Golang ld.Link類代碼示例

func pereloc1(ctxt *ld.Link, r *ld.Reloc, sectoff int64) bool {
	var v uint32

	rs := r.Xsym

	if rs.Dynid < 0 {
		ctxt.Diag("reloc %d to non-coff symbol %s type=%d", r.Type, rs.Name, rs.Type)
		return false
	}

	ld.Thearch.Lput(uint32(sectoff))
	ld.Thearch.Lput(uint32(rs.Dynid))

	switch r.Type {
	default:
		return false

	case obj.R_ADDR:
		v = ld.IMAGE_REL_I386_DIR32

	case obj.R_CALL,
		obj.R_PCREL:
		v = ld.IMAGE_REL_I386_REL32
	}

	ld.Thearch.Wput(uint16(v))

	return true
}

func machoreloc1(ctxt *ld.Link, r *ld.Reloc, sectoff int64) int {
	var v uint32

	rs := r.Xsym

	if rs.Type == obj.SHOSTOBJ || r.Type == obj.R_PCREL {
		if rs.Dynid < 0 {
			ctxt.Diag("reloc %d to non-macho symbol %s type=%d", r.Type, rs.Name, rs.Type)
			return -1
		}

		v = uint32(rs.Dynid)
		v |= 1 << 27 // external relocation
	} else {
		v = uint32(rs.Sect.Extnum)
		if v == 0 {
			ctxt.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, rs.Sect.Name, rs.Type)
			return -1
		}
	}

	switch r.Type {
	default:
		return -1

	case obj.R_ADDR:
		v |= ld.MACHO_X86_64_RELOC_UNSIGNED << 28

	case obj.R_CALL:
		v |= 1 << 24 // pc-relative bit
		v |= ld.MACHO_X86_64_RELOC_BRANCH << 28

		// NOTE: Only works with 'external' relocation. Forced above.
	case obj.R_PCREL:
		v |= 1 << 24 // pc-relative bit
		v |= ld.MACHO_X86_64_RELOC_SIGNED << 28
	}

	switch r.Siz {
	default:
		return -1

	case 1:
		v |= 0 << 25

	case 2:
		v |= 1 << 25

	case 4:
		v |= 2 << 25

	case 8:
		v |= 3 << 25
	}

	ld.Thearch.Lput(uint32(sectoff))
	ld.Thearch.Lput(v)
	return 0
}

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)
		got := ld.Linklookup(ctxt, ".got.plt", 0)
		rel := ld.Linklookup(ctxt, ".rel.plt", 0)
		if plt.Size == 0 {
			elfsetupplt(ctxt)
		}

		// 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 == obj.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 {
		ctxt.Diag("addpltsym: unsupported binary format")
	}
}

func gentext(ctxt *ld.Link) {
	if ctxt.DynlinkingGo() {
		genaddmoduledata(ctxt)
	}

	if ld.Linkmode == ld.LinkInternal {
		genplt(ctxt)
	}
}

// Convert the direct jump relocation r to refer to a trampoline if the target is too far
func trampoline(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol) {
	switch r.Type {
	case obj.R_CALLARM:
		// r.Add is the instruction
		// low 24-bit encodes the target address
		t := (ld.Symaddr(r.Sym) + int64(signext24(r.Add&0xffffff)*4) - (s.Value + int64(r.Off))) / 4
		if t > 0x7fffff || t < -0x800000 || (*ld.FlagDebugTramp > 1 && s.File != r.Sym.File) {
			// direct call too far, need to insert trampoline.
			// look up existing trampolines first. if we found one within the range
			// of direct call, we can reuse it. otherwise create a new one.
			offset := (signext24(r.Add&0xffffff) + 2) * 4
			var tramp *ld.Symbol
			for i := 0; ; i++ {
				name := r.Sym.Name + fmt.Sprintf("%+d-tramp%d", offset, i)
				tramp = ctxt.Syms.Lookup(name, int(r.Sym.Version))
				if tramp.Type == obj.SDYNIMPORT {
					// don't reuse trampoline defined in other module
					continue
				}
				if tramp.Value == 0 {
					// either the trampoline does not exist -- we need to create one,
					// or found one the address which is not assigned -- this will be
					// laid down immediately after the current function. use this one.
					break
				}

				t = (ld.Symaddr(tramp) - 8 - (s.Value + int64(r.Off))) / 4
				if t >= -0x800000 && t < 0x7fffff {
					// found an existing trampoline that is not too far
					// we can just use it
					break
				}
			}
			if tramp.Type == 0 {
				// trampoline does not exist, create one
				ctxt.AddTramp(tramp)
				if ctxt.DynlinkingGo() {
					if immrot(uint32(offset)) == 0 {
						ld.Errorf(s, "odd offset in dynlink direct call: %v+%d", r.Sym, offset)
					}
					gentrampdyn(tramp, r.Sym, int64(offset))
				} else if ld.Buildmode == ld.BuildmodeCArchive || ld.Buildmode == ld.BuildmodeCShared || ld.Buildmode == ld.BuildmodePIE {
					gentramppic(tramp, r.Sym, int64(offset))
				} else {
					gentramp(tramp, r.Sym, int64(offset))
				}
			}
			// modify reloc to point to tramp, which will be resolved later
			r.Sym = tramp
			r.Add = r.Add&0xff000000 | 0xfffffe // clear the offset embedded in the instruction
			r.Done = 0
		}
	default:
		ld.Errorf(s, "trampoline called with non-jump reloc: %v", r.Type)
	}
}

// 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 !ctxt.DynlinkingGo() {
		return
	}
	addmoduledata := ctxt.Syms.Lookup("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 := ctxt.Syms.Lookup("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 = ctxt.Syms.Lookup("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 := ctxt.Syms.Lookup("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)
}

// Convert the direct jump relocation r to refer to a trampoline if the target is too far
func trampoline(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol) {
	switch r.Type {
	case obj.R_CALLARM:
		// r.Add is the instruction
		// low 24-bit encodes the target address
		t := (ld.Symaddr(r.Sym) + int64(signext24(r.Add&0xffffff)*4) - (s.Value + int64(r.Off))) / 4
		if t > 0x7fffff || t < -0x800000 || (*ld.FlagDebugTramp > 1 && s.File != r.Sym.File) {
			// direct call too far, need to insert trampoline
			offset := (signext24(r.Add&0xffffff) + 2) * 4
			var tramp *ld.Symbol
			for i := 0; ; i++ {
				name := r.Sym.Name + fmt.Sprintf("%+d-tramp%d", offset, i)
				tramp = ctxt.Syms.Lookup(name, int(r.Sym.Version))
				if tramp.Value == 0 {
					// either the trampoline does not exist -- we need to create one,
					// or found one the address which is not assigned -- this will be
					// laid down immediately after the current function. use this one.
					break
				}

				t = (ld.Symaddr(tramp) - 8 - (s.Value + int64(r.Off))) / 4
				if t >= -0x800000 && t < 0x7fffff {
					// found an existing trampoline that is not too far
					// we can just use it
					break
				}
			}
			if tramp.Type == 0 {
				// trampoline does not exist, create one
				ctxt.AddTramp(tramp)
				tramp.Size = 12 // 3 instructions
				tramp.P = make([]byte, tramp.Size)
				t = ld.Symaddr(r.Sym) + 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)
			}
			// modify reloc to point to tramp, which will be resolved later
			r.Sym = tramp
			r.Add = r.Add&0xff000000 | 0xfffffe // clear the offset embedded in the instruction
			r.Done = 0
		}
	default:
		ld.Errorf(s, "trampoline called with non-jump reloc: %v", r.Type)
	}
}

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

	got := ld.Linklookup(ctxt, ".got", 0)
	s.Got = int32(got.Size)

	ld.Addaddrplus(ctxt, got, s, 0)

	if ld.Iself {
	} else {
		ctxt.Diag("addgotsyminternal: unsupported binary format")
	}
}

func archrelocaddr(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, val *int64) int {
	var o1, o2 uint32
	if ctxt.Arch.ByteOrder == binary.BigEndian {
		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(ctxt, r.Sym) + r.Add
	if t < 0 || t >= 1<<31 {
		ctxt.Diag("relocation for %s is too big (>=2G): %d", s.Name, ld.Symaddr(ctxt, r.Sym))
	}
	if t&0x8000 != 0 {
		t += 0x10000
	}

	switch r.Type {
	case obj.R_ADDRPOWER:
		o1 |= (uint32(t) >> 16) & 0xffff
		o2 |= uint32(t) & 0xffff

	case obj.R_ADDRPOWER_DS:
		o1 |= (uint32(t) >> 16) & 0xffff
		if t&3 != 0 {
			ctxt.Diag("bad DS reloc for %s: %d", s.Name, ld.Symaddr(ctxt, r.Sym))
		}
		o2 |= uint32(t) & 0xfffc

	default:
		return -1
	}

	if ctxt.Arch.ByteOrder == binary.BigEndian {
		*val = int64(o1)<<32 | int64(o2)
	} else {
		*val = int64(o2)<<32 | int64(o1)
	}
	return 0
}

func genaddmoduledata(ctxt *ld.Link) {
	addmoduledata := ctxt.Syms.ROLookup("runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		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)
	}
	// addis r2, r12, [email protected]
	rel := ld.Addrel(initfunc)
	rel.Off = int32(initfunc.Size)
	rel.Siz = 8
	rel.Sym = ctxt.Syms.Lookup(".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 = ctxt.Syms.Lookup("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)

	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)
}

// Return the value of .TOC. for symbol s
func symtoc(ctxt *ld.Link, s *ld.Symbol) int64 {
	var toc *ld.Symbol

	if s.Outer != nil {
		toc = ld.Linkrlookup(ctxt, ".TOC.", int(s.Outer.Version))
	} else {
		toc = ld.Linkrlookup(ctxt, ".TOC.", int(s.Version))
	}

	if toc == nil {
		ctxt.Diag("TOC-relative relocation in object without .TOC.")
		return 0
	}

	return toc.Value
}

func archrelocvariant(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, t int64) int64 {
	switch r.Variant & ld.RV_TYPE_MASK {
	default:
		ctxt.Diag("unexpected relocation variant %d", r.Variant)
		return t

	case ld.RV_NONE:
		return t

	case ld.RV_390_DBL:
		if (t & 1) != 0 {
			ctxt.Diag("%s+%v is not 2-byte aligned", r.Sym.Name, r.Sym.Value)
		}
		return t >> 1
	}
}

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

	ld.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 {
		ctxt.Diag("addgotsym: unsupported binary format")
	}
}

func archreloc(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, val *int64) int {
	if ld.Linkmode == ld.LinkExternal {
		switch r.Type {
		case obj.R_CALLARM:
			r.Done = 0

			// set up addend for eventual relocation via outer symbol.
			rs := r.Sym

			r.Xadd = r.Add
			if r.Xadd&0x800000 != 0 {
				r.Xadd |= ^0xffffff
			}
			r.Xadd *= 4
			for rs.Outer != nil {
				r.Xadd += ld.Symaddr(ctxt, rs) - ld.Symaddr(ctxt, rs.Outer)
				rs = rs.Outer
			}

			if rs.Type != obj.SHOSTOBJ && rs.Type != obj.SDYNIMPORT && rs.Sect == nil {
				ctxt.Diag("missing section for %s", rs.Name)
			}
			r.Xsym = rs

			// ld64 for arm seems to want the symbol table to contain offset
			// into the section rather than pseudo virtual address that contains
			// the section load address.
			// we need to compensate that by removing the instruction's address
			// from addend.
			if ld.HEADTYPE == obj.Hdarwin {
				r.Xadd -= ld.Symaddr(ctxt, s) + int64(r.Off)
			}

			*val = int64(braddoff(int32(0xff000000&uint32(r.Add)), int32(0xffffff&uint32(r.Xadd/4))))
			return 0
		}

		return -1
	}

	switch r.Type {
	case obj.R_CONST:
		*val = r.Add
		return 0

	case obj.R_GOTOFF:
		*val = ld.Symaddr(ctxt, r.Sym) + r.Add - ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".got", 0))
		return 0

		// The following three arch specific relocations are only for generation of
	// Linux/ARM ELF's PLT entry (3 assembler instruction)
	case obj.R_PLT0: // add ip, pc, #0xXX00000
		if ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".got.plt", 0)) < ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".plt", 0)) {
			ctxt.Diag(".got.plt should be placed after .plt section.")
		}
		*val = 0xe28fc600 + (0xff & (int64(uint32(ld.Symaddr(ctxt, r.Sym)-(ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".plt", 0))+int64(r.Off))+r.Add)) >> 20))
		return 0

	case obj.R_PLT1: // add ip, ip, #0xYY000
		*val = 0xe28cca00 + (0xff & (int64(uint32(ld.Symaddr(ctxt, r.Sym)-(ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".plt", 0))+int64(r.Off))+r.Add+4)) >> 12))

		return 0

	case obj.R_PLT2: // ldr pc, [ip, #0xZZZ]!
		*val = 0xe5bcf000 + (0xfff & int64(uint32(ld.Symaddr(ctxt, r.Sym)-(ld.Symaddr(ctxt, ld.Linklookup(ctxt, ".plt", 0))+int64(r.Off))+r.Add+8)))

		return 0

	case obj.R_CALLARM: // bl XXXXXX or b YYYYYY
		*val = int64(braddoff(int32(0xff000000&uint32(r.Add)), int32(0xffffff&uint32((ld.Symaddr(ctxt, r.Sym)+int64((uint32(r.Add))*4)-(s.Value+int64(r.Off)))/4))))

		return 0
	}

	return -1
}

func adddynrel(ctxt *ld.Link, s *ld.Symbol, r *ld.Reloc) {
	targ := r.Sym
	ctxt.Cursym = s

	switch r.Type {
	default:
		if r.Type >= 256 {
			ctxt.Diag("unexpected relocation type %d", r.Type)
			return
		}

		// Handle relocations found in ELF object files.
	case 256 + ld.R_ARM_PLT32:
		r.Type = obj.R_CALLARM

		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ld.Linklookup(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.Exitf("R_ARM_THM_CALL, are you using -marm?")
		return

	case 256 + ld.R_ARM_GOT32: // R_ARM_GOT_BREL
		if targ.Type != obj.SDYNIMPORT {
			addgotsyminternal(ctxt, targ)
		} else {
			addgotsym(ctxt, targ)
		}

		r.Type = obj.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 != obj.SDYNIMPORT {
			addgotsyminternal(ctxt, targ)
		} else {
			addgotsym(ctxt, targ)
		}

		r.Type = obj.R_PCREL
		r.Sym = ld.Linklookup(ctxt, ".got", 0)
		r.Add += int64(targ.Got) + 4
		return

	case 256 + ld.R_ARM_GOTOFF: // R_ARM_GOTOFF32
		r.Type = obj.R_GOTOFF

		return

	case 256 + ld.R_ARM_GOTPC: // R_ARM_BASE_PREL
		r.Type = obj.R_PCREL

		r.Sym = ld.Linklookup(ctxt, ".got", 0)
		r.Add += 4
		return

	case 256 + ld.R_ARM_CALL:
		r.Type = obj.R_CALLARM
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ld.Linklookup(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 = obj.R_PCREL

		r.Add += 4
		return

	case 256 + ld.R_ARM_ABS32:
		if targ.Type == obj.SDYNIMPORT {
			ctxt.Diag("unexpected R_ARM_ABS32 relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.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 = obj.R_CALLARM
		if targ.Type == obj.SDYNIMPORT {
//.........這裏部分代碼省略.........