Example #1
0
// 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
}
Example #2
0
// 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
}
Example #3
0
func Addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) int64 {
	s.Reachable = true
	i := s.Size
	s.Size += 4
	ld.Symgrow(ctxt, s, s.Size)
	r := ld.Addrel(s)
	r.Sym = t
	r.Off = int32(i)
	r.Type = ld.R_CALL
	r.Siz = 4
	return i + int64(r.Siz)
}
Example #4
0
func addpltreloc(ctxt *ld.Link, plt *ld.LSym, got *ld.LSym, sym *ld.LSym, typ int) *ld.Reloc {
	r := ld.Addrel(plt)
	r.Sym = got
	r.Off = int32(plt.Size)
	r.Siz = 4
	r.Type = int32(typ)
	r.Add = int64(sym.Got) - 8

	plt.Reachable = true
	plt.Size += 4
	ld.Symgrow(ctxt, plt, plt.Size)

	return r
}
Example #5
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)
		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")
	}
}