// 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.Reachable = true
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
}
// 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 = obj.R_CALL
r.Siz = 4
}
func Addcall(ctxt *ld.Link, s *ld.LSym, t *ld.LSym) int64 {
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
return i + int64(r.Siz)
}
func addpltreloc(ctxt *ld.Link, plt *ld.Symbol, got *ld.Symbol, sym *ld.Symbol, 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
}
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.Local = true
thunkfunc.Reachable = true
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)
if ld.Ctxt.Etextp != nil {
ld.Ctxt.Etextp.Next = thunkfunc
} else {
ld.Ctxt.Textp = thunkfunc
}
ld.Ctxt.Etextp = 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.Reachable = true
initfunc := ld.Linklookup(ld.Ctxt, "go.link.addmoduledata", 0)
initfunc.Type = obj.STEXT
initfunc.Local = true
initfunc.Reachable = true
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.Etextp.Next = initfunc
ld.Ctxt.Etextp = initfunc
initarray_entry := ld.Linklookup(ld.Ctxt, "go.link.addmoduledatainit", 0)
initarray_entry.Reachable = true
initarray_entry.Local = true
initarray_entry.Type = obj.SINITARR
ld.Addaddr(ld.Ctxt, initarray_entry, initfunc)
}
func gentext(ctxt *ld.Link) {
if !ld.DynlinkingGo() && ld.Buildmode != ld.BuildmodePIE && ld.Buildmode != ld.BuildmodeCShared {
return
}
// Generate little thunks that load the PC of the next instruction into a register.
for _, r := range [...]struct {
name string
num uint8
}{
{"ax", 0},
{"cx", 1},
{"dx", 2},
{"bx", 3},
// sp
{"bp", 5},
{"si", 6},
{"di", 7},
} {
thunkfunc := ld.Linklookup(ctxt, "__x86.get_pc_thunk."+r.name, 0)
thunkfunc.Type = obj.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)
ctxt.Textp = append(ctxt.Textp, thunkfunc)
}
addmoduledata := ld.Linklookup(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(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(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, ld.Linklookup(ctxt, "__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(ctxt, initfunc, initfunc.Size)
r := ld.Addrel(initfunc)
r.Sym = ld.Linklookup(ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
r.Off = int32(i)
r.Type = obj.R_PCREL
r.Add = 12
r.Siz = 4
o(0xe8)
addcall(ctxt, initfunc, addmoduledata)
o(0x5b)
o(0xc3)
ctxt.Textp = append(ctxt.Textp, initfunc)
initarray_entry := ld.Linklookup(ctxt, "go.link.addmoduledatainit", 0)
initarray_entry.Attr |= ld.AttrReachable
initarray_entry.Attr |= ld.AttrLocal
initarray_entry.Type = obj.SINITARR
ld.Addaddr(ctxt, initarray_entry, initfunc)
}