cmd/internal/obj: support arbitrarily sized string data

Updates #14786.

Change-Id: I5fe889886f772167386cd10390ac50abc1383937
Reviewed-on: https://go-review.googlesource.com/20607
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

src/cmd/compile/internal/gc/obj.go

@@ -223,16 +223,7 @@ func stringsym(s string) (hdr, data *Sym) {
 	symdata.Flags |= SymUniq
 	symdata.Def = newname(symdata)
 
-	off = 0
-	var m int
-	for n := 0; n < len(s); n += m {
-		m = 8
-		if m > len(s)-n {
-			m = len(s) - n
-		}
-		off = dsname(symdata, off, s[n:n+m])
-	}
-
+	off = dsname(symdata, 0, s)
 	ggloblsym(symdata, int32(off), obj.DUPOK|obj.RODATA|obj.LOCAL)
 
 	return symhdr, symdata
@@ -241,22 +232,12 @@ func stringsym(s string) (hdr, data *Sym) {
 var slicebytes_gen int
 
 func slicebytes(nam *Node, s string, len int) {
-	var m int
-
 	slicebytes_gen++
 	symname := fmt.Sprintf(".gobytes.%d", slicebytes_gen)
 	sym := Pkglookup(symname, localpkg)
 	sym.Def = newname(sym)
 
-	off := 0
-	for n := 0; n < len; n += m {
-		m = 8
-		if m > len-n {
-			m = len - n
-		}
-		off = dsname(sym, off, s[n:n+m])
-	}
-
+	off := dsname(sym, 0, s)
 	ggloblsym(sym, int32(off), obj.NOPTR|obj.LOCAL)
 
 	if nam.Op != ONAME {

src/cmd/internal/obj/data.go

@@ -54,7 +54,7 @@ func Symgrow(ctxt *Link, s *LSym, lsiz int64) {
 
 // prepwrite prepares to write data of size siz into s at offset off.
 func (s *LSym) prepwrite(ctxt *Link, off, siz int64) {
-	if off < 0 || siz < 0 || off >= 1<<30 || siz >= 100 {
+	if off < 0 || siz < 0 || off >= 1<<30 {
 		log.Fatalf("prepwrite: bad off=%d siz=%d", off, siz)
 	}
 	if s.Type == SBSS || s.Type == STLSBSS {
@@ -80,7 +80,7 @@ func (s *LSym) WriteInt(ctxt *Link, off, siz int64, i int64) {
 	s.prepwrite(ctxt, off, siz)
 	switch siz {
 	default:
-		ctxt.Diag("WriteInt bad integer: %d", siz)
+		ctxt.Diag("WriteInt: bad integer size: %d", siz)
 	case 1:
 		s.P[off] = byte(i)
 	case 2:
@@ -95,6 +95,9 @@ func (s *LSym) WriteInt(ctxt *Link, off, siz int64, i int64) {
 // WriteAddr writes an address of size siz into s at offset off.
 // rsym and roff specify the relocation for the address.
 func (s *LSym) WriteAddr(ctxt *Link, off, siz int64, rsym *LSym, roff int64) {
+	if siz != int64(ctxt.Arch.Ptrsize) {
+		ctxt.Diag("WriteAddr: bad address size: %d", siz)
+	}
 	s.prepwrite(ctxt, off, siz)
 	r := Addrel(s)
 	r.Off = int32(off)
@@ -106,6 +109,9 @@ func (s *LSym) WriteAddr(ctxt *Link, off, siz int64, rsym *LSym, roff int64) {
 
 // WriteString writes a string of size siz into s at offset off.
 func (s *LSym) WriteString(ctxt *Link, off, siz int64, str string) {
+	if siz < int64(len(str)) {
+		ctxt.Diag("WriteString: bad string size: %d < %d", siz, len(str))
+	}
 	s.prepwrite(ctxt, off, siz)
 	copy(s.P[off:off+siz], str)
 }