cmd/internal/ld: handle TLS and imported symbols more regularly

For shared libraries we need to be more flexible in how these symbols
are handled (e.g. sometimes tlsg needs to be global, or you can get
a SDYNIMPORT symbol that has .Hide == true) so handling these cases
in genasmsym makes everything much more regular.

Even ignoring shared libraries, I think this is a bit cleaner.

Change-Id: If5beb093a261e79f4496183226e1765ee7aa6717
Reviewed-on: https://go-review.googlesource.com/8230
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/ld/lib.go

@@ -430,7 +430,6 @@ func loadlib() {
 		tlsg.Type = STLSBSS
 	}
 	tlsg.Size = int64(Thearch.Ptrsize)
-	tlsg.Hide = 1
 	tlsg.Reachable = true
 	Ctxt.Tlsg = tlsg
 
@@ -1375,7 +1374,6 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 				continue
 			}
 			put(s, s.Name, 'D', Symaddr(s), s.Size, int(s.Version), s.Gotype)
-			continue
 
 		case SBSS,
 			SNOPTRBSS:
@@ -1386,18 +1384,31 @@ func genasmsym(put func(*LSym, string, int, int64, int64, int, *LSym)) {
 				Diag("%s should not be bss (size=%d type=%d special=%d)", s.Name, int(len(s.P)), s.Type, s.Special)
 			}
 			put(s, s.Name, 'B', Symaddr(s), s.Size, int(s.Version), s.Gotype)
-			continue
 
 		case SFILE:
 			put(nil, s.Name, 'f', s.Value, 0, int(s.Version), nil)
-			continue
 
 		case SHOSTOBJ:
-			if HEADTYPE == Hwindows {
+			if HEADTYPE == Hwindows || Iself {
 				put(s, s.Name, 'U', s.Value, 0, int(s.Version), nil)
 			}
-			continue
 
+		case SDYNIMPORT:
+			if !s.Reachable {
+				continue
+			}
+			put(s, s.Extname, 'U', 0, 0, int(s.Version), nil)
+
+		case STLSBSS:
+			if Linkmode == LinkExternal && HEADTYPE != Hopenbsd {
+				var type_ int
+				if goos == "android" {
+					type_ = 'B'
+				} else {
+					type_ = 't'
+				}
+				put(s, s.Name, type_, Symaddr(s), s.Size, int(s.Version), s.Gotype)
+			}
 		}
 	}
 

src/cmd/internal/ld/symtab.go

@@ -98,22 +98,34 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 
 	case 'B':
 		type_ = STT_OBJECT
+
+	case 'U':
+		type_ = STT_NOTYPE
+
+	case 't':
+		type_ = STT_TLS
 	}
 
 	xo := x
 	for xo.Outer != nil {
 		xo = xo.Outer
 	}
-	if xo.Sect == nil {
-		Ctxt.Cursym = x
-		Diag("missing section in putelfsym")
-		return
-	}
 
-	if (xo.Sect.(*Section)).Elfsect == nil {
-		Ctxt.Cursym = x
-		Diag("missing ELF section in putelfsym")
-		return
+	var elfshnum int
+	if xo.Type == SDYNIMPORT || xo.Type == SHOSTOBJ {
+		elfshnum = SHN_UNDEF
+	} else {
+		if xo.Sect == nil {
+			Ctxt.Cursym = x
+			Diag("missing section in putelfsym")
+			return
+		}
+		if (xo.Sect.(*Section)).Elfsect == nil {
+			Ctxt.Cursym = x
+			Diag("missing ELF section in putelfsym")
+			return
+		}
+		elfshnum = ((xo.Sect.(*Section)).Elfsect.(*ElfShdr)).shnum
 	}
 
 	// One pass for each binding: STB_LOCAL, STB_GLOBAL,
@@ -128,7 +140,7 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 	// to get the exported symbols put into the dynamic symbol table.
 	// To avoid filling the dynamic table with lots of unnecessary symbols,
 	// mark all Go symbols local (not global) in the final executable.
-	if Linkmode == LinkExternal && x.Cgoexport&CgoExportStatic == 0 {
+	if Linkmode == LinkExternal && x.Cgoexport&CgoExportStatic == 0 && elfshnum != SHN_UNDEF {
 		bind = STB_LOCAL
 	}
 
@@ -137,14 +149,14 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 	}
 
 	off := putelfstr(s)
-	if Linkmode == LinkExternal {
+	if Linkmode == LinkExternal && elfshnum != SHN_UNDEF {
 		addr -= int64((xo.Sect.(*Section)).Vaddr)
 	}
 	other := STV_DEFAULT
 	if x.Type&SHIDDEN != 0 {
 		other = STV_HIDDEN
 	}
-	putelfsyment(off, addr, size, bind<<4|type_&0xf, ((xo.Sect.(*Section)).Elfsect.(*ElfShdr)).shnum, other)
+	putelfsyment(off, addr, size, bind<<4|type_&0xf, elfshnum, other)
 	x.Elfsym = int32(numelfsym)
 	numelfsym++
 }
@@ -178,43 +190,9 @@ func Asmelfsym() {
 	elfbind = STB_LOCAL
 	genasmsym(putelfsym)
 
-	if Linkmode == LinkExternal && HEADTYPE != Hopenbsd {
-		s := Linklookup(Ctxt, "runtime.tlsg", 0)
-		if s.Sect == nil {
-			Ctxt.Cursym = nil
-			Diag("missing section for %s", s.Name)
-			Errorexit()
-		}
-
-		if goos == "android" {
-			// Android emulates runtime.tlsg as a regular variable.
-			putelfsyment(putelfstr(s.Name), 0, s.Size, STB_LOCAL<<4|STT_OBJECT, ((s.Sect.(*Section)).Elfsect.(*ElfShdr)).shnum, 0)
-		} else {
-			putelfsyment(putelfstr(s.Name), 0, s.Size, STB_LOCAL<<4|STT_TLS, ((s.Sect.(*Section)).Elfsect.(*ElfShdr)).shnum, 0)
-		}
-
-		s.Elfsym = int32(numelfsym)
-		numelfsym++
-	}
-
 	elfbind = STB_GLOBAL
 	elfglobalsymndx = numelfsym
 	genasmsym(putelfsym)
-
-	var name string
-	for s := Ctxt.Allsym; s != nil; s = s.Allsym {
-		if s.Type != SHOSTOBJ && (s.Type != SDYNIMPORT || !s.Reachable) {
-			continue
-		}
-		if s.Type == SDYNIMPORT {
-			name = s.Extname
-		} else {
-			name = s.Name
-		}
-		putelfsyment(putelfstr(name), 0, 0, STB_GLOBAL<<4|STT_NOTYPE, 0, 0)
-		s.Elfsym = int32(numelfsym)
-		numelfsym++
-	}
 }
 
 func putplan9sym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *LSym) {