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go/src/cmd/link/internal/ppc64/asm.go
Than McIntosh 0722a49b37 [dev.link] cmd/link: remove elf sym fields from sym.Symbol 
Remove the "ElfSym" and "LocalElfSym" fields from sym.Symbol,
replacing uses with loader method calls as needed.

Change-Id: I3828f13203ece2bdc03eeb09ab37a5c94e21a726
Reviewed-on: https://go-review.googlesource.com/c/go/+/230462
Reviewed-by: Cherry Zhang <cherryyz@google.com>
2020-04-28 19:04:47 +00:00

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// Inferno utils/5l/asm.c
// https://bitbucket.org/inferno-os/inferno-os/src/default/utils/5l/asm.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 ppc64
import (
"cmd/internal/objabi"
"cmd/internal/sys"
"cmd/link/internal/ld"
"cmd/link/internal/loader"
"cmd/link/internal/sym"
"debug/elf"
"encoding/binary"
"fmt"
"log"
"strings"
"sync"
)
func genplt2(ctxt *ld.Link, ldr *loader.Loader) {
// The ppc64 ABI PLT has similar concepts to other
// architectures, but is laid out quite differently. When we
// see an R_PPC64_REL24 relocation to a dynamic symbol
// (indicating that the call needs to go through the PLT), we
// generate up to three stubs and reserve a PLT slot.
//
// 1) The call site will be bl x; nop (where the relocation
// applies to the bl). We rewrite this to bl x_stub; ld
// r2,24(r1). The ld is necessary because x_stub will save
// r2 (the TOC pointer) at 24(r1) (the "TOC save slot").
//
// 2) We reserve space for a pointer in the .plt section (once
// per referenced dynamic function). .plt is a data
// section filled solely by the dynamic linker (more like
// .plt.got on other architectures). Initially, the
// dynamic linker will fill each slot with a pointer to the
// corresponding x@plt entry point.
//
// 3) We generate the "call stub" x_stub (once per dynamic
// function/object file pair). This saves the TOC in the
// TOC save slot, reads the function pointer from x's .plt
// slot and calls it like any other global entry point
// (including setting r12 to the function address).
//
// 4) We generate the "symbol resolver stub" x@plt (once per
// dynamic function). This is solely a branch to the glink
// resolver stub.
//
// 5) We generate the glink resolver stub (only once). This
// computes which symbol resolver stub we came through and
// invokes the dynamic resolver via a pointer provided by
// the dynamic linker. This will patch up the .plt slot to
// point directly at the function so future calls go
// straight from the call stub to the real function, and
// then call the function.
// NOTE: It's possible we could make ppc64 closer to other
// architectures: ppc64's .plt is like .plt.got on other
// platforms and ppc64's .glink is like .plt on other
// platforms.
// Find all R_PPC64_REL24 relocations that reference dynamic
// imports. Reserve PLT entries for these symbols and
// generate call stubs. The call stubs need to live in .text,
// which is why we need to do this pass this early.
//
// This assumes "case 1" from the ABI, where the caller needs
// us to save and restore the TOC pointer.
var stubs []loader.Sym
for _, s := range ctxt.Textp2 {
relocs := ldr.Relocs(s)
for i := 0; i < relocs.Count(); i++ {
r := relocs.At2(i)
if r.Type() != objabi.ElfRelocOffset+objabi.RelocType(elf.R_PPC64_REL24) || ldr.SymType(r.Sym()) != sym.SDYNIMPORT {
continue
}
// Reserve PLT entry and generate symbol
// resolver
addpltsym2(ctxt, ldr, r.Sym())
// Generate call stub. Important to note that we're looking
// up the stub using the same version as the parent symbol (s),
// needed so that symtoc() will select the right .TOC. symbol
// when processing the stub. In older versions of the linker
// this was done by setting stub.Outer to the parent, but
// if the stub has the right version initially this is not needed.
n := fmt.Sprintf("%s.%s", ldr.SymName(s), ldr.SymName(r.Sym()))
stub := ldr.CreateSymForUpdate(n, ldr.SymVersion(s))
if stub.Size() == 0 {
stubs = append(stubs, stub.Sym())
gencallstub2(ctxt, ldr, 1, stub, r.Sym())
}
// Update the relocation to use the call stub
r.SetSym(stub.Sym())
// make sure the data is writeable
if ldr.AttrReadOnly(s) {
panic("can't write to read-only sym data")
}
// Restore TOC after bl. The compiler put a
// nop here for us to overwrite.
sp := ldr.Data(s)
const o1 = 0xe8410018 // ld r2,24(r1)
ctxt.Arch.ByteOrder.PutUint32(sp[r.Off()+4:], o1)
}
}
// Put call stubs at the beginning (instead of the end).
// So when resolving the relocations to calls to the stubs,
// the addresses are known and trampolines can be inserted
// when necessary.
ctxt.Textp2 = append(stubs, ctxt.Textp2...)
}
func genaddmoduledata2(ctxt *ld.Link, ldr *loader.Loader) {
initfunc, addmoduledata := ld.PrepareAddmoduledata(ctxt)
if initfunc == nil {
return
}
o := func(op uint32) {
initfunc.AddUint32(ctxt.Arch, op)
}
// addis r2, r12, .TOC.-func@ha
toc := ctxt.DotTOC2[0]
rel1 := loader.Reloc{
Off: 0,
Size: 8,
Type: objabi.R_ADDRPOWER_PCREL,
Sym: toc,
}
initfunc.AddReloc(rel1)
o(0x3c4c0000)
// addi r2, r2, .TOC.-func@l
o(0x38420000)
// mflr r31
o(0x7c0802a6)
// stdu r31, -32(r1)
o(0xf801ffe1)
// addis r3, r2, local.moduledata@got@ha
var tgt loader.Sym
if s := ldr.Lookup("local.moduledata", 0); s != 0 {
tgt = s
} else if s := ldr.Lookup("local.pluginmoduledata", 0); s != 0 {
tgt = s
} else {
tgt = ldr.LookupOrCreateSym("runtime.firstmoduledata", 0)
}
rel2 := loader.Reloc{
Off: int32(initfunc.Size()),
Size: 8,
Type: objabi.R_ADDRPOWER_GOT,
Sym: tgt,
}
initfunc.AddReloc(rel2)
o(0x3c620000)
// ld r3, local.moduledata@got@l(r3)
o(0xe8630000)
// bl runtime.addmoduledata
rel3 := loader.Reloc{
Off: int32(initfunc.Size()),
Size: 4,
Type: objabi.R_CALLPOWER,
Sym: addmoduledata,
}
initfunc.AddReloc(rel3)
o(0x48000001)
// nop
o(0x60000000)
// ld r31, 0(r1)
o(0xe8010000)
// mtlr r31
o(0x7c0803a6)
// addi r1,r1,32
o(0x38210020)
// blr
o(0x4e800020)
}
func gentext2(ctxt *ld.Link, ldr *loader.Loader) {
if ctxt.DynlinkingGo() {
genaddmoduledata2(ctxt, ldr)
}
if ctxt.LinkMode == ld.LinkInternal {
genplt2(ctxt, ldr)
}
}
// Construct a call stub in stub that calls symbol targ via its PLT
// entry.
func gencallstub2(ctxt *ld.Link, ldr *loader.Loader, abicase int, stub *loader.SymbolBuilder, targ loader.Sym) {
if abicase != 1 {
// If we see R_PPC64_TOCSAVE or R_PPC64_REL24_NOTOC
// relocations, we'll need to implement cases 2 and 3.
log.Fatalf("gencallstub only implements case 1 calls")
}
plt := ctxt.PLT2
stub.SetType(sym.STEXT)
// Save TOC pointer in TOC save slot
stub.AddUint32(ctxt.Arch, 0xf8410018) // std r2,24(r1)
// Load the function pointer from the PLT.
rel := loader.Reloc{
Off: int32(stub.Size()),
Size: 2,
Add: int64(ldr.SymPlt(targ)),
Type: objabi.R_POWER_TOC,
Sym: plt,
}
if ctxt.Arch.ByteOrder == binary.BigEndian {
rel.Off += int32(rel.Size)
}
ri1 := stub.AddReloc(rel)
ldr.SetRelocVariant(stub.Sym(), int(ri1), sym.RV_POWER_HA)
stub.AddUint32(ctxt.Arch, 0x3d820000) // addis r12,r2,targ@plt@toc@ha
rel2 := loader.Reloc{
Off: int32(stub.Size()),
Size: 2,
Add: int64(ldr.SymPlt(targ)),
Type: objabi.R_POWER_TOC,
Sym: plt,
}
if ctxt.Arch.ByteOrder == binary.BigEndian {
rel2.Off += int32(rel.Size)
}
ri2 := stub.AddReloc(rel2)
ldr.SetRelocVariant(stub.Sym(), int(ri2), sym.RV_POWER_LO)
stub.AddUint32(ctxt.Arch, 0xe98c0000) // ld r12,targ@plt@toc@l(r12)
// Jump to the loaded pointer
stub.AddUint32(ctxt.Arch, 0x7d8903a6) // mtctr r12
stub.AddUint32(ctxt.Arch, 0x4e800420) // bctr
}
func adddynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
if target.IsElf() {
return addelfdynrel2(target, ldr, syms, s, r, rIdx)
} else if target.IsAIX() {
return ld.Xcoffadddynrel2(target, ldr, syms, s, r, rIdx)
}
return false
}
func addelfdynrel2(target *ld.Target, ldr *loader.Loader, syms *ld.ArchSyms, s loader.Sym, r *loader.Reloc2, rIdx int) bool {
targ := r.Sym()
var targType sym.SymKind
if targ != 0 {
targType = ldr.SymType(targ)
}
switch r.Type() {
default:
if r.Type() >= objabi.ElfRelocOffset {
ldr.Errorf(s, "unexpected relocation type %d (%s)", r.Type(), sym.RelocName(target.Arch, r.Type()))
return false
}
// Handle relocations found in ELF object files.
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL24):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_CALLPOWER)
// This is a local call, so the caller isn't setting
// up r12 and r2 is the same for the caller and
// callee. Hence, we need to go to the local entry
// point. (If we don't do this, the callee will try
// to use r12 to compute r2.)
su.SetRelocAdd(rIdx, r.Add()+int64(ldr.SymLocalentry(targ))*4)
if targType == sym.SDYNIMPORT {
// Should have been handled in elfsetupplt
ldr.Errorf(s, "unexpected R_PPC64_REL24 for dyn import")
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC_REL32):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
su.SetRelocAdd(rIdx, r.Add()+4)
if targType == sym.SDYNIMPORT {
ldr.Errorf(s, "unexpected R_PPC_REL32 for dyn import")
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_ADDR64):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_ADDR)
if targType == sym.SDYNIMPORT {
// These happen in .toc sections
ld.Adddynsym2(ldr, target, syms, targ)
rela := ldr.MakeSymbolUpdater(syms.Rela2)
rela.AddAddrPlus(target.Arch, s, int64(r.Off()))
rela.AddUint64(target.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(targ)), uint32(elf.R_PPC64_ADDR64)))
rela.AddUint64(target.Arch, uint64(r.Add()))
su.SetRelocType(rIdx, objabi.ElfRelocOffset) // ignore during relocsym
}
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO|sym.RV_CHECK_OVERFLOW)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HA):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HA|sym.RV_CHECK_OVERFLOW)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_HI):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HI|sym.RV_CHECK_OVERFLOW)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_DS):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_DS|sym.RV_CHECK_OVERFLOW)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_TOC16_LO_DS):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_POWER_TOC)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_DS)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_LO):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_LO)
su.SetRelocAdd(rIdx, r.Add()+2) // Compensate for relocation size of 2
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HI):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HI|sym.RV_CHECK_OVERFLOW)
su.SetRelocAdd(rIdx, r.Add()+2)
return true
case objabi.ElfRelocOffset + objabi.RelocType(elf.R_PPC64_REL16_HA):
su := ldr.MakeSymbolUpdater(s)
su.SetRelocType(rIdx, objabi.R_PCREL)
ldr.SetRelocVariant(s, rIdx, sym.RV_POWER_HA|sym.RV_CHECK_OVERFLOW)
su.SetRelocAdd(rIdx, r.Add()+2)
return true
}
// Handle references to ELF symbols from our own object files.
if targType != sym.SDYNIMPORT {
return true
}
// TODO(austin): Translate our relocations to ELF
return false
}
func xcoffreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
rs := r.Xsym
emitReloc := func(v uint16, off uint64) {
out.Write64(uint64(sectoff) + off)
out.Write32(uint32(rs.Dynid))
out.Write16(v)
}
var v uint16
switch r.Type {
default:
return false
case objabi.R_ADDR:
v = ld.XCOFF_R_POS
if r.Siz == 4 {
v |= 0x1F << 8
} else {
v |= 0x3F << 8
}
emitReloc(v, 0)
case objabi.R_ADDRPOWER_TOCREL:
case objabi.R_ADDRPOWER_TOCREL_DS:
emitReloc(ld.XCOFF_R_TOCU|(0x0F<<8), 2)
emitReloc(ld.XCOFF_R_TOCL|(0x0F<<8), 6)
case objabi.R_POWER_TLS_LE:
emitReloc(ld.XCOFF_R_TLS_LE|0x0F<<8, 2)
case objabi.R_CALLPOWER:
if r.Siz != 4 {
return false
}
emitReloc(ld.XCOFF_R_RBR|0x19<<8, 0)
case objabi.R_XCOFFREF:
emitReloc(ld.XCOFF_R_REF|0x3F<<8, 0)
}
return true
}
func elfreloc1(ctxt *ld.Link, r *sym.Reloc, sectoff int64) bool {
// Beware that bit0~bit15 start from the third byte of a instruction in Big-Endian machines.
if r.Type == objabi.R_ADDR || r.Type == objabi.R_POWER_TLS || r.Type == objabi.R_CALLPOWER {
} else {
if ctxt.Arch.ByteOrder == binary.BigEndian {
sectoff += 2
}
}
ctxt.Out.Write64(uint64(sectoff))
elfsym := ld.ElfSymForReloc(ctxt, r.Xsym)
switch r.Type {
default:
return false
case objabi.R_ADDR:
switch r.Siz {
case 4:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR32) | uint64(elfsym)<<32)
case 8:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR64) | uint64(elfsym)<<32)
default:
return false
}
case objabi.R_POWER_TLS:
ctxt.Out.Write64(uint64(elf.R_PPC64_TLS) | uint64(elfsym)<<32)
case objabi.R_POWER_TLS_LE:
ctxt.Out.Write64(uint64(elf.R_PPC64_TPREL16) | uint64(elfsym)<<32)
case objabi.R_POWER_TLS_IE:
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT_TPREL16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT_TPREL16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_LO) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_DS:
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_ADDR16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_GOT:
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_GOT16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_PCREL:
ctxt.Out.Write64(uint64(elf.R_PPC64_REL16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_REL16_LO) | uint64(elfsym)<<32)
r.Xadd += 4
case objabi.R_ADDRPOWER_TOCREL:
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_LO) | uint64(elfsym)<<32)
case objabi.R_ADDRPOWER_TOCREL_DS:
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_HA) | uint64(elfsym)<<32)
ctxt.Out.Write64(uint64(r.Xadd))
ctxt.Out.Write64(uint64(sectoff + 4))
ctxt.Out.Write64(uint64(elf.R_PPC64_TOC16_LO_DS) | uint64(elfsym)<<32)
case objabi.R_CALLPOWER:
if r.Siz != 4 {
return false
}
ctxt.Out.Write64(uint64(elf.R_PPC64_REL24) | uint64(elfsym)<<32)
}
ctxt.Out.Write64(uint64(r.Xadd))
return true
}
func elfsetupplt(ctxt *ld.Link, plt, got *loader.SymbolBuilder, dynamic loader.Sym) {
if plt.Size() == 0 {
// The dynamic linker stores the address of the
// dynamic resolver and the DSO identifier in the two
// doublewords at the beginning of the .plt section
// before the PLT array. Reserve space for these.
plt.SetSize(16)
}
}
func machoreloc1(arch *sys.Arch, out *ld.OutBuf, s *sym.Symbol, r *sym.Reloc, sectoff int64) bool {
return false
}
// Return the value of .TOC. for symbol s
func symtoc(syms *ld.ArchSyms, s *sym.Symbol) int64 {
v := s.Version
if s.Outer != nil {
v = s.Outer.Version
}
toc := syms.DotTOC[v]
if toc == nil {
ld.Errorf(s, "TOC-relative relocation in object without .TOC.")
return 0
}
return toc.Value
}
// archreloctoc relocates a TOC relative symbol.
// If the symbol pointed by this TOC relative symbol is in .data or .bss, the
// default load instruction can be changed to an addi instruction and the
// symbol address can be used directly.
// This code is for AIX only.
func archreloctoc(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) int64 {
if target.IsLinux() {
ld.Errorf(s, "archrelocaddr called for %s relocation\n", r.Sym.Name)
}
var o1, o2 uint32
o1 = uint32(val >> 32)
o2 = uint32(val)
var t int64
useAddi := false
const prefix = "TOC."
var tarSym *sym.Symbol
if strings.HasPrefix(r.Sym.Name, prefix) {
tarSym = r.Sym.R[0].Sym
} else {
ld.Errorf(s, "archreloctoc called for a symbol without TOC anchor")
}
if target.IsInternal() && tarSym != nil && tarSym.Attr.Reachable() && (tarSym.Sect.Seg == &ld.Segdata) {
t = ld.Symaddr(tarSym) + r.Add - syms.TOC.Value
// change ld to addi in the second instruction
o2 = (o2 & 0x03FF0000) | 0xE<<26
useAddi = true
} else {
t = ld.Symaddr(r.Sym) + r.Add - syms.TOC.Value
}
if t != int64(int32(t)) {
ld.Errorf(s, "TOC relocation for %s is too big to relocate %s: 0x%x", s.Name, r.Sym, t)
}
if t&0x8000 != 0 {
t += 0x10000
}
o1 |= uint32((t >> 16) & 0xFFFF)
switch r.Type {
case objabi.R_ADDRPOWER_TOCREL_DS:
if useAddi {
o2 |= uint32(t) & 0xFFFF
} else {
if t&3 != 0 {
ld.Errorf(s, "bad DS reloc for %s: %d", s.Name, ld.Symaddr(r.Sym))
}
o2 |= uint32(t) & 0xFFFC
}
default:
return -1
}
return int64(o1)<<32 | int64(o2)
}
// archrelocaddr relocates a symbol address.
// This code is for AIX only.
func archrelocaddr(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) int64 {
if target.IsAIX() {
ld.Errorf(s, "archrelocaddr called for %s relocation\n", r.Sym.Name)
}
var o1, o2 uint32
if target.IsBigEndian() {
o1 = uint32(val >> 32)
o2 = uint32(val)
} else {
o1 = uint32(val)
o2 = uint32(val >> 32)
}
// We are spreading a 31-bit address across two instructions, putting the
// high (adjusted) part in the low 16 bits of the first instruction and the
// low part in the low 16 bits of the second instruction, or, in the DS case,
// bits 15-2 (inclusive) of the address into bits 15-2 of the second
// instruction (it is an error in this case if the low 2 bits of the address
// are non-zero).
t := ld.Symaddr(r.Sym) + r.Add
if t < 0 || t >= 1<<31 {
ld.Errorf(s, "relocation for %s is too big (>=2G): 0x%x", s.Name, ld.Symaddr(r.Sym))
}
if t&0x8000 != 0 {
t += 0x10000
}
switch r.Type {
case objabi.R_ADDRPOWER:
o1 |= (uint32(t) >> 16) & 0xffff
o2 |= uint32(t) & 0xffff
case objabi.R_ADDRPOWER_DS:
o1 |= (uint32(t) >> 16) & 0xffff
if t&3 != 0 {
ld.Errorf(s, "bad DS reloc for %s: %d", s.Name, ld.Symaddr(r.Sym))
}
o2 |= uint32(t) & 0xfffc
default:
return -1
}
if target.IsBigEndian() {
return int64(o1)<<32 | int64(o2)
}
return int64(o2)<<32 | int64(o1)
}
// resolve direct jump relocation r in s, and add trampoline if necessary
func trampoline(ctxt *ld.Link, ldr *loader.Loader, ri int, rs, s loader.Sym) {
// Trampolines are created if the branch offset is too large and the linker cannot insert a call stub to handle it.
// For internal linking, trampolines are always created for long calls.
// For external linking, the linker can insert a call stub to handle a long call, but depends on having the TOC address in
// r2. For those build modes with external linking where the TOC address is not maintained in r2, trampolines must be created.
if ctxt.IsExternal() && (ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE) {
// No trampolines needed since r2 contains the TOC
return
}
relocs := ldr.Relocs(s)
r := relocs.At2(ri)
t := ldr.SymValue(rs) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
switch r.Type() {
case objabi.R_CALLPOWER:
// If branch offset is too far then create a trampoline.
if (ctxt.IsExternal() && ldr.SymSect(s) != ldr.SymSect(rs)) || (ctxt.IsInternal() && int64(int32(t<<6)>>6) != t) || (*ld.FlagDebugTramp > 1 && ldr.SymPkg(s) != ldr.SymPkg(rs)) {
var tramp loader.Sym
for i := 0; ; i++ {
// Using r.Add as part of the name is significant in functions like duffzero where the call
// target is at some offset within the function. Calls to duff+8 and duff+256 must appear as
// distinct trampolines.
name := ldr.SymName(rs)
if r.Add() == 0 {
name = name + fmt.Sprintf("-tramp%d", i)
} else {
name = name + fmt.Sprintf("%+x-tramp%d", r.Add(), i)
}
// Look up the trampoline in case it already exists
tramp = ldr.LookupOrCreateSym(name, int(ldr.SymVersion(rs)))
if ldr.SymValue(tramp) == 0 {
break
}
t = ldr.SymValue(tramp) + r.Add() - (ldr.SymValue(s) + int64(r.Off()))
// With internal linking, the trampoline can be used if it is not too far.
// With external linking, the trampoline must be in this section for it to be reused.
if (ctxt.IsInternal() && int64(int32(t<<6)>>6) == t) || (ctxt.IsExternal() && ldr.SymSect(s) == ldr.SymSect(tramp)) {
break
}
}
if ldr.SymType(tramp) == 0 {
if ctxt.DynlinkingGo() || ctxt.BuildMode == ld.BuildModeCArchive || ctxt.BuildMode == ld.BuildModeCShared || ctxt.BuildMode == ld.BuildModePIE {
// Should have returned for above cases
ctxt.Errorf(s, "unexpected trampoline for shared or dynamic linking")
} else {
trampb := ldr.MakeSymbolUpdater(tramp)
ctxt.AddTramp(trampb)
gentramp(ctxt, ldr, trampb, rs, r.Add())
}
}
sb := ldr.MakeSymbolUpdater(s)
relocs := sb.Relocs()
r := relocs.At2(ri)
r.SetSym(tramp)
r.SetAdd(0) // This was folded into the trampoline target address
}
default:
ctxt.Errorf(s, "trampoline called with non-jump reloc: %d (%s)", r.Type(), sym.RelocName(ctxt.Arch, r.Type()))
}
}
func gentramp(ctxt *ld.Link, ldr *loader.Loader, tramp *loader.SymbolBuilder, target loader.Sym, offset int64) {
tramp.SetSize(16) // 4 instructions
P := make([]byte, tramp.Size())
t := ldr.SymValue(target) + offset
var o1, o2 uint32
if ctxt.IsAIX() {
// On AIX, the address is retrieved with a TOC symbol.
// For internal linking, the "Linux" way might still be used.
// However, all text symbols are accessed with a TOC symbol as
// text relocations aren't supposed to be possible.
// So, keep using the external linking way to be more AIX friendly.
o1 = uint32(0x3fe20000) // lis r2, toctargetaddr hi
o2 = uint32(0xebff0000) // ld r31, toctargetaddr lo
toctramp := ldr.CreateSymForUpdate("TOC."+ldr.SymName(tramp.Sym()), 0)
toctramp.SetType(sym.SXCOFFTOC)
toctramp.SetReachable(true)
toctramp.AddAddrPlus(ctxt.Arch, target, offset)
r := loader.Reloc{
Off: 0,
Type: objabi.R_ADDRPOWER_TOCREL_DS,
Size: 8, // generates 2 relocations: HA + LO
Sym: toctramp.Sym(),
}
tramp.AddReloc(r)
} else {
// Used for default build mode for an executable
// Address of the call target is generated using
// relocation and doesn't depend on r2 (TOC).
o1 = uint32(0x3fe00000) // lis r31,targetaddr hi
o2 = uint32(0x3bff0000) // addi r31,targetaddr lo
// With external linking, the target address must be
// relocated using LO and HA
if ctxt.IsExternal() {
r := loader.Reloc{
Off: 0,
Type: objabi.R_ADDRPOWER,
Size: 8, // generates 2 relocations: HA + LO
Sym: target,
Add: offset,
}
tramp.AddReloc(r)
} else {
// adjustment needed if lo has sign bit set
// when using addi to compute address
val := uint32((t & 0xffff0000) >> 16)
if t&0x8000 != 0 {
val += 1
}
o1 |= val // hi part of addr
o2 |= uint32(t & 0xffff) // lo part of addr
}
}
o3 := uint32(0x7fe903a6) // mtctr r31
o4 := uint32(0x4e800420) // bctr
ctxt.Arch.ByteOrder.PutUint32(P, o1)
ctxt.Arch.ByteOrder.PutUint32(P[4:], o2)
ctxt.Arch.ByteOrder.PutUint32(P[8:], o3)
ctxt.Arch.ByteOrder.PutUint32(P[12:], o4)
tramp.SetData(P)
}
func archreloc(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, val int64) (int64, bool) {
if target.IsExternal() {
// On AIX, relocations (except TLS ones) must be also done to the
// value with the current addresses.
switch r.Type {
default:
if target.IsAIX() {
return val, false
}
case objabi.R_POWER_TLS, objabi.R_POWER_TLS_LE, objabi.R_POWER_TLS_IE:
r.Done = false
// check Outer is nil, Type is TLSBSS?
r.Xadd = r.Add
r.Xsym = r.Sym
return val, true
case objabi.R_ADDRPOWER,
objabi.R_ADDRPOWER_DS,
objabi.R_ADDRPOWER_TOCREL,
objabi.R_ADDRPOWER_TOCREL_DS,
objabi.R_ADDRPOWER_GOT,
objabi.R_ADDRPOWER_PCREL:
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 += ld.Symaddr(rs) - ld.Symaddr(rs.Outer)
rs = rs.Outer
}
if rs.Type != sym.SHOSTOBJ && rs.Type != sym.SDYNIMPORT && rs.Type != sym.SUNDEFEXT && rs.Sect == nil {
ld.Errorf(s, "missing section for %s", rs.Name)
}
r.Xsym = rs
if !target.IsAIX() {
return val, true
}
case objabi.R_CALLPOWER:
r.Done = false
r.Xsym = r.Sym
r.Xadd = r.Add
if !target.IsAIX() {
return val, true
}
}
}
switch r.Type {
case objabi.R_CONST:
return r.Add, true
case objabi.R_GOTOFF:
return ld.Symaddr(r.Sym) + r.Add - ld.Symaddr(syms.GOT), true
case objabi.R_ADDRPOWER_TOCREL, objabi.R_ADDRPOWER_TOCREL_DS:
return archreloctoc(target, syms, r, s, val), true
case objabi.R_ADDRPOWER, objabi.R_ADDRPOWER_DS:
return archrelocaddr(target, syms, r, s, val), true
case objabi.R_CALLPOWER:
// Bits 6 through 29 = (S + A - P) >> 2
t := ld.Symaddr(r.Sym) + r.Add - (s.Value + int64(r.Off))
if t&3 != 0 {
ld.Errorf(s, "relocation for %s+%d is not aligned: %d", r.Sym.Name, r.Off, t)
}
// If branch offset is too far then create a trampoline.
if int64(int32(t<<6)>>6) != t {
ld.Errorf(s, "direct call too far: %s %x", r.Sym.Name, t)
}
return val | int64(uint32(t)&^0xfc000003), true
case objabi.R_POWER_TOC: // S + A - .TOC.
return ld.Symaddr(r.Sym) + r.Add - symtoc(syms, s), true
case objabi.R_POWER_TLS_LE:
// The thread pointer points 0x7000 bytes after the start of the
// thread local storage area as documented in section "3.7.2 TLS
// Runtime Handling" of "Power Architecture 64-Bit ELF V2 ABI
// Specification".
v := r.Sym.Value - 0x7000
if target.IsAIX() {
// On AIX, the thread pointer points 0x7800 bytes after
// the TLS.
v -= 0x800
}
if int64(int16(v)) != v {
ld.Errorf(s, "TLS offset out of range %d", v)
}
return (val &^ 0xffff) | (v & 0xffff), true
}
return val, false
}
func archrelocvariant(target *ld.Target, syms *ld.ArchSyms, r *sym.Reloc, s *sym.Symbol, t int64) int64 {
switch r.Variant & sym.RV_TYPE_MASK {
default:
ld.Errorf(s, "unexpected relocation variant %d", r.Variant)
fallthrough
case sym.RV_NONE:
return t
case sym.RV_POWER_LO:
if r.Variant&sym.RV_CHECK_OVERFLOW != 0 {
// Whether to check for signed or unsigned
// overflow depends on the instruction
var o1 uint32
if target.IsBigEndian() {
o1 = binary.BigEndian.Uint32(s.P[r.Off-2:])
} else {
o1 = binary.LittleEndian.Uint32(s.P[r.Off:])
}
switch o1 >> 26 {
case 24, // ori
26, // xori
28: // andi
if t>>16 != 0 {
goto overflow
}
default:
if int64(int16(t)) != t {
goto overflow
}
}
}
return int64(int16(t))
case sym.RV_POWER_HA:
t += 0x8000
fallthrough
// Fallthrough
case sym.RV_POWER_HI:
t >>= 16
if r.Variant&sym.RV_CHECK_OVERFLOW != 0 {
// Whether to check for signed or unsigned
// overflow depends on the instruction
var o1 uint32
if target.IsBigEndian() {
o1 = binary.BigEndian.Uint32(s.P[r.Off-2:])
} else {
o1 = binary.LittleEndian.Uint32(s.P[r.Off:])
}
switch o1 >> 26 {
case 25, // oris
27, // xoris
29: // andis
if t>>16 != 0 {
goto overflow
}
default:
if int64(int16(t)) != t {
goto overflow
}
}
}
return int64(int16(t))
case sym.RV_POWER_DS:
var o1 uint32
if target.IsBigEndian() {
o1 = uint32(binary.BigEndian.Uint16(s.P[r.Off:]))
} else {
o1 = uint32(binary.LittleEndian.Uint16(s.P[r.Off:]))
}
if t&3 != 0 {
ld.Errorf(s, "relocation for %s+%d is not aligned: %d", r.Sym.Name, r.Off, t)
}
if (r.Variant&sym.RV_CHECK_OVERFLOW != 0) && int64(int16(t)) != t {
goto overflow
}
return int64(o1)&0x3 | int64(int16(t))
}
overflow:
ld.Errorf(s, "relocation for %s+%d is too big: %d", r.Sym.Name, r.Off, t)
return t
}
func addpltsym2(ctxt *ld.Link, ldr *loader.Loader, s loader.Sym) {
if ldr.SymPlt(s) >= 0 {
return
}
ld.Adddynsym2(ldr, &ctxt.Target, &ctxt.ArchSyms, s)
if ctxt.IsELF {
plt := ldr.MakeSymbolUpdater(ctxt.PLT2)
rela := ldr.MakeSymbolUpdater(ctxt.RelaPLT2)
if plt.Size() == 0 {
panic("plt is not set up")
}
// Create the glink resolver if necessary
glink := ensureglinkresolver2(ctxt, ldr)
// Write symbol resolver stub (just a branch to the
// glink resolver stub)
rel := loader.Reloc{
Off: int32(glink.Size()),
Size: 4,
Type: objabi.R_CALLPOWER,
Sym: glink.Sym(),
}
glink.AddReloc(rel)
glink.AddUint32(ctxt.Arch, 0x48000000) // b .glink
// In the ppc64 ABI, the dynamic linker is responsible
// for writing the entire PLT. We just need to
// reserve 8 bytes for each PLT entry and generate a
// JMP_SLOT dynamic relocation for it.
//
// TODO(austin): ABI v1 is different
ldr.SetPlt(s, int32(plt.Size()))
plt.Grow(plt.Size() + 8)
rela.AddAddrPlus(ctxt.Arch, plt.Sym(), int64(ldr.SymPlt(s)))
rela.AddUint64(ctxt.Arch, ld.ELF64_R_INFO(uint32(ldr.SymDynid(s)), uint32(elf.R_PPC64_JMP_SLOT)))
rela.AddUint64(ctxt.Arch, 0)
} else {
ctxt.Errorf(s, "addpltsym: unsupported binary format")
}
}
// Generate the glink resolver stub if necessary and return the .glink section
func ensureglinkresolver2(ctxt *ld.Link, ldr *loader.Loader) *loader.SymbolBuilder {
gs := ldr.LookupOrCreateSym(".glink", 0)
glink := ldr.MakeSymbolUpdater(gs)
if glink.Size() != 0 {
return glink
}
// This is essentially the resolver from the ppc64 ELF ABI.
// At entry, r12 holds the address of the symbol resolver stub
// for the target routine and the argument registers hold the
// arguments for the target routine.
//
// This stub is PIC, so first get the PC of label 1 into r11.
// Other things will be relative to this.
glink.AddUint32(ctxt.Arch, 0x7c0802a6) // mflr r0
glink.AddUint32(ctxt.Arch, 0x429f0005) // bcl 20,31,1f
glink.AddUint32(ctxt.Arch, 0x7d6802a6) // 1: mflr r11
glink.AddUint32(ctxt.Arch, 0x7c0803a6) // mtlf r0
// Compute the .plt array index from the entry point address.
// Because this is PIC, everything is relative to label 1b (in
// r11):
// r0 = ((r12 - r11) - (res_0 - r11)) / 4 = (r12 - res_0) / 4
glink.AddUint32(ctxt.Arch, 0x3800ffd0) // li r0,-(res_0-1b)=-48
glink.AddUint32(ctxt.Arch, 0x7c006214) // add r0,r0,r12
glink.AddUint32(ctxt.Arch, 0x7c0b0050) // sub r0,r0,r11
glink.AddUint32(ctxt.Arch, 0x7800f082) // srdi r0,r0,2
// r11 = address of the first byte of the PLT
glink.AddSymRef(ctxt.Arch, ctxt.PLT2, 0, objabi.R_ADDRPOWER, 8)
glink.AddUint32(ctxt.Arch, 0x3d600000) // addis r11,0,.plt@ha
glink.AddUint32(ctxt.Arch, 0x396b0000) // addi r11,r11,.plt@l
// Load r12 = dynamic resolver address and r11 = DSO
// identifier from the first two doublewords of the PLT.
glink.AddUint32(ctxt.Arch, 0xe98b0000) // ld r12,0(r11)
glink.AddUint32(ctxt.Arch, 0xe96b0008) // ld r11,8(r11)
// Jump to the dynamic resolver
glink.AddUint32(ctxt.Arch, 0x7d8903a6) // mtctr r12
glink.AddUint32(ctxt.Arch, 0x4e800420) // bctr
// The symbol resolvers must immediately follow.
// res_0:
// Add DT_PPC64_GLINK .dynamic entry, which points to 32 bytes
// before the first symbol resolver stub.
du := ldr.MakeSymbolUpdater(ctxt.Dynamic2)
ld.Elfwritedynentsymplus2(ctxt, du, ld.DT_PPC64_GLINK, glink.Sym(), glink.Size()-32)
return glink
}
func asmb(ctxt *ld.Link, _ *loader.Loader) {
if ctxt.IsELF {
ld.Asmbelfsetup()
}
var wg sync.WaitGroup
for _, sect := range ld.Segtext.Sections {
offset := sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff
// Handle additional text sections with Codeblk
if sect.Name == ".text" {
ld.WriteParallel(&wg, ld.Codeblk, ctxt, offset, sect.Vaddr, sect.Length)
} else {
ld.WriteParallel(&wg, ld.Datblk, ctxt, offset, sect.Vaddr, sect.Length)
}
}
for _, sect := range ld.Segtext.Sections[1:] {
offset := sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff
ld.WriteParallel(&wg, ld.Datblk, ctxt, offset, sect.Vaddr, sect.Length)
}
if ld.Segrodata.Filelen > 0 {
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segrodata.Fileoff, ld.Segrodata.Vaddr, ld.Segrodata.Filelen)
}
if ld.Segrelrodata.Filelen > 0 {
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segrelrodata.Fileoff, ld.Segrelrodata.Vaddr, ld.Segrelrodata.Filelen)
}
ld.WriteParallel(&wg, ld.Datblk, ctxt, ld.Segdata.Fileoff, ld.Segdata.Vaddr, ld.Segdata.Filelen)
ld.WriteParallel(&wg, ld.Dwarfblk, ctxt, ld.Segdwarf.Fileoff, ld.Segdwarf.Vaddr, ld.Segdwarf.Filelen)
wg.Wait()
}
func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
ld.Lcsize = 0
symo := uint32(0)
if !*ld.FlagS {
// TODO: rationalize
switch ctxt.HeadType {
default:
if ctxt.IsELF {
symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
symo = uint32(ld.Rnd(int64(symo), int64(*ld.FlagRound)))
}
case objabi.Hplan9:
symo = uint32(ld.Segdata.Fileoff + ld.Segdata.Filelen)
case objabi.Haix:
// Nothing to do
}
ctxt.Out.SeekSet(int64(symo))
switch ctxt.HeadType {
default:
if ctxt.IsELF {
ld.Asmelfsym(ctxt)
ctxt.Out.Write(ld.Elfstrdat)
if ctxt.LinkMode == ld.LinkExternal {
ld.Elfemitreloc(ctxt)
}
}
case objabi.Hplan9:
ld.Asmplan9sym(ctxt)
sym := ctxt.Syms.Lookup("pclntab", 0)
if sym != nil {
ld.Lcsize = int32(len(sym.P))
ctxt.Out.Write(sym.P)
}
case objabi.Haix:
// symtab must be added once sections have been created in ld.Asmbxcoff
}
}
ctxt.Out.SeekSet(0)
switch ctxt.HeadType {
default:
case objabi.Hplan9: /* plan 9 */
ctxt.Out.Write32(0x647) /* magic */
ctxt.Out.Write32(uint32(ld.Segtext.Filelen)) /* sizes */
ctxt.Out.Write32(uint32(ld.Segdata.Filelen))
ctxt.Out.Write32(uint32(ld.Segdata.Length - ld.Segdata.Filelen))
ctxt.Out.Write32(uint32(ld.Symsize)) /* nsyms */
ctxt.Out.Write32(uint32(ld.Entryvalue(ctxt))) /* va of entry */
ctxt.Out.Write32(0)
ctxt.Out.Write32(uint32(ld.Lcsize))
case objabi.Hlinux,
objabi.Hfreebsd,
objabi.Hnetbsd,
objabi.Hopenbsd:
ld.Asmbelf(ctxt, int64(symo))
case objabi.Haix:
fileoff := uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
fileoff = uint32(ld.Rnd(int64(fileoff), int64(*ld.FlagRound)))
ld.Asmbxcoff(ctxt, int64(fileoff))
}
if *ld.FlagC {
fmt.Printf("textsize=%d\n", ld.Segtext.Filelen)
fmt.Printf("datsize=%d\n", ld.Segdata.Filelen)
fmt.Printf("bsssize=%d\n", ld.Segdata.Length-ld.Segdata.Filelen)
fmt.Printf("symsize=%d\n", ld.Symsize)
fmt.Printf("lcsize=%d\n", ld.Lcsize)
fmt.Printf("total=%d\n", ld.Segtext.Filelen+ld.Segdata.Length+uint64(ld.Symsize)+uint64(ld.Lcsize))
}
}
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