Exemple #1
0
func addpltsym(ctxt *ld.Link, s *ld.LSym) {
	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()
		}

		// 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 {
		ld.Diag("addpltsym: unsupported binary format")
	}
}
Exemple #2
0
func addgotsym(ctxt *ld.Link, s *ld.LSym) {
	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 {
		ld.Diag("addgotsym: unsupported binary format")
	}
}
Exemple #3
0
func addpltsym(ctxt *ld.Link, s *ld.LSym) {
	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()
		}

		// .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, obj.R_PLT0) // add lr, pc, #0xXX00000
		addpltreloc(ctxt, plt, got, s, obj.R_PLT1) // add lr, lr, #0xYY000
		addpltreloc(ctxt, plt, got, s, obj.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.Diag("addpltsym: unsupported binary format")
	}
}
Exemple #4
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 == 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(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 == int64(ld.SysArch.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)
}
Exemple #5
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_ARM_PLT32:
		r.Type = obj.R_CALLARM

		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ld.Ctxt, targ)
			r.Sym = ld.Linklookup(ld.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(ld.Ctxt, targ)
		} else {
			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_ARM_GOT_PREL: // GOT(nil) + A - nil
		if targ.Type != obj.SDYNIMPORT {
			addgotsyminternal(ld.Ctxt, targ)
		} else {
			addgotsym(ld.Ctxt, targ)
		}

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

	case 256 + ld.R_ARM_CALL:
		r.Type = obj.R_CALLARM
		if targ.Type == obj.SDYNIMPORT {
			addpltsym(ld.Ctxt, targ)
			r.Sym = ld.Linklookup(ld.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 {
			ld.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(ld.Ctxt, targ)
			r.Sym = ld.Linklookup(ld.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(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_ARM_GLOB_DAT)) // we need a nil + A dynamic reloc
			r.Type = obj.R_CONST                                                               // write r->add during relocsym
			r.Sym = nil
			return
		}
	}

	ld.Ctxt.Cursym = s
	ld.Diag("unsupported relocation for dynamic symbol %s (type=%d stype=%d)", targ.Name, r.Type, targ.Type)
}