cmd/link, etc: introduce SymKind type

Moves the grouping of symbol kinds (sections) into cmd/internal/obj
to keep it near the definition. Groundwork for CL 28538.

Change-Id: I99112981e69b028f366e1333f31cd7defd4ff82c
Reviewed-on: https://go-review.googlesource.com/28691
Run-TryBot: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/internal/goobj/read.go

@@ -29,50 +29,48 @@ type SymKind int
 // TODO(rsc): Give idiomatic Go names.
 // TODO(rsc): Reduce the number of symbol types in the object files.
 const (
-	_ SymKind = iota
-
 	// readonly, executable
-	STEXT      SymKind = obj.STEXT
-	SELFRXSECT SymKind = obj.SELFRXSECT
+	STEXT      = SymKind(obj.STEXT)
+	SELFRXSECT = SymKind(obj.SELFRXSECT)
 
 	// readonly, non-executable
-	STYPE      SymKind = obj.STYPE
-	SSTRING    SymKind = obj.SSTRING
-	SGOSTRING  SymKind = obj.SGOSTRING
-	SGOFUNC    SymKind = obj.SGOFUNC
-	SRODATA    SymKind = obj.SRODATA
-	SFUNCTAB   SymKind = obj.SFUNCTAB
-	STYPELINK  SymKind = obj.STYPELINK
-	SITABLINK  SymKind = obj.SITABLINK
-	SSYMTAB    SymKind = obj.SSYMTAB // TODO: move to unmapped section
-	SPCLNTAB   SymKind = obj.SPCLNTAB
-	SELFROSECT SymKind = obj.SELFROSECT
+	STYPE      = SymKind(obj.STYPE)
+	SSTRING    = SymKind(obj.SSTRING)
+	SGOSTRING  = SymKind(obj.SGOSTRING)
+	SGOFUNC    = SymKind(obj.SGOFUNC)
+	SRODATA    = SymKind(obj.SRODATA)
+	SFUNCTAB   = SymKind(obj.SFUNCTAB)
+	STYPELINK  = SymKind(obj.STYPELINK)
+	SITABLINK  = SymKind(obj.SITABLINK)
+	SSYMTAB    = SymKind(obj.SSYMTAB) // TODO: move to unmapped section
+	SPCLNTAB   = SymKind(obj.SPCLNTAB)
+	SELFROSECT = SymKind(obj.SELFROSECT)
 
 	// writable, non-executable
-	SMACHOPLT  SymKind = obj.SMACHOPLT
-	SELFSECT   SymKind = obj.SELFSECT
-	SMACHO     SymKind = obj.SMACHO // Mach-O __nl_symbol_ptr
-	SMACHOGOT  SymKind = obj.SMACHOGOT
-	SWINDOWS   SymKind = obj.SWINDOWS
-	SELFGOT    SymKind = obj.SELFGOT
-	SNOPTRDATA SymKind = obj.SNOPTRDATA
-	SINITARR   SymKind = obj.SINITARR
-	SDATA      SymKind = obj.SDATA
-	SBSS       SymKind = obj.SBSS
-	SNOPTRBSS  SymKind = obj.SNOPTRBSS
-	STLSBSS    SymKind = obj.STLSBSS
+	SMACHOPLT  = SymKind(obj.SMACHOPLT)
+	SELFSECT   = SymKind(obj.SELFSECT)
+	SMACHO     = SymKind(obj.SMACHO) // Mach-O __nl_symbol_ptr
+	SMACHOGOT  = SymKind(obj.SMACHOGOT)
+	SWINDOWS   = SymKind(obj.SWINDOWS)
+	SELFGOT    = SymKind(obj.SELFGOT)
+	SNOPTRDATA = SymKind(obj.SNOPTRDATA)
+	SINITARR   = SymKind(obj.SINITARR)
+	SDATA      = SymKind(obj.SDATA)
+	SBSS       = SymKind(obj.SBSS)
+	SNOPTRBSS  = SymKind(obj.SNOPTRBSS)
+	STLSBSS    = SymKind(obj.STLSBSS)
 
 	// not mapped
-	SXREF             SymKind = obj.SXREF
-	SMACHOSYMSTR      SymKind = obj.SMACHOSYMSTR
-	SMACHOSYMTAB      SymKind = obj.SMACHOSYMTAB
-	SMACHOINDIRECTPLT SymKind = obj.SMACHOINDIRECTPLT
-	SMACHOINDIRECTGOT SymKind = obj.SMACHOINDIRECTGOT
-	SFILE             SymKind = obj.SFILE
-	SFILEPATH         SymKind = obj.SFILEPATH
-	SCONST            SymKind = obj.SCONST
-	SDYNIMPORT        SymKind = obj.SDYNIMPORT
-	SHOSTOBJ          SymKind = obj.SHOSTOBJ
+	SXREF             = SymKind(obj.SXREF)
+	SMACHOSYMSTR      = SymKind(obj.SMACHOSYMSTR)
+	SMACHOSYMTAB      = SymKind(obj.SMACHOSYMTAB)
+	SMACHOINDIRECTPLT = SymKind(obj.SMACHOINDIRECTPLT)
+	SMACHOINDIRECTGOT = SymKind(obj.SMACHOINDIRECTGOT)
+	SFILE             = SymKind(obj.SFILE)
+	SFILEPATH         = SymKind(obj.SFILEPATH)
+	SCONST            = SymKind(obj.SCONST)
+	SDYNIMPORT        = SymKind(obj.SDYNIMPORT)
+	SHOSTOBJ          = SymKind(obj.SHOSTOBJ)
 )
 
 var symKindStrings = []string{

src/cmd/internal/obj/link.go

@@ -316,7 +316,7 @@ const (
 // An LSym is the sort of symbol that is written to an object file.
 type LSym struct {
 	Name      string
-	Type      int16
+	Type      SymKind
 	Version   int16
 	Dupok     bool
 	Cfunc     bool
@@ -371,9 +371,16 @@ type Pcln struct {
 	Lastindex   int
 }
 
-// LSym.type
+// A SymKind describes the kind of memory represented by a symbol.
+type SymKind int16
+
+// Defined SymKind values.
+//
+// TODO(rsc): Give idiomatic Go names.
+// TODO(rsc): Reduce the number of symbol types in the object files.
+//go:generate stringer -type=SymKind
 const (
-	Sxxx = iota
+	Sxxx SymKind = iota
 	STEXT
 	SELFRXSECT
 
@@ -434,12 +441,39 @@ const (
 	SHOSTOBJ
 	SDWARFSECT
 	SDWARFINFO
-	SSUB       = 1 << 8
-	SMASK      = SSUB - 1
-	SHIDDEN    = 1 << 9
-	SCONTAINER = 1 << 10 // has a sub-symbol
+	SSUB       = SymKind(1 << 8)
+	SMASK      = SymKind(SSUB - 1)
+	SHIDDEN    = SymKind(1 << 9)
+	SCONTAINER = SymKind(1 << 10) // has a sub-symbol
 )
 
+// ReadOnly are the symbol kinds that form read-only sections. In some
+// cases, if they will require relocations, they are transformed into
+// rel-ro sections using RelROMap.
+var ReadOnly = []SymKind{
+	STYPE,
+	SSTRING,
+	SGOSTRING,
+	SGOSTRINGHDR,
+	SGOFUNC,
+	SGCBITS,
+	SRODATA,
+	SFUNCTAB,
+}
+
+// RelROMap describes the transformation of read-only symbols to rel-ro
+// symbols.
+var RelROMap = map[SymKind]SymKind{
+	STYPE:        STYPERELRO,
+	SSTRING:      SSTRINGRELRO,
+	SGOSTRING:    SGOSTRINGRELRO,
+	SGOSTRINGHDR: SGOSTRINGHDRRELRO,
+	SGOFUNC:      SGOFUNCRELRO,
+	SGCBITS:      SGCBITSRELRO,
+	SRODATA:      SRODATARELRO,
+	SFUNCTAB:     SFUNCTABRELRO,
+}
+
 type Reloc struct {
 	Off  int32
 	Siz  uint8

src/cmd/internal/obj/symkind_string.go

+// Code generated by "stringer -type=SymKind"; DO NOT EDIT
+
+package obj
+
+import "fmt"
+
+const _SymKind_name = "SxxxSTEXTSELFRXSECTSTYPESSTRINGSGOSTRINGSGOSTRINGHDRSGOFUNCSGCBITSSRODATASFUNCTABSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOSTRINGHDRRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSELFROSECTSMACHOPLTSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASBSSSNOPTRBSSSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILESFILEPATHSCONSTSDYNIMPORTSHOSTOBJSDWARFSECTSDWARFINFO"
+
+var _SymKind_index = [...]uint16{0, 4, 9, 19, 24, 31, 40, 52, 59, 66, 73, 81, 91, 103, 117, 134, 146, 158, 170, 183, 192, 201, 208, 216, 226, 235, 243, 249, 258, 266, 273, 283, 291, 296, 300, 309, 316, 321, 333, 345, 362, 379, 384, 393, 399, 409, 417, 427, 437}
+
+func (i SymKind) String() string {
+	if i < 0 || i >= SymKind(len(_SymKind_index)-1) {
+		return fmt.Sprintf("SymKind(%d)", i)
+	}
+	return _SymKind_name[_SymKind_index[i]:_SymKind_index[i+1]]
+}

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

@@ -1168,7 +1168,7 @@ func (d bySizeAndName) Less(i, j int) bool {
 
 const cutoff int64 = 2e9 // 2 GB (or so; looks better in errors than 2^31)
 
-func checkdatsize(ctxt *Link, datsize int64, symn int) {
+func checkdatsize(ctxt *Link, datsize int64, symn obj.SymKind) {
 	if datsize > cutoff {
 		ctxt.Diag("too much data in section %v (over %d bytes)", symn, cutoff)
 	}
@@ -1210,8 +1210,8 @@ func (ctxt *Link) dodata() {
 		// "read only" data with relocations needs to go in its own section
 		// when building a shared library. We do this by boosting objects of
 		// type SXXX with relocations to type SXXXRELRO.
-		for symnro := int16(obj.STYPE); symnro < obj.STYPERELRO; symnro++ {
-			symnrelro := symnro + obj.STYPERELRO - obj.STYPE
+		for _, symnro := range obj.ReadOnly {
+			symnrelro := obj.RelROMap[symnro]
 
 			ro := []*Symbol{}
 			relro := data[symnrelro]
@@ -1256,7 +1256,7 @@ func (ctxt *Link) dodata() {
 	var dataMaxAlign [obj.SXREF]int32
 	var wg sync.WaitGroup
 	for symn := range data {
-		symn := symn
+		symn := obj.SymKind(symn)
 		wg.Add(1)
 		go func() {
 			data[symn], dataMaxAlign[symn] = dodataSect(ctxt, symn, data[symn])
@@ -1271,14 +1271,14 @@ func (ctxt *Link) dodata() {
 	// to generate garbage collection information.
 	datsize := int64(0)
 
-	// Writable sections.
-	writableSects := []int{
+	// Writable data sections that do not need any specialized handling.
+	writable := []obj.SymKind{
 		obj.SELFSECT,
 		obj.SMACHO,
 		obj.SMACHOGOT,
 		obj.SWINDOWS,
 	}
-	for _, symn := range writableSects {
+	for _, symn := range writable {
 		for _, s := range data[symn] {
 			sect := addsection(&Segdata, s.Name, 06)
 			sect.Align = symalign(s)
@@ -1489,24 +1489,14 @@ func (ctxt *Link) dodata() {
 		Linklookup(ctxt, "runtime.types", 0).Sect = sect
 		Linklookup(ctxt, "runtime.etypes", 0).Sect = sect
 	}
-	roSects := []int{
-		obj.STYPE,
-		obj.SSTRING,
-		obj.SGOSTRING,
-		obj.SGOSTRINGHDR,
-		obj.SGOFUNC,
-		obj.SGCBITS,
-		obj.SRODATA,
-		obj.SFUNCTAB,
-	}
-	for _, symn := range roSects {
+	for _, symn := range obj.ReadOnly {
 		align := dataMaxAlign[symn]
 		if sect.Align < align {
 			sect.Align = align
 		}
 	}
 	datsize = Rnd(datsize, int64(sect.Align))
-	for _, symn := range roSects {
+	for _, symn := range obj.ReadOnly {
 		for _, s := range data[symn] {
 			datsize = aligndatsize(datsize, s)
 			s.Sect = sect
@@ -1540,24 +1530,16 @@ func (ctxt *Link) dodata() {
 		sect.Vaddr = 0
 		Linklookup(ctxt, "runtime.types", 0).Sect = sect
 		Linklookup(ctxt, "runtime.etypes", 0).Sect = sect
-		relroSects := []int{
-			obj.STYPERELRO,
-			obj.SSTRINGRELRO,
-			obj.SGOSTRINGRELRO,
-			obj.SGOSTRINGHDRRELRO,
-			obj.SGOFUNCRELRO,
-			obj.SGCBITSRELRO,
-			obj.SRODATARELRO,
-			obj.SFUNCTABRELRO,
-		}
-		for _, symn := range relroSects {
+		for _, symnro := range obj.ReadOnly {
+			symn := obj.RelROMap[symnro]
 			align := dataMaxAlign[symn]
 			if sect.Align < align {
 				sect.Align = align
 			}
 		}
 		datsize = Rnd(datsize, int64(sect.Align))
-		for _, symn := range relroSects {
+		for _, symnro := range obj.ReadOnly {
+			symn := obj.RelROMap[symnro]
 			for _, s := range data[symn] {
 				datsize = aligndatsize(datsize, s)
 				if s.Outer != nil && s.Outer.Sect != nil && s.Outer.Sect != sect {
@@ -1739,13 +1721,13 @@ func (ctxt *Link) dodata() {
 	}
 }
 
-func dodataSect(ctxt *Link, symn int, syms []*Symbol) (result []*Symbol, maxAlign int32) {
+func dodataSect(ctxt *Link, symn obj.SymKind, syms []*Symbol) (result []*Symbol, maxAlign int32) {
 	if Headtype == obj.Hdarwin {
 		// Some symbols may no longer belong in syms
 		// due to movement in machosymorder.
 		newSyms := make([]*Symbol, 0, len(syms))
 		for _, s := range syms {
-			if int(s.Type) == symn {
+			if s.Type == symn {
 				newSyms = append(newSyms, s)
 			}
 		}

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

@@ -1949,9 +1949,9 @@ func Symaddr(ctxt *Link, s *Symbol) int64 {
 	return s.Value
 }
 
-func (ctxt *Link) xdefine(p string, t int, v int64) {
+func (ctxt *Link) xdefine(p string, t obj.SymKind, v int64) {
 	s := Linklookup(ctxt, p, 0)
-	s.Type = int16(t)
+	s.Type = t
 	s.Value = v
 	s.Attr |= AttrReachable
 	s.Attr |= AttrSpecial

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

@@ -42,7 +42,7 @@ import (
 type Symbol struct {
 	Name        string
 	Extname     string
-	Type        int16
+	Type        obj.SymKind
 	Version     int16
 	Attr        Attribute
 	Localentry  uint8

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

@@ -254,7 +254,7 @@ func (r *objReader) readSym() {
 	if c, err := r.rd.ReadByte(); c != symPrefix || err != nil {
 		log.Fatalln("readSym out of sync")
 	}
-	t := r.readInt()
+	t := obj.SymKind(r.readInt())
 	s := r.readSymIndex()
 	flags := r.readInt()
 	dupok := flags&1 != 0
@@ -302,9 +302,9 @@ overwrite:
 		log.Fatalf("missing type for %s in %s", s.Name, r.pn)
 	}
 	if t == obj.SBSS && (s.Type == obj.SRODATA || s.Type == obj.SNOPTRBSS) {
-		t = int(s.Type)
+		t = s.Type
 	}
-	s.Type = int16(t)
+	s.Type = t
 	if s.Size < int64(size) {
 		s.Size = int64(size)
 	}

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

@@ -386,7 +386,7 @@ func (ctxt *Link) symtab() {
 		symtyperel = s
 	}
 
-	groupSym := func(name string, t int16) *Symbol {
+	groupSym := func(name string, t obj.SymKind) *Symbol {
 		s := Linklookup(ctxt, name, 0)
 		s.Type = t
 		s.Size = 0