Golang ld.Addrel函數代碼示例

func genaddmoduledata() {
	addmoduledata := ld.Linkrlookup(ld.Ctxt, "runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		return
	}
	addmoduledata.Attr |= ld.AttrReachable
	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Attr |= ld.AttrLocal
	initfunc.Attr |= ld.AttrReachable
	o := func(op uint32) {
		ld.Adduint32(ld.Ctxt, initfunc, op)
	}
	// addis r2, r12, [email protected]
	rel := ld.Addrel(initfunc)
	rel.Off = int32(initfunc.Size)
	rel.Siz = 8
	rel.Sym = ld.Linklookup(ld.Ctxt, ".TOC.", 0)
	rel.Type = obj.R_ADDRPOWER_PCREL
	o(0x3c4c0000)
	// addi r2, r2, [email protected]
	o(0x38420000)
	// mflr r31
	o(0x7c0802a6)
	// stdu r31, -32(r1)
	o(0xf801ffe1)
	// addis r3, r2, [email protected]@ha
	rel = ld.Addrel(initfunc)
	rel.Off = int32(initfunc.Size)
	rel.Siz = 8
	rel.Sym = ld.Linklookup(ld.Ctxt, "local.moduledata", 0)
	rel.Type = obj.R_ADDRPOWER_GOT
	o(0x3c620000)
	// ld r3, [email protected]@l(r3)
	o(0xe8630000)
	// bl runtime.addmoduledata
	rel = ld.Addrel(initfunc)
	rel.Off = int32(initfunc.Size)
	rel.Siz = 4
	rel.Sym = addmoduledata
	rel.Type = obj.R_CALLPOWER
	o(0x48000001)
	// nop
	o(0x60000000)
	// ld r31, 0(r1)
	o(0xe8010000)
	// mtlr r31
	o(0x7c0803a6)
	// addi r1,r1,32
	o(0x38210020)
	// blr
	o(0x4e800020)

	ld.Ctxt.Textp = append(ld.Ctxt.Textp, initfunc)
	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
	initarray_entry.Attr |= ld.AttrReachable
	initarray_entry.Attr |= ld.AttrLocal
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
}

func gentext() {
	if !ld.DynlinkingGo() {
		return
	}
	addmoduledata := ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		// we're linking a module containing the runtime -> no need for
		// an init function
		return
	}
	addmoduledata.Attr |= ld.AttrReachable
	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Attr |= ld.AttrLocal
	initfunc.Attr |= ld.AttrReachable
	o := func(op uint32) {
		ld.Adduint32(ld.Ctxt, initfunc, op)
	}
	// 0000000000000000 <local.dso_init>:
	// 0:	90000000 	adrp	x0, 0 <runtime.firstmoduledata>
	// 	0: R_AARCH64_ADR_PREL_PG_HI21	local.moduledata
	// 4:	91000000 	add	x0, x0, #0x0
	// 	4: R_AARCH64_ADD_ABS_LO12_NC	local.moduledata
	o(0x90000000)
	o(0x91000000)
	rel := ld.Addrel(initfunc)
	rel.Off = 0
	rel.Siz = 8
	rel.Sym = ld.Ctxt.Moduledata
	rel.Type = obj.R_ADDRARM64

	// 8:	14000000 	bl	0 <runtime.addmoduledata>
	// 	8: R_AARCH64_CALL26	runtime.addmoduledata
	o(0x14000000)
	rel = ld.Addrel(initfunc)
	rel.Off = 8
	rel.Siz = 4
	rel.Sym = ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
	rel.Type = obj.R_CALLARM64 // Really should be R_AARCH64_JUMP26 but doesn't seem to make any difference

	if ld.Ctxt.Etextp != nil {
		ld.Ctxt.Etextp.Next = initfunc
	} else {
		ld.Ctxt.Textp = initfunc
	}
	ld.Ctxt.Etextp = initfunc
	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
	initarray_entry.Attr |= ld.AttrReachable
	initarray_entry.Attr |= ld.AttrLocal
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
}

// gentext generates assembly to append the local moduledata to the global
// moduledata linked list at initialization time. This is only done if the runtime
// is in a different module.
//
// <go.link.addmoduledata>:
// 	larl  %r2, <local.moduledata>
// 	jg    <[email protected]>
//	undef
//
// The job of appending the moduledata is delegated to runtime.addmoduledata.
func gentext(ctxt *ld.Link) {
	if !ld.DynlinkingGo() {
		return
	}
	addmoduledata := ld.Linklookup(ctxt, "runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		// we're linking a module containing the runtime -> no need for
		// an init function
		return
	}
	addmoduledata.Attr |= ld.AttrReachable
	initfunc := ld.Linklookup(ctxt, "go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Attr |= ld.AttrLocal
	initfunc.Attr |= ld.AttrReachable

	// larl %r2, <local.moduledata>
	ld.Adduint8(ctxt, initfunc, 0xc0)
	ld.Adduint8(ctxt, initfunc, 0x20)
	lmd := ld.Addrel(initfunc)
	lmd.Off = int32(initfunc.Size)
	lmd.Siz = 4
	lmd.Sym = ctxt.Moduledata
	lmd.Type = obj.R_PCREL
	lmd.Variant = ld.RV_390_DBL
	lmd.Add = 2 + int64(lmd.Siz)
	ld.Adduint32(ctxt, initfunc, 0)

	// jg <runtime.addmoduledata[@plt]>
	ld.Adduint8(ctxt, initfunc, 0xc0)
	ld.Adduint8(ctxt, initfunc, 0xf4)
	rel := ld.Addrel(initfunc)
	rel.Off = int32(initfunc.Size)
	rel.Siz = 4
	rel.Sym = ld.Linklookup(ctxt, "runtime.addmoduledata", 0)
	rel.Type = obj.R_CALL
	rel.Variant = ld.RV_390_DBL
	rel.Add = 2 + int64(rel.Siz)
	ld.Adduint32(ctxt, initfunc, 0)

	// undef (for debugging)
	ld.Adduint32(ctxt, initfunc, 0)

	ctxt.Textp = append(ctxt.Textp, initfunc)
	initarray_entry := ld.Linklookup(ctxt, "go.link.addmoduledatainit", 0)
	initarray_entry.Attr |= ld.AttrLocal
	initarray_entry.Attr |= ld.AttrReachable
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ctxt, initarray_entry, initfunc)
}

func gentext() {
	if !ld.DynlinkingGo() {
		return
	}
	addmoduledata := ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		// we're linking a module containing the runtime -> no need for
		// an init function
		return
	}
	addmoduledata.Reachable = true
	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Local = true
	initfunc.Reachable = true
	o := func(op uint32) {
		ld.Adduint32(ld.Ctxt, initfunc, op)
	}
	o(0xe59f0004)
	o(0xe08f0000)

	o(0xeafffffe)
	rel := ld.Addrel(initfunc)
	rel.Off = 8
	rel.Siz = 4
	rel.Sym = ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
	rel.Type = obj.R_CALLARM
	rel.Add = 0xeafffffe // vomit

	o(0x00000000)
	rel = ld.Addrel(initfunc)
	rel.Off = 12
	rel.Siz = 4
	rel.Sym = ld.Ctxt.Moduledata
	rel.Type = obj.R_PCREL
	rel.Add = 4

	if ld.Ctxt.Etextp != nil {
		ld.Ctxt.Etextp.Next = initfunc
	} else {
		ld.Ctxt.Textp = initfunc
	}
	ld.Ctxt.Etextp = initfunc
	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
	initarray_entry.Reachable = true
	initarray_entry.Local = true
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
}

// 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 = obj.R_ADDRPOWER

	// addis r11,0,[email protected]; addi r11,r11,[email protected]
	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 gentext(ctxt *ld.Link) {
	if !ctxt.DynlinkingGo() {
		return
	}
	addmoduledata := ctxt.Syms.Lookup("runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT && ld.Buildmode != ld.BuildmodePlugin {
		// we're linking a module containing the runtime -> no need for
		// an init function
		return
	}
	addmoduledata.Attr |= ld.AttrReachable
	initfunc := ctxt.Syms.Lookup("go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Attr |= ld.AttrLocal
	initfunc.Attr |= ld.AttrReachable
	o := func(op uint32) {
		ld.Adduint32(ctxt, initfunc, op)
	}
	o(0xe59f0004)
	o(0xe08f0000)

	o(0xeafffffe)
	rel := ld.Addrel(initfunc)
	rel.Off = 8
	rel.Siz = 4
	rel.Sym = ctxt.Syms.Lookup("runtime.addmoduledata", 0)
	rel.Type = obj.R_CALLARM
	rel.Add = 0xeafffffe // vomit

	o(0x00000000)
	rel = ld.Addrel(initfunc)
	rel.Off = 12
	rel.Siz = 4
	rel.Sym = ctxt.Moduledata
	rel.Type = obj.R_PCREL
	rel.Add = 4

	if ld.Buildmode == ld.BuildmodePlugin {
		ctxt.Textp = append(ctxt.Textp, addmoduledata)
	}
	ctxt.Textp = append(ctxt.Textp, initfunc)
	initarray_entry := ctxt.Syms.Lookup("go.link.addmoduledatainit", 0)
	initarray_entry.Attr |= ld.AttrReachable
	initarray_entry.Attr |= ld.AttrLocal
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ctxt, initarray_entry, initfunc)
}

// Construct a call stub in stub that calls symbol targ via its PLT
// entry.
func gencallstub(abicase int, stub *ld.Symbol, targ *ld.Symbol) {
	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 = obj.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 = obj.R_POWER_TOC
	r.Variant = ld.RV_POWER_HA
	ld.Adduint32(ld.Ctxt, stub, 0x3d820000) // addis r12,r2,[email protected]@[email protected]
	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 = obj.R_POWER_TOC
	r.Variant = ld.RV_POWER_LO
	ld.Adduint32(ld.Ctxt, stub, 0xe98c0000) // ld r12,[email protected]@[email protected](r12)

	// Jump to the loaded pointer
	ld.Adduint32(ld.Ctxt, stub, 0x7d8903a6) // mtctr r12
	ld.Adduint32(ld.Ctxt, stub, 0x4e800420) // bctr
}

// Append 4 bytes to s and create a R_CALL relocation targeting t to fill them in.
func addcall(ctxt *ld.Link, s *ld.Symbol, t *ld.Symbol) {
	s.Attr |= ld.AttrReachable
	i := s.Size
	s.Size += 4
	ld.Symgrow(s, s.Size)
	r := ld.Addrel(s)
	r.Sym = t
	r.Off = int32(i)
	r.Type = obj.R_CALL
	r.Siz = 4
}

// Append 4 bytes to s and create a R_CALL relocation targeting t to fill them in.
func addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) {
	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 = obj.R_CALL
	r.Siz = 4
}

func Addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) int64 {
	s.Attr |= ld.AttrReachable
	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 = obj.R_CALL
	r.Siz = 4
	return i + int64(r.Siz)
}

func addpltreloc(ctxt *ld.Link, plt *ld.Symbol, got *ld.Symbol, sym *ld.Symbol, 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.Attr |= ld.AttrReachable
	plt.Size += 4
	ld.Symgrow(ctxt, plt, plt.Size)

	return r
}

func addpltsym(ctxt *ld.Link, s *ld.Symbol) {
	if s.Plt >= 0 {
		return
	}

	ld.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 = obj.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")
	}
}

// generate a trampoline to target+offset in position independent code
func gentramppic(tramp, target *ld.Symbol, offset int64) {
	tramp.Size = 16 // 4 instructions
	tramp.P = make([]byte, tramp.Size)
	o1 := uint32(0xe5900000 | 11<<12 | 15<<16 | 4)  // MOVW 4(R15), R11 // R15 is actual pc + 8
	o2 := uint32(0xe0800000 | 11<<12 | 15<<16 | 11) // ADD R15, R11, R11
	o3 := uint32(0xe12fff10 | 11)                   // JMP  (R11)
	o4 := uint32(0)                                 // WORD $(target-pc) // filled in with relocation
	ld.SysArch.ByteOrder.PutUint32(tramp.P, o1)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[4:], o2)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[8:], o3)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[12:], o4)

	r := ld.Addrel(tramp)
	r.Off = 12
	r.Type = obj.R_PCREL
	r.Siz = 4
	r.Sym = target
	r.Add = offset + 4
}

// generate a trampoline to target+offset
func gentramp(tramp, target *ld.Symbol, offset int64) {
	tramp.Size = 12 // 3 instructions
	tramp.P = make([]byte, tramp.Size)
	t := ld.Symaddr(target) + int64(offset)
	o1 := uint32(0xe5900000 | 11<<12 | 15<<16) // MOVW (R15), R11 // R15 is actual pc + 8
	o2 := uint32(0xe12fff10 | 11)              // JMP  (R11)
	o3 := uint32(t)                            // WORD $target
	ld.SysArch.ByteOrder.PutUint32(tramp.P, o1)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[4:], o2)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[8:], o3)

	if ld.Linkmode == ld.LinkExternal {
		r := ld.Addrel(tramp)
		r.Off = 8
		r.Type = obj.R_ADDR
		r.Siz = 4
		r.Sym = target
		r.Add = offset
	}
}

// generate a trampoline to target+offset in dynlink mode (using GOT)
func gentrampdyn(tramp, target *ld.Symbol, offset int64) {
	tramp.Size = 20                                 // 5 instructions
	o1 := uint32(0xe5900000 | 11<<12 | 15<<16 | 8)  // MOVW 8(R15), R11 // R15 is actual pc + 8
	o2 := uint32(0xe0800000 | 11<<12 | 15<<16 | 11) // ADD R15, R11, R11
	o3 := uint32(0xe5900000 | 11<<12 | 11<<16)      // MOVW (R11), R11
	o4 := uint32(0xe12fff10 | 11)                   // JMP  (R11)
	o5 := uint32(0)                                 // WORD [email protected] // filled in with relocation
	o6 := uint32(0)
	if offset != 0 {
		// insert an instruction to add offset
		tramp.Size = 24 // 6 instructions
		o6 = o5
		o5 = o4
		o4 = uint32(0xe2800000 | 11<<12 | 11<<16 | immrot(uint32(offset))) // ADD $offset, R11, R11
		o1 = uint32(0xe5900000 | 11<<12 | 15<<16 | 12)                     // MOVW 12(R15), R11
	}
	tramp.P = make([]byte, tramp.Size)
	ld.SysArch.ByteOrder.PutUint32(tramp.P, o1)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[4:], o2)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[8:], o3)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[12:], o4)
	ld.SysArch.ByteOrder.PutUint32(tramp.P[16:], o5)
	if offset != 0 {
		ld.SysArch.ByteOrder.PutUint32(tramp.P[20:], o6)
	}

	r := ld.Addrel(tramp)
	r.Off = 16
	r.Type = obj.R_GOTPCREL
	r.Siz = 4
	r.Sym = target
	r.Add = 8
	if offset != 0 {
		// increase reloc offset by 4 as we inserted an ADD instruction
		r.Off = 20
		r.Add = 12
	}
}