...
Run Format

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

Documentation: cmd/link/internal/arm

  // Inferno utils/5l/asm.c
  // https://bitbucket.org/inferno-os/inferno-os/src/default/utils/5l/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 arm
  
  import (
  	"cmd/internal/objabi"
  	"cmd/link/internal/ld"
  	"fmt"
  	"log"
  )
  
  // This assembler:
  //
  //         .align 2
  // local.dso_init:
  //         ldr r0, .Lmoduledata
  // .Lloadfrom:
  //         ldr r0, [r0]
  //         b runtime.addmoduledata@plt
  // .align 2
  // .Lmoduledata:
  //         .word local.moduledata(GOT_PREL) + (. - (.Lloadfrom + 4))
  // assembles to:
  //
  // 00000000 <local.dso_init>:
  //    0:        e59f0004        ldr     r0, [pc, #4]    ; c <local.dso_init+0xc>
  //    4:        e5900000        ldr     r0, [r0]
  //    8:        eafffffe        b       0 <runtime.addmoduledata>
  //                      8: R_ARM_JUMP24 runtime.addmoduledata
  //    c:        00000004        .word   0x00000004
  //                      c: R_ARM_GOT_PREL       local.moduledata
  
  func gentext(ctxt *ld.Link) {
  	if !ctxt.DynlinkingGo() {
  		return
  	}
  	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 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 = objabi.R_CALLARM
  	rel.Add = 0xeafffffe // vomit
  
  	o(0x00000000)
  	rel = ld.Addrel(initfunc)
  	rel.Off = 12
  	rel.Siz = 4
  	rel.Sym = ctxt.Moduledata
  	rel.Type = objabi.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 = ld.SINITARR
  	ld.Addaddr(ctxt, initarray_entry, initfunc)
  }
  
  // Preserve highest 8 bits of a, and do addition to lower 24-bit
  // of a and b; used to adjust ARM branch instruction's target
  func braddoff(a int32, b int32) int32 {
  	return int32((uint32(a))&0xff000000 | 0x00ffffff&uint32(a+b))
  }
  
  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_ARM_PLT32:
  		r.Type = objabi.R_CALLARM
  
  		if targ.Type == ld.SDYNIMPORT {
  			addpltsym(ctxt, targ)
  			r.Sym = ctxt.Syms.Lookup(".plt", 0)
  			r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
  		}
  
  		return true
  
  	case 256 + ld.R_ARM_THM_PC22: // R_ARM_THM_CALL
  		ld.Exitf("R_ARM_THM_CALL, are you using -marm?")
  		return false
  
  	case 256 + ld.R_ARM_GOT32: // R_ARM_GOT_BREL
  		if targ.Type != ld.SDYNIMPORT {
  			addgotsyminternal(ctxt, targ)
  		} else {
  			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_ARM_GOT_PREL: // GOT(nil) + A - nil
  		if targ.Type != ld.SDYNIMPORT {
  			addgotsyminternal(ctxt, targ)
  		} else {
  			addgotsym(ctxt, targ)
  		}
  
  		r.Type = objabi.R_PCREL
  		r.Sym = ctxt.Syms.Lookup(".got", 0)
  		r.Add += int64(targ.Got) + 4
  		return true
  
  	case 256 + ld.R_ARM_GOTOFF: // R_ARM_GOTOFF32
  		r.Type = objabi.R_GOTOFF
  
  		return true
  
  	case 256 + ld.R_ARM_GOTPC: // R_ARM_BASE_PREL
  		r.Type = objabi.R_PCREL
  
  		r.Sym = ctxt.Syms.Lookup(".got", 0)
  		r.Add += 4
  		return true
  
  	case 256 + ld.R_ARM_CALL:
  		r.Type = objabi.R_CALLARM
  		if targ.Type == ld.SDYNIMPORT {
  			addpltsym(ctxt, targ)
  			r.Sym = ctxt.Syms.Lookup(".plt", 0)
  			r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
  		}
  
  		return true
  
  	case 256 + ld.R_ARM_REL32: // R_ARM_REL32
  		r.Type = objabi.R_PCREL
  
  		r.Add += 4
  		return true
  
  	case 256 + ld.R_ARM_ABS32:
  		if targ.Type == ld.SDYNIMPORT {
  			ld.Errorf(s, "unexpected R_ARM_ABS32 relocation for dynamic symbol %s", targ.Name)
  		}
  		r.Type = objabi.R_ADDR
  		return true
  
  		// 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 true
  
  	case 256 + ld.R_ARM_PC24,
  		256 + ld.R_ARM_JUMP24:
  		r.Type = objabi.R_CALLARM
  		if targ.Type == ld.SDYNIMPORT {
  			addpltsym(ctxt, targ)
  			r.Sym = ctxt.Syms.Lookup(".plt", 0)
  			r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
  		}
  
  		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_CALLARM:
  		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_ARM_GLOB_DAT)) // we need a nil + A dynamic reloc
  			r.Type = objabi.R_CONST                                                         // write r->add during relocsym
  			r.Sym = nil
  			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_ARM_ABS32 | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  
  	case objabi.R_PCREL:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_ARM_REL32 | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  
  	case objabi.R_CALLARM:
  		if r.Siz == 4 {
  			if r.Add&0xff000000 == 0xeb000000 { // BL
  				ld.Thearch.Lput(ld.R_ARM_CALL | uint32(elfsym)<<8)
  			} else {
  				ld.Thearch.Lput(ld.R_ARM_JUMP24 | uint32(elfsym)<<8)
  			}
  		} else {
  			return -1
  		}
  
  	case objabi.R_TLS_LE:
  		ld.Thearch.Lput(ld.R_ARM_TLS_LE32 | uint32(elfsym)<<8)
  
  	case objabi.R_TLS_IE:
  		ld.Thearch.Lput(ld.R_ARM_TLS_IE32 | uint32(elfsym)<<8)
  
  	case objabi.R_GOTPCREL:
  		if r.Siz == 4 {
  			ld.Thearch.Lput(ld.R_ARM_GOT_PREL | uint32(elfsym)<<8)
  		} else {
  			return -1
  		}
  	}
  
  	return 0
  }
  
  func elfsetupplt(ctxt *ld.Link) {
  	plt := ctxt.Syms.Lookup(".plt", 0)
  	got := ctxt.Syms.Lookup(".got.plt", 0)
  	if plt.Size == 0 {
  		// str lr, [sp, #-4]!
  		ld.Adduint32(ctxt, plt, 0xe52de004)
  
  		// ldr lr, [pc, #4]
  		ld.Adduint32(ctxt, plt, 0xe59fe004)
  
  		// add lr, pc, lr
  		ld.Adduint32(ctxt, plt, 0xe08fe00e)
  
  		// ldr pc, [lr, #8]!
  		ld.Adduint32(ctxt, plt, 0xe5bef008)
  
  		// .word &GLOBAL_OFFSET_TABLE[0] - .
  		ld.Addpcrelplus(ctxt, plt, got, 4)
  
  		// the first .plt entry requires 3 .plt.got entries
  		ld.Adduint32(ctxt, got, 0)
  
  		ld.Adduint32(ctxt, got, 0)
  		ld.Adduint32(ctxt, got, 0)
  	}
  }
  
  func machoreloc1(s *ld.Symbol, r *ld.Reloc, sectoff int64) int {
  	var v uint32
  
  	rs := r.Xsym
  
  	if r.Type == objabi.R_PCREL {
  		if rs.Type == ld.SHOSTOBJ {
  			ld.Errorf(s, "pc-relative relocation of external symbol is not supported")
  			return -1
  		}
  		if r.Siz != 4 {
  			return -1
  		}
  
  		// emit a pair of "scattered" relocations that
  		// resolve to the difference of section addresses of
  		// the symbol and the instruction
  		// this value is added to the field being relocated
  		o1 := uint32(sectoff)
  		o1 |= 1 << 31 // scattered bit
  		o1 |= ld.MACHO_ARM_RELOC_SECTDIFF << 24
  		o1 |= 2 << 28 // size = 4
  
  		o2 := uint32(0)
  		o2 |= 1 << 31 // scattered bit
  		o2 |= ld.MACHO_ARM_RELOC_PAIR << 24
  		o2 |= 2 << 28 // size = 4
  
  		ld.Thearch.Lput(o1)
  		ld.Thearch.Lput(uint32(ld.Symaddr(rs)))
  		ld.Thearch.Lput(o2)
  		ld.Thearch.Lput(uint32(s.Value + int64(r.Off)))
  		return 0
  	}
  
  	if rs.Type == ld.SHOSTOBJ || r.Type == objabi.R_CALLARM {
  		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_CALLARM:
  		v |= 1 << 24 // pc-relative bit
  		v |= ld.MACHO_ARM_RELOC_BR24 << 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
  }
  
  // sign extend a 24-bit integer
  func signext24(x int64) int32 {
  	return (int32(x) << 8) >> 8
  }
  
  // encode an immediate in ARM's imm12 format. copied from ../../../internal/obj/arm/asm5.go
  func immrot(v uint32) uint32 {
  	for i := 0; i < 16; i++ {
  		if v&^0xff == 0 {
  			return uint32(i<<8) | v | 1<<25
  		}
  		v = v<<2 | v>>30
  	}
  	return 0
  }
  
  // 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 objabi.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 == ld.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)
  	}
  }
  
  // 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 = objabi.R_ADDR
  		r.Siz = 4
  		r.Sym = target
  		r.Add = offset
  	}
  }
  
  // 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 = objabi.R_PCREL
  	r.Siz = 4
  	r.Sym = target
  	r.Add = offset + 4
  }
  
  // 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 $target@GOT // 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 = objabi.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
  	}
  }
  
  func archreloc(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, val *int64) int {
  	if ld.Linkmode == ld.LinkExternal {
  		switch r.Type {
  		case objabi.R_CALLARM:
  			r.Done = 0
  
  			// set up addend for eventual relocation via outer symbol.
  			rs := r.Sym
  
  			r.Xadd = int64(signext24(r.Add & 0xffffff))
  			r.Xadd *= 4
  			for rs.Outer != nil {
  				r.Xadd += ld.Symaddr(rs) - ld.Symaddr(rs.Outer)
  				rs = rs.Outer
  			}
  
  			if rs.Type != ld.SHOSTOBJ && rs.Type != ld.SDYNIMPORT && rs.Sect == nil {
  				ld.Errorf(s, "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 == objabi.Hdarwin {
  				r.Xadd -= ld.Symaddr(s) + int64(r.Off)
  			}
  
  			if r.Xadd/4 > 0x7fffff || r.Xadd/4 < -0x800000 {
  				ld.Errorf(s, "direct call too far %d", r.Xadd/4)
  			}
  
  			*val = int64(braddoff(int32(0xff000000&uint32(r.Add)), int32(0xffffff&uint32(r.Xadd/4))))
  			return 0
  		}
  
  		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
  
  	// The following three arch specific relocations are only for generation of
  	// Linux/ARM ELF's PLT entry (3 assembler instruction)
  	case objabi.R_PLT0: // add ip, pc, #0xXX00000
  		if ld.Symaddr(ctxt.Syms.Lookup(".got.plt", 0)) < ld.Symaddr(ctxt.Syms.Lookup(".plt", 0)) {
  			ld.Errorf(s, ".got.plt should be placed after .plt section.")
  		}
  		*val = 0xe28fc600 + (0xff & (int64(uint32(ld.Symaddr(r.Sym)-(ld.Symaddr(ctxt.Syms.Lookup(".plt", 0))+int64(r.Off))+r.Add)) >> 20))
  		return 0
  
  	case objabi.R_PLT1: // add ip, ip, #0xYY000
  		*val = 0xe28cca00 + (0xff & (int64(uint32(ld.Symaddr(r.Sym)-(ld.Symaddr(ctxt.Syms.Lookup(".plt", 0))+int64(r.Off))+r.Add+4)) >> 12))
  
  		return 0
  
  	case objabi.R_PLT2: // ldr pc, [ip, #0xZZZ]!
  		*val = 0xe5bcf000 + (0xfff & int64(uint32(ld.Symaddr(r.Sym)-(ld.Symaddr(ctxt.Syms.Lookup(".plt", 0))+int64(r.Off))+r.Add+8)))
  
  		return 0
  
  	case objabi.R_CALLARM: // bl XXXXXX or b YYYYYY
  		// 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.Errorf(s, "direct call too far: %s %x", r.Sym.Name, t)
  		}
  		*val = int64(braddoff(int32(0xff000000&uint32(r.Add)), int32(0xffffff&t)))
  
  		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 addpltreloc(ctxt *ld.Link, plt *ld.Symbol, got *ld.Symbol, sym *ld.Symbol, typ objabi.RelocType) *ld.Reloc {
  	r := ld.Addrel(plt)
  	r.Sym = got
  	r.Off = int32(plt.Size)
  	r.Siz = 4
  	r.Type = typ
  	r.Add = int64(sym.Got) - 8
  
  	plt.Attr |= ld.AttrReachable
  	plt.Size += 4
  	ld.Symgrow(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 := 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)
  		}
  
  		// .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, objabi.R_PLT0) // add lr, pc, #0xXX00000
  		addpltreloc(ctxt, plt, got, s, objabi.R_PLT1) // add lr, lr, #0xYY000
  		addpltreloc(ctxt, plt, got, s, objabi.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.Errorf(s, "addpltsym: unsupported binary format")
  	}
  }
  
  func addgotsyminternal(ctxt *ld.Link, s *ld.Symbol) {
  	if s.Got >= 0 {
  		return
  	}
  
  	got := ctxt.Syms.Lookup(".got", 0)
  	s.Got = int32(got.Size)
  
  	ld.Addaddrplus(ctxt, got, s, 0)
  
  	if ld.Iself {
  	} else {
  		ld.Errorf(s, "addgotsyminternal: 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_ARM_GLOB_DAT))
  	} 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))
  	ld.Codeblk(ctxt, int64(sect.Vaddr), int64(sect.Length))
  	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))
  	}
  
  	/* output symbol table */
  	ld.Symsize = 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))
  		}
  
  		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.Hdarwin:
  			if ld.Linkmode == ld.LinkExternal {
  				ld.Machoemitreloc(ctxt)
  			}
  		}
  	}
  
  	if ctxt.Debugvlog != 0 {
  		ctxt.Logf("%5.2f header\n", ld.Cputime())
  	}
  	ld.Cseek(0)
  	switch ld.Headtype {
  	default:
  	case objabi.Hplan9: /* plan 9 */
  		ld.Lputb(0x647)                      /* 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(0)
  		ld.Lputb(uint32(ld.Lcsize))
  
  	case objabi.Hlinux,
  		objabi.Hfreebsd,
  		objabi.Hnetbsd,
  		objabi.Hopenbsd,
  		objabi.Hnacl:
  		ld.Asmbelf(ctxt, int64(symo))
  
  	case objabi.Hdarwin:
  		ld.Asmbmacho(ctxt)
  	}
  
  	ld.Cflush()
  	if *ld.FlagC {
  		fmt.Printf("textsize=%d\n", ld.Segtext.Filelen)
  		fmt.Printf("datsize=%d\n", ld.Segdata.Filelen)
  		fmt.Printf("bsssize=%d\n", ld.Segdata.Length-ld.Segdata.Filelen)
  		fmt.Printf("symsize=%d\n", ld.Symsize)
  		fmt.Printf("lcsize=%d\n", ld.Lcsize)
  		fmt.Printf("total=%d\n", ld.Segtext.Filelen+ld.Segdata.Length+uint64(ld.Symsize)+uint64(ld.Lcsize))
  	}
  }
  

View as plain text