cmd/link: replace SHIDDEN bit in SymKind with a bit of Attribute

This is https://go-review.googlesource.com/42025 but with some more fixes --
hidden symbols implicitly passed "Type == 0 || Type == SXREF" checks. (This
sort of thing is part of why I wanted to make this change)

Change-Id: I2273ee98570fd7f2dd8a799c692a2083c014235e
Reviewed-on: https://go-review.googlesource.com/42330
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/link/internal/amd64/asm.go

@@ -113,7 +113,9 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_X86_64_PC32 relocation for dynamic symbol %s", targ.Name)
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
+		// sense and should be removed when someone has thought about it properly.
+		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
 			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
 		}
 		r.Type = objabi.R_PCREL

src/cmd/link/internal/arm64/asm.go

@@ -239,7 +239,7 @@ func archreloc(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol, val *int64) bool {
 			// (https://sourceware.org/bugzilla/show_bug.cgi?id=18270). So
 			// we convert the adrp; ld64 + R_ARM64_GOTPCREL into adrp;
 			// add + R_ADDRARM64.
-			if !(r.Sym.Version != 0 || (r.Sym.Type&sym.SHIDDEN != 0) || r.Sym.Attr.Local()) && r.Sym.Type == sym.STEXT && ctxt.DynlinkingGo() {
+			if !(r.Sym.Version != 0 || r.Sym.Attr.VisibilityHidden() || r.Sym.Attr.Local()) && r.Sym.Type == sym.STEXT && ctxt.DynlinkingGo() {
 				if o2&0xffc00000 != 0xf9400000 {
 					ld.Errorf(s, "R_ARM64_GOTPCREL against unexpected instruction %x", o2)
 				}

src/cmd/link/internal/ld/data.go

@@ -122,7 +122,7 @@ func relocsym(ctxt *Link, s *sym.Symbol) {
 			continue
 		}
 
-		if r.Sym != nil && (r.Sym.Type&(sym.SMASK|sym.SHIDDEN) == 0 || r.Sym.Type&sym.SMASK == sym.SXREF) {
+		if r.Sym != nil && ((r.Sym.Type == 0 && !r.Sym.Attr.VisibilityHidden()) || r.Sym.Type&sym.SMASK == sym.SXREF) {
 			// When putting the runtime but not main into a shared library
 			// these symbols are undefined and that's OK.
 			if ctxt.BuildMode == BuildModeShared {

src/cmd/link/internal/ld/lib.go

@@ -2159,7 +2159,9 @@ func undefsym(ctxt *Link, s *sym.Symbol) {
 		if r.Sym == nil { // happens for some external ARM relocs
 			continue
 		}
-		if r.Sym.Type == sym.Sxxx || r.Sym.Type == sym.SXREF {
+		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
+		// sense and should be removed when someone has thought about it properly.
+		if (r.Sym.Type == sym.Sxxx || r.Sym.Type == sym.SXREF) && !r.Sym.Attr.VisibilityHidden() {
 			Errorf(s, "undefined: %q", r.Sym.Name)
 		}
 		if !r.Sym.Attr.Reachable() && r.Type != objabi.R_WEAKADDROFF {

src/cmd/link/internal/ld/pe.go

@@ -679,7 +679,7 @@ func (f *peFile) writeSymbols(ctxt *Link) {
 			}
 		}
 		class := IMAGE_SYM_CLASS_EXTERNAL
-		if s.Version != 0 || (s.Type&sym.SHIDDEN != 0) || s.Attr.Local() {
+		if s.Version != 0 || s.Attr.VisibilityHidden() || s.Attr.Local() {
 			class = IMAGE_SYM_CLASS_STATIC
 		}
 		f.writeSymbol(ctxt.Out, s, value, sect, typ, uint8(class))

src/cmd/link/internal/ld/symtab.go

@@ -128,7 +128,7 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go
 	// maybe one day STB_WEAK.
 	bind := STB_GLOBAL
 
-	if x.Version != 0 || (x.Type&sym.SHIDDEN != 0) || x.Attr.Local() {
+	if x.Version != 0 || x.Attr.VisibilityHidden() || x.Attr.Local() {
 		bind = STB_LOCAL
 	}
 
@@ -145,7 +145,12 @@ func putelfsym(ctxt *Link, x *sym.Symbol, s string, t SymbolType, addr int64, go
 		addr -= int64(xo.Sect.Vaddr)
 	}
 	other := STV_DEFAULT
-	if x.Type&sym.SHIDDEN != 0 {
+	if x.Attr.VisibilityHidden() {
+		// TODO(mwhudson): We only set AttrVisibilityHidden in ldelf, i.e. when
+		// internally linking. But STV_HIDDEN visibility only matters in object
+		// files and shared libraries, and as we are a long way from implementing
+		// internal linking for shared libraries and only create object files when
+		// externally linking, I don't think this makes a lot of sense.
 		other = STV_HIDDEN
 	}
 	if ctxt.Arch.Family == sys.PPC64 && typ == STT_FUNC && x.Attr.Shared() && x.Name != "runtime.duffzero" && x.Name != "runtime.duffcopy" {

src/cmd/link/internal/loadelf/ldelf.go

@@ -1043,8 +1043,7 @@ func readelfsym(arch *sys.Arch, syms *sym.Symbols, elfobj *ElfObj, i int, elfsym
 				// set dupok generally. See http://codereview.appspot.com/5823055/
 				// comment #5 for details.
 				if s != nil && elfsym.other == 2 {
-					s.Type |= sym.SHIDDEN
-					s.Attr |= sym.AttrDuplicateOK
+					s.Attr |= sym.AttrDuplicateOK | sym.AttrVisibilityHidden
 				}
 			}
 
@@ -1060,7 +1059,7 @@ func readelfsym(arch *sys.Arch, syms *sym.Symbols, elfobj *ElfObj, i int, elfsym
 				// so put it in the hash table.
 				if needSym != 0 {
 					s = syms.Lookup(elfsym.name, localSymVersion)
-					s.Type |= sym.SHIDDEN
+					s.Attr |= sym.AttrVisibilityHidden
 				}
 
 				break
@@ -1072,14 +1071,14 @@ func readelfsym(arch *sys.Arch, syms *sym.Symbols, elfobj *ElfObj, i int, elfsym
 				// don't bother to add them into the hash table
 				s = syms.Newsym(elfsym.name, localSymVersion)
 
-				s.Type |= sym.SHIDDEN
+				s.Attr |= sym.AttrVisibilityHidden
 			}
 
 		case ElfSymBindWeak:
 			if needSym != 0 {
 				s = syms.Lookup(elfsym.name, 0)
 				if elfsym.other == 2 {
-					s.Type |= sym.SHIDDEN
+					s.Attr |= sym.AttrVisibilityHidden
 				}
 			}
 
@@ -1089,7 +1088,9 @@ func readelfsym(arch *sys.Arch, syms *sym.Symbols, elfobj *ElfObj, i int, elfsym
 		}
 	}
 
-	if s != nil && s.Type == 0 && elfsym.type_ != ElfSymTypeSection {
+	// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
+	// sense and should be removed when someone has thought about it properly.
+	if s != nil && s.Type == 0 && !s.Attr.VisibilityHidden() && elfsym.type_ != ElfSymTypeSection {
 		s.Type = sym.SXREF
 	}
 	elfsym.sym = s

src/cmd/link/internal/s390x/asm.go

@@ -134,7 +134,9 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_390_PCnn relocation for dynamic symbol %s", targ.Name)
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
+		// sense and should be removed when someone has thought about it properly.
+		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
 			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
 		}
 		r.Type = objabi.R_PCREL

src/cmd/link/internal/sym/attribute.go

@@ -52,7 +52,12 @@ const (
 	AttrMakeTypelink
 	// AttrShared marks symbols compiled with the -shared option.
 	AttrShared
-	// 14 attributes defined so far.
+	// AttrVisibilityHidden symbols are ELF symbols with
+	// visibility set to STV_HIDDEN. They become local symbols in
+	// the final executable. Only relevant when internally linking
+	// on an ELF platform.
+	AttrVisibilityHidden
+	// 15 attributes defined so far.
 )
 
 func (a Attribute) DuplicateOK() bool      { return a&AttrDuplicateOK != 0 }
@@ -69,6 +74,7 @@ func (a Attribute) Local() bool            { return a&AttrLocal != 0 }
 func (a Attribute) ReflectMethod() bool    { return a&AttrReflectMethod != 0 }
 func (a Attribute) MakeTypelink() bool     { return a&AttrMakeTypelink != 0 }
 func (a Attribute) Shared() bool           { return a&AttrShared != 0 }
+func (a Attribute) VisibilityHidden() bool { return a&AttrVisibilityHidden != 0 }
 
 func (a Attribute) CgoExport() bool {
 	return a.CgoExportDynamic() || a.CgoExportStatic()

src/cmd/link/internal/sym/symkind.go

@@ -107,7 +107,6 @@ const (
 	SDWARFLOC
 	SSUB       = SymKind(1 << 8)
 	SMASK      = SymKind(SSUB - 1)
-	SHIDDEN    = SymKind(1 << 9)
 	SCONTAINER = SymKind(1 << 10) // has a sub-symbol
 )
 

src/cmd/link/internal/x86/asm.go

@@ -182,7 +182,9 @@ func adddynrel(ctxt *ld.Link, s *sym.Symbol, r *sym.Reloc) bool {
 		if targ.Type == sym.SDYNIMPORT {
 			ld.Errorf(s, "unexpected R_386_PC32 relocation for dynamic symbol %s", targ.Name)
 		}
-		if targ.Type == 0 || targ.Type == sym.SXREF {
+		// TODO(mwhudson): the test of VisibilityHidden here probably doesn't make
+		// sense and should be removed when someone has thought about it properly.
+		if (targ.Type == 0 || targ.Type == sym.SXREF) && !targ.Attr.VisibilityHidden() {
 			ld.Errorf(s, "unknown symbol %s in pcrel", targ.Name)
 		}
 		r.Type = objabi.R_PCREL