Example #1
0
File: asm.go Project: achanda/go
// 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)
	}
}
Example #2
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 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)
	}
}
Example #3
0
func adddynrel(s *ld.LSym, r *ld.Reloc) {
	targ := r.Sym
	ld.Ctxt.Cursym = s

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

		// Handle relocations found in ELF object files.
	case 256 + ld.R_386_PC32:
		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
		}
		if targ.Type == 0 || targ.Type == obj.SXREF {
			ld.Diag("unknown symbol %s in pcrel", targ.Name)
		}
		r.Type = obj.R_PCREL
		r.Add += 4
		return

	case 256 + ld.R_386_PLT32:
		r.Type = obj.R_PCREL
		r.Add += 4
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ld.Ctxt, targ)
			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
			r.Add += int64(targ.Plt)
		}

		return

	case 256 + ld.R_386_GOT32, 256 + ld.R_386_GOT32X:
		if targ.Type != obj.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 = obj.R_GOTOFF
				return
			}

			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 = obj.R_ADDR
				return
			}

			ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
			return
		}

		addgotsym(ld.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_386_GOTOFF:
		r.Type = obj.R_GOTOFF
		return

	case 256 + ld.R_386_GOTPC:
		r.Type = obj.R_PCREL
		r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
		r.Add += 4
		return

	case 256 + ld.R_386_32:
		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected R_386_32 relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.R_ADDR
		return

	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 0:
		r.Type = obj.R_ADDR
		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected reloc for dynamic symbol %s", targ.Name)
		}
		return

	case 512 + ld.MACHO_GENERIC_RELOC_VANILLA*2 + 1:
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ld.Ctxt, targ)
			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
			r.Add = int64(targ.Plt)
			r.Type = obj.R_PCREL
			return
		}

		r.Type = obj.R_PCREL
		return

	case 512 + ld.MACHO_FAKE_GOTPCREL:
		if targ.Type != obj.SDYNIMPORT {
			// have symbol
			// turn MOVL of GOT entry into LEAL of symbol itself
			if r.Off < 2 || s.P[r.Off-2] != 0x8b {
				ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
				return
			}

			s.P[r.Off-2] = 0x8d
			r.Type = obj.R_PCREL
			return
		}

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

	// Handle references to ELF symbols from our own object files.
	if targ.Type != obj.SDYNIMPORT {
		return
	}

	switch r.Type {
	case obj.R_CALL,
		obj.R_PCREL:
		addpltsym(ld.Ctxt, targ)
		r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
		r.Add = int64(targ.Plt)
		return

	case obj.R_ADDR:
		if s.Type != obj.SDATA {
			break
		}
		if ld.Iself {
			ld.Adddynsym(ld.Ctxt, targ)
			rel := ld.Linklookup(ld.Ctxt, ".rel", 0)
			ld.Addaddrplus(ld.Ctxt, rel, s, int64(r.Off))
			ld.Adduint32(ld.Ctxt, rel, ld.ELF32_R_INFO(uint32(targ.Dynid), ld.R_386_32))
			r.Type = obj.R_CONST // write r->add during relocsym
			r.Sym = nil
			return
		}

		if ld.HEADTYPE == obj.Hdarwin && s.Size == 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(ld.Ctxt, targ)

			got := ld.Linklookup(ld.Ctxt, ".got", 0)
			s.Type = got.Type | obj.SSUB
			s.Outer = got
			s.Sub = got.Sub
			got.Sub = s
			s.Value = got.Size
			ld.Adduint32(ld.Ctxt, got, 0)
			ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.got", 0), uint32(targ.Dynid))
			r.Type = 256 // ignore during relocsym
			return
		}

		if ld.HEADTYPE == obj.Hwindows && s.Size == PtrSize {
			// nothing to do, the relocation will be laid out in pereloc1
			return
		}
	}

	ld.Ctxt.Cursym = s
	ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
Example #4
0
File: asm.go Project: SpiderOak/go
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 {
			addpltsym(ctxt, targ)
			r.Sym = ld.Linklookup(ctxt, ".plt", 0)
			r.Add = int64(braddoff(int32(r.Add), targ.Plt/4))
		}

		return
	}

	// Handle references to ELF symbols from our own object files.
	if targ.Type != obj.SDYNIMPORT {
		return
	}

	switch r.Type {
	case obj.R_CALLARM:
		addpltsym(ctxt, targ)
		r.Sym = ld.Linklookup(ctxt, ".plt", 0)
		r.Add = int64(targ.Plt)
		return

	case obj.R_ADDR:
		if s.Type != obj.SDATA {
			break
		}
		if ld.Iself {
			ld.Adddynsym(ctxt, targ)
			rel := ld.Linklookup(ctxt, ".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 = obj.R_CONST                                                            // write r->add during relocsym
			r.Sym = nil
			return
		}
	}

	ctxt.Cursym = s
	ctxt.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
Example #5
0
File: asm.go Project: sreis/go
func adddynrel(s *ld.LSym, r *ld.Reloc) {
	targ := r.Sym
	ld.Ctxt.Cursym = s

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

		// Handle relocations found in ELF object files.
	case 256 + ld.R_X86_64_PC32:
		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
		}
		if targ.Type == 0 || targ.Type == obj.SXREF {
			ld.Diag("unknown symbol %s in pcrel", targ.Name)
		}
		r.Type = obj.R_PCREL
		r.Add += 4
		return

	case 256 + ld.R_X86_64_PLT32:
		r.Type = obj.R_PCREL
		r.Add += 4
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(targ)
			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
			r.Add += int64(targ.Plt)
		}

		return

	case 256 + ld.R_X86_64_GOTPCREL, 256 + ld.R_X86_64_GOTPCRELX, 256 + ld.R_X86_64_REX_GOTPCRELX:
		if targ.Type != obj.SDYNIMPORT {
			// have symbol
			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
				// turn MOVQ of GOT entry into LEAQ of symbol itself
				s.P[r.Off-2] = 0x8d

				r.Type = obj.R_PCREL
				r.Add += 4
				return
			}
		}

		// fall back to using GOT and hope for the best (CMOV*)
		// TODO: just needs relocation, no need to put in .dynsym
		addgotsym(targ)

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

	case 256 + ld.R_X86_64_64:
		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected R_X86_64_64 relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.R_ADDR
		return

	// Handle relocations found in Mach-O object files.
	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 0,
		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
		512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
		// TODO: What is the difference between all these?
		r.Type = obj.R_ADDR

		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected reloc for dynamic symbol %s", targ.Name)
		}
		return

	case 512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(targ)
			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
			r.Add = int64(targ.Plt)
			r.Type = obj.R_PCREL
			return
		}
		fallthrough

		// fall through
	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
		r.Type = obj.R_PCREL

		if targ.Type == obj.SDYNIMPORT {
			ld.Diag("unexpected pc-relative reloc for dynamic symbol %s", targ.Name)
		}
		return

	case 512 + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
		if targ.Type != obj.SDYNIMPORT {
			// have symbol
			// turn MOVQ of GOT entry into LEAQ of symbol itself
			if r.Off < 2 || s.P[r.Off-2] != 0x8b {
				ld.Diag("unexpected GOT_LOAD reloc for non-dynamic symbol %s", targ.Name)
				return
			}

			s.P[r.Off-2] = 0x8d
			r.Type = obj.R_PCREL
			return
		}
		fallthrough

		// fall through
	case 512 + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
		if targ.Type != obj.SDYNIMPORT {
			ld.Diag("unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
		}
		addgotsym(targ)
		r.Type = obj.R_PCREL
		r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
		r.Add += int64(targ.Got)
		return
	}

	// Handle references to ELF symbols from our own object files.
	if targ.Type != obj.SDYNIMPORT {
		return
	}

	switch r.Type {
	case obj.R_CALL,
		obj.R_PCREL:
		if ld.HEADTYPE == obj.Hwindows {
			// nothing to do, the relocation will be laid out in pereloc1
			return
		} else {
			// for both ELF and Mach-O
			addpltsym(targ)
			r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
			r.Add = int64(targ.Plt)
			return
		}

	case obj.R_ADDR:
		if s.Type == obj.STEXT && ld.Iself {
			if ld.HEADTYPE == obj.Hsolaris {
				addpltsym(targ)
				r.Sym = ld.Linklookup(ld.Ctxt, ".plt", 0)
				r.Add += int64(targ.Plt)
				return
			}
			// The code is asking for the address of an external
			// function. We provide it with the address of the
			// correspondent GOT symbol.
			addgotsym(targ)

			r.Sym = ld.Linklookup(ld.Ctxt, ".got", 0)
			r.Add += int64(targ.Got)
			return
		}

		if s.Type != obj.SDATA {
			break
		}
		if ld.Iself {
			ld.Adddynsym(ld.Ctxt, targ)
			rela := ld.Linklookup(ld.Ctxt, ".rela", 0)
			ld.Addaddrplus(ld.Ctxt, rela, s, int64(r.Off))
			if r.Siz == 8 {
				ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_64))
			} else {
				ld.Adduint64(ld.Ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_32))
			}
			ld.Adduint64(ld.Ctxt, rela, uint64(r.Add))
			r.Type = 256 // ignore during relocsym
			return
		}

		if ld.HEADTYPE == obj.Hdarwin && s.Size == int64(ld.Thearch.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(ld.Ctxt, targ)

			got := ld.Linklookup(ld.Ctxt, ".got", 0)
			s.Type = got.Type | obj.SSUB
			s.Outer = got
			s.Sub = got.Sub
			got.Sub = s
			s.Value = got.Size
			ld.Adduint64(ld.Ctxt, got, 0)
			ld.Adduint32(ld.Ctxt, ld.Linklookup(ld.Ctxt, ".linkedit.got", 0), uint32(targ.Dynid))
			r.Type = 256 // ignore during relocsym
			return
		}

		if ld.HEADTYPE == obj.Hwindows {
			// nothing to do, the relocation will be laid out in pereloc1
			return
		}
	}

	ld.Ctxt.Cursym = s
	ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
Example #6
0
File: asm.go Project: hurkgu/go
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_390_12,
		256 + ld.R_390_GOT12:
		ctxt.Diag("s390x 12-bit relocations have not been implemented (relocation type %d)", r.Type-256)
		return

	case 256 + ld.R_390_8,
		256 + ld.R_390_16,
		256 + ld.R_390_32,
		256 + ld.R_390_64:
		if targ.Type == obj.SDYNIMPORT {
			ctxt.Diag("unexpected R_390_nn relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.R_ADDR
		return

	case 256 + ld.R_390_PC16,
		256 + ld.R_390_PC32,
		256 + ld.R_390_PC64:
		if targ.Type == obj.SDYNIMPORT {
			ctxt.Diag("unexpected R_390_PCnn relocation for dynamic symbol %s", targ.Name)
		}
		if targ.Type == 0 || targ.Type == obj.SXREF {
			ctxt.Diag("unknown symbol %s in pcrel", targ.Name)
		}
		r.Type = obj.R_PCREL
		r.Add += int64(r.Siz)
		return

	case 256 + ld.R_390_GOT16,
		256 + ld.R_390_GOT32,
		256 + ld.R_390_GOT64:
		ctxt.Diag("unimplemented S390x relocation: %v", r.Type-256)
		return

	case 256 + ld.R_390_PLT16DBL,
		256 + ld.R_390_PLT32DBL:
		r.Type = obj.R_PCREL
		r.Variant = ld.RV_390_DBL
		r.Add += int64(r.Siz)
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ld.Linklookup(ctxt, ".plt", 0)
			r.Add += int64(targ.Plt)
		}
		return

	case 256 + ld.R_390_PLT32,
		256 + ld.R_390_PLT64:
		r.Type = obj.R_PCREL
		r.Add += int64(r.Siz)
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ld.Linklookup(ctxt, ".plt", 0)
			r.Add += int64(targ.Plt)
		}
		return

	case 256 + ld.R_390_COPY:
		ctxt.Diag("unimplemented S390x relocation: %v", r.Type-256)

	case 256 + ld.R_390_GLOB_DAT:
		ctxt.Diag("unimplemented S390x relocation: %v", r.Type-256)

	case 256 + ld.R_390_JMP_SLOT:
		ctxt.Diag("unimplemented S390x relocation: %v", r.Type-256)

	case 256 + ld.R_390_RELATIVE:
		ctxt.Diag("unimplemented S390x relocation: %v", r.Type-256)

	case 256 + ld.R_390_GOTOFF:
		if targ.Type == obj.SDYNIMPORT {
			ctxt.Diag("unexpected R_390_GOTOFF relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.R_GOTOFF
		return

	case 256 + ld.R_390_GOTPC:
		r.Type = obj.R_PCREL
		r.Sym = ld.Linklookup(ctxt, ".got", 0)
		r.Add += int64(r.Siz)
		return

	case 256 + ld.R_390_PC16DBL,
		256 + ld.R_390_PC32DBL:
		r.Type = obj.R_PCREL
		r.Variant = ld.RV_390_DBL
		r.Add += int64(r.Siz)
		if targ.Type == obj.SDYNIMPORT {
			ctxt.Diag("unexpected R_390_PCnnDBL relocation for dynamic symbol %s", targ.Name)
		}
		return

	case 256 + ld.R_390_GOTPCDBL:
		r.Type = obj.R_PCREL
		r.Variant = ld.RV_390_DBL
		r.Sym = ld.Linklookup(ctxt, ".got", 0)
		r.Add += int64(r.Siz)
		return

	case 256 + ld.R_390_GOTENT:
		addgotsym(ctxt, targ)

		r.Type = obj.R_PCREL
		r.Variant = ld.RV_390_DBL
		r.Sym = ld.Linklookup(ctxt, ".got", 0)
		r.Add += int64(targ.Got)
		r.Add += int64(r.Siz)
		return
	}
	// Handle references to ELF symbols from our own object files.
	if targ.Type != obj.SDYNIMPORT {
		return
	}

	ctxt.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}
Example #7
0
File: asm.go Project: danny8002/go
func genplt() {
	var s *ld.LSym
	var stub *ld.LSym
	var pprevtextp **ld.LSym
	var r *ld.Reloc
	var n string
	var o1 uint32
	var i int

	// The ppc64 ABI PLT has similar concepts to other
	// architectures, but is laid out quite differently.  When we
	// see an R_PPC64_REL24 relocation to a dynamic symbol
	// (indicating that the call needs to go through the PLT), we
	// generate up to three stubs and reserve a PLT slot.
	//
	// 1) The call site will be bl x; nop (where the relocation
	//    applies to the bl).  We rewrite this to bl x_stub; ld
	//    r2,24(r1).  The ld is necessary because x_stub will save
	//    r2 (the TOC pointer) at 24(r1) (the "TOC save slot").
	//
	// 2) We reserve space for a pointer in the .plt section (once
	//    per referenced dynamic function).  .plt is a data
	//    section filled solely by the dynamic linker (more like
	//    .plt.got on other architectures).  Initially, the
	//    dynamic linker will fill each slot with a pointer to the
	//    corresponding x@plt entry point.
	//
	// 3) We generate the "call stub" x_stub (once per dynamic
	//    function/object file pair).  This saves the TOC in the
	//    TOC save slot, reads the function pointer from x's .plt
	//    slot and calls it like any other global entry point
	//    (including setting r12 to the function address).
	//
	// 4) We generate the "symbol resolver stub" x@plt (once per
	//    dynamic function).  This is solely a branch to the glink
	//    resolver stub.
	//
	// 5) We generate the glink resolver stub (only once).  This
	//    computes which symbol resolver stub we came through and
	//    invokes the dynamic resolver via a pointer provided by
	//    the dynamic linker.  This will patch up the .plt slot to
	//    point directly at the function so future calls go
	//    straight from the call stub to the real function, and
	//    then call the function.

	// NOTE: It's possible we could make ppc64 closer to other
	// architectures: ppc64's .plt is like .plt.got on other
	// platforms and ppc64's .glink is like .plt on other
	// platforms.

	// Find all R_PPC64_REL24 relocations that reference dynamic
	// imports.  Reserve PLT entries for these symbols and
	// generate call stubs.  The call stubs need to live in .text,
	// which is why we need to do this pass this early.
	//
	// This assumes "case 1" from the ABI, where the caller needs
	// us to save and restore the TOC pointer.
	pprevtextp = &ld.Ctxt.Textp

	for s = *pprevtextp; s != nil; pprevtextp, s = &s.Next, s.Next {
		for i = range s.R {
			r = &s.R[i]
			if r.Type != 256+ld.R_PPC64_REL24 || r.Sym.Type != obj.SDYNIMPORT {
				continue
			}

			// Reserve PLT entry and generate symbol
			// resolver
			addpltsym(ld.Ctxt, r.Sym)

			// Generate call stub
			n = fmt.Sprintf("%s.%s", s.Name, r.Sym.Name)

			stub = ld.Linklookup(ld.Ctxt, n, 0)
			stub.Reachable = stub.Reachable || s.Reachable
			if stub.Size == 0 {
				// Need outer to resolve .TOC.
				stub.Outer = s

				// Link in to textp before s (we could
				// do it after, but would have to skip
				// the subsymbols)
				*pprevtextp = stub

				stub.Next = s
				pprevtextp = &stub.Next

				gencallstub(1, stub, r.Sym)
			}

			// Update the relocation to use the call stub
			r.Sym = stub

			// Restore TOC after bl.  The compiler put a
			// nop here for us to overwrite.
			o1 = 0xe8410018 // ld r2,24(r1)
			ld.Ctxt.Arch.ByteOrder.PutUint32(s.P[r.Off+4:], o1)
		}
	}

}
Example #8
0
File: asm.go Project: achanda/go
// resolve direct jump relocation r in s, and add trampoline if necessary
func trampoline(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol) {

	t := ld.Symaddr(r.Sym) + r.Add - (s.Value + int64(r.Off))
	switch r.Type {
	case obj.R_CALLPOWER:

		// If branch offset is too far then create a trampoline.

		if int64(int32(t<<6)>>6) != t || (*ld.FlagDebugTramp > 1 && s.File != r.Sym.File) {
			var tramp *ld.Symbol
			for i := 0; ; i++ {

				// Using r.Add as part of the name is significant in functions like duffzero where the call
				// target is at some offset within the function.  Calls to duff+8 and duff+256 must appear as
				// distinct trampolines.

				name := r.Sym.Name
				if r.Add == 0 {
					name = name + fmt.Sprintf("-tramp%d", i)
				} else {
					name = name + fmt.Sprintf("%+x-tramp%d", r.Add, i)
				}

				// Look up the trampoline in case it already exists

				tramp = ctxt.Syms.Lookup(name, int(r.Sym.Version))
				if tramp.Value == 0 {
					break
				}

				t = ld.Symaddr(tramp) + r.Add - (s.Value + int64(r.Off))

				// If the offset of the trampoline that has been found is within range, use it.
				if int64(int32(t<<6)>>6) == t {
					break
				}
			}
			if tramp.Type == 0 {
				ctxt.AddTramp(tramp)
				tramp.Size = 16 // 4 instructions
				tramp.P = make([]byte, tramp.Size)
				t = ld.Symaddr(r.Sym) + r.Add
				f := t & 0xffff0000
				o1 := uint32(0x3fe00000 | (f >> 16)) // lis r31,trampaddr hi (r31 is temp reg)
				f = t & 0xffff
				o2 := uint32(0x63ff0000 | f) // ori r31,trampaddr lo
				o3 := uint32(0x7fe903a6)     // mtctr
				o4 := uint32(0x4e800420)     // bctr
				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.Sym = tramp
			r.Add = 0 // This was folded into the trampoline target address
			r.Done = 0
		}
	default:
		ld.Errorf(s, "trampoline called with non-jump reloc: %v", r.Type)
	}
}
Example #9
0
File: asm.go Project: achanda/go
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_X86_64_PC32:
		if targ.Type == obj.SDYNIMPORT {
			ld.Errorf(s, "unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
		}
		if targ.Type == 0 || targ.Type == obj.SXREF {
			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
		}
		r.Type = obj.R_PCREL
		r.Add += 4
		return true

	case 256 + ld.R_X86_64_PLT32:
		r.Type = obj.R_PCREL
		r.Add += 4
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ctxt.Syms.Lookup(".plt", 0)
			r.Add += int64(targ.Plt)
		}

		return true

	case 256 + ld.R_X86_64_GOTPCREL, 256 + ld.R_X86_64_GOTPCRELX, 256 + ld.R_X86_64_REX_GOTPCRELX:
		if targ.Type != obj.SDYNIMPORT {
			// have symbol
			if r.Off >= 2 && s.P[r.Off-2] == 0x8b {
				// turn MOVQ of GOT entry into LEAQ of symbol itself
				s.P[r.Off-2] = 0x8d

				r.Type = obj.R_PCREL
				r.Add += 4
				return true
			}
		}

		// fall back to using GOT and hope for the best (CMOV*)
		// TODO: just needs relocation, no need to put in .dynsym
		addgotsym(ctxt, targ)

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

	case 256 + ld.R_X86_64_64:
		if targ.Type == obj.SDYNIMPORT {
			ld.Errorf(s, "unexpected R_X86_64_64 relocation for dynamic symbol %s", targ.Name)
		}
		r.Type = obj.R_ADDR
		return true

	// Handle relocations found in Mach-O object files.
	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 0,
		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 0,
		512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 0:
		// TODO: What is the difference between all these?
		r.Type = obj.R_ADDR

		if targ.Type == obj.SDYNIMPORT {
			ld.Errorf(s, "unexpected reloc for dynamic symbol %s", targ.Name)
		}
		return true

	case 512 + ld.MACHO_X86_64_RELOC_BRANCH*2 + 1:
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ctxt, targ)
			r.Sym = ctxt.Syms.Lookup(".plt", 0)
			r.Add = int64(targ.Plt)
			r.Type = obj.R_PCREL
			return true
		}
		fallthrough

		// fall through
	case 512 + ld.MACHO_X86_64_RELOC_UNSIGNED*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_1*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_2*2 + 1,
		512 + ld.MACHO_X86_64_RELOC_SIGNED_4*2 + 1:
		r.Type = obj.R_PCREL

		if targ.Type == obj.SDYNIMPORT {
			ld.Errorf(s, "unexpected pc-relative reloc for dynamic symbol %s", targ.Name)
		}
		return true

	case 512 + ld.MACHO_X86_64_RELOC_GOT_LOAD*2 + 1:
		if targ.Type != obj.SDYNIMPORT {
			// have symbol
			// turn MOVQ of GOT entry into LEAQ of symbol itself
			if r.Off < 2 || s.P[r.Off-2] != 0x8b {
				ld.Errorf(s, "unexpected GOT_LOAD reloc for non-dynamic symbol %s", targ.Name)
				return false
			}

			s.P[r.Off-2] = 0x8d
			r.Type = obj.R_PCREL
			return true
		}
		fallthrough

		// fall through
	case 512 + ld.MACHO_X86_64_RELOC_GOT*2 + 1:
		if targ.Type != obj.SDYNIMPORT {
			ld.Errorf(s, "unexpected GOT reloc for non-dynamic symbol %s", targ.Name)
		}
		addgotsym(ctxt, targ)
		r.Type = obj.R_PCREL
		r.Sym = ctxt.Syms.Lookup(".got", 0)
		r.Add += int64(targ.Got)
		return true
	}

	switch r.Type {
	case obj.R_CALL,
		obj.R_PCREL:
		if targ.Type != obj.SDYNIMPORT {
			// nothing to do, the relocation will be laid out in reloc
			return true
		}
		if ld.Headtype == obj.Hwindows || ld.Headtype == obj.Hwindowsgui {
			// nothing to do, the relocation will be laid out in pereloc1
			return true
		} else {
			// for both ELF and Mach-O
			addpltsym(ctxt, targ)
			r.Sym = ctxt.Syms.Lookup(".plt", 0)
			r.Add = int64(targ.Plt)
			return true
		}

	case obj.R_ADDR:
		if s.Type == obj.STEXT && ld.Iself {
			if ld.Headtype == obj.Hsolaris {
				addpltsym(ctxt, targ)
				r.Sym = ctxt.Syms.Lookup(".plt", 0)
				r.Add += int64(targ.Plt)
				return true
			}
			// The code is asking for the address of an external
			// function. We provide it with the address of the
			// correspondent GOT symbol.
			addgotsym(ctxt, targ)

			r.Sym = ctxt.Syms.Lookup(".got", 0)
			r.Add += int64(targ.Got)
			return true
		}

		// Process dynamic relocations for the data sections.
		if ld.Buildmode == ld.BuildmodePIE && ld.Linkmode == ld.LinkInternal {
			// When internally linking, generate dynamic relocations
			// for all typical R_ADDR relocations. The exception
			// are those R_ADDR that are created as part of generating
			// the dynamic relocations and must be resolved statically.
			//
			// There are three phases relevant to understanding this:
			//
			//	dodata()  // we are here
			//	address() // symbol address assignment
			//	reloc()   // resolution of static R_ADDR relocs
			//
			// At this point symbol addresses have not been
			// assigned yet (as the final size of the .rela section
			// will affect the addresses), and so we cannot write
			// the Elf64_Rela.r_offset now. Instead we delay it
			// until after the 'address' phase of the linker is
			// complete. We do this via Addaddrplus, which creates
			// a new R_ADDR relocation which will be resolved in
			// the 'reloc' phase.
			//
			// These synthetic static R_ADDR relocs must be skipped
			// now, or else we will be caught in an infinite loop
			// of generating synthetic relocs for our synthetic
			// relocs.
			switch s.Name {
			case ".dynsym", ".rela", ".got.plt", ".dynamic":
				return false
			}
		} else {
			// Either internally linking a static executable,
			// in which case we can resolve these relocations
			// statically in the 'reloc' phase, or externally
			// linking, in which case the relocation will be
			// prepared in the 'reloc' phase and passed to the
			// external linker in the 'asmb' phase.
			if s.Type != obj.SDATA && s.Type != obj.SRODATA {
				break
			}
		}

		if ld.Iself {
			// TODO: We generate a R_X86_64_64 relocation for every R_ADDR, even
			// though it would be more efficient (for the dynamic linker) if we
			// generated R_X86_RELATIVE instead.
			ld.Adddynsym(ctxt, targ)
			rela := ctxt.Syms.Lookup(".rela", 0)
			ld.Addaddrplus(ctxt, rela, s, int64(r.Off))
			if r.Siz == 8 {
				ld.Adduint64(ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_64))
			} else {
				// TODO: never happens, remove.
				ld.Adduint64(ctxt, rela, ld.ELF64_R_INFO(uint32(targ.Dynid), ld.R_X86_64_32))
			}
			ld.Adduint64(ctxt, rela, uint64(r.Add))
			r.Type = 256 // ignore during relocsym
			return true
		}

		if ld.Headtype == obj.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 | obj.SSUB
			s.Outer = got
			s.Sub = got.Sub
			got.Sub = s
			s.Value = got.Size
			ld.Adduint64(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 == obj.Hwindows || ld.Headtype == obj.Hwindowsgui {
			// nothing to do, the relocation will be laid out in pereloc1
			return true
		}
	}

	return false
}