Exemplo n.º 1
0
// Append 4 bytes to s and create a R_CALL relocation targeting t to fill them in.
func addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) {
	s.Attr |= ld.AttrReachable
	i := s.Size
	s.Size += 4
	ld.Symgrow(ctxt, s, s.Size)
	r := ld.Addrel(s)
	r.Sym = t
	r.Off = int32(i)
	r.Type = obj.R_CALL
	r.Siz = 4
}
Exemplo n.º 2
0
func addpltreloc(ctxt *ld.Link, plt *ld.LSym, got *ld.LSym, sym *ld.LSym, typ int) *ld.Reloc {
	r := ld.Addrel(plt)
	r.Sym = got
	r.Off = int32(plt.Size)
	r.Siz = 4
	r.Type = int32(typ)
	r.Add = int64(sym.Got) - 8

	plt.Attr |= ld.AttrReachable
	plt.Size += 4
	ld.Symgrow(ctxt, plt, plt.Size)

	return r
}
Exemplo n.º 3
0
func gentext() {
	if !ld.DynlinkingGo() && ld.Buildmode != ld.BuildmodePIE && ld.Buildmode != ld.BuildmodeCShared {
		return
	}

	thunkfunc := ld.Linklookup(ld.Ctxt, "__x86.get_pc_thunk.cx", 0)
	thunkfunc.Type = obj.STEXT
	thunkfunc.Attr |= ld.AttrLocal
	thunkfunc.Attr |= ld.AttrReachable
	o := func(op ...uint8) {
		for _, op1 := range op {
			ld.Adduint8(ld.Ctxt, thunkfunc, op1)
		}
	}
	// 8b 0c 24	mov    (%esp),%ecx
	o(0x8b, 0x0c, 0x24)
	// c3		ret
	o(0xc3)

	ld.Ctxt.Textp = append(ld.Ctxt.Textp, thunkfunc)

	addmoduledata := ld.Linklookup(ld.Ctxt, "runtime.addmoduledata", 0)
	if addmoduledata.Type == obj.STEXT {
		// we're linking a module containing the runtime -> no need for
		// an init function
		return
	}

	addmoduledata.Attr |= ld.AttrReachable

	initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
	initfunc.Type = obj.STEXT
	initfunc.Attr |= ld.AttrLocal
	initfunc.Attr |= ld.AttrReachable
	o = func(op ...uint8) {
		for _, op1 := range op {
			ld.Adduint8(ld.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 ld.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(ld.Ctxt, initfunc, ld.Linklookup(ld.Ctxt, "__x86.get_pc_thunk.cx", 0))

	o(0x8d, 0x81)
	ld.Addpcrelplus(ld.Ctxt, initfunc, ld.Ctxt.Moduledata, 6)

	o(0x8d, 0x99)
	i := initfunc.Size
	initfunc.Size += 4
	ld.Symgrow(ld.Ctxt, initfunc, initfunc.Size)
	r := ld.Addrel(initfunc)
	r.Sym = ld.Linklookup(ld.Ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
	r.Off = int32(i)
	r.Type = obj.R_PCREL
	r.Add = 12
	r.Siz = 4

	o(0xe8)
	addcall(ld.Ctxt, initfunc, addmoduledata)

	o(0x5b)

	o(0xc3)

	ld.Ctxt.Textp = append(ld.Ctxt.Textp, initfunc)
	initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
	initarray_entry.Attr |= ld.AttrReachable
	initarray_entry.Attr |= ld.AttrLocal
	initarray_entry.Type = obj.SINITARR
	ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
}