cmd/oldlink: port bug fixes to old linker

This CL ports CL 234105 and CL 240621 to the old linker, which
fix critical bugs (runtime crashes).

Updates #39049.
Updates #39927.

Change-Id: I47afc84349119e320d2e60d64b7188a410835d2b
Reviewed-on: https://go-review.googlesource.com/c/go/+/241087
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Than McIntosh <[email protected]>
Reviewed-by: Jeremy Faller <[email protected]>

src/cmd/oldlink/internal/arm/asm.go

@@ -390,8 +390,12 @@ func trampoline(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol) {
 			offset := (signext24(r.Add&0xffffff) + 2) * 4
 			var tramp *sym.Symbol
 			for i := 0; ; i++ {
-				name := r.Sym.Name + fmt.Sprintf("%+d-tramp%d", offset, i)
+				oName := r.Sym.Name
+				name := oName + fmt.Sprintf("%+d-tramp%d", offset, i)
 				tramp = ctxt.Syms.Lookup(name, int(r.Sym.Version))
+				if oName == "runtime.deferreturn" {
+					tramp.Attr.Set(sym.AttrDeferReturnTramp, true)
+				}
 				if tramp.Type == sym.SDYNIMPORT {
 					// don't reuse trampoline defined in other module
 					continue

src/cmd/oldlink/internal/ld/decodesym.go

@@ -11,6 +11,7 @@ import (
 	"cmd/oldlink/internal/sym"
 	"debug/elf"
 	"fmt"
+	"log"
 )
 
 // Decoding the type.* symbols.	 This has to be in sync with
@@ -93,7 +94,7 @@ func decodetypeHasUncommon(arch *sys.Arch, p []byte) bool {
 func findShlibSection(ctxt *Link, path string, addr uint64) *elf.Section {
 	for _, shlib := range ctxt.Shlibs {
 		if shlib.Path == path {
-			for _, sect := range shlib.File.Sections {
+			for _, sect := range shlib.File.Sections[1:] { // skip the NULL section
 				if sect.Addr <= addr && addr <= sect.Addr+sect.Size {
 					return sect
 				}
@@ -112,9 +113,15 @@ func decodetypeGcprog(ctxt *Link, s *sym.Symbol) []byte {
 			// A gcprog is a 4-byte uint32 indicating length, followed by
 			// the actual program.
 			progsize := make([]byte, 4)
-			sect.ReadAt(progsize, int64(addr-sect.Addr))
+			_, err := sect.ReadAt(progsize, int64(addr-sect.Addr))
+			if err != nil {
+				log.Fatal(err)
+			}
 			progbytes := make([]byte, ctxt.Arch.ByteOrder.Uint32(progsize))
-			sect.ReadAt(progbytes, int64(addr-sect.Addr+4))
+			_, err = sect.ReadAt(progbytes, int64(addr-sect.Addr+4))
+			if err != nil {
+				log.Fatal(err)
+			}
 			return append(progsize, progbytes...)
 		}
 		Exitf("cannot find gcprog for %s", s.Name)
@@ -124,14 +131,6 @@ func decodetypeGcprog(ctxt *Link, s *sym.Symbol) []byte {
 }
 
 func decodetypeGcprogShlib(ctxt *Link, s *sym.Symbol) uint64 {
-	if ctxt.Arch.Family == sys.ARM64 {
-		for _, shlib := range ctxt.Shlibs {
-			if shlib.Path == s.File {
-				return shlib.gcdataAddresses[s]
-			}
-		}
-		return 0
-	}
 	return decodeInuxi(ctxt.Arch, s.P[2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize):], ctxt.Arch.PtrSize)
 }
 
@@ -141,8 +140,15 @@ func decodetypeGcmask(ctxt *Link, s *sym.Symbol) []byte {
 		ptrdata := decodetypePtrdata(ctxt.Arch, s.P)
 		sect := findShlibSection(ctxt, s.File, addr)
 		if sect != nil {
-			r := make([]byte, ptrdata/int64(ctxt.Arch.PtrSize))
-			sect.ReadAt(r, int64(addr-sect.Addr))
+			bits := ptrdata / int64(ctxt.Arch.PtrSize)
+			r := make([]byte, (bits+7)/8)
+			// ldshlibsyms avoids closing the ELF file so sect.ReadAt works.
+			// If we remove this read (and the ones in decodetypeGcprog), we
+			// can close the file.
+			_, err := sect.ReadAt(r, int64(addr-sect.Addr))
+			if err != nil {
+				log.Fatal(err)
+			}
 			return r
 		}
 		Exitf("cannot find gcmask for %s", s.Name)

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

@@ -2010,7 +2010,9 @@ func ldshlibsyms(ctxt *Link, shlib string) {
 		Errorf(nil, "cannot open shared library: %s", libpath)
 		return
 	}
-	defer f.Close()
+	// Keep the file open as decodetypeGcprog needs to read from it.
+	// TODO: fix. Maybe mmap the file.
+	//defer f.Close()
 
 	hash, err := readnote(f, ELF_NOTE_GO_NAME, ELF_NOTE_GOABIHASH_TAG)
 	if err != nil {

src/cmd/oldlink/internal/ld/pcln.go

@@ -276,7 +276,7 @@ func (ctxt *Link) pclntab() {
 				// set the resumption point to PC_B.
 				lastWasmAddr = uint32(r.Add)
 			}
-			if r.Type.IsDirectCall() && r.Sym != nil && r.Sym.Name == "runtime.deferreturn" {
+			if r.Type.IsDirectCall() && r.Sym != nil && (r.Sym.Name == "runtime.deferreturn" || r.Sym.Attr.DeferReturnTramp()) {
 				if ctxt.Arch.Family == sys.Wasm {
 					deferreturn = lastWasmAddr - 1
 				} else {

src/cmd/oldlink/internal/ppc64/asm.go

@@ -667,7 +667,8 @@ func trampoline(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol) {
 				// target is at some offset within the function.  Calls to duff+8 and duff+256 must appear as
 				// distinct trampolines.
 
-				name := r.Sym.Name
+				oName := r.Sym.Name
+				name := oName
 				if r.Add == 0 {
 					name = name + fmt.Sprintf("-tramp%d", i)
 				} else {
@@ -677,6 +678,9 @@ func trampoline(ctxt *ld.Link, r *sym.Reloc, s *sym.Symbol) {
 				// Look up the trampoline in case it already exists
 
 				tramp = ctxt.Syms.Lookup(name, int(r.Sym.Version))
+				if oName == "runtime.deferreturn" {
+					tramp.Attr.Set(sym.AttrDeferReturnTramp, true)
+				}
 				if tramp.Value == 0 {
 					break
 				}

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

@@ -81,7 +81,10 @@ const (
 	// AttrReadOnly indicates whether the symbol's content (Symbol.P) is backed by
 	// read-only memory.
 	AttrReadOnly
-	// 19 attributes defined so far.
+	// AttrDeferReturnTramp indicates the symbol is a trampoline of a deferreturn
+	// call.
+	AttrDeferReturnTramp
+	// 20 attributes defined so far.
 )
 
 func (a Attribute) DuplicateOK() bool      { return a&AttrDuplicateOK != 0 }
@@ -103,6 +106,7 @@ func (a Attribute) SubSymbol() bool        { return a&AttrSubSymbol != 0 }
 func (a Attribute) Container() bool        { return a&AttrContainer != 0 }
 func (a Attribute) TopFrame() bool         { return a&AttrTopFrame != 0 }
 func (a Attribute) ReadOnly() bool         { return a&AttrReadOnly != 0 }
+func (a Attribute) DeferReturnTramp() bool { return a&AttrDeferReturnTramp != 0 }
 
 func (a Attribute) CgoExport() bool {
 	return a.CgoExportDynamic() || a.CgoExportStatic()