target.Arch.PtrSize > 4 && siz == 4 {
st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x (%#x + %#x)", ldr.SymName(rs), uint64(o), ldr.SymValue(rs), r.Add())
errorexit()
}
case objabi.R_DWARFSECREF:
if ldr.SymSect(rs) == nil {
st.err.Errorf(s, "missing DWARF section for relocation target %s", ldr.SymName(rs))
}
if target.IsExternal() {
// 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 !target.IsDarwin() {
nExtReloc++
}
xadd := r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr)
o = xadd
if target.IsElf() && target.IsAMD64() {
o = 0
}
break
}
o = ldr.SymValue(rs) + r.Add() - int64(ldr.SymSect(rs).Vaddr)
case objabi.R_METHODOFF:
if !ldr.AttrReachable(rs) {
// Set it to a sentinel value. The runtime knows this is not pointing to
// anything valid.
o = -1
break
}
fallthrough
case objabi.R_ADDROFF:
if weak && !ldr.AttrReachable(rs) {
continue
}
if ldr.SymSect(rs) == nil {
st.err.Errorf(s, "unreachable sym in relocation: %s", ldr.SymName(rs))
continue
}
// 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 ldr.SymSect(rs).Name == ".text" {
o = ldr.SymValue(rs) - int64(Segtext.Sections[0].Vaddr) + r.Add()
} else {
o = ldr.SymValue(rs) - int64(ldr.SymSect(rs).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 = ldr.SymValue(rs) + r.Add() - ldr.SymValue(loader.Sym(ldr.SymUnit(rs).Textp[0]))
// r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call.
case objabi.R_GOTPCREL:
if target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 {
nExtReloc++
o = r.Add()
break
}
if target.Is386() && target.IsExternal() && target.IsELF {
nExtReloc++ // need two ELF relocations on 386, see ../x86/asm.go:elfreloc1
}
fallthrough
case objabi.R_CALL, objabi.R_PCREL:
if target.IsExternal() && rs != 0 && rst == sym.SUNDEFEXT {
// pass through to the external linker.
nExtReloc++
o = 0
break
}
if target.IsExternal() && rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) {
nExtReloc++
// set up addend for eventual relocation via outer symbol.
rs := rs
rs, off := FoldSubSymbolOffset(ldr, rs)
xadd := r.Add() + off - int64(siz) // relative to address after the relocated chunk
rst := ldr.SymType(rs)
if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && ldr.SymSect(rs) == nil {
st.err.Errorf(s, "missing section for relocation target %s", ldr.SymName(rs))
}
o = xadd
if target.IsElf() {
if target.IsAMD64() {
o = 0
}
} else if target.IsDarwin() {
if rt == objabi.R_CALL {
if target.IsExternal() && rst == sym.SDYNIMPORT {
if target.IsAMD64() {
// AMD64 dynamic relocations are relative to the end of the relocation.
o += int64(siz)
}
} else {
if rst != sym.SHOSTOBJ {
o += int64(uint64(ldr.SymValue(rs)) - ldr.SymSect(rs).Vaddr)
}
o -= int64(off) // relative to section offset, not symbol
}
} else {
o += int64(siz)
}
} else if target.IsWindows() && target.IsAMD64() { // 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(siz)
} else {
st.err.Errorf(s, "unhandled pcrel relocation to %s on %v", ldr.SymName(rs), target.HeadType)
}
break
}
o = 0
if rs != 0 {
o = ldr.SymValue(rs)
}
o += r.Add() - (ldr.SymValue(s) + int64(off) + int64(siz))
case objabi.R_SIZE:
o = ldr.SymSize(rs) + r.Add()
case objabi.R_XCOFFREF:
if !target.IsAIX() {
st.err.Errorf(s, "find XCOFF R_REF on non-XCOFF files")
}
if !target.IsExternal() {
st.err.Errorf(s, "find XCOFF R_REF with internal linking")
}
nExtReloc++
continue
case objabi.R_DWARFFILEREF:
// We don't renumber files in dwarf.go:writelines anymore.
continue
case objabi.R_CONST:
o = r.Add()
case objabi.R_GOTOFF:
o = ldr.SymValue(rs) + r.Add() - ldr.SymValue(syms.GOT)
}
if target.IsPPC64() || target.IsS390X() {
if rv != sym.RV_NONE {
o = thearch.Archrelocvariant(target, ldr, r, rv, s, o, P)
}
}
switch siz {
default:
st.err.Errorf(s, "bad reloc size %#x for %s", uint32(siz), ldr.SymName(rs))
case 1:
P[off] = byte(int8(o))
case 2:
if o != int64(int16(o)) {
st.err.Errorf(s, "relocation address for %s is too big: %#x", ldr.SymName(rs), o)
}
target.Arch.ByteOrder.PutUint16(P[off:], uint16(o))
case 4:
if rt == objabi.R_PCREL || rt == objabi.R_CALL {
if o != int64(int32(o)) {
st.err.Errorf(s, "pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), o)
}
} else {
if o != int64(int32(o)) && o != int64(uint32(o)) {
st.err.Errorf(s, "non-pc-relative relocation address for %s is too big: %#x", ldr.SymName(rs), uint64(o))
}
}
target.Arch.ByteOrder.PutUint32(P[off:], uint32(o))
case 8:
target.Arch.ByteOrder.PutUint64(P[off:], uint64(o))
}
}
if target.IsExternal() {
// We'll stream out the external relocations in asmb2 (e.g. elfrelocsect)
// and we only need the count here.
atomic.AddUint32(&ldr.SymSect(s).Relcount, uint32(nExtReloc))
}
}
// Convert a Go relocation to an external relocation.
func extreloc(ctxt *Link, ldr *loader.Loader, s loader.Sym, r loader.Reloc) (loader.ExtReloc, bool) {
var rr loader.ExtReloc
target := &ctxt.Target
siz := int32(r.Siz())
if siz == 0 { // informational relocation - no work to do
return rr, false
}
rt := r.Type()
if rt >= objabi.ElfRelocOffset {
return rr, false
}
rr.Type = rt
rr.Size = uint8(siz)
// TODO(mundaym): remove this special case - see issue 14218.
if target.IsS390X() {
switch rt {
case objabi.R_PCRELDBL:
rt = objabi.R_PCREL
}
}
switch rt {
default:
return thearch.Extreloc(target, ldr, r, s)
case objabi.R_TLS_LE, objabi.R_TLS_IE:
if target.IsElf() {
rs := r.Sym()
rr.Xsym = rs
if rr.Xsym == 0 {
rr.Xsym = ctxt.Tlsg
}
rr.Xadd = r.Add()
break
}
return rr, false
case objabi.R_ADDR:
// set up addend for eventual relocation via outer symbol.
rs := r.Sym()
if r.Weak() && !ldr.AttrReachable(rs) {
rs = ctxt.ArchSyms.unreachableMethod
}
rs, off := FoldSubSymbolOffset(ldr, rs)
rr.Xadd = r.Add() + off
rr.Xsym = rs
case objabi.R_DWARFSECREF:
// 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 target.IsDarwin() {
return rr, false
}
rs := r.Sym()
rr.Xsym = loader.Sym(ldr.SymSect(rs).Sym)
rr.Xadd = r.Add() + ldr.SymValue(rs) - int64(ldr.SymSect(rs).Vaddr)
// r.Sym() can be 0 when CALL $(constant) is transformed from absolute PC to relative PC call.
case objabi.R_GOTPCREL, objabi.R_CALL, objabi.R_PCREL:
rs := r.Sym()
if rt == objabi.R_GOTPCREL && target.IsDynlinkingGo() && target.IsDarwin() && rs != 0 {
rr.Xadd = r.Add()
rr.Xadd -= int64(siz) // relative to address after the relocated chunk
rr.Xsym = rs
break
}
if rs != 0 && ldr.SymType(rs) == sym.SUNDEFEXT {
// pass through to the external linker.
rr.Xadd = 0
if target.IsElf() {
rr.Xadd -= int64(siz)
}
rr.Xsym = rs
break
}
if rs != 0 && (ldr.SymSect(rs) != ldr.SymSect(s) || rt == objabi.R_GOTPCREL) {
// set up addend for eventual relocation via outer symbol.
rs := rs
rs, off := FoldSubSymbolOffset(ldr, rs)
rr.Xadd = r.Add() + off
rr.Xadd -= int64(siz) // relative to address after the relocated chunk
rr.Xsym = rs
break
}
return rr, false
case objabi.R_XCOFFREF:
return ExtrelocSimple(ldr, r), true
// These reloc types don't need external relocations.
case objabi.R_ADDROFF, objabi.R_METHODOFF, objabi.R_ADDRCUOFF,
objabi.R_SIZE, objabi.R_CONST, objabi.R_GOTOFF:
return rr, false
}
return rr, true
}
// ExtrelocSimple creates a simple external relocation from r, with the same
// symbol and addend.
func ExtrelocSimple(ldr *loader.Loader, r loader.Reloc) loader.ExtReloc {
var rr loader.ExtReloc
rs := r.Sym()
rr.Xsym = rs
rr.Xadd = r.Add()
rr.Type = r.Type()
rr.Size = r.Siz()
return rr
}
// ExtrelocViaOuterSym creates an external relocation from r targeting the
// outer symbol and folding the subsymbol's offset into the addend.
func ExtrelocViaOuterSym(ldr *loader.Loader, r loader.Reloc, s loader.Sym) loader.ExtReloc {
// set up addend for eventual relocation via outer symbol.
var rr loader.ExtReloc
rs := r.Sym()
rs, off := FoldSubSymbolOffset(ldr, rs)
rr.Xadd = r.Add() + off
rst := ldr.SymType(rs)
if rst != sym.SHOSTOBJ && rst != sym.SDYNIMPORT && rst != sym.SUNDEFEXT && ldr.SymSect(rs) == nil {
ldr.Errorf(s, "missing section for %s", ldr.SymName(rs))
}
rr.Xsym = rs
rr.Type = r.Type()
rr.Size = r.Siz()
return rr
}
// relocSymState hold state information needed when making a series of
// successive calls to relocsym(). The items here are invariant
// (meaning that they are set up once initially and then don't change
// during the execution of relocsym), with the exception of a slice
// used to facilitate batch allocation of external relocations. Calls
// to relocsym happen in parallel; the assumption is that each
// parallel thread will have its own state object.
type relocSymState struct {
target *Target
ldr *loader.Loader
err *ErrorReporter
syms *ArchSyms
}
// makeRelocSymState creates a relocSymState container object to
// pass to relocsym(). If relocsym() calls happen in parallel,
// each parallel thread should have its own state object.
func (ctxt *Link) makeRelocSymState() *relocSymState {
return &relocSymState{
target: &ctxt.Target,
ldr: ctxt.loader,
err: &ctxt.ErrorReporter,
syms: &ctxt.ArchSyms,
}
}
func windynrelocsym(ctxt *Link, rel *loader.SymbolBuilder, s loader.Sym) {
var su *loader.SymbolBuilder
relocs := ctxt.loader.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if r.IsMarker() {
continue // skip marker relocations
}
targ := r.Sym()
if targ == 0 {
continue
}
if !ctxt.loader.AttrReachable(targ) {
if r.Weak() {
continue
}
ctxt.Errorf(s, "dynamic relocation to unreachable symbol %s",
ctxt.loader.SymName(targ))
}
tplt := ctxt.loader.SymPlt(targ)
tgot := ctxt.loader.SymGot(targ)
if tplt == -2 && tgot != -2 { // make dynimport JMP table for PE object files.
tplt := int32(rel.Size())
ctxt.loader.SetPlt(targ, tplt)
if su == nil {
su = ctxt.loader.MakeSymbolUpdater(s)
}
r.SetSym(rel.Sym())
r.SetAdd(int64(tplt))
// jmp *addr
switch ctxt.Arch.Family {
default:
ctxt.Errorf(s, "unsupported arch %v", ctxt.Arch.Family)
return
case sys.I386:
rel.AddUint8(0xff)
rel.AddUint8(0x25)
rel.AddAddrPlus(ctxt.Arch, targ, 0)
rel.AddUint8(0x90)
rel.AddUint8(0x90)
case sys.AMD64:
rel.AddUint8(0xff)
rel.AddUint8(0x24)
rel.AddUint8(0x25)
rel.AddAddrPlus4(ctxt.Arch, targ, 0)
rel.AddUint8(0x90)
}
} else if tplt >= 0 {
if su == nil {
su = ctxt.loader.MakeSymbolUpdater(s)
}
r.SetSym(rel.Sym())
r.SetAdd(int64(tplt))
}
}
}
// windynrelocsyms generates jump table to C library functions that will be
// added later. windynrelocsyms writes the table into .rel symbol.
func (ctxt *Link) windynrelocsyms() {
if !(ctxt.IsWindows() && iscgo && ctxt.IsInternal()) {
return
}
rel := ctxt.loader.CreateSymForUpdate(".rel", 0)
rel.SetType(sym.STEXT)
for _, s := range ctxt.Textp {
windynrelocsym(ctxt, rel, s)
}
ctxt.Textp = append(ctxt.Textp, rel.Sym())
}
func dynrelocsym(ctxt *Link, s loader.Sym) {
target := &ctxt.Target
ldr := ctxt.loader
syms := &ctxt.ArchSyms
relocs := ldr.Relocs(s)
for ri := 0; ri < relocs.Count(); ri++ {
r := relocs.At(ri)
if r.IsMarker() {
continue // skip marker relocations
}
rSym := r.Sym()
if r.Weak() && !ldr.AttrReachable(rSym) {
continue
}
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(target, ldr, syms, s, r, ri)
continue
}
if rSym != 0 && ldr.SymType(rSym) == sym.SDYNIMPORT || r.Type() >= objabi.ElfRelocOffset {
if rSym != 0 && !ldr.AttrReachable(rSym) {
ctxt.Errorf(s, "dynamic relocation to unreachable symbol %s", ldr.SymName(rSym))
}
if !thearch.Adddynrel(target, ldr, syms, s, r, ri) {
ctxt.Errorf(s, "unsupported dynamic relocation for symbol %s (type=%d (%s) stype=%d (%s))", ldr.SymName(rSym), r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymType(rSym), ldr.SymType(rSym))
}
}
}
}
func (state *dodataState) dynreloc(ctxt *Link) {
if ctxt.HeadType == objabi.Hwindows {
return
}
// -d suppresses dynamic loader format, so we may as well not
// compute these sections or mark their symbols as reachable.
if *FlagD {
return
}
for _, s := range ctxt.Textp {
dynrelocsym(ctxt, s)
}
for _, syms := range state.data {
for _, s := range syms {
dynrelocsym(ctxt, s)
}
}
if ctxt.IsELF {
elfdynhash(ctxt)
}
}
func CodeblkPad(ctxt *Link, out *OutBuf, addr int64, size int64, pad []byte) {
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.Textp, addr, size, pad)
}
const blockSize = 1 << 20 // 1MB chunks written at a time.
// writeBlocks writes a specified chunk of symbols to the output buffer. It
// breaks the write up into ≥blockSize chunks to write them out, and schedules
// as many goroutines as necessary to accomplish this task. This call then
// blocks, waiting on the writes to complete. Note that we use the sem parameter
// to limit the number of concurrent writes taking place.
func writeBlocks(ctxt *Link, out *OutBuf, sem chan int, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
for i, s := range syms {
if ldr.SymValue(s) >= addr && !ldr.AttrSubSymbol(s) {
syms = syms[i:]
break
}
}
var wg sync.WaitGroup
max, lastAddr, written := int64(blockSize), addr+size, int64(0)
for addr < lastAddr {
// Find the last symbol we'd write.
idx := -1
for i, s := range syms {
if ldr.AttrSubSymbol(s) {
continue
}
// If the next symbol's size would put us out of bounds on the total length,
// stop looking.
end := ldr.SymValue(s) + ldr.SymSize(s)
if end > lastAddr {
break
}
// We're gonna write this symbol.
idx = i
// If we cross over the max size, we've got enough symbols.
if end > addr+max {
break
}
}
// If we didn't find any symbols to write, we're done here.
if idx < 0 {
break
}
// Compute the length to write, including padding.
// We need to write to the end address (lastAddr), or the next symbol's
// start address, whichever comes first. If there is no more symbols,
// just write to lastAddr. This ensures we don't leave holes between the
// blocks or at the end.
length := int64(0)
if idx+1 < len(syms) {
// Find the next top-level symbol.
// Skip over sub symbols so we won't split a containter symbol
// into two blocks.
next := syms[idx+1]
for ldr.AttrSubSymbol(next) {
idx++
next = syms[idx+1]
}
length = ldr.SymValue(next) - addr
}
if length == 0 || length > lastAddr-addr {
length = lastAddr - addr
}
// Start the block output operator.
if o, err := out.View(uint64(out.Offset() + written)); err == nil {
sem <- 1
wg.Add(1)
go func(o *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
writeBlock(ctxt, o, ldr, syms, addr, size, pad)
wg.Done()
<-sem
}(o, ldr, syms, addr, length, pad)
} else { // output not mmaped, don't parallelize.
writeBlock(ctxt, out, ldr, syms, addr, length, pad)
}
// Prepare for the next loop.
if idx != -1 {
syms = syms[idx+1:]
}
written += length
addr += length
}
wg.Wait()
}
func writeBlock(ctxt *Link, out *OutBuf, ldr *loader.Loader, syms []loader.Sym, addr, size int64, pad []byte) {
st := ctxt.makeRelocSymState()
// This doesn't distinguish the memory size from the file
// size, and it lays out the file based on Symbol.Value, which
// is the virtual address. DWARF compression changes file sizes,
// so dwarfcompress will fix this up later if necessary.
eaddr := addr + size
for _, s := range syms {
if ldr.AttrSubSymbol(s) {
continue
}
val := ldr.SymValue(s)
if val >= eaddr {
break
}
if val < addr {
ldr.Errorf(s, "phase error: addr=%#x but sym=%#x type=%v sect=%v", addr, val, ldr.SymType(s), ldr.SymSect(s).Name)
errorexit()
}
if addr < val {
out.WriteStringPad("", int(val-addr), pad)
addr = val
}
P := out.WriteSym(ldr, s)
st.relocsym(s, P)
if f, ok := ctxt.generatorSyms[s]; ok {
f(ctxt, s)
}
addr += int64(len(P))
siz := ldr.SymSize(s)
if addr < val+siz {
out.WriteStringPad("", int(val+siz-addr), pad)
addr = val + siz
}
if addr != val+siz {
ldr.Errorf(s, "phase error: addr=%#x value+size=%#x", addr, val+siz)
errorexit()
}
if val+siz >= eaddr {
break
}
}
if addr < eaddr {
out.WriteStringPad("", int(eaddr-addr), pad)
}
}
type writeFn func(*Link, *OutBuf, int64, int64)
// writeParallel handles scheduling parallel execution of data write functions.
func writeParallel(wg *sync.WaitGroup, fn writeFn, ctxt *Link, seek, vaddr, length uint64) {
if out, err := ctxt.Out.View(seek); err != nil {
ctxt.Out.SeekSet(int64(seek))
fn(ctxt, ctxt.Out, int64(vaddr), int64(length))
} else {
wg.Add(1)
go func() {
defer wg.Done()
fn(ctxt, out, int64(vaddr), int64(length))
}()
}
}
func datblk(ctxt *Link, out *OutBuf, addr, size int64) {
writeDatblkToOutBuf(ctxt, out, addr, size)
}
// Used only on Wasm for now.
func DatblkBytes(ctxt *Link, addr int64, size int64) []byte {
buf := make([]byte, size)
out := &OutBuf{heap: buf}
writeDatblkToOutBuf(ctxt, out, addr, size)
return buf
}
func writeDatblkToOutBuf(ctxt *Link, out *OutBuf, addr int64, size int64) {
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, ctxt.datap, addr, size, zeros[:])
}
func dwarfblk(ctxt *Link, out *OutBuf, addr int64, size int64) {
// Concatenate the section symbol lists into a single list to pass
// to writeBlocks.
//
// NB: ideally we would do a separate writeBlocks call for each
// section, but this would run the risk of undoing any file offset
// adjustments made during layout.
n := 0
for i := range dwarfp {
n += len(dwarfp[i].syms)
}
syms := make([]loader.Sym, 0, n)
for i := range dwarfp {
syms = append(syms, dwarfp[i].syms...)
}
writeBlocks(ctxt, out, ctxt.outSem, ctxt.loader, syms, 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
}
// addstrdata sets the initial value of the string variable name to value.
func addstrdata(arch *sys.Arch, l *loader.Loader, name, value string) {
s := l.Lookup(name, 0)
if s == 0 {
return
}
if goType := l.SymGoType(s); goType == 0 {
return
} else if typeName := l.SymName(goType); typeName != "type.string" {
Errorf(nil, "%s: cannot set with -X: not a var of type string (%s)", name, typeName)
return
}
if !l.AttrReachable(s) {
return // don't bother setting unreachable variable
}
bld := l.MakeSymbolUpdater(s)
if bld.Type() == sym.SBSS {
bld.SetType(sym.SDATA)
}
p := fmt.Sprintf("%s.str", name)
sbld := l.CreateSymForUpdate(p, 0)
sbld.Addstring(value)
sbld.SetType(sym.SRODATA)
bld.SetSize(0)
bld.SetData(make([]byte, 0, arch.PtrSize*2))
bld.SetReadOnly(false)
bld.ResetRelocs()
bld.AddAddrPlus(arch, sbld.Sym(), 0)
bld.AddUint(arch, uint64(len(value)))
}
func (ctxt *Link) dostrdata() {
for _, name := range strnames {
addstrdata(ctxt.Arch, ctxt.loader, name, strdata[name])
}
}
// 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, ldr *loader.Loader, s *loader.SymbolBuilder, symname, str string) {
sdata := ldr.CreateSymForUpdate(symname, 0)
if sdata.Type() != sym.Sxxx {
ctxt.Errorf(s.Sym(), "duplicate symname in addgostring: %s", symname)
}
sdata.SetLocal(true)
sdata.SetType(sym.SRODATA)
sdata.SetSize(int64(len(str)))
sdata.SetData([]byte(str))
s.AddAddr(ctxt.Arch, sdata.Sym())
s.AddUint(ctxt.Arch, uint64(len(str)))
}
func addinitarrdata(ctxt *Link, ldr *loader.Loader, s loader.Sym) {
p := ldr.SymName(s) + ".ptr"
sp := ldr.CreateSymForUpdate(p, 0)
sp.SetType(sym.SINITARR)
sp.SetSize(0)
sp.SetDuplicateOK(true)
sp.AddAddr(ctxt.Arch, s)
}
// symalign returns the required alignment for the given symbol s.
func symalign(ldr *loader.Loader, s loader.Sym) int32 {
min := int32(thearch.Minalign)
align := ldr.SymAlign(s)
if align >= min {
return align
} else if align != 0 {
return min
}
align = int32(thearch.Maxalign)
ssz := ldr.SymSize(s)
for int64(align) > ssz && align > min {
align >>= 1
}
ldr.SetSymAlign(s, align)
return align
}
func aligndatsize(state *dodataState, datsize int64, s loader.Sym) int64 {
return Rnd(datsize, int64(symalign(state.ctxt.loader, s)))
}
const debugGCProg = false
type GCProg struct {
ctxt *Link
sym *loader.SymbolBuilder
w gcprog.Writer
}
func (p *GCProg) Init(ctxt *Link, name string) {
p.ctxt = ctxt
p.sym = ctxt.loader.CreateSymForUpdate(name, 0)
p.w.Init(p.writeByte())
if debugGCProg {
fmt.Fprintf(os.Stderr, "ld: start GCProg %s\n", name)
p.w.Debug(os.Stderr)
}
}
func (p *GCProg) writeByte() 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 loader.Sym) {
ldr := p.ctxt.loader
typ := ldr.SymGoType(s)
// 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 == 0 {
switch ldr.SymName(s) {
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
}
p.ctxt.Errorf(p.sym.Sym(), "missing Go type information for global symbol %s: size %d", ldr.SymName(s), ldr.SymSize(s))
return
}
ptrsize := int64(p.ctxt.Arch.PtrSize)
typData := ldr.Data(typ)
nptr := decodetypePtrdata(p.ctxt.Arch, typData) / ptrsize
if debugGCProg {
fmt.Fprintf(os.Stderr, "gcprog sym: %s at %d (ptr=%d+%d)\n", ldr.SymName(s), ldr.SymValue(s), ldr.SymValue(s)/ptrsize, nptr)
}
sval := ldr.SymValue(s)
if decodetypeUsegcprog(p.ctxt.Arch, typData) == 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(sval/ptrsize + i)
}
}
return
}
// Copy program.
prog := decodetypeGcprog(p.ctxt, typ)
p.w.ZeroUntil(sval / ptrsize)
p.w.Append(prog[4:], nptr)
}
// 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 (state *dodataState) checkdatsize(symn sym.SymKind) {
if state.datsize > cutoff {
Errorf(nil, "too much data in section %v (over %v bytes)", symn, cutoff)
}
}
// fixZeroSizedSymbols gives a few special symbols with zero size some space.
func fixZeroSizedSymbols(ctxt *Link) {
// 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.
//
// On AIX, as all DATA sections are merged together, ld might not put
// these symbols at the beginning of their respective section if there
// aren't real symbols, their alignment might not match the
// first symbol alignment. Therefore, there are explicitly put at the
// beginning of their section with the same alignment.
if !(ctxt.DynlinkingGo() && ctxt.HeadType == objabi.Hdarwin) && !(ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
return
}
ldr := ctxt.loader
bss := ldr.CreateSymForUpdate("runtime.bss", 0)
bss.SetSize(8)
ldr.SetAttrSpecial(bss.Sym(), false)
ebss := ldr.CreateSymForUpdate("runtime.ebss", 0)
ldr.SetAttrSpecial(ebss.Sym(), false)
data := ldr.CreateSymForUpdate("runtime.data", 0)
data.SetSize(8)
ldr.SetAttrSpecial(data.Sym(), false)
edata := ldr.CreateSymForUpdate("runtime.edata", 0)
ldr.SetAttrSpecial(edata.Sym(), false)
if ctxt.HeadType == objabi.Haix {
// XCOFFTOC symbols are part of .data section.
edata.SetType(sym.SXCOFFTOC)
}
types := ldr.CreateSymForUpdate("runtime.types", 0)
types.SetType(sym.STYPE)
types.SetSize(8)
ldr.SetAttrSpecial(types.Sym(), false)
etypes := ldr.CreateSymForUpdate("runtime.etypes", 0)
etypes.SetType(sym.SFUNCTAB)
ldr.SetAttrSpecial(etypes.Sym(), false)
if ctxt.HeadType == objabi.Haix {
rodata := ldr.CreateSymForUpdate("runtime.rodata", 0)
rodata.SetType(sym.SSTRING)
rodata.SetSize(8)
ldr.SetAttrSpecial(rodata.Sym(), false)
erodata := ldr.CreateSymForUpdate("runtime.erodata", 0)
ldr.SetAttrSpecial(erodata.Sym(), false)
}
}
// makeRelroForSharedLib creates a section of readonly data if necessary.
func (state *dodataState) makeRelroForSharedLib(target *Link) {
if !target.UseRelro() {
return
}
// "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.
ldr := target.loader
for _, symnro := range sym.ReadOnly {
symnrelro := sym.RelROMap[symnro]
ro := []loader.Sym{}
relro := state.data[symnrelro]
for _, s := range state.data[symnro] {
relocs := ldr.Relocs(s)
isRelro := relocs.Count() > 0
switch state.symType(s) {
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
case sym.SFUNCTAB:
if ldr.SymName(s) == "runtime.etypes" {
// runtime.etypes must be at the end of
// the relro data.
isRelro = true
}
case sym.SGOFUNC:
// The only SGOFUNC symbols that contain relocations are .stkobj,
// and their relocations are of type objabi.R_ADDROFF,
// which always get resolved during linking.
isRelro = false
}
if isRelro {
state.setSymType(s, symnrelro)
if outer := ldr.OuterSym(s); outer != 0 {
state.setSymType(outer, symnrelro)
}
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 outer := ldr.OuterSym(s); outer != 0 {
st := state.symType(s)
ost := state.symType(outer)
if st != ost {
state.ctxt.Errorf(s, "inconsistent types for symbol and its Outer %s (%v != %v)",
ldr.SymName(outer), st, ost)
}
}
}
state.data[symnro] = ro
state.data[symnrelro] = relro
}
}
// dodataState holds bits of state information needed by dodata() and the
// various helpers it calls. The lifetime of these items should not extend
// past the end of dodata().
type dodataState struct {
// Link context
ctxt *Link
// Data symbols bucketed by type.
data [sym.SXREF][]loader.Sym
// Max alignment for each flavor of data symbol.
dataMaxAlign [sym.SXREF]int32
// Overridden sym type
symGroupType []sym.SymKind
// Current data size so far.
datsize int64
}
// A note on symType/setSymType below:
//
// In the legacy linker, the types of symbols (notably data symbols) are
// changed during the symtab() phase so as to insure that similar symbols
// are bucketed together, then their types are changed back again during
// dodata. Symbol to section assignment also plays tricks along these lines
// in the case where a relro segment is needed.
//
// The value returned from setType() below reflects the effects of
// any overrides made by symtab and/or dodata.
// symType returns the (possibly overridden) type of 's'.
func (state *dodataState) symType(s loader.Sym) sym.SymKind {
if int(s) < len(state.symGroupType) {
if override := state.symGroupType[s]; override != 0 {
return override
}
}
return state.ctxt.loader.SymType(s)
}
// setSymType sets a new override type for 's'.
func (state *dodataState) setSymType(s loader.Sym, kind sym.SymKind) {
if s == 0 {
panic("bad")
}
if int(s) < len(state.symGroupType) {
state.symGroupType[s] = kind
} else {
su := state.ctxt.loader.MakeSymbolUpdater(s)
su.SetType(kind)
}
}
func (ctxt *Link) dodata(symGroupType []sym.SymKind) {
// Give zeros sized symbols space if necessary.
fixZeroSizedSymbols(ctxt)
// Collect data symbols by type into data.
state := dodataState{ctxt: ctxt, symGroupType: symGroupType}
ldr := ctxt.loader
for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ {
if !ldr.AttrReachable(s) || ldr.AttrSpecial(s) || ldr.AttrSubSymbol(s) ||
!ldr.TopLevelSym(s) {
continue
}
st := state.symType(s)
if st <= sym.STEXT || st >= sym.SXREF {
continue
}
state.data[st] = append(state.data[st], s)
// Similarly with checking the onlist attr.
if ldr.AttrOnList(s) {
log.Fatalf("symbol %s listed multiple times", ldr.SymName(s))
}
ldr.SetAttrOnList(s, true)
}
// 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)
}
state.dynreloc(ctxt)
// Move any RO data with relocations to a separate section.
state.makeRelroForSharedLib(ctxt)
// Set alignment for the symbol with the largest known index,
// so as to trigger allocation of the loader's internal
// alignment array. This will avoid data races in the parallel
// section below.
lastSym := loader.Sym(ldr.NSym() - 1)
ldr.SetSymAlign(lastSym, ldr.SymAlign(lastSym))
// Sort symbols.
var wg sync.WaitGroup
for symn := range state.data {
symn := sym.SymKind(symn)
wg.Add(1)
go func() {
state.data[symn], state.dataMaxAlign[symn] = state.dodataSect(ctxt, symn, state.data[symn])
wg.Done()
}()
}
wg.Wait()
if ctxt.IsELF {
// Make .rela and .rela.plt contiguous, the ELF ABI requires this
// and Solaris actually cares.
syms := state.data[sym.SELFROSECT]
reli, plti := -1, -1
for i, s := range syms {
switch ldr.SymName(s) {
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.
ldr.SetSymAlign(rel, int32(ctxt.Arch.RegSize))
ldr.SetSymAlign(plt, int32(ctxt.Arch.RegSize))
}
state.data[sym.SELFROSECT] = syms
}
if ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal {
// These symbols must have the same alignment as their section.
// Otherwise, ld might change the layout of Go sections.
ldr.SetSymAlign(ldr.Lookup("runtime.data", 0), state.dataMaxAlign[sym.SDATA])
ldr.SetSymAlign(ldr.Lookup("runtime.bss", 0), state.dataMaxAlign[sym.SBSS])
}
// Create *sym.Section objects and assign symbols to sections for
// data/rodata (and related) symbols.
state.allocateDataSections(ctxt)
// Create *sym.Section objects and assign symbols to sections for
// DWARF symbols.
state.allocateDwarfSections(ctxt)
/* number the sections */
n := int16(1)
for _, sect := range Segtext.Sections {
sect.Extnum = n
n++
}
for _, sect := range Segrodata.Sections {
sect.Extnum = n
n++
}
for _, sect := range Segrelrodata.Sections {
sect.Extnum = n
n++
}
for _, sect := range Segdata.Sections {
sect.Extnum = n
n++
}
for _, sect := range Segdwarf.Sections {
sect.Extnum = n
n++
}
}
// allocateDataSectionForSym creates a new sym.Section into which a a
// single symbol will be placed. Here "seg" is the segment into which
// the section will go, "s" is the symbol to be placed into the new
// section, and "rwx" contains permissions for the section.
func (state *dodataState) allocateDataSectionForSym(seg *sym.Segment, s loader.Sym, rwx int) *sym.Section {
ldr := state.ctxt.loader
sname := ldr.SymName(s)
sect := addsection(ldr, state.ctxt.Arch, seg, sname, rwx)
sect.Align = symalign(ldr, s)
state.datsize = Rnd(state.datsize, int64(sect.Align))
sect.Vaddr = uint64(state.datsize)
return sect
}
// allocateNamedDataSection creates a new sym.Section for a category
// of data symbols. Here "seg" is the segment into which the section
// will go, "sName" is the name to give to the section, "types" is a
// range of symbol types to be put into the section, and "rwx"
// contains permissions for the section.
func (state *dodataState) allocateNamedDataSection(seg *sym.Segment, sName string, types []sym.SymKind, rwx int) *sym.Section {
sect := addsection(state.ctxt.loader, state.ctxt.Arch, seg, sName, rwx)
if len(types) == 0 {
sect.Align = 1
} else if len(types) == 1 {
sect.Align = state.dataMaxAlign[types[0]]
} else {
for _, symn := range types {
align := state.dataMaxAlign[symn]
if sect.Align < align {
sect.Align = align
}
}
}
state.datsize = Rnd(state.datsize, int64(sect.Align))
sect.Vaddr = uint64(state.datsize)
return sect
}
// assignDsymsToSection assigns a collection of data symbols to a
// newly created section. "sect" is the section into which to place
// the symbols, "syms" holds the list of symbols to assign,
// "forceType" (if non-zero) contains a new sym type to apply to each
// sym during the assignment, and "aligner" is a hook to call to
// handle alignment during the assignment process.
func (state *dodataState) assignDsymsToSection(sect *sym.Section, syms []loader.Sym, forceType sym.SymKind, aligner func(state *dodataState, datsize int64, s loader.Sym) int64) {
ldr := state.ctxt.loader
for _, s := range syms {
state.datsize = aligner(state, state.datsize, s)
ldr.SetSymSect(s, sect)
if forceType != sym.Sxxx {
state.setSymType(s, forceType)
}
ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
state.datsize += ldr.SymSize(s)
}
sect.Length = uint64(state.datsize) - sect.Vaddr
}
func (state *dodataState) assignToSection(sect *sym.Section, symn sym.SymKind, forceType sym.SymKind) {
state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize)
state.checkdatsize(symn)
}
// allocateSingleSymSections walks through the bucketed data symbols
// with type 'symn', creates a new section for each sym, and assigns
// the sym to a newly created section. Section name is set from the
// symbol name. "Seg" is the segment into which to place the new
// section, "forceType" is the new sym.SymKind to assign to the symbol
// within the section, and "rwx" holds section permissions.
func (state *dodataState) allocateSingleSymSections(seg *sym.Segment, symn sym.SymKind, forceType sym.SymKind, rwx int) {
ldr := state.ctxt.loader
for _, s := range state.data[symn] {
sect := state.allocateDataSectionForSym(seg, s, rwx)
ldr.SetSymSect(s, sect)
state.setSymType(s, forceType)
ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
state.datsize += ldr.SymSize(s)
sect.Length = uint64(state.datsize) - sect.Vaddr
}
state.checkdatsize(symn)
}
// allocateNamedSectionAndAssignSyms creates a new section with the
// specified name, then walks through the bucketed data symbols with
// type 'symn' and assigns each of them to this new section. "Seg" is
// the segment into which to place the new section, "secName" is the
// name to give to the new section, "forceType" (if non-zero) contains
// a new sym type to apply to each sym during the assignment, and
// "rwx" holds section permissions.
func (state *dodataState) allocateNamedSectionAndAssignSyms(seg *sym.Segment, secName string, symn sym.SymKind, forceType sym.SymKind, rwx int) *sym.Section {
sect := state.allocateNamedDataSection(seg, secName, []sym.SymKind{symn}, rwx)
state.assignDsymsToSection(sect, state.data[symn], forceType, aligndatsize)
return sect
}
// allocateDataSections allocates sym.Section objects for data/rodata
// (and related) symbols, and then assigns symbols to those sections.
func (state *dodataState) allocateDataSections(ctxt *Link) {
// 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.
// Writable data sections that do not need any specialized handling.
writable := []sym.SymKind{
sym.SBUILDINFO,
sym.SELFSECT,
sym.SMACHO,
sym.SMACHOGOT,
sym.SWINDOWS,
}
for _, symn := range writable {
state.allocateSingleSymSections(&Segdata, symn, sym.SDATA, 06)
}
ldr := ctxt.loader
// .got
if len(state.data[sym.SELFGOT]) > 0 {
state.allocateNamedSectionAndAssignSyms(&Segdata, ".got", sym.SELFGOT, sym.SDATA, 06)
}
/* pointer-free data */
sect := state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrdata", sym.SNOPTRDATA, sym.SDATA, 06)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrdata", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrdata", 0), sect)
hasinitarr := ctxt.linkShared
/* shared library initializer */
switch ctxt.BuildMode {
case BuildModeCArchive, BuildModeCShared, BuildModeShared, BuildModePlugin:
hasinitarr = true
}
if ctxt.HeadType == objabi.Haix {
if len(state.data[sym.SINITARR]) > 0 {
Errorf(nil, "XCOFF format doesn't allow .init_array section")
}
}
if hasinitarr && len(state.data[sym.SINITARR]) > 0 {
state.allocateNamedSectionAndAssignSyms(&Segdata, ".init_array", sym.SINITARR, sym.Sxxx, 06)
}
/* data */
sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".data", sym.SDATA, sym.SDATA, 06)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.data", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.edata", 0), sect)
dataGcEnd := state.datsize - int64(sect.Vaddr)
// On AIX, TOC entries must be the last of .data
// These aren't part of gc as they won't change during the runtime.
state.assignToSection(sect, sym.SXCOFFTOC, sym.SDATA)
state.checkdatsize(sym.SDATA)
sect.Length = uint64(state.datsize) - sect.Vaddr
/* bss */
sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".bss", sym.SBSS, sym.Sxxx, 06)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.bss", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.ebss", 0), sect)
bssGcEnd := state.datsize - int64(sect.Vaddr)
// Emit gcdata for bss symbols now that symbol values have been assigned.
gcsToEmit := []struct {
symName string
symKind sym.SymKind
gcEnd int64
}{
{"runtime.gcdata", sym.SDATA, dataGcEnd},
{"runtime.gcbss", sym.SBSS, bssGcEnd},
}
for _, g := range gcsToEmit {
var gc GCProg
gc.Init(ctxt, g.symName)
for _, s := range state.data[g.symKind] {
gc.AddSym(s)
}
gc.End(g.gcEnd)
}
/* pointer-free bss */
sect = state.allocateNamedSectionAndAssignSyms(&Segdata, ".noptrbss", sym.SNOPTRBSS, sym.Sxxx, 06)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.noptrbss", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.enoptrbss", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.end", 0), sect)
// Coverage instrumentation counters for libfuzzer.
if len(state.data[sym.SLIBFUZZER_EXTRA_COUNTER]) > 0 {
sect := state.allocateNamedSectionAndAssignSyms(&Segdata, "__libfuzzer_extra_counters", sym.SLIBFUZZER_EXTRA_COUNTER, sym.Sxxx, 06)
ldr.SetSymSect(ldr.LookupOrCreateSym("internal/fuzz._counters", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("internal/fuzz._ecounters", 0), sect)
}
if len(state.data[sym.STLSBSS]) > 0 {
var sect *sym.Section
// FIXME: not clear why it is sometimes necessary to suppress .tbss section creation.
if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && (ctxt.LinkMode == LinkExternal || !*FlagD) {
sect = addsection(ldr, ctxt.Arch, &Segdata, ".tbss", 06)
sect.Align = int32(ctxt.Arch.PtrSize)
// FIXME: why does this need to be set to zero?
sect.Vaddr = 0
}
state.datsize = 0
for _, s := range state.data[sym.STLSBSS] {
state.datsize = aligndatsize(state, state.datsize, s)
if sect != nil {
ldr.SetSymSect(s, sect)
}
ldr.SetSymValue(s, state.datsize)
state.datsize += ldr.SymSize(s)
}
state.checkdatsize(sym.STLSBSS)
if sect != nil {
sect.Length = uint64(state.datsize)
}
}
/*
* We finished data, begin read-only data.
* Not all systems support a separate read-only non-executable data section.
* ELF and Windows PE systems do.
* OS X and Plan 9 do not.
* 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 if ctxt.HeadType == objabi.Hwindows {
segro = &Segrodata
} else {
segro = &Segtext
}
state.datsize = 0
/* read-only executable ELF, Mach-O sections */
if len(state.data[sym.STEXT]) != 0 {
culprit := ldr.SymName(state.data[sym.STEXT][0])
Errorf(nil, "dodata found an sym.STEXT symbol: %s", culprit)
}
state.allocateSingleSymSections(&Segtext, sym.SELFRXSECT, sym.SRODATA, 05)
state.allocateSingleSymSections(&Segtext, sym.SMACHOPLT, sym.SRODATA, 05)
/* read-only data */
sect = state.allocateNamedDataSection(segro, ".rodata", sym.ReadOnly, 04)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.rodata", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.erodata", 0), sect)
if !ctxt.UseRelro() {
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect)
}
for _, symn := range sym.ReadOnly {
symnStartValue := state.datsize
state.assignToSection(sect, symn, sym.SRODATA)
setCarrierSize(symn, state.datsize-symnStartValue)
if ctxt.HeadType == objabi.Haix {
// Read-only symbols might be wrapped inside their outer
// symbol.
// XCOFF symbol table needs to know the size of
// these outer symbols.
xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn)
}
}
/* read-only ELF, Mach-O sections */
state.allocateSingleSymSections(segro, sym.SELFROSECT, sym.SRODATA, 04)
// 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.
const relroPerm = 06
const fallbackPerm = 04
relroSecPerm := fallbackPerm
genrelrosecname := func(suffix string) string {
if suffix == "" {
return ".rodata"
}
return suffix
}
seg := segro
if ctxt.UseRelro() {
segrelro := &Segrelrodata
if ctxt.LinkMode == LinkExternal && !ctxt.IsAIX() && !ctxt.IsDarwin() {
// 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.
segrelro = segro
} else {
// Reset datsize for new segment.
state.datsize = 0
}
if !ctxt.IsDarwin() { // We don't need the special names on darwin.
genrelrosecname = func(suffix string) string {
return ".data.rel.ro" + suffix
}
}
relroReadOnly := []sym.SymKind{}
for _, symnro := range sym.ReadOnly {
symn := sym.RelROMap[symnro]
relroReadOnly = append(relroReadOnly, symn)
}
seg = segrelro
relroSecPerm = relroPerm
/* data only written by relocations */
sect = state.allocateNamedDataSection(segrelro, genrelrosecname(""), relroReadOnly, relroSecPerm)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.types", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.etypes", 0), sect)
for i, symnro := range sym.ReadOnly {
if i == 0 && symnro == sym.STYPE && ctxt.HeadType != objabi.Haix {
// Skip forward so that no type
// reference uses a zero offset.
// This is unlikely but possible in small
// programs with no other read-only data.
state.datsize++
}
symn := sym.RelROMap[symnro]
symnStartValue := state.datsize
for _, s := range state.data[symn] {
outer := ldr.OuterSym(s)
if s != 0 && ldr.SymSect(outer) != nil && ldr.SymSect(outer) != sect {
ctxt.Errorf(s, "s.Outer (%s) in different section from s, %s != %s", ldr.SymName(outer), ldr.SymSect(outer).Name, sect.Name)
}
}
state.assignToSection(sect, symn, sym.SRODATA)
setCarrierSize(symn, state.datsize-symnStartValue)
if ctxt.HeadType == objabi.Haix {
// Read-only symbols might be wrapped inside their outer
// symbol.
// XCOFF symbol table needs to know the size of
// these outer symbols.
xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn)
}
}
sect.Length = uint64(state.datsize) - sect.Vaddr
}
/* typelink */
sect = state.allocateNamedDataSection(seg, genrelrosecname(".typelink"), []sym.SymKind{sym.STYPELINK}, relroSecPerm)
typelink := ldr.CreateSymForUpdate("runtime.typelink", 0)
ldr.SetSymSect(typelink.Sym(), sect)
typelink.SetType(sym.SRODATA)
state.datsize += typelink.Size()
state.checkdatsize(sym.STYPELINK)
sect.Length = uint64(state.datsize) - sect.Vaddr
/* itablink */
sect = state.allocateNamedDataSection(seg, genrelrosecname(".itablink"), []sym.SymKind{sym.SITABLINK}, relroSecPerm)
itablink := ldr.CreateSymForUpdate("runtime.itablink", 0)
ldr.SetSymSect(itablink.Sym(), sect)
itablink.SetType(sym.SRODATA)
state.datsize += itablink.Size()
state.checkdatsize(sym.SITABLINK)
sect.Length = uint64(state.datsize) - sect.Vaddr
/* gosymtab */
sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gosymtab"), sym.SSYMTAB, sym.SRODATA, relroSecPerm)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.symtab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.esymtab", 0), sect)
/* gopclntab */
sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gopclntab"), sym.SPCLNTAB, sym.SRODATA, relroSecPerm)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pcheader", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.funcnametab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.cutab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.filetab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pctab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.functab", 0), sect)
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.epclntab", 0), sect)
setCarrierSize(sym.SPCLNTAB, int64(sect.Length))
if ctxt.HeadType == objabi.Haix {
xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SPCLNTAB)
}
// 6g uses 4-byte relocation offsets, so the entire segment must fit in 32 bits.
if state.datsize != int64(uint32(state.datsize)) {
Errorf(nil, "read-only data segment too large: %d", state.datsize)
}
siz := 0
for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ {
siz += len(state.data[symn])
}
ctxt.datap = make([]loader.Sym, 0, siz)
for symn := sym.SELFRXSECT; symn < sym.SXREF; symn++ {
ctxt.datap = append(ctxt.datap, state.data[symn]...)
}
}
// allocateDwarfSections allocates sym.Section objects for DWARF
// symbols, and assigns symbols to sections.
func (state *dodataState) allocateDwarfSections(ctxt *Link) {
alignOne := func(state *dodataState, datsize int64, s loader.Sym) int64 { return datsize }
ldr := ctxt.loader
for i := 0; i < len(dwarfp); i++ {
// First the section symbol.
s := dwarfp[i].secSym()
sect := state.allocateNamedDataSection(&Segdwarf, ldr.SymName(s), []sym.SymKind{}, 04)
ldr.SetSymSect(s, sect)
sect.Sym = sym.LoaderSym(s)
curType := ldr.SymType(s)
state.setSymType(s, sym.SRODATA)
ldr.SetSymValue(s, int64(uint64(state.datsize)-sect.Vaddr))
state.datsize += ldr.SymSize(s)
// Then any sub-symbols for the section symbol.
subSyms := dwarfp[i].subSyms()
state.assignDsymsToSection(sect, subSyms, sym.SRODATA, alignOne)
for j := 0; j < len(subSyms); j++ {
s := subSyms[j]
if ctxt.HeadType == objabi.Haix && curType == sym.SDWARFLOC {
// Update the size of .debug_loc for this symbol's
// package.
addDwsectCUSize(".debug_loc", ldr.SymPkg(s), uint64(ldr.SymSize(s)))
}
}
sect.Length = uint64(state.datsize) - sect.Vaddr
state.checkdatsize(curType)
}
}
type symNameSize struct {
name string
sz int64
val int64
sym loader.Sym
}
func (state *dodataState) dodataSect(ctxt *Link, symn sym.SymKind, syms []loader.Sym) (result []loader.Sym, maxAlign int32) {
var head, tail loader.Sym
ldr := ctxt.loader
sl := make([]symNameSize, len(syms))
for k, s := range syms {
ss := ldr.SymSize(s)
sl[k] = symNameSize{name: ldr.SymName(s), sz: ss, sym: s}
ds := int64(len(ldr.Data(s)))
switch {
case ss < ds:
ctxt.Errorf(s, "initialize bounds (%d < %d)", ss, ds)
case ss < 0:
ctxt.Errorf(s, "negative size (%d bytes)", ss)
case ss > cutoff:
ctxt.Errorf(s, "symbol too large (%d bytes)", ss)
}
// 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) || (ctxt.HeadType == objabi.Haix && ctxt.LinkMode == LinkExternal) {
switch ldr.SymName(s) {
case "runtime.text", "runtime.bss", "runtime.data", "runtime.types", "runtime.rodata":
head = s
continue
case "runtime.etext", "runtime.ebss", "runtime.edata", "runtime.etypes", "runtime.erodata":
tail = s
continue
}
}
}
// 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).
checkSize := symn != sym.SELFGOT
// Perform the sort.
if symn != sym.SPCLNTAB {
sort.Slice(sl, func(i, j int) bool {
si, sj := sl[i].sym, sl[j].sym
switch {
case si == head, sj == tail:
return true
case sj == head, si == tail:
return false
}
if checkSize {
isz := sl[i].sz
jsz := sl[j].sz
if isz != jsz {
return isz < jsz
}
}
iname := sl[i].name
jname := sl[j].name
if iname != jname {
return iname < jname
}
return si < sj
})
} else {
// PCLNTAB was built internally, and has the proper order based on value.
// Sort the symbols as such.
for k, s := range syms {
sl[k].val = ldr.SymValue(s)
}
sort.Slice(sl, func(i, j int) bool { return sl[i].val < sl[j].val })
}
// Set alignment, construct result
syms = syms[:0]
for k := range sl {
s := sl[k].sym
if s != head && s != tail {
align := symalign(ldr, s)
if maxAlign < align {
maxAlign = align
}
}
syms = append(syms, s)
}
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
}
ldr := ctxt.loader
s := ldr.CreateSymForUpdate("go.buildid", 0)
// 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.SetType(sym.STEXT)
s.SetData([]byte(data))
s.SetSize(int64(len(data)))
ctxt.Textp = append(ctxt.Textp, 0)
copy(ctxt.Textp[1:], ctxt.Textp)
ctxt.Textp[0] = s.Sym()
}
func (ctxt *Link) buildinfo() {
if ctxt.linkShared || ctxt.BuildMode == BuildModePlugin {
// -linkshared and -buildmode=plugin get confused
// about the relocations in go.buildinfo
// pointing at the other data sections.
// The version information is only available in executables.
return
}
ldr := ctxt.loader
s := ldr.CreateSymForUpdate(".go.buildinfo", 0)
// On AIX, .go.buildinfo must be in the symbol table as
// it has relocations.
s.SetNotInSymbolTable(!ctxt.IsAIX())
s.SetType(sym.SBUILDINFO)
s.SetAlign(16)
// The \xff is invalid UTF-8, meant to make it less likely
// to find one of these accidentally.
const prefix = "\xff Go buildinf:" // 14 bytes, plus 2 data bytes filled in below
data := make([]byte, 32)
copy(data, prefix)
data[len(prefix)] = byte(ctxt.Arch.PtrSize)
data[len(prefix)+1] = 0
if ctxt.Arch.ByteOrder == binary.BigEndian {
data[len(prefix)+1] = 1
}
s.SetData(data)
s.SetSize(int64(len(data)))
r, _ := s.AddRel(objabi.R_ADDR)
r.SetOff(16)
r.SetSiz(uint8(ctxt.Arch.PtrSize))
r.SetSym(ldr.LookupOrCreateSym("runtime.buildVersion", 0))
r, _ = s.AddRel(objabi.R_ADDR)
r.SetOff(16 + int32(ctxt.Arch.PtrSize))
r.SetSiz(uint8(ctxt.Arch.PtrSize))
r.SetSym(ldr.LookupOrCreateSym("runtime.modinfo", 0))
}
// assign addresses to text
func (ctxt *Link) textaddress() {
addsection(ctxt.loader, 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)
ldr := ctxt.loader
text := ctxt.xdefine("runtime.text", sym.STEXT, 0)
etext := ctxt.xdefine("runtime.etext", sym.STEXT, 0)
ldr.SetSymSect(text, sect)
if ctxt.IsAIX() && ctxt.IsExternal() {
// Setting runtime.text has a real symbol prevents ld to
// change its base address resulting in wrong offsets for
// reflect methods.
u := ldr.MakeSymbolUpdater(text)
u.SetAlign(sect.Align)
u.SetSize(8)
}
if (ctxt.DynlinkingGo() && ctxt.IsDarwin()) || (ctxt.IsAIX() && ctxt.IsExternal()) {
ldr.SetSymSect(etext, sect)
ctxt.Textp = append(ctxt.Textp, etext, 0)
copy(ctxt.Textp[1:], ctxt.Textp)
ctxt.Textp[0] = text
}
start := uint64(Rnd(*FlagTextAddr, int64(Funcalign)))
va := start
n := 1
sect.Vaddr = va
limit := thearch.TrampLimit
if limit == 0 {
limit = 1 << 63 // unlimited
}
if *FlagDebugTextSize != 0 {
limit = uint64(*FlagDebugTextSize)
}
if *FlagDebugTramp > 1 {
limit = 1 // debug mode, force generating trampolines for everything
}
if ctxt.IsAIX() && ctxt.IsExternal() {
// On AIX, normally we won't generate direct calls to external symbols,
// except in one test, cmd/go/testdata/script/link_syso_issue33139.txt.
// That test doesn't make much sense, and I'm not sure it ever works.
// Just generate trampoline for now (which will turn a direct call to
// an indirect call, which at least builds).
limit = 1
}
// First pass: assign addresses assuming the program is small and
// don't generate trampolines.
big := false
for _, s := range ctxt.Textp {
sect, n, va = assignAddress(ctxt, sect, n, s, va, false, big)
if va-start >= limit {
big = true
break
}
}
// Second pass: only if it is too big, insert trampolines for too-far
// jumps and targets with unknown addresses.
if big {
// reset addresses
for _, s := range ctxt.Textp {
if ldr.OuterSym(s) != 0 || s == text {
continue
}
oldv := ldr.SymValue(s)
for sub := s; sub != 0; sub = ldr.SubSym(sub) {
ldr.SetSymValue(sub, ldr.SymValue(sub)-oldv)
}
}
va = start
ntramps := 0
for _, s := range ctxt.Textp {
sect, n, va = assignAddress(ctxt, sect, n, s, va, false, big)
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]
if ctxt.IsAIX() && strings.HasPrefix(ldr.SymName(tramp), "runtime.text.") {
// Already set in assignAddress
continue
}
sect, n, va = assignAddress(ctxt, sect, n, tramp, va, true, big)
}
}
// merge tramps into Textp, keeping Textp in address order
if ntramps != 0 {
newtextp := make([]loader.Sym, 0, len(ctxt.Textp)+ntramps)
i := 0
for _, s := range ctxt.Textp {
for ; i < ntramps && ldr.SymValue(ctxt.tramps[i]) < ldr.SymValue(s); i++ {
newtextp = append(newtextp, ctxt.tramps[i])
}
newtextp = append(newtextp, s)
}
newtextp = append(newtextp, ctxt.tramps[i:ntramps]...)
ctxt.Textp = newtextp
}
}
sect.Length = va - sect.Vaddr
ldr.SetSymSect(etext, sect)
if ldr.SymValue(etext) == 0 {
// Set the address of the start/end symbols, if not already
// (i.e. not darwin+dynlink or AIX+external, see above).
ldr.SetSymValue(etext, int64(va))
ldr.SetSymValue(text, int64(Segtext.Sections[0].Vaddr))
}
}
// assigns address for a text symbol, returns (possibly new) section, its number, and the address
func assignAddress(ctxt *Link, sect *sym.Section, n int, s loader.Sym, va uint64, isTramp, big bool) (*sym.Section, int, uint64) {
ldr := ctxt.loader
if thearch.AssignAddress != nil {
return thearch.AssignAddress(ldr, sect, n, s, va, isTramp)
}
ldr.SetSymSect(s, sect)
if ldr.AttrSubSymbol(s) {
return sect, n, va
}
align := ldr.SymAlign(s)
if align == 0 {
align = int32(Funcalign)
}
va = uint64(Rnd(int64(va), int64(align)))
if sect.Align < align {
sect.Align = align
}
funcsize := uint64(MINFUNC) // spacing required for findfunctab
if ldr.SymSize(s) > MINFUNC {
funcsize = uint64(ldr.SymSize(s))
}
// If we need to split text sections, and this function doesn't fit in the current
// section, then create a new one.
//
// Only break at outermost syms.
if big && splitTextSections(ctxt) && ldr.OuterSym(s) == 0 {
// For debugging purposes, allow text size limit to be cranked down,
// so as to stress test the code that handles multiple text sections.
var textSizelimit uint64 = thearch.TrampLimit
if *FlagDebugTextSize != 0 {
textSizelimit = uint64(*FlagDebugTextSize)
}
// Sanity check: make sure the limit is larger than any
// individual text symbol.
if funcsize > textSizelimit {
panic(fmt.Sprintf("error: text size limit %d less than text symbol %s size of %d", textSizelimit, ldr.SymName(s), funcsize))
}
if va-sect.Vaddr+funcsize+maxSizeTrampolines(ctxt, ldr, s, isTramp) > textSizelimit {
sectAlign := int32(thearch.Funcalign)
if ctxt.IsPPC64() {
// Align the next text section to the worst case function alignment likely
// to be encountered when processing function symbols. The start address
// is rounded against the final alignment of the text section later on in
// (*Link).address. This may happen due to usage of PCALIGN directives
// larger than Funcalign, or usage of ISA 3.1 prefixed instructions
// (see ISA 3.1 Book I 1.9).
const ppc64maxFuncalign = 64
sectAlign = ppc64maxFuncalign
va = uint64(Rnd(int64(va), ppc64maxFuncalign))
}
// Set the length for the previous text section
sect.Length = va - sect.Vaddr
// Create new section, set the starting Vaddr
sect = addsection(ctxt.loader, ctxt.Arch, &Segtext, ".text", 05)
sect.Vaddr = va
sect.Align = sectAlign
ldr.SetSymSect(s, sect)
// Create a symbol for the start of the secondary text sections
ntext := ldr.CreateSymForUpdate(fmt.Sprintf("runtime.text.%d", n), 0)
ntext.SetSect(sect)
if ctxt.IsAIX() {
// runtime.text.X must be a real symbol on AIX.
// Assign its address directly in order to be the
// first symbol of this new section.
ntext.SetType(sym.STEXT)
ntext.SetSize(int64(MINFUNC))
ntext.SetOnList(true)
ntext.SetAlign(sectAlign)
ctxt.tramps = append(ctxt.tramps, ntext.Sym())
ntext.SetValue(int64(va))
va += uint64(ntext.Size())
if align := ldr.SymAlign(s); align != 0 {
va = uint64(Rnd(int64(va), int64(align)))
} else {
va = uint64(Rnd(int64(va), int64(Funcalign)))
}
}
n++
}
}
ldr.SetSymValue(s, 0)
for sub := s; sub != 0; sub = ldr.SubSym(sub) {
ldr.SetSymValue(sub, ldr.SymValue(sub)+int64(va))
if ctxt.Debugvlog > 2 {
fmt.Println("assign text address:", ldr.SymName(sub), ldr.SymValue(sub))
}
}
va += funcsize
return sect, n, va
}
// Return whether we may need to split text sections.
//
// On PPC64x whem external linking a text section should not be larger than 2^25 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 system linker to modify the long
// calls appropriately. The limit allows for the space needed for tables inserted by the
// linker.
//
// The same applies to Darwin/ARM64, with 2^27 byte threshold.
func splitTextSections(ctxt *Link) bool {
return (ctxt.IsPPC64() || (ctxt.IsARM64() && ctxt.IsDarwin())) && ctxt.IsExternal()
}
// On Wasm, we reserve 4096 bytes for zero page, then 8192 bytes for wasm_exec.js
// to store command line args and environment variables.
// Data sections starts from at least address 12288.
// Keep in sync with wasm_exec.js.
const wasmMinDataAddr = 4096 + 8192
// address assigns virtual addresses to all segments and sections and
// returns all segments in file order.
func (ctxt *Link) address() []*sym.Segment {
var order []*sym.Segment // Layout order
va := uint64(*FlagTextAddr)
order = append(order, &Segtext)
Segtext.Rwx = 05
Segtext.Vaddr = va
for i, s := range Segtext.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
if ctxt.IsWasm() && i == 0 && va < wasmMinDataAddr {
va = wasmMinDataAddr
}
}
Segtext.Length = va - uint64(*FlagTextAddr)
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)))
order = append(order, &Segrodata)
Segrodata.Rwx = 04
Segrodata.Vaddr = va
for _, s := range Segrodata.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segrodata.Length = va - Segrodata.Vaddr
}
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)))
if ctxt.HeadType == objabi.Haix {
// Relro data are inside data segment on AIX.
va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
}
order = append(order, &Segrelrodata)
Segrelrodata.Rwx = 06
Segrelrodata.Vaddr = va
for _, s := range Segrelrodata.Sections {
va = uint64(Rnd(int64(va), int64(s.Align)))
s.Vaddr = va
va += s.Length
}
Segrelrodata.Length = va - Segrelrodata.Vaddr
}
va = uint64(Rnd(int64(va), int64(*FlagRound)))
if ctxt.HeadType == objabi.Haix && len(Segrelrodata.Sections) == 0 {
// Data sections are moved to an unreachable segment
// to ensure that they are position-independent.
// Already done if relro sections exist.
va += uint64(XCOFFDATABASE) - uint64(XCOFFTEXTBASE)
}
order = append(order, &Segdata)
Segdata.Rwx = 06
Segdata.Vaddr = va
var data *sym.Section
var noptr *sym.Section
var bss *sym.Section
var noptrbss *sym.Section
var fuzzCounters *sym.Section
for i, s := range Segdata.Sections {
if (ctxt.IsELF || ctxt.HeadType == objabi.Haix) && s.Name == ".tbss" {
continue
}
vlen := int64(s.Length)
if i+1 < len(Segdata.Sections) && !((ctxt.IsELF || ctxt.HeadType == objabi.Haix) && 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
switch s.Name {
case ".data":
data = s
case ".noptrdata":
noptr = s
case ".bss":
bss = s
case ".noptrbss":
noptrbss = s
case "__libfuzzer_extra_counters":
fuzzCounters = s
}
}
// Assign Segdata's Filelen omitting the BSS. We do this here
// simply because right now we know where the BSS starts.
Segdata.Filelen = bss.Vaddr - Segdata.Vaddr
va = uint64(Rnd(int64(va), int64(*FlagRound)))
order = append(order, &Segdwarf)
Segdwarf.Rwx = 06
Segdwarf.Vaddr = va
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
}
ldr := ctxt.loader
var (
rodata = ldr.SymSect(ldr.LookupOrCreateSym("runtime.rodata", 0))
symtab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.symtab", 0))
pclntab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0))
types = ldr.SymSect(ldr.LookupOrCreateSym("runtime.types", 0))
)
for _, s := range ctxt.datap {
if sect := ldr.SymSect(s); sect != nil {
ldr.AddToSymValue(s, int64(sect.Vaddr))
}
v := ldr.SymValue(s)
for sub := ldr.SubSym(s); sub != 0; sub = ldr.SubSym(sub) {
ldr.AddToSymValue(sub, v)
}
}
for _, si := range dwarfp {
for _, s := range si.syms {
if sect := ldr.SymSect(s); sect != nil {
ldr.AddToSymValue(s, int64(sect.Vaddr))
}
sub := ldr.SubSym(s)
if sub != 0 {
panic(fmt.Sprintf("unexpected sub-sym for %s %s", ldr.SymName(s), ldr.SymType(s).String()))
}
v := ldr.SymValue(s)
for ; sub != 0; sub = ldr.SubSym(sub) {
ldr.AddToSymValue(s, v)
}
}
}
if ctxt.BuildMode == BuildModeShared {
s := ldr.LookupOrCreateSym("go.link.abihashbytes", 0)
sect := ldr.SymSect(ldr.LookupOrCreateSym(".note.go.abihash", 0))
ldr.SetSymSect(s, sect)
ldr.SetSymValue(s, int64(sect.Vaddr+16))
}
// 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)
if ctxt.HeadType != objabi.Haix || ctxt.LinkMode != LinkExternal {
// Addresses are already set on AIX with external linker
// because these symbols are part of their sections.
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))
s := ldr.Lookup("runtime.gcdata", 0)
ldr.SetAttrLocal(s, true)
ctxt.xdefine("runtime.egcdata", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s))
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcdata", 0), ldr.SymSect(s))
s = ldr.LookupOrCreateSym("runtime.gcbss", 0)
ldr.SetAttrLocal(s, true)
ctxt.xdefine("runtime.egcbss", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s))
ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcbss", 0), ldr.SymSect(s))
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.defineInternal("runtime.pcheader", sym.SRODATA)
ctxt.defineInternal("runtime.funcnametab", sym.SRODATA)
ctxt.defineInternal("runtime.cutab", sym.SRODATA)
ctxt.defineInternal("runtime.filetab", sym.SRODATA)
ctxt.defineInternal("runtime.pctab", sym.SRODATA)
ctxt.defineInternal("runtime.functab", sym.SRODATA)
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))
if fuzzCounters != nil {
ctxt.xdefine("internal/fuzz._counters", sym.SLIBFUZZER_EXTRA_COUNTER, int64(fuzzCounters.Vaddr))
ctxt.xdefine("internal/fuzz._ecounters", sym.SLIBFUZZER_EXTRA_COUNTER, int64(fuzzCounters.Vaddr+fuzzCounters.Length))
}
if ctxt.IsSolaris() {
// On Solaris, in the runtime it sets the external names of the
// end symbols. Unset them and define separate symbols, so we
// keep both.
etext := ldr.Lookup("runtime.etext", 0)
edata := ldr.Lookup("runtime.edata", 0)
end := ldr.Lookup("runtime.end", 0)
ldr.SetSymExtname(etext, "runtime.etext")
ldr.SetSymExtname(edata, "runtime.edata")
ldr.SetSymExtname(end, "runtime.end")
ctxt.xdefine("_etext", ldr.SymType(etext), ldr.SymValue(etext))
ctxt.xdefine("_edata", ldr.SymType(edata), ldr.SymValue(edata))
ctxt.xdefine("_end", ldr.SymType(end), ldr.SymValue(end))
ldr.SetSymSect(ldr.Lookup("_etext", 0), ldr.SymSect(etext))
ldr.SetSymSect(ldr.Lookup("_edata", 0), ldr.SymSect(edata))
ldr.SetSymSect(ldr.Lookup("_end", 0), ldr.SymSect(end))
}
if ctxt.IsPPC64() && ctxt.IsElf() {
// Resolve .TOC. symbols for all objects. Only one TOC region is supported. If a
// GOT section is present, compute it as suggested by the ELFv2 ABI. Otherwise,
// choose a similar offset from the start of the data segment.
tocAddr := int64(Segdata.Vaddr) + 0x8000
if gotAddr := ldr.SymValue(ctxt.GOT); gotAddr != 0 {
tocAddr = gotAddr + 0x8000
}
for i, _ := range ctxt.DotTOC {
if i >= sym.SymVerABICount && i < sym.SymVerStatic { // these versions are not used currently
continue
}
if toc := ldr.Lookup(".TOC.", i); toc != 0 {
ldr.SetSymValue(toc, tocAddr)
}
}
}
return order
}
// layout assigns file offsets and lengths to the segments in order.
// Returns the file size containing all the segments.
func (ctxt *Link) layout(order []*sym.Segment) uint64 {
var prev *sym.Segment
for _, seg := range order {
if prev == nil {
seg.Fileoff = uint64(HEADR)
} else {
switch ctxt.HeadType {
default:
// Assuming the previous segment was
// aligned, the following rounding
// should ensure that this segment's
// VA ≡ Fileoff mod FlagRound.
seg.Fileoff = uint64(Rnd(int64(prev.Fileoff+prev.Filelen), int64(*FlagRound)))
if seg.Vaddr%uint64(*FlagRound) != seg.Fileoff%uint64(*FlagRound) {
Exitf("bad segment rounding (Vaddr=%#x Fileoff=%#x FlagRound=%#x)", seg.Vaddr, seg.Fileoff, *FlagRound)
}
case objabi.Hwindows:
seg.Fileoff = prev.Fileoff + uint64(Rnd(int64(prev.Filelen), PEFILEALIGN))
case objabi.Hplan9:
seg.Fileoff = prev.Fileoff + prev.Filelen
}
}
if seg != &Segdata {
// Link.address already set Segdata.Filelen to
// account for BSS.
seg.Filelen = seg.Length
}
prev = seg
}
return prev.Fileoff + prev.Filelen
}
// add a trampoline with symbol s (to be laid down after the current function)
func (ctxt *Link) AddTramp(s *loader.SymbolBuilder) {
s.SetType(sym.STEXT)
s.SetReachable(true)
s.SetOnList(true)
ctxt.tramps = append(ctxt.tramps, s.Sym())
if *FlagDebugTramp > 0 && ctxt.Debugvlog > 0 {
ctxt.Logf("trampoline %s inserted\n", s.Name())
}
}
// compressSyms compresses syms and returns the contents of the
// compressed section. If the section would get larger, it returns nil.
func compressSyms(ctxt *Link, syms []loader.Sym) []byte {
ldr := ctxt.loader
var total int64
for _, sym := range syms {
total += ldr.SymSize(sym)
}
var buf bytes.Buffer
buf.Write([]byte("ZLIB"))
var sizeBytes [8]byte
binary.BigEndian.PutUint64(sizeBytes[:], uint64(total))
buf.Write(sizeBytes[:])
var relocbuf []byte // temporary buffer for applying relocations
// Using zlib.BestSpeed achieves very nearly the same
// compression levels of zlib.DefaultCompression, but takes
// substantially less time. This is important because DWARF
// compression can be a significant fraction of link time.
z, err := zlib.NewWriterLevel(&buf, zlib.BestSpeed)
if err != nil {
log.Fatalf("NewWriterLevel failed: %s", err)
}
st := ctxt.makeRelocSymState()
for _, s := range syms {
// Symbol data may be read-only. Apply relocations in a
// temporary buffer, and immediately write it out.
P := ldr.Data(s)
relocs := ldr.Relocs(s)
if relocs.Count() != 0 {
relocbuf = append(relocbuf[:0], P...)
P = relocbuf
st.relocsym(s, P)
}
if _, err := z.Write(P); err != nil {
log.Fatalf("compression failed: %s", err)
}
for i := ldr.SymSize(s) - int64(len(P)); i > 0; {
b := zeros[:]
if i < int64(len(b)) {
b = b[:i]
}
n, err := z.Write(b)
if err != nil {
log.Fatalf("compression failed: %s", err)
}
i -= int64(n)
}
}
if err := z.Close(); err != nil {
log.Fatalf("compression failed: %s", err)
}
if int64(buf.Len()) >= total {
// Compression didn't save any space.
return nil
}
return buf.Bytes()
}