func elfsetupplt() {
plt := ld.Linklookup(ld.Ctxt, ".plt", 0)
got := ld.Linklookup(ld.Ctxt, ".got.plt", 0)
if plt.Size == 0 {
// pushl got+4
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x35)
ld.Addaddrplus(ld.Ctxt, plt, got, 4)
// jmp *got+8
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x25)
ld.Addaddrplus(ld.Ctxt, plt, got, 8)
// zero pad
ld.Adduint32(ld.Ctxt, plt, 0)
// assume got->size == 0 too
ld.Addaddrplus(ld.Ctxt, got, ld.Linklookup(ld.Ctxt, ".dynamic", 0), 0)
ld.Adduint32(ld.Ctxt, got, 0)
ld.Adduint32(ld.Ctxt, got, 0)
}
}
func addpltsym(ctxt *ld.Link, s *ld.LSym) {
if s.Plt >= 0 {
return
}
adddynsym(ctxt, s)
if ld.Iself {
plt := ld.Linklookup(ctxt, ".plt", 0)
got := ld.Linklookup(ctxt, ".got.plt", 0)
rel := ld.Linklookup(ctxt, ".rel.plt", 0)
if plt.Size == 0 {
elfsetupplt()
}
// jmpq *got+size
ld.Adduint8(ctxt, plt, 0xff)
ld.Adduint8(ctxt, plt, 0x25)
ld.Addaddrplus(ctxt, plt, got, got.Size)
// add to got: pointer to current pos in plt
ld.Addaddrplus(ctxt, got, plt, plt.Size)
// pushl $x
ld.Adduint8(ctxt, plt, 0x68)
ld.Adduint32(ctxt, plt, uint32(rel.Size))
// jmp .plt
ld.Adduint8(ctxt, plt, 0xe9)
ld.Adduint32(ctxt, plt, uint32(-(plt.Size + 4)))
// rel
ld.Addaddrplus(ctxt, rel, got, got.Size-4)
ld.Adduint32(ctxt, rel, ld.ELF32_R_INFO(uint32(s.Dynid), ld.R_386_JMP_SLOT))
s.Plt = int32(plt.Size - 16)
} else if ld.HEADTYPE == ld.Hdarwin {
// Same laziness as in 6l.
plt := ld.Linklookup(ctxt, ".plt", 0)
addgotsym(ctxt, s)
ld.Adduint32(ctxt, ld.Linklookup(ctxt, ".linkedit.plt", 0), uint32(s.Dynid))
// jmpq *got+size(IP)
s.Plt = int32(plt.Size)
ld.Adduint8(ctxt, plt, 0xff)
ld.Adduint8(ctxt, plt, 0x25)
ld.Addaddrplus(ctxt, plt, ld.Linklookup(ctxt, ".got", 0), int64(s.Got))
} else {
ld.Diag("addpltsym: unsupported binary format")
}
}
func adddynsym(ctxt *ld.Link, s *ld.LSym) {
if s.Dynid >= 0 {
return
}
if ld.Iself {
s.Dynid = int32(ld.Nelfsym)
ld.Nelfsym++
d := ld.Linklookup(ctxt, ".dynsym", 0)
/* name */
name := s.Extname
ld.Adduint32(ctxt, d, uint32(ld.Addstring(ld.Linklookup(ctxt, ".dynstr", 0), name)))
/* value */
if s.Type == ld.SDYNIMPORT {
ld.Adduint32(ctxt, d, 0)
} else {
ld.Addaddr(ctxt, d, s)
}
/* size */
ld.Adduint32(ctxt, d, 0)
/* type */
t := ld.STB_GLOBAL << 4
if s.Cgoexport != 0 && s.Type&ld.SMASK == ld.STEXT {
t |= ld.STT_FUNC
} else {
t |= ld.STT_OBJECT
}
ld.Adduint8(ctxt, d, uint8(t))
ld.Adduint8(ctxt, d, 0)
/* shndx */
if s.Type == ld.SDYNIMPORT {
ld.Adduint16(ctxt, d, ld.SHN_UNDEF)
} else {
ld.Adduint16(ctxt, d, 1)
}
} else if ld.HEADTYPE == ld.Hdarwin {
ld.Diag("adddynsym: missed symbol %s (%s)", s.Name, s.Extname)
} else if ld.HEADTYPE == ld.Hwindows {
} else // already taken care of
{
ld.Diag("adddynsym: unsupported binary format")
}
}
func elfsetupplt() {
plt := ld.Linklookup(ld.Ctxt, ".plt", 0)
got := ld.Linklookup(ld.Ctxt, ".got.plt", 0)
if plt.Size == 0 {
// pushq got+8(IP)
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x35)
ld.Addpcrelplus(ld.Ctxt, plt, got, 8)
// jmpq got+16(IP)
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x25)
ld.Addpcrelplus(ld.Ctxt, plt, got, 16)
// nopl 0(AX)
ld.Adduint32(ld.Ctxt, plt, 0x00401f0f)
// assume got->size == 0 too
ld.Addaddrplus(ld.Ctxt, got, ld.Linklookup(ld.Ctxt, ".dynamic", 0), 0)
ld.Adduint64(ld.Ctxt, got, 0)
ld.Adduint64(ld.Ctxt, got, 0)
}
}
func adddynsym(ctxt *ld.Link, s *ld.LSym) {
if s.Dynid >= 0 {
return
}
if ld.Iself {
s.Dynid = int32(ld.Nelfsym)
ld.Nelfsym++
d := ld.Linklookup(ctxt, ".dynsym", 0)
/* name */
name := s.Extname
ld.Adduint32(ctxt, d, uint32(ld.Addstring(ld.Linklookup(ctxt, ".dynstr", 0), name)))
/* value */
if s.Type == ld.SDYNIMPORT {
ld.Adduint32(ctxt, d, 0)
} else {
ld.Addaddr(ctxt, d, s)
}
/* size */
ld.Adduint32(ctxt, d, 0)
/* type */
t := ld.STB_GLOBAL << 4
if (s.Cgoexport&ld.CgoExportDynamic != 0) && s.Type&ld.SMASK == ld.STEXT {
t |= ld.STT_FUNC
} else {
t |= ld.STT_OBJECT
}
ld.Adduint8(ctxt, d, uint8(t))
ld.Adduint8(ctxt, d, 0)
/* shndx */
if s.Type == ld.SDYNIMPORT {
ld.Adduint16(ctxt, d, ld.SHN_UNDEF)
} else {
ld.Adduint16(ctxt, d, 1)
}
} else {
ld.Diag("adddynsym: unsupported binary format")
}
}
func elfsetupplt() {
plt := ld.Linklookup(ld.Ctxt, ".plt", 0)
got := ld.Linklookup(ld.Ctxt, ".got.plt", 0)
if plt.Size == 0 {
// str lr, [sp, #-4]!
ld.Adduint32(ld.Ctxt, plt, 0xe52de004)
// ldr lr, [pc, #4]
ld.Adduint32(ld.Ctxt, plt, 0xe59fe004)
// add lr, pc, lr
ld.Adduint32(ld.Ctxt, plt, 0xe08fe00e)
// ldr pc, [lr, #8]!
ld.Adduint32(ld.Ctxt, plt, 0xe5bef008)
// .word &GLOBAL_OFFSET_TABLE[0] - .
ld.Addpcrelplus(ld.Ctxt, plt, got, 4)
// the first .plt entry requires 3 .plt.got entries
ld.Adduint32(ld.Ctxt, got, 0)
ld.Adduint32(ld.Ctxt, got, 0)
ld.Adduint32(ld.Ctxt, got, 0)
}
}
func addgotsym(ctxt *ld.Link, s *ld.LSym) {
if s.Got >= 0 {
return
}
adddynsym(ctxt, s)
got := ld.Linklookup(ctxt, ".got", 0)
s.Got = int32(got.Size)
ld.Adduint32(ctxt, got, 0)
if ld.Iself {
rel := ld.Linklookup(ctxt, ".rel", 0)
ld.Addaddrplus(ctxt, rel, got, int64(s.Got))
ld.Adduint32(ctxt, rel, ld.ELF32_R_INFO(uint32(s.Dynid), ld.R_ARM_GLOB_DAT))
} else {
ld.Diag("addgotsym: unsupported binary format")
}
}
// Construct a call stub in stub that calls symbol targ via its PLT
// entry.
func gencallstub(abicase int, stub *ld.LSym, targ *ld.LSym) {
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 := ld.Linklookup(ld.Ctxt, ".plt", 0)
stub.Type = ld.STEXT
// Save TOC pointer in TOC save slot
ld.Adduint32(ld.Ctxt, stub, 0xf8410018) // std r2,24(r1)
// Load the function pointer from the PLT.
r := ld.Addrel(stub)
r.Off = int32(stub.Size)
r.Sym = plt
r.Add = int64(targ.Plt)
r.Siz = 2
if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
r.Off += int32(r.Siz)
}
r.Type = ld.R_POWER_TOC
r.Variant = ld.RV_POWER_HA
ld.Adduint32(ld.Ctxt, stub, 0x3d820000) // addis r12,r2,targ@plt@toc@ha
r = ld.Addrel(stub)
r.Off = int32(stub.Size)
r.Sym = plt
r.Add = int64(targ.Plt)
r.Siz = 2
if ld.Ctxt.Arch.ByteOrder == binary.BigEndian {
r.Off += int32(r.Siz)
}
r.Type = ld.R_POWER_TOC
r.Variant = ld.RV_POWER_LO
ld.Adduint32(ld.Ctxt, stub, 0xe98c0000) // ld r12,targ@plt@toc@l(r12)
// Jump to the loaded pointer
ld.Adduint32(ld.Ctxt, stub, 0x7d8903a6) // mtctr r12
ld.Adduint32(ld.Ctxt, stub, 0x4e800420) // bctr
}
func adddynsym(ctxt *ld.Link, s *ld.LSym) {
if s.Dynid >= 0 {
return
}
if ld.Iself {
s.Dynid = int32(ld.Nelfsym)
ld.Nelfsym++
d := ld.Linklookup(ctxt, ".dynsym", 0)
name := s.Extname
ld.Adduint32(ctxt, d, uint32(ld.Addstring(ld.Linklookup(ctxt, ".dynstr", 0), name)))
/* type */
t := ld.STB_GLOBAL << 4
if s.Cgoexport != 0 && s.Type&ld.SMASK == ld.STEXT {
t |= ld.STT_FUNC
} else {
t |= ld.STT_OBJECT
}
ld.Adduint8(ctxt, d, uint8(t))
/* reserved */
ld.Adduint8(ctxt, d, 0)
/* section where symbol is defined */
if s.Type == ld.SDYNIMPORT {
ld.Adduint16(ctxt, d, ld.SHN_UNDEF)
} else {
ld.Adduint16(ctxt, d, 1)
}
/* value */
if s.Type == ld.SDYNIMPORT {
ld.Adduint64(ctxt, d, 0)
} else {
ld.Addaddr(ctxt, d, s)
}
/* size of object */
ld.Adduint64(ctxt, d, uint64(s.Size))
if s.Cgoexport&ld.CgoExportDynamic == 0 && s.Dynimplib != "" && needlib(s.Dynimplib) != 0 {
ld.Elfwritedynent(ld.Linklookup(ctxt, ".dynamic", 0), ld.DT_NEEDED, uint64(ld.Addstring(ld.Linklookup(ctxt, ".dynstr", 0), s.Dynimplib)))
}
} else if ld.HEADTYPE == ld.Hdarwin {
ld.Diag("adddynsym: missed symbol %s (%s)", s.Name, s.Extname)
} else if ld.HEADTYPE == ld.Hwindows {
} else // already taken care of
{
ld.Diag("adddynsym: unsupported binary format")
}
}
func adddynsym(ctxt *ld.Link, s *ld.LSym) {
if s.Dynid >= 0 {
return
}
if ld.Iself {
s.Dynid = int32(ld.Nelfsym)
ld.Nelfsym++
d := ld.Linklookup(ctxt, ".dynsym", 0)
name := s.Extname
ld.Adduint32(ctxt, d, uint32(ld.Addstring(ld.Linklookup(ctxt, ".dynstr", 0), name)))
/* type */
t := ld.STB_GLOBAL << 4
if s.Cgoexport != 0 && s.Type&ld.SMASK == ld.STEXT {
t |= ld.STT_FUNC
} else {
t |= ld.STT_OBJECT
}
ld.Adduint8(ctxt, d, uint8(t))
/* reserved */
ld.Adduint8(ctxt, d, 0)
/* section where symbol is defined */
if s.Type == ld.SDYNIMPORT {
ld.Adduint16(ctxt, d, ld.SHN_UNDEF)
} else {
ld.Adduint16(ctxt, d, 1)
}
/* value */
if s.Type == ld.SDYNIMPORT {
ld.Adduint64(ctxt, d, 0)
} else {
ld.Addaddr(ctxt, d, s)
}
/* size of object */
ld.Adduint64(ctxt, d, uint64(s.Size))
} else {
ld.Diag("adddynsym: unsupported binary format")
}
}
func addpltsym(ctxt *ld.Link, s *ld.LSym) {
if s.Plt >= 0 {
return
}
adddynsym(ctxt, s)
if ld.Iself {
plt := ld.Linklookup(ctxt, ".plt", 0)
rela := ld.Linklookup(ctxt, ".rela.plt", 0)
if plt.Size == 0 {
elfsetupplt()
}
// Create the glink resolver if necessary
glink := ensureglinkresolver()
// Write symbol resolver stub (just a branch to the
// glink resolver stub)
r := ld.Addrel(glink)
r.Sym = glink
r.Off = int32(glink.Size)
r.Siz = 4
r.Type = ld.R_CALLPOWER
ld.Adduint32(ctxt, glink, 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
s.Plt = int32(plt.Size)
plt.Size += 8
ld.Addaddrplus(ctxt, rela, plt, int64(s.Plt))
ld.Adduint64(ctxt, rela, ld.ELF64_R_INFO(uint32(s.Dynid), ld.R_PPC64_JMP_SLOT))
ld.Adduint64(ctxt, rela, 0)
} else {
ld.Diag("addpltsym: unsupported binary format")
}
}
func addgotsym(s *ld.LSym) {
if s.Got >= 0 {
return
}
adddynsym(ld.Ctxt, s)
got := ld.Linklookup(ld.Ctxt, ".got", 0)
s.Got = int32(got.Size)
ld.Adduint64(ld.Ctxt, got, 0)
if ld.Iself {
rela := ld.Linklookup(ld.Ctxt, ".rela", 0)
ld.Addaddrplus(ld.Ctxt, rela, got, int64(s.Got))
ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(s.Dynid), ld.R_X86_64_GLOB_DAT))
ld.Adduint64(ld.Ctxt, rela, 0)
} else if ld.HEADTYPE == ld.Hdarwin {
ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.got", 0), uint32(s.Dynid))
} else {
ld.Diag("addgotsym: unsupported binary format")
}
}
func addpltsym(ctxt *ld.Link, s *ld.LSym) {
if s.Plt >= 0 {
return
}
adddynsym(ctxt, s)
if ld.Iself {
plt := ld.Linklookup(ctxt, ".plt", 0)
got := ld.Linklookup(ctxt, ".got.plt", 0)
rel := ld.Linklookup(ctxt, ".rel.plt", 0)
if plt.Size == 0 {
elfsetupplt()
}
// .got entry
s.Got = int32(got.Size)
// In theory, all GOT should point to the first PLT entry,
// Linux/ARM's dynamic linker will do that for us, but FreeBSD/ARM's
// dynamic linker won't, so we'd better do it ourselves.
ld.Addaddrplus(ctxt, got, plt, 0)
// .plt entry, this depends on the .got entry
s.Plt = int32(plt.Size)
addpltreloc(ctxt, plt, got, s, ld.R_PLT0) // add lr, pc, #0xXX00000
addpltreloc(ctxt, plt, got, s, ld.R_PLT1) // add lr, lr, #0xYY000
addpltreloc(ctxt, plt, got, s, ld.R_PLT2) // ldr pc, [lr, #0xZZZ]!
// rel
ld.Addaddrplus(ctxt, rel, got, int64(s.Got))
ld.Adduint32(ctxt, rel, ld.ELF32_R_INFO(uint32(s.Dynid), ld.R_ARM_JUMP_SLOT))
} else {
ld.Diag("addpltsym: unsupported binary format")
}
}
func adddynrel(s *ld.LSym, r *ld.Reloc) {
targ := r.Sym
ld.Ctxt.Cursym = s
switch r.Type {
default:
if r.Type >= 256 {
ld.Diag("unexpected relocation type %d", r.Type)
return
}
// Handle relocations found in ELF object files.
case 256 + ld.R_X86_64_PC32:
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
}
if targ.Type == 0 || targ.Type == ld.SXREF {
ld.Diag("unknown symbol %s in pcrel", targ.Name)
}
r.Type = ld.R_PCREL
r.Add += 4
return
case 256 + ld.R_X86_64_PLT32:
r.Type = ld.R_PCREL
r.Add += 4
if targ.Type == ld.SDYNIMPORT {
addpltsym(targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add += int64(targ.Plt)
}
return
case 256 + ld.R_X86_64_GOTPCREL:
if targ.Type != ld.SDYNIMPORT {
// have symbol
if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
// turn MOVQ of GOT entry into LEAQ of symbol itself
s.P[r.Off-2] = 0x8d
r.Type = ld.R_PCREL
r.Add += 4
return
}
}
// fall back to using GOT and hope for the best (CMOV*)
// TODO: just needs relocation, no need to put in .dynsym
addgotsym(targ)
r.Type = ld.R_PCREL
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += 4
r.Add += int64(targ.Got)
return
case 256 + ld.R_X86_64_64:
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected R_X86_64_64 relocation for dynamic symbol %s", targ.Name)
}
r.Type = ld.R_ADDR
return
// Handle relocations found in Mach-O object files.
case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 0,
512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
// TODO: What is the difference between all these?
r.Type = ld.R_ADDR
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected reloc for dynamic symbol %s", targ.Name)
}
return
case 512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
if targ.Type == ld.SDYNIMPORT {
addpltsym(targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(targ.Plt)
r.Type = ld.R_PCREL
return
}
fallthrough
// fall through
case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 1,
512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 1,
512 + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
512 + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
512 + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
r.Type = ld.R_PCREL
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected pc-relative reloc for dynamic symbol %s", targ.Name)
}
return
case 512 + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
if targ.Type != ld.SDYNIMPORT {
// have symbol
// turn MOVQ of GOT entry into LEAQ of symbol itself
if r.Off < 2 || s.P[r.Off-2] != 0x8b {
ld.Diag("unexpected GOT_LOAD reloc for non-dynamic symbol %s", targ.Name)
return
}
s.P[r.Off-2] = 0x8d
r.Type = ld.R_PCREL
return
}
fallthrough
// fall through
case 512 + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
if targ.Type != ld.SDYNIMPORT {
ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
}
addgotsym(targ)
r.Type = ld.R_PCREL
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += int64(targ.Got)
return
}
// Handle references to ELF symbols from our own object files.
if targ.Type != ld.SDYNIMPORT {
return
}
switch r.Type {
case ld.R_CALL,
ld.R_PCREL:
if ld.HEADTYPE == ld.Hwindows {
// nothing to do, the relocation will be laid out in pereloc1
return
} else {
// for both ELF and Mach-O
addpltsym(targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(targ.Plt)
return
}
case ld.R_ADDR:
if s.Type == ld.STEXT && ld.Iself {
// The code is asking for the address of an external
// function. We provide it with the address of the
// correspondent GOT symbol.
addgotsym(targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += int64(targ.Got)
return
}
if s.Type != ld.SDATA {
break
}
if ld.Iself {
adddynsym(ld.Ctxt, targ)
rela := ld.Linklookup(ld.Ctxt, ".rela", 0)
ld.Addaddrplus(ld.Ctxt, rela, s, int64(r.Off))
if r.Siz == 8 {
ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_64))
} else {
ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_32))
}
ld.Adduint64(ld.Ctxt, rela, uint64(r.Add))
r.Type = 256 // ignore during relocsym
return
}
if ld.HEADTYPE == ld.Hdarwin && s.Size == int64(ld.Thearch.Ptrsize) && r.Off == 0 {
// Mach-O relocations are a royal pain to lay out.
// They use a compact stateful bytecode representation
// that is too much bother to deal with.
// Instead, interpret the C declaration
// void *_Cvar_stderr = &stderr;
// as making _Cvar_stderr the name of a GOT entry
// for stderr. This is separate from the usual GOT entry,
// just in case the C code assigns to the variable,
// and of course it only works for single pointers,
// but we only need to support cgo and that's all it needs.
adddynsym(ld.Ctxt, targ)
got := ld.Linklookup(ld.Ctxt, ".got", 0)
s.Type = got.Type | ld.SSUB
s.Outer = got
s.Sub = got.Sub
got.Sub = s
s.Value = got.Size
ld.Adduint64(ld.Ctxt, got, 0)
ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.got", 0), uint32(targ.Dynid))
r.Type = 256 // ignore during relocsym
return
}
if ld.HEADTYPE == ld.Hwindows {
// nothing to do, the relocation will be laid out in pereloc1
return
}
}
ld.Ctxt.Cursym = s
ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
func adddynrel(s *ld.LSym, r *ld.Reloc) {
targ := r.Sym
ld.Ctxt.Cursym = s
switch r.Type {
default:
if r.Type >= 256 {
ld.Diag("unexpected relocation type %d", r.Type)
return
}
// Handle relocations found in ELF object files.
case 256 + ld.R_386_PC32:
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
}
if targ.Type == 0 || targ.Type == ld.SXREF {
ld.Diag("unknown symbol %s in pcrel", targ.Name)
}
r.Type = ld.R_PCREL
r.Add += 4
return
case 256 + ld.R_386_PLT32:
r.Type = ld.R_PCREL
r.Add += 4
if targ.Type == ld.SDYNIMPORT {
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add += int64(targ.Plt)
}
return
case 256 + ld.R_386_GOT32:
if targ.Type != ld.SDYNIMPORT {
// have symbol
if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
// turn MOVL of GOT entry into LEAL of symbol address, relative to GOT.
s.P[r.Off-2] = 0x8d
r.Type = ld.R_GOTOFF
return
}
if r.Off >= 2 && s.P[r.Off-2] == 0xff && s.P[r.Off-1] == 0xb3 {
// turn PUSHL of GOT entry into PUSHL of symbol itself.
// use unnecessary SS prefix to keep instruction same length.
s.P[r.Off-2] = 0x36
s.P[r.Off-1] = 0x68
r.Type = ld.R_ADDR
return
}
ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
return
}
addgotsym(ld.Ctxt, targ)
r.Type = ld.R_CONST // write r->add during relocsym
r.Sym = nil
r.Add += int64(targ.Got)
return
case 256 + ld.R_386_GOTOFF:
r.Type = ld.R_GOTOFF
return
case 256 + ld.R_386_GOTPC:
r.Type = ld.R_PCREL
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += 4
return
case 256 + ld.R_386_32:
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected R_386_32 relocation for dynamic symbol %s", targ.Name)
}
r.Type = ld.R_ADDR
return
case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
r.Type = ld.R_ADDR
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected reloc for dynamic symbol %s", targ.Name)
}
return
case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
if targ.Type == ld.SDYNIMPORT {
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(targ.Plt)
r.Type = ld.R_PCREL
return
}
r.Type = ld.R_PCREL
return
case 512 + ld.MACHO_FAKE_GOTPCREL:
if targ.Type != ld.SDYNIMPORT {
// have symbol
// turn MOVL of GOT entry into LEAL of symbol itself
if r.Off < 2 || s.P[r.Off-2] != 0x8b {
ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
return
}
s.P[r.Off-2] = 0x8d
r.Type = ld.R_PCREL
return
}
addgotsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += int64(targ.Got)
r.Type = ld.R_PCREL
return
}
// Handle references to ELF symbols from our own object files.
if targ.Type != ld.SDYNIMPORT {
return
}
switch r.Type {
case ld.R_CALL,
ld.R_PCREL:
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(targ.Plt)
return
case ld.R_ADDR:
if s.Type != ld.SDATA {
break
}
if ld.Iself {
adddynsym(ld.Ctxt, targ)
rel := ld.Linklookup(ld.Ctxt, ".rel", 0)
ld.Addaddrplus(ld.Ctxt, rel, s, int64(r.Off))
ld.Adduint32(ld.Ctxt, rel, ld.ELF32_R_INFO(uint32(targ.Dynid), ld.R_386_32))
r.Type = ld.R_CONST // write r->add during relocsym
r.Sym = nil
return
}
if ld.HEADTYPE == ld.Hdarwin && s.Size == PtrSize && r.Off == 0 {
// Mach-O relocations are a royal pain to lay out.
// They use a compact stateful bytecode representation
// that is too much bother to deal with.
// Instead, interpret the C declaration
// void *_Cvar_stderr = &stderr;
// as making _Cvar_stderr the name of a GOT entry
// for stderr. This is separate from the usual GOT entry,
// just in case the C code assigns to the variable,
// and of course it only works for single pointers,
// but we only need to support cgo and that's all it needs.
adddynsym(ld.Ctxt, targ)
got := ld.Linklookup(ld.Ctxt, ".got", 0)
s.Type = got.Type | ld.SSUB
s.Outer = got
s.Sub = got.Sub
got.Sub = s
s.Value = got.Size
ld.Adduint32(ld.Ctxt, got, 0)
ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.got", 0), uint32(targ.Dynid))
r.Type = 256 // ignore during relocsym
return
}
if ld.HEADTYPE == ld.Hwindows && s.Size == PtrSize {
// nothing to do, the relocation will be laid out in pereloc1
return
}
}
ld.Ctxt.Cursym = s
ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
func adddynrela(rel *ld.LSym, s *ld.LSym, r *ld.Reloc) {
ld.Addaddrplus(ld.Ctxt, rel, s, int64(r.Off))
ld.Adduint32(ld.Ctxt, rel, ld.R_ARM_RELATIVE)
}
// Generate the glink resolver stub if necessary and return the .glink section
func ensureglinkresolver() *ld.LSym {
glink := ld.Linklookup(ld.Ctxt, ".glink", 0)
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.
ld.Adduint32(ld.Ctxt, glink, 0x7c0802a6) // mflr r0
ld.Adduint32(ld.Ctxt, glink, 0x429f0005) // bcl 20,31,1f
ld.Adduint32(ld.Ctxt, glink, 0x7d6802a6) // 1: mflr r11
ld.Adduint32(ld.Ctxt, glink, 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
ld.Adduint32(ld.Ctxt, glink, 0x3800ffd0) // li r0,-(res_0-1b)=-48
ld.Adduint32(ld.Ctxt, glink, 0x7c006214) // add r0,r0,r12
ld.Adduint32(ld.Ctxt, glink, 0x7c0b0050) // sub r0,r0,r11
ld.Adduint32(ld.Ctxt, glink, 0x7800f082) // srdi r0,r0,2
// r11 = address of the first byte of the PLT
r := ld.Addrel(glink)
r.Off = int32(glink.Size)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Siz = 8
r.Type = ld.R_ADDRPOWER
// addis r11,0,.plt@ha; addi r11,r11,.plt@l
r.Add = 0x3d600000<<32 | 0x396b0000
glink.Size += 8
// Load r12 = dynamic resolver address and r11 = DSO
// identifier from the first two doublewords of the PLT.
ld.Adduint32(ld.Ctxt, glink, 0xe98b0000) // ld r12,0(r11)
ld.Adduint32(ld.Ctxt, glink, 0xe96b0008) // ld r11,8(r11)
// Jump to the dynamic resolver
ld.Adduint32(ld.Ctxt, glink, 0x7d8903a6) // mtctr r12
ld.Adduint32(ld.Ctxt, glink, 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.
s := ld.Linklookup(ld.Ctxt, ".dynamic", 0)
ld.Elfwritedynentsymplus(s, ld.DT_PPC64_GLINK, glink, glink.Size-32)
return glink
}
func adddynrel(s *ld.LSym, r *ld.Reloc) {
targ := r.Sym
ld.Ctxt.Cursym = s
switch r.Type {
default:
if r.Type >= 256 {
ld.Diag("unexpected relocation type %d", r.Type)
return
}
// Handle relocations found in ELF object files.
case 256 + ld.R_ARM_PLT32:
r.Type = ld.R_CALLARM
if targ.Type == ld.SDYNIMPORT {
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
}
return
case 256 + ld.R_ARM_THM_PC22: // R_ARM_THM_CALL
ld.Diag("R_ARM_THM_CALL, are you using -marm?")
ld.Errorexit()
return
case 256 + ld.R_ARM_GOT32: // R_ARM_GOT_BREL
if targ.Type != ld.SDYNIMPORT {
addgotsyminternal(ld.Ctxt, targ)
} else {
addgotsym(ld.Ctxt, targ)
}
r.Type = ld.R_CONST // write r->add during relocsym
r.Sym = nil
r.Add += int64(targ.Got)
return
case 256 + ld.R_ARM_GOT_PREL: // GOT(nil) + A - nil
if targ.Type != ld.SDYNIMPORT {
addgotsyminternal(ld.Ctxt, targ)
} else {
addgotsym(ld.Ctxt, targ)
}
r.Type = ld.R_PCREL
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += int64(targ.Got) + 4
return
case 256 + ld.R_ARM_GOTOFF: // R_ARM_GOTOFF32
r.Type = ld.R_GOTOFF
return
case 256 + ld.R_ARM_GOTPC: // R_ARM_BASE_PREL
r.Type = ld.R_PCREL
r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
r.Add += 4
return
case 256 + ld.R_ARM_CALL:
r.Type = ld.R_CALLARM
if targ.Type == ld.SDYNIMPORT {
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
}
return
case 256 + ld.R_ARM_REL32: // R_ARM_REL32
r.Type = ld.R_PCREL
r.Add += 4
return
case 256 + ld.R_ARM_ABS32:
if targ.Type == ld.SDYNIMPORT {
ld.Diag("unexpected R_ARM_ABS32 relocation for dynamic symbol %s", targ.Name)
}
r.Type = ld.R_ADDR
return
// we can just ignore this, because we are targeting ARM V5+ anyway
case 256 + ld.R_ARM_V4BX:
if r.Sym != nil {
// R_ARM_V4BX is ABS relocation, so this symbol is a dummy symbol, ignore it
r.Sym.Type = 0
}
r.Sym = nil
return
case 256 + ld.R_ARM_PC24,
256 + ld.R_ARM_JUMP24:
r.Type = ld.R_CALLARM
if targ.Type == ld.SDYNIMPORT {
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
}
return
}
// Handle references to ELF symbols from our own object files.
if targ.Type != ld.SDYNIMPORT {
return
}
switch r.Type {
case ld.R_CALLARM:
addpltsym(ld.Ctxt, targ)
r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
r.Add = int64(targ.Plt)
return
case ld.R_ADDR:
if s.Type != ld.SDATA {
break
}
if ld.Iself {
adddynsym(ld.Ctxt, targ)
rel := ld.Linklookup(ld.Ctxt, ".rel", 0)
ld.Addaddrplus(ld.Ctxt, rel, s, int64(r.Off))
ld.Adduint32(ld.Ctxt, rel, ld.ELF32_R_INFO(uint32(targ.Dynid), ld.R_ARM_GLOB_DAT)) // we need a nil + A dynmic reloc
r.Type = ld.R_CONST // write r->add during relocsym
r.Sym = nil
return
}
}
ld.Ctxt.Cursym = s
ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
func addpltsym(s *ld.LSym) {
if s.Plt >= 0 {
return
}
adddynsym(ld.Ctxt, s)
if ld.Iself {
plt := ld.Linklookup(ld.Ctxt, ".plt", 0)
got := ld.Linklookup(ld.Ctxt, ".got.plt", 0)
rela := ld.Linklookup(ld.Ctxt, ".rela.plt", 0)
if plt.Size == 0 {
elfsetupplt()
}
// jmpq *got+size(IP)
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x25)
ld.Addpcrelplus(ld.Ctxt, plt, got, got.Size)
// add to got: pointer to current pos in plt
ld.Addaddrplus(ld.Ctxt, got, plt, plt.Size)
// pushq $x
ld.Adduint8(ld.Ctxt, plt, 0x68)
ld.Adduint32(ld.Ctxt, plt, uint32((got.Size-24-8)/8))
// jmpq .plt
ld.Adduint8(ld.Ctxt, plt, 0xe9)
ld.Adduint32(ld.Ctxt, plt, uint32(-(plt.Size + 4)))
// rela
ld.Addaddrplus(ld.Ctxt, rela, got, got.Size-8)
ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(s.Dynid), ld.R_X86_64_JMP_SLOT))
ld.Adduint64(ld.Ctxt, rela, 0)
s.Plt = int32(plt.Size - 16)
} else if ld.HEADTYPE == ld.Hdarwin {
// To do lazy symbol lookup right, we're supposed
// to tell the dynamic loader which library each
// symbol comes from and format the link info
// section just so. I'm too lazy (ha!) to do that
// so for now we'll just use non-lazy pointers,
// which don't need to be told which library to use.
//
// http://networkpx.blogspot.com/2009/09/about-lcdyldinfoonly-command.html
// has details about what we're avoiding.
addgotsym(s)
plt := ld.Linklookup(ld.Ctxt, ".plt", 0)
ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.plt", 0), uint32(s.Dynid))
// jmpq *got+size(IP)
s.Plt = int32(plt.Size)
ld.Adduint8(ld.Ctxt, plt, 0xff)
ld.Adduint8(ld.Ctxt, plt, 0x25)
ld.Addpcrelplus(ld.Ctxt, plt, ld.Linklookup(ld.Ctxt, ".got", 0), int64(s.Got))
} else {
ld.Diag("addpltsym: unsupported binary format")
}
}