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Source file src/cmd/link/internal/x86/asm.go

Documentation: cmd/link/internal/x86

  // Inferno utils/8l/asm.c
  // https://bitbucket.org/inferno-os/inferno-os/src/default/utils/8l/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 x86
  
  import (
  	"cmd/internal/objabi"
  	"cmd/link/internal/ld"
  	"log"
  )
  
  // 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 = objabi.R_CALL
  	r.Siz = 4
  }
  
  func gentext(ctxt *ld.Link) {
  	if ctxt.DynlinkingGo() {
  		// We need get_pc_thunk.
  	} else {
  		switch ld.Buildmode {
  		case ld.BuildmodeCArchive:
  			if !ld.Iself {
  				return
  			}
  		case ld.BuildmodePIE, ld.BuildmodeCShared, ld.BuildmodePlugin:
  			// We need get_pc_thunk.
  		default:
  			return
  		}
  	}
  
  	// Generate little thunks that load the PC of the next instruction into a register.
  	thunks := make([]*ld.Symbol, 0, 7+len(ctxt.Textp))
  	for _, r := range [...]struct {
  		name string
  		num  uint8
  	}{
  		{"ax", 0},
  		{"cx", 1},
  		{"dx", 2},
  		{"bx", 3},
  		// sp
  		{"bp", 5},
  		{"si", 6},
  		{"di", 7},
  	} {
  		thunkfunc := ctxt.Syms.Lookup("__x86.get_pc_thunk."+r.name, 0)
  		thunkfunc.Type = ld.STEXT
  		thunkfunc.Attr |= ld.AttrLocal
  		thunkfunc.Attr |= ld.AttrReachable //TODO: remove?
  		o := func(op ...uint8) {
  			for _, op1 := range op {
  				ld.Adduint8(ctxt, thunkfunc, op1)
  			}
  		}
  		// 8b 04 24	mov    (%esp),%eax
  		// Destination register is in bits 3-5 of the middle byte, so add that in.
  		o(0x8b, 0x04+r.num<<3, 0x24)
  		// c3		ret
  		o(0xc3)
  
  		thunks = append(thunks, thunkfunc)
  	}
  	ctxt.Textp = append(thunks, ctxt.Textp...) // keep Textp in dependency order
  
  	addmoduledata := ctxt.Syms.Lookup("runtime.addmoduledata", 0)
  	if addmoduledata.Type == ld.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 = ld.STEXT
  	initfunc.Attr |= ld.AttrLocal
  	initfunc.Attr |= ld.AttrReachable
  	o := func(op ...uint8) {
  		for _, op1 := range op {
  			ld.Adduint8(ctxt, initfunc, op1)
  		}
  	}
  
  	// go.link.addmoduledata:
  	//      53                      push %ebx
  	//      e8 00 00 00 00          call __x86.get_pc_thunk.cx + R_CALL __x86.get_pc_thunk.cx
  	//      8d 81 00 00 00 00       lea 0x0(%ecx), %eax + R_PCREL ctxt.Moduledata
  	//      8d 99 00 00 00 00       lea 0x0(%ecx), %ebx + R_GOTPC _GLOBAL_OFFSET_TABLE_
  	//      e8 00 00 00 00          call runtime.addmoduledata@plt + R_CALL runtime.addmoduledata
  	//      5b                      pop %ebx
  	//      c3                      ret
  
  	o(0x53)
  
  	o(0xe8)
  	addcall(ctxt, initfunc, ctxt.Syms.Lookup("__x86.get_pc_thunk.cx", 0))
  
  	o(0x8d, 0x81)
  	ld.Addpcrelplus(ctxt, initfunc, ctxt.Moduledata, 6)
  
  	o(0x8d, 0x99)
  	i := initfunc.Size
  	initfunc.Size += 4
  	ld.Symgrow(initfunc, initfunc.Size)
  	r := ld.Addrel(initfunc)
  	r.Sym = ctxt.Syms.Lookup("_GLOBAL_OFFSET_TABLE_", 0)
  	r.Off = int32(i)
  	r.Type = objabi.R_PCREL
  	r.Add = 12
  	r.Siz = 4
  
  	o(0xe8)
  	addcall(ctxt, initfunc, addmoduledata)
  
  	o(0x5b)
  
  	o(0xc3)
  
  	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 = ld.SINITARR
  	ld.Addaddr(ctxt, initarray_entry, initfunc)
  }
  
  func adddynrel(ctxt *ld.Link, s *ld.Symbol, r *ld.Reloc) bool {
  	targ := r.Sym
  
  	switch r.Type {
  	default:
  		if r.Type >= 256 {
  			ld.Errorf(s, "unexpected relocation type %d", r.Type)
  			return false
  		}
  
  		// Handle relocations found in ELF object files.
  	case 256 + ld.R_386_PC32:
  		if targ.Type == ld.SDYNIMPORT {
  			ld.Errorf(s, "unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
  		}
  		if targ.Type == 0 || targ.Type == ld.SXREF {
  			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
  		}
  		r.Type = objabi.R_PCREL
  		r.Add += 4
  		return true
  
  	case 256 + ld.R_386_PLT32:
  		r.Type = objabi.R_PCREL
  		r.Add += 4
  		if targ.Type == ld.SDYNIMPORT {
  			addpltsym(ctxt, targ)
  			r.Sym = ctxt.Syms.Lookup(".plt", 0)
  			r.Add += int64(targ.Plt)
  		}
  
  		return true
  
  	case 256 + ld.R_386_GOT32, 256 + ld.R_386_GOT32X:
  		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 = objabi.R_GOTOFF
  				return true
  			}
  
  			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 = objabi.R_ADDR
  				return true
  			}
  
  			ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
  			return false
  		}
  
  		addgotsym(ctxt, targ)
  		r.Type = objabi.R_CONST // write r->add during relocsym
  		r.Sym = nil
  		r.Add += int64(targ.Got)
  		return true
  
  	case 256 + ld.R_386_GOTOFF:
  		r.Type = objabi.R_GOTOFF
  		return true
  
  	case 256 + ld.R_386_GOTPC:
  		r.Type = objabi.R_PCREL
  		r.Sym = ctxt.Syms.Lookup(".got", 0)
  		r.Add += 4
  		return true
  
  	case 256 + ld.R_386_32:
  		if targ.Type == ld.SDYNIMPORT {
  			ld.Errorf(s, "unexpected R_386_32 relocation for dynamic symbol %s", targ.Name)
  		}
  		r.Type = objabi.R_ADDR
  		return true
  
  	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
  		r.Type = objabi.R_ADDR
  		if targ.Type == ld.SDYNIMPORT {
  			ld.Errorf(s, "unexpected reloc for dynamic symbol %s", targ.Name)
  		}
  		return true
  
  	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
  		if targ.Type == ld.SDYNIMPORT {
  			addpltsym(ctxt, targ)
  			r.Sym = ctxt.Syms.Lookup(".plt", 0)
  			r.Add = int64(targ.Plt)
  			r.Type = objabi.R_PCREL
  			return true
  		}
  
  		r.Type = objabi.R_PCREL
  		return true
  
  	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.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
  				return false
  			}
  
  			s.P[r.Off-2] = 0x8d
  			r.Type = objabi.R_PCREL
  			return true
  		}
  
  		addgotsym(ctxt, targ)
  		r.Sym = ctxt.Syms.Lookup(".got", 0)
  		r.Add += int64(targ.Got)
  		r.Type = objabi.R_PCREL
  		return true
  	}
  
  	// Handle references to ELF symbols from our own object files.
  	if targ.Type != ld.SDYNIMPORT {
  		return true
  	}
  	switch r.Type {
  	case objabi.R_CALL,
  		objabi.R_PCREL:
  		addpltsym(ctxt, targ)
  		r.Sym = ctxt.Syms.Lookup(".plt", 0)
  		r.Add = int64(targ.Plt)
  		return true
  
  	case objabi.R_ADDR:
  		if s.Type != ld.SDATA {
  			break
  		}
  		if ld.Iself {
  			ld.Adddynsym(ctxt, targ)
  			rel := ctxt.Syms.Lookup(".rel", 0)
  			ld.Addaddrplus(ctxt, rel, s, int64(r.Off))
  			ld.Adduint32(ctxt, rel, ld.ELF32_R_INFO(uint32(targ.Dynid), ld.R_386_32))
  			r.Type = objabi.R_CONST // write r->add during relocsym
  			r.Sym = nil
  			return true
  		}
  
  		if ld.Headtype == objabi.Hdarwin && s.Size == int64(ld.SysArch.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.
  			ld.Adddynsym(ctxt, targ)
  
  			got := ctxt.Syms.Lookup(".got", 0)
  			s.Type = got.Type | ld.SSUB
  			s.Outer = got
  			s.Sub = got.Sub
  			got.Sub = s
  			s.Value = got.Size
  			ld.Adduint32(ctxt, got, 0)
  			ld.Adduint32(ctxt, ctxt.Syms.Lookup(".linkedit.got", 0), uint32(targ.Dynid))
  			r.Type = 256 // ignore during relocsym
  			return true
  		}
  
  		if ld.Headtype == objabi.Hwindows && s.Size == int64(ld.SysArch.PtrSize) {
  			// nothing to do, the relocation will be laid out in pereloc1
  			return true
  		}
  	}
  
  	return false
  }
  
  func elfreloc1(ctxt *ld.Link, r *ld.Reloc, sectoff int64) int {
  	ld.Thearch.Lput(uint32(sectoff))
  
  	elfsym := r.Xsym.ElfsymForReloc()
  	switch r.Type {
  	default:
  		return -1
  
  	case objabi.R_ADDR:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_386_32 | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  
  	case objabi.R_GOTPCREL:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_386_GOTPC)
  			if r.Xsym.Name != "_GLOBAL_OFFSET_TABLE_" {
  				ld.Thearch.Lput(uint32(sectoff))
  				ld.Thearch.Lput(ld.R_386_GOT32 | uint32(elfsym)<<8)
  			}
  		} else {
  			return -1
  		}
  
  	case objabi.R_CALL:
  		if r.Siz == 4 {
  			if r.Xsym.Type == ld.SDYNIMPORT {
  				ld.Thearch.Lput(ld.R_386_PLT32 | uint32(elfsym)<<8)
  			} else {
  				ld.Thearch.Lput(ld.R_386_PC32 | uint32(elfsym)<<8)
  			}
  		} else {
  			return -1
  		}
  
  	case objabi.R_PCREL:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_386_PC32 | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  
  	case objabi.R_TLS_LE:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_386_TLS_LE | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  
  	case objabi.R_TLS_IE:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_386_GOTPC)
  			ld.Thearch.Lput(uint32(sectoff))
  			ld.Thearch.Lput(ld.R_386_TLS_GOTIE | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  	}
  
  	return 0
  }
  
  func machoreloc1(s *ld.Symbol, r *ld.Reloc, sectoff int64) int {
  	var v uint32
  
  	rs := r.Xsym
  
  	if rs.Type == ld.SHOSTOBJ {
  		if rs.Dynid < 0 {
  			ld.Errorf(s, "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 {
  			ld.Errorf(s, "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 objabi.R_ADDR:
  		v |= ld.MACHO_GENERIC_RELOC_VANILLA << 28
  
  	case objabi.R_CALL,
  		objabi.R_PCREL:
  		v |= 1 << 24 // pc-relative bit
  		v |= ld.MACHO_GENERIC_RELOC_VANILLA << 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 pereloc1(s *ld.Symbol, r *ld.Reloc, sectoff int64) bool {
  	var v uint32
  
  	rs := r.Xsym
  
  	if rs.Dynid < 0 {
  		ld.Errorf(s, "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 objabi.R_DWARFREF:
  		v = ld.IMAGE_REL_I386_SECREL
  
  	case objabi.R_ADDR:
  		v = ld.IMAGE_REL_I386_DIR32
  
  	case objabi.R_CALL,
  		objabi.R_PCREL:
  		v = ld.IMAGE_REL_I386_REL32
  	}
  
  	ld.Thearch.Wput(uint16(v))
  
  	return true
  }
  
  func archreloc(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, val *int64) int {
  	if ld.Linkmode == ld.LinkExternal {
  		return -1
  	}
  	switch r.Type {
  	case objabi.R_CONST:
  		*val = r.Add
  		return 0
  
  	case objabi.R_GOTOFF:
  		*val = ld.Symaddr(r.Sym) + r.Add - ld.Symaddr(ctxt.Syms.Lookup(".got", 0))
  		return 0
  	}
  
  	return -1
  }
  
  func archrelocvariant(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, t int64) int64 {
  	log.Fatalf("unexpected relocation variant")
  	return t
  }
  
  func elfsetupplt(ctxt *ld.Link) {
  	plt := ctxt.Syms.Lookup(".plt", 0)
  	got := ctxt.Syms.Lookup(".got.plt", 0)
  	if plt.Size == 0 {
  		// pushl got+4
  		ld.Adduint8(ctxt, plt, 0xff)
  
  		ld.Adduint8(ctxt, plt, 0x35)
  		ld.Addaddrplus(ctxt, plt, got, 4)
  
  		// jmp *got+8
  		ld.Adduint8(ctxt, plt, 0xff)
  
  		ld.Adduint8(ctxt, plt, 0x25)
  		ld.Addaddrplus(ctxt, plt, got, 8)
  
  		// zero pad
  		ld.Adduint32(ctxt, plt, 0)
  
  		// assume got->size == 0 too
  		ld.Addaddrplus(ctxt, got, ctxt.Syms.Lookup(".dynamic", 0), 0)
  
  		ld.Adduint32(ctxt, got, 0)
  		ld.Adduint32(ctxt, got, 0)
  	}
  }
  
  func addpltsym(ctxt *ld.Link, s *ld.Symbol) {
  	if s.Plt >= 0 {
  		return
  	}
  
  	ld.Adddynsym(ctxt, s)
  
  	if ld.Iself {
  		plt := ctxt.Syms.Lookup(".plt", 0)
  		got := ctxt.Syms.Lookup(".got.plt", 0)
  		rel := ctxt.Syms.Lookup(".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 == objabi.Hdarwin {
  		// Same laziness as in 6l.
  
  		plt := ctxt.Syms.Lookup(".plt", 0)
  
  		addgotsym(ctxt, s)
  
  		ld.Adduint32(ctxt, ctxt.Syms.Lookup(".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, ctxt.Syms.Lookup(".got", 0), int64(s.Got))
  	} else {
  		ld.Errorf(s, "addpltsym: unsupported binary format")
  	}
  }
  
  func addgotsym(ctxt *ld.Link, s *ld.Symbol) {
  	if s.Got >= 0 {
  		return
  	}
  
  	ld.Adddynsym(ctxt, s)
  	got := ctxt.Syms.Lookup(".got", 0)
  	s.Got = int32(got.Size)
  	ld.Adduint32(ctxt, got, 0)
  
  	if ld.Iself {
  		rel := ctxt.Syms.Lookup(".rel", 0)
  		ld.Addaddrplus(ctxt, rel, got, int64(s.Got))
  		ld.Adduint32(ctxt, rel, ld.ELF32_R_INFO(uint32(s.Dynid), ld.R_386_GLOB_DAT))
  	} else if ld.Headtype == objabi.Hdarwin {
  		ld.Adduint32(ctxt, ctxt.Syms.Lookup(".linkedit.got", 0), uint32(s.Dynid))
  	} else {
  		ld.Errorf(s, "addgotsym: unsupported binary format")
  	}
  }
  
  func asmb(ctxt *ld.Link) {
  	if ctxt.Debugvlog != 0 {
  		ctxt.Logf("%5.2f asmb\n", ld.Cputime())
  	}
  
  	if ld.Iself {
  		ld.Asmbelfsetup()
  	}
  
  	sect := ld.Segtext.Sections[0]
  	ld.Cseek(int64(sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff))
  	// 0xCC is INT $3 - breakpoint instruction
  	ld.CodeblkPad(ctxt, int64(sect.Vaddr), int64(sect.Length), []byte{0xCC})
  	for _, sect = range ld.Segtext.Sections[1:] {
  		ld.Cseek(int64(sect.Vaddr - ld.Segtext.Vaddr + ld.Segtext.Fileoff))
  		ld.Datblk(ctxt, int64(sect.Vaddr), int64(sect.Length))
  	}
  
  	if ld.Segrodata.Filelen > 0 {
  		if ctxt.Debugvlog != 0 {
  			ctxt.Logf("%5.2f rodatblk\n", ld.Cputime())
  		}
  
  		ld.Cseek(int64(ld.Segrodata.Fileoff))
  		ld.Datblk(ctxt, int64(ld.Segrodata.Vaddr), int64(ld.Segrodata.Filelen))
  	}
  	if ld.Segrelrodata.Filelen > 0 {
  		if ctxt.Debugvlog != 0 {
  			ctxt.Logf("%5.2f relrodatblk\n", ld.Cputime())
  		}
  		ld.Cseek(int64(ld.Segrelrodata.Fileoff))
  		ld.Datblk(ctxt, int64(ld.Segrelrodata.Vaddr), int64(ld.Segrelrodata.Filelen))
  	}
  
  	if ctxt.Debugvlog != 0 {
  		ctxt.Logf("%5.2f datblk\n", ld.Cputime())
  	}
  
  	ld.Cseek(int64(ld.Segdata.Fileoff))
  	ld.Datblk(ctxt, int64(ld.Segdata.Vaddr), int64(ld.Segdata.Filelen))
  
  	ld.Cseek(int64(ld.Segdwarf.Fileoff))
  	ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
  
  	machlink := uint32(0)
  	if ld.Headtype == objabi.Hdarwin {
  		machlink = uint32(ld.Domacholink(ctxt))
  	}
  
  	ld.Symsize = 0
  	ld.Spsize = 0
  	ld.Lcsize = 0
  	symo := uint32(0)
  	if !*ld.FlagS {
  		// TODO: rationalize
  		if ctxt.Debugvlog != 0 {
  			ctxt.Logf("%5.2f sym\n", ld.Cputime())
  		}
  		switch ld.Headtype {
  		default:
  			if ld.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.Hdarwin:
  			symo = uint32(ld.Segdwarf.Fileoff + uint64(ld.Rnd(int64(ld.Segdwarf.Filelen), int64(*ld.FlagRound))) + uint64(machlink))
  
  		case objabi.Hwindows:
  			symo = uint32(ld.Segdwarf.Fileoff + ld.Segdwarf.Filelen)
  			symo = uint32(ld.Rnd(int64(symo), ld.PEFILEALIGN))
  		}
  
  		ld.Cseek(int64(symo))
  		switch ld.Headtype {
  		default:
  			if ld.Iself {
  				if ctxt.Debugvlog != 0 {
  					ctxt.Logf("%5.2f elfsym\n", ld.Cputime())
  				}
  				ld.Asmelfsym(ctxt)
  				ld.Cflush()
  				ld.Cwrite(ld.Elfstrdat)
  
  				if ld.Linkmode == ld.LinkExternal {
  					ld.Elfemitreloc(ctxt)
  				}
  			}
  
  		case objabi.Hplan9:
  			ld.Asmplan9sym(ctxt)
  			ld.Cflush()
  
  			sym := ctxt.Syms.Lookup("pclntab", 0)
  			if sym != nil {
  				ld.Lcsize = int32(len(sym.P))
  				for i := 0; int32(i) < ld.Lcsize; i++ {
  					ld.Cput(sym.P[i])
  				}
  
  				ld.Cflush()
  			}
  
  		case objabi.Hwindows:
  			if ctxt.Debugvlog != 0 {
  				ctxt.Logf("%5.2f dwarf\n", ld.Cputime())
  			}
  
  		case objabi.Hdarwin:
  			if ld.Linkmode == ld.LinkExternal {
  				ld.Machoemitreloc(ctxt)
  			}
  		}
  	}
  
  	if ctxt.Debugvlog != 0 {
  		ctxt.Logf("%5.2f headr\n", ld.Cputime())
  	}
  	ld.Cseek(0)
  	switch ld.Headtype {
  	default:
  	case objabi.Hplan9: /* plan9 */
  		magic := int32(4*11*11 + 7)
  
  		ld.Lputb(uint32(magic))              /* magic */
  		ld.Lputb(uint32(ld.Segtext.Filelen)) /* sizes */
  		ld.Lputb(uint32(ld.Segdata.Filelen))
  		ld.Lputb(uint32(ld.Segdata.Length - ld.Segdata.Filelen))
  		ld.Lputb(uint32(ld.Symsize))          /* nsyms */
  		ld.Lputb(uint32(ld.Entryvalue(ctxt))) /* va of entry */
  		ld.Lputb(uint32(ld.Spsize))           /* sp offsets */
  		ld.Lputb(uint32(ld.Lcsize))           /* line offsets */
  
  	case objabi.Hdarwin:
  		ld.Asmbmacho(ctxt)
  
  	case objabi.Hlinux,
  		objabi.Hfreebsd,
  		objabi.Hnetbsd,
  		objabi.Hopenbsd,
  		objabi.Hnacl:
  		ld.Asmbelf(ctxt, int64(symo))
  
  	case objabi.Hwindows:
  		ld.Asmbpe(ctxt)
  	}
  
  	ld.Cflush()
  }
  

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