cmd/link: add all pe section names to pe symbol table

dwarf relocations refer to dwarf section symbols, so dwarf
section symbols must be present in pe symbol table before we
write dwarf relocations.

.ctors pe section already refer to .text symbol.

Write all pe section name symbols into symbol table, so we
can use them whenever we need them.

This CL also simplified some code.

For #10776.

Change-Id: I9b8c680ea75904af90c797a06bbb1f4df19e34b6
Reviewed-on: https://go-review.googlesource.com/36978Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

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

@@ -2033,9 +2033,6 @@ func (ctxt *Link) textaddress() {
 		ctxt.Textp[0] = text
 	}
 
-	if Headtype == obj.Hwindows || Headtype == obj.Hwindowsgui {
-		ctxt.Syms.Lookup(".text", 0).Sect = sect
-	}
 	va := uint64(*FlagTextAddr)
 	n := 1
 	sect.Vaddr = va
@@ -2295,9 +2292,6 @@ func (ctxt *Link) address() {
 
 	ctxt.xdefine("runtime.text", obj.STEXT, int64(text.Vaddr))
 	ctxt.xdefine("runtime.etext", obj.STEXT, int64(lasttext.Vaddr+lasttext.Length))
-	if Headtype == obj.Hwindows || Headtype == obj.Hwindowsgui {
-		ctxt.xdefine(".text", obj.STEXT, int64(text.Vaddr))
-	}
 
 	// If there are multiple text sections, create runtime.text.n for
 	// their section Vaddr, using n for index

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

@@ -18,6 +18,7 @@ import (
 )
 
 const (
+	// TODO: the Microsoft doco says IMAGE_SYM_DTYPE_ARRAY is 3 (same with IMAGE_SYM_DTYPE_POINTER and IMAGE_SYM_DTYPE_FUNCTION)
 	IMAGE_SYM_UNDEFINED              = 0
 	IMAGE_SYM_ABSOLUTE               = -1
 	IMAGE_SYM_DEBUG                  = -2

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

@@ -964,6 +964,25 @@ func newPEDWARFSection(ctxt *Link, name string, size int64) *IMAGE_SECTION_HEADE
 func writePESymTableRecords(ctxt *Link) int {
 	var symcnt int
 
+	writeOneSymbol := func(s *Symbol, addr int64, sectidx int, typ uint16, class uint8) {
+		// write COFF symbol table record
+		if len(s.Name) > 8 {
+			Lputl(0)
+			Lputl(uint32(strtbladd(s.Name)))
+		} else {
+			strnput(s.Name, 8)
+		}
+		Lputl(uint32(addr))
+		Wputl(uint16(sectidx))
+		Wputl(typ)
+		Cput(class)
+		Cput(0) // no aux entries
+
+		s.Dynid = int32(symcnt)
+
+		symcnt++
+	}
+
 	put := func(ctxt *Link, s *Symbol, name string, type_ SymbolType, addr int64, gotype *Symbol) {
 		if s == nil {
 			return
@@ -978,16 +997,13 @@ func writePESymTableRecords(ctxt *Link) int {
 		}
 
 		// Only windows/386 requires underscore prefix on external symbols.
-		// Include .text symbol as external, because .ctors section relocations refer to it.
 		if SysArch.Family == sys.I386 &&
 			Linkmode == LinkExternal &&
-			(s.Type == obj.SHOSTOBJ ||
-				s.Attr.CgoExport() ||
-				s.Name == ".text") {
+			(s.Type == obj.SHOSTOBJ || s.Attr.CgoExport()) {
 			s.Name = "_" + s.Name
 		}
 
-		var typ uint16
+		typ := uint16(IMAGE_SYM_TYPE_NULL)
 		var sect int
 		var value int64
 		// Note: although address of runtime.edata (type SDATA) is at the start of .bss section
@@ -1008,35 +1024,21 @@ func writePESymTableRecords(ctxt *Link) int {
 		} else {
 			Errorf(s, "addpesym %#x", addr)
 		}
-
-		// write COFF symbol table record
-		if len(s.Name) > 8 {
-			Lputl(0)
-			Lputl(uint32(strtbladd(s.Name)))
-		} else {
-			strnput(s.Name, 8)
-		}
-		Lputl(uint32(value))
-		Wputl(uint16(sect))
-		if typ != 0 {
-			Wputl(typ)
-		} else if Linkmode == LinkExternal {
-			Wputl(0)
-		} else {
-			Wputl(0x0308) // "array of structs"
+		if typ != IMAGE_SYM_TYPE_NULL {
+		} else if Linkmode != LinkExternal {
+			// TODO: fix IMAGE_SYM_DTYPE_ARRAY value and use following expression, instead of 0x0308
+			typ = IMAGE_SYM_DTYPE_ARRAY<<8 + IMAGE_SYM_TYPE_STRUCT
+			typ = 0x0308 // "array of structs"
 		}
-		Cput(2) // storage class: external
-		Cput(0) // no aux entries
-
-		s.Dynid = int32(symcnt)
-
-		symcnt++
+		writeOneSymbol(s, value, sect, typ, IMAGE_SYM_CLASS_EXTERNAL)
 	}
 
 	if Linkmode == LinkExternal {
-		s := ctxt.Syms.Lookup(".text", 0)
-		if s.Type == obj.STEXT {
-			put(ctxt, s, s.Name, TextSym, s.Value, nil)
+		// Include section symbols as external, because
+		// .ctors and .debug_* section relocations refer to it.
+		for idx, name := range shNames {
+			sym := ctxt.Syms.Lookup(name, 0)
+			writeOneSymbol(sym, 0, idx+1, IMAGE_SYM_TYPE_NULL, IMAGE_SYM_CLASS_STATIC)
 		}
 	}