cmd/link: don't generate .gosymtab section

Since Go 1.2 the section is always empty.

Also remove the code looking for .gosymtab in cmd/internal/objfile.

For #76038

Change-Id: Icd34c870ed0c6da8001e8d32305f79905ee2b066
Reviewed-on: https://go-review.googlesource.com/c/go/+/717200
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Commit-Queue: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>

Author: ianlancetaylor

src/cmd/internal/objfile/elf.go

@@ -64,40 +64,26 @@ func (f *elfFile) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *elfFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *elfFile) pcln() (textStart uint64, pclntab []byte, err error) {
 	if sect := f.elf.Section(".text"); sect != nil {
 		textStart = sect.Addr
 	}
 
-	sect := f.elf.Section(".gosymtab")
-	if sect == nil {
-		// try .data.rel.ro.gosymtab, for PIE binaries
-		sect = f.elf.Section(".data.rel.ro.gosymtab")
-	}
-	if sect != nil {
-		if symtab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
-		}
-	} else {
-		// if both sections failed, try the symbol
-		symtab = f.symbolData("runtime.symtab", "runtime.esymtab")
-	}
-
-	sect = f.elf.Section(".gopclntab")
+	sect := f.elf.Section(".gopclntab")
 	if sect == nil {
 		// try .data.rel.ro.gopclntab, for PIE binaries
 		sect = f.elf.Section(".data.rel.ro.gopclntab")
 	}
 	if sect != nil {
 		if pclntab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
+			return 0, nil, err
 		}
 	} else {
 		// if both sections failed, try the symbol
 		pclntab = f.symbolData("runtime.pclntab", "runtime.epclntab")
 	}
 
-	return textStart, symtab, pclntab, nil
+	return textStart, pclntab, nil
 }
 
 func (f *elfFile) text() (textStart uint64, text []byte, err error) {

src/cmd/internal/objfile/goobj.go

@@ -221,10 +221,10 @@ func (f *goobjFile) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *goobjFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *goobjFile) pcln() (textStart uint64, pclntab []byte, err error) {
 	// Should never be called. We implement Liner below, callers
 	// should use that instead.
-	return 0, nil, nil, fmt.Errorf("pcln not available in go object file")
+	return 0, nil, fmt.Errorf("pcln not available in go object file")
 }
 
 // PCToLine returns the file name, line, and function data for the given pc.

src/cmd/internal/objfile/macho.go

@@ -79,21 +79,16 @@ func (f *machoFile) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *machoFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *machoFile) pcln() (textStart uint64, pclntab []byte, err error) {
 	if sect := f.macho.Section("__text"); sect != nil {
 		textStart = sect.Addr
 	}
-	if sect := f.macho.Section("__gosymtab"); sect != nil {
-		if symtab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
-		}
-	}
 	if sect := f.macho.Section("__gopclntab"); sect != nil {
 		if pclntab, err = sect.Data(); err != nil {
-			return 0, nil, nil, err
+			return 0, nil, err
 		}
 	}
-	return textStart, symtab, pclntab, nil
+	return textStart, pclntab, nil
 }
 
 func (f *machoFile) text() (textStart uint64, text []byte, err error) {

src/cmd/internal/objfile/objfile.go

@@ -18,7 +18,7 @@ import (
 
 type rawFile interface {
 	symbols() (syms []Sym, err error)
-	pcln() (textStart uint64, symtab, pclntab []byte, err error)
+	pcln() (textStart uint64, pclntab []byte, err error)
 	text() (textStart uint64, text []byte, err error)
 	goarch() string
 	loadAddress() (uint64, error)
@@ -141,7 +141,7 @@ func (e *Entry) PCLineTable() (Liner, error) {
 		return pcln, nil
 	}
 	// Otherwise, read the pcln tables and build a Liner out of that.
-	textStart, symtab, pclntab, err := e.raw.pcln()
+	textStart, pclntab, err := e.raw.pcln()
 	if err != nil {
 		return nil, err
 	}
@@ -154,7 +154,7 @@ func (e *Entry) PCLineTable() (Liner, error) {
 			}
 		}
 	}
-	return gosym.NewTable(symtab, gosym.NewLineTable(pclntab, textStart))
+	return gosym.NewTable(nil, gosym.NewLineTable(pclntab, textStart))
 }
 
 func (e *Entry) Text() (uint64, []byte, error) {

src/cmd/internal/objfile/pe.go

@@ -90,10 +90,10 @@ func (f *peFile) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *peFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *peFile) pcln() (textStart uint64, pclntab []byte, err error) {
 	imageBase, err := f.imageBase()
 	if err != nil {
-		return 0, nil, nil, err
+		return 0, nil, err
 	}
 
 	if sect := f.pe.Section(".text"); sect != nil {
@@ -104,17 +104,10 @@ func (f *peFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
 		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
 		var err2 error
 		if pclntab, err2 = loadPETable(f.pe, "pclntab", "epclntab"); err2 != nil {
-			return 0, nil, nil, err
-		}
-	}
-	if symtab, err = loadPETable(f.pe, "runtime.symtab", "runtime.esymtab"); err != nil {
-		// Same as above.
-		var err2 error
-		if symtab, err2 = loadPETable(f.pe, "symtab", "esymtab"); err2 != nil {
-			return 0, nil, nil, err
+			return 0, nil, err
 		}
 	}
-	return textStart, symtab, pclntab, nil
+	return textStart, pclntab, nil
 }
 
 func (f *peFile) text() (textStart uint64, text []byte, err error) {

src/cmd/internal/objfile/plan9obj.go

@@ -71,24 +71,17 @@ func (f *plan9File) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *plan9File) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *plan9File) pcln() (textStart uint64, pclntab []byte, err error) {
 	textStart = f.plan9.LoadAddress + f.plan9.HdrSize
 	if pclntab, err = loadPlan9Table(f.plan9, "runtime.pclntab", "runtime.epclntab"); err != nil {
 		// We didn't find the symbols, so look for the names used in 1.3 and earlier.
 		// TODO: Remove code looking for the old symbols when we no longer care about 1.3.
 		var err2 error
 		if pclntab, err2 = loadPlan9Table(f.plan9, "pclntab", "epclntab"); err2 != nil {
-			return 0, nil, nil, err
+			return 0, nil, err
 		}
 	}
-	if symtab, err = loadPlan9Table(f.plan9, "runtime.symtab", "runtime.esymtab"); err != nil {
-		// Same as above.
-		var err2 error
-		if symtab, err2 = loadPlan9Table(f.plan9, "symtab", "esymtab"); err2 != nil {
-			return 0, nil, nil, err
-		}
-	}
-	return textStart, symtab, pclntab, nil
+	return textStart, pclntab, nil
 }
 
 func (f *plan9File) text() (textStart uint64, text []byte, err error) {

src/cmd/internal/objfile/xcoff.go

@@ -87,15 +87,14 @@ func (f *xcoffFile) symbols() ([]Sym, error) {
 	return syms, nil
 }
 
-func (f *xcoffFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
+func (f *xcoffFile) pcln() (textStart uint64, pclntab []byte, err error) {
 	if sect := f.xcoff.Section(".text"); sect != nil {
 		textStart = sect.VirtualAddress
 	}
 	if pclntab, err = loadXCOFFTable(f.xcoff, "runtime.pclntab", "runtime.epclntab"); err != nil {
-		return 0, nil, nil, err
+		return 0, nil, err
 	}
-	symtab, _ = loadXCOFFTable(f.xcoff, "runtime.symtab", "runtime.esymtab") // ignore error, this symbol is not useful anyway
-	return textStart, symtab, pclntab, nil
+	return textStart, pclntab, nil
 }
 
 func (f *xcoffFile) text() (textStart uint64, text []byte, err error) {

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

@@ -2238,11 +2238,6 @@ func (state *dodataState) allocateDataSections(ctxt *Link) {
 	state.checkdatsize(sym.SITABLINK)
 	sect.Length = uint64(state.datsize) - sect.Vaddr
 
-	/* gosymtab */
-	sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gosymtab"), sym.SSYMTAB, sym.SRODATA, relroSecPerm)
-	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.symtab", 0), sect)
-	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.esymtab", 0), sect)
-
 	/* gopclntab */
 	sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gopclntab"), sym.SPCLNTAB, sym.SRODATA, relroSecPerm)
 	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect)
@@ -2985,7 +2980,6 @@ func (ctxt *Link) address() []*sym.Segment {
 	ldr := ctxt.loader
 	var (
 		rodata  = ldr.SymSect(ldr.LookupOrCreateSym("runtime.rodata", 0))
-		symtab  = ldr.SymSect(ldr.LookupOrCreateSym("runtime.symtab", 0))
 		pclntab = ldr.SymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0))
 		types   = ldr.SymSect(ldr.LookupOrCreateSym("runtime.types", 0))
 	)
@@ -3065,8 +3059,6 @@ func (ctxt *Link) address() []*sym.Segment {
 	ctxt.xdefine("runtime.egcbss", sym.SRODATA, ldr.SymAddr(s)+ldr.SymSize(s))
 	ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.egcbss", 0), ldr.SymSect(s))
 
-	ctxt.xdefine("runtime.symtab", sym.SRODATA, int64(symtab.Vaddr))
-	ctxt.xdefine("runtime.esymtab", sym.SRODATA, int64(symtab.Vaddr+symtab.Length))
 	ctxt.xdefine("runtime.pclntab", sym.SRODATA, int64(pclntab.Vaddr))
 	ctxt.defineInternal("runtime.pcheader", sym.SRODATA)
 	ctxt.defineInternal("runtime.funcnametab", sym.SRODATA)

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

@@ -1477,7 +1477,6 @@ func (ctxt *Link) doelf() {
 	}
 	shstrtabAddstring(relro_prefix + ".typelink")
 	shstrtabAddstring(relro_prefix + ".itablink")
-	shstrtabAddstring(relro_prefix + ".gosymtab")
 	shstrtabAddstring(relro_prefix + ".gopclntab")
 
 	if ctxt.IsExternal() {
@@ -1487,7 +1486,6 @@ func (ctxt *Link) doelf() {
 		shstrtabAddstring(elfRelType + ".rodata")
 		shstrtabAddstring(elfRelType + relro_prefix + ".typelink")
 		shstrtabAddstring(elfRelType + relro_prefix + ".itablink")
-		shstrtabAddstring(elfRelType + relro_prefix + ".gosymtab")
 		shstrtabAddstring(elfRelType + relro_prefix + ".gopclntab")
 		shstrtabAddstring(elfRelType + ".noptrdata")
 		shstrtabAddstring(elfRelType + ".data")

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

@@ -37,7 +37,7 @@ func TestMachoSectionsReadOnly(t *testing.T) {
 			args:             []string{"-ldflags", "-linkmode=internal"},
 			prog:             prog,
 			mustInternalLink: true,
-			wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink", "__gosymtab", "__gopclntab"},
+			wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink", "__gopclntab"},
 		},
 		{
 			name:        "linkmode-external",