loader.go

			continue
		}
		if s.Name != "" && s.Version >= 0 {
			syms.Add(s)
		} else {
			syms.Allsym = append(syms.Allsym, s)
		}
		if s.Version < 0 {
			s.Version = int16(anonVerReplacement)
		}
	}
}

// allocSym allocates a new symbol backing.
func (l *Loader) allocSym(name string, version int) *sym.Symbol {
	batch := l.symBatch
	if len(batch) == 0 {
		batch = make([]sym.Symbol, 1000)
	}
	s := &batch[0]
	l.symBatch = batch[1:]

	s.Dynid = -1
	s.Name = name
	s.Version = int16(version)

	return s
}

// installSym sets the underlying sym.Symbol for the specified sym index.
func (l *Loader) installSym(i Sym, s *sym.Symbol) {
	if s == nil {
		panic("installSym nil symbol")
	}
	if l.Syms[i] != nil {
		panic("sym already present in addNewSym")
	}
	if l.IsExternal(i) {
		// temporary sanity check: make sure that the payload
		// is empty, e.g. nobody has added symbol content already.
		pp := l.getPayload(i)
		if pp != nil && (len(pp.relocs) != 0 || len(pp.data) != 0) {
			panic("expected empty payload")
		}
	}
	l.Syms[i] = s
}

// addNewSym adds a new sym.Symbol to the i-th index in the list of symbols.
func (l *Loader) addNewSym(i Sym, name string, ver int, unit *sym.CompilationUnit, t sym.SymKind) *sym.Symbol {
	s := l.allocSym(name, ver)
	if s.Type != 0 && s.Type != sym.SXREF {
		fmt.Println("symbol already processed:", unit.Lib, i, s)
		panic("symbol already processed")
	}
	if t == sym.SBSS && (s.Type == sym.SRODATA || s.Type == sym.SNOPTRBSS) {
		t = s.Type
	}
	s.Type = t
	s.Unit = unit
	l.growSyms(int(i))
	l.installSym(i, s)
	return s
}

// loadObjSyms creates sym.Symbol objects for the live Syms in the
// object corresponding to object reader "r". Return value is the
// number of sym.Reloc entries required for all the new symbols.
func loadObjSyms(l *Loader, syms *sym.Symbols, r *oReader) int {
	istart := l.startIndex(r)
	nr := 0

	for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
		// If it's been previously loaded in host object loading, we don't need to do it again.
		if s := l.Syms[istart+Sym(i)]; s != nil {
			// Mark symbol as reachable as it wasn't marked as such before.
			s.Attr.Set(sym.AttrReachable, l.Reachable.Has(istart+Sym(i)))
			nr += r.NReloc(i)
			continue
		}
		osym := goobj2.Sym{}
		osym.Read(r.Reader, r.SymOff(i))
		name := strings.Replace(osym.Name, "\"\".", r.pkgprefix, -1)
		if name == "" {
			continue
		}
		ver := abiToVer(osym.ABI, r.version)
		if osym.ABI != goobj2.SymABIstatic && l.symsByName[ver][name] != istart+Sym(i) {
			continue
		}

		t := sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)]
		if t == sym.SXREF {
			log.Fatalf("bad sxref")
		}
		if t == 0 {
			log.Fatalf("missing type for %s in %s", name, r.unit.Lib)
		}
		if !l.Reachable.Has(istart+Sym(i)) && !(t == sym.SRODATA && strings.HasPrefix(name, "type.")) && name != "runtime.addmoduledata" && name != "runtime.lastmoduledatap" {
			// No need to load unreachable symbols.
			// XXX some type symbol's content may be needed in DWARF code, but they are not marked.
			// XXX reference to runtime.addmoduledata may be generated later by the linker in plugin mode.
			continue
		}

		s := l.addNewSym(istart+Sym(i), name, ver, r.unit, t)
		s.Attr.Set(sym.AttrReachable, l.Reachable.Has(istart+Sym(i)))
		nr += r.NReloc(i)
	}
	return nr
}

// funcInfoSym records the sym.Symbol for a function, along with a copy
// of the corresponding goobj2.Sym and the index of its FuncInfo aux sym.
// We use this to delay populating FuncInfo until we can batch-allocate
// slices for their sub-objects.
type funcInfoSym struct {
	s    *sym.Symbol // sym.Symbol for a live function
	osym goobj2.Sym  // object file symbol data for that function
	isym int         // global symbol index of FuncInfo aux sym for func
}

// funcAllocInfo records totals/counts for all functions in an objfile;
// used to help with bulk allocation of sym.Symbol sub-objects.
type funcAllocInfo struct {
	symPtr  uint32 // number of *sym.Symbol's needed in file slices
	inlCall uint32 // number of sym.InlinedCall's needed in inltree slices
	pcData  uint32 // number of sym.Pcdata's needed in pdata slices
	fdOff   uint32 // number of int64's needed in all Funcdataoff slices
}

// loadSymbol loads a single symbol by name.
// NB: This function does NOT set the symbol as reachable.
func (l *Loader) loadSymbol(name string, version int) *sym.Symbol {
	global := l.Lookup(name, version)

	// If we're already loaded, bail.
	if global != 0 && int(global) < len(l.Syms) && l.Syms[global] != nil {
		return l.Syms[global]
	}

	// Read the symbol.
	r, i := l.toLocal(global)
	istart := l.startIndex(r)

	osym := goobj2.Sym{}
	osym.Read(r.Reader, r.SymOff(int(i)))
	if l.symsByName[version][name] != istart+Sym(i) {
		return nil
	}

	return l.addNewSym(istart+Sym(i), name, version, r.unit, sym.AbiSymKindToSymKind[objabi.SymKind(osym.Type)])
}

// LookupOrCreate looks up a symbol by name, and creates one if not found.
// Either way, it will also create a sym.Symbol for it, if not already.
// This should only be called when interacting with parts of the linker
// that still works on sym.Symbols (i.e. internal cgo linking, for now).
func (l *Loader) LookupOrCreate(name string, version int) *sym.Symbol {
	i := l.Lookup(name, version)
	if i != 0 {
		// symbol exists
		if int(i) < len(l.Syms) && l.Syms[i] != nil {
			return l.Syms[i]
		}
		if l.IsExternal(i) {
			panic("Can't load an external symbol.")
		}
		return l.loadSymbol(name, version)
	}
	i = l.AddExtSym(name, version)
	s := l.allocSym(name, version)
	l.Syms[i] = s
	return s
}

// CreateExtSym creates a new external symbol with the specified name
// without adding it to any lookup tables, returning a Sym index for it.
func (l *Loader) CreateExtSym(name string) Sym {
	return l.newExtSym(name, sym.SymVerABI0)
}

// Create creates a symbol with the specified name, returning a
// sym.Symbol object for it. This method is intended for static/hidden
// symbols discovered while loading host objects. We can see more than
// one instance of a given static symbol with the same name/version,
// so we can't add them to the lookup tables "as is". Instead assign
// them fictitious (unique) versions, starting at -1 and decreasing by
// one for each newly created symbol, and record them in the
// extStaticSyms hash.
func (l *Loader) Create(name string) *sym.Symbol {
	i := l.max + 1
	l.max++
	if l.extStart == 0 {
		l.extStart = i
	}

	// Assign a new unique negative version -- this is to mark the
	// symbol so that it can be skipped when ExtractSymbols is adding
	// ext syms to the sym.Symbols hash.
	l.anonVersion--
	ver := l.anonVersion
	l.growSyms(int(i))
	s := l.allocSym(name, ver)
	l.installSym(i, s)
	l.extStaticSyms[nameVer{name, ver}] = i

	return s
}

func loadObjFull(l *Loader, r *oReader) {
	lib := r.unit.Lib
	istart := l.startIndex(r)

	resolveSymRef := func(s goobj2.SymRef) *sym.Symbol {
		i := l.resolve(r, s)
		return l.Syms[i]
	}

	funcs := []funcInfoSym{}
	fdsyms := []*sym.Symbol{}
	var funcAllocCounts funcAllocInfo
	pcdataBase := r.PcdataBase()
	rslice := []Reloc{}
	for i, n := 0, r.NSym()+r.NNonpkgdef(); i < n; i++ {
		osym := goobj2.Sym{}
		osym.Read(r.Reader, r.SymOff(i))
		name := strings.Replace(osym.Name, "\"\".", r.pkgprefix, -1)
		if name == "" {
			continue
		}
		ver := abiToVer(osym.ABI, r.version)
		dupok := osym.Dupok()
		if dupok {
			if dupsym := l.symsByName[ver][name]; dupsym != istart+Sym(i) {
				if l.Reachable.Has(dupsym) {
					// A dupok symbol is resolved to another package. We still need
					// to record its presence in the current package, as the trampoline
					// pass expects packages are laid out in dependency order.
					s := l.Syms[dupsym]
					if s.Type == sym.STEXT {
						lib.DupTextSyms = append(lib.DupTextSyms, s)
					}
				}
				continue
			}
		}

		s := l.Syms[istart+Sym(i)]
		if s == nil {
			continue
		}
		if s.Name != name { // Sanity check. We can remove it in the final version.
			fmt.Println("name mismatch:", lib, i, s.Name, name)
			panic("name mismatch")
		}

		local := osym.Local()
		makeTypelink := osym.Typelink()
		size := osym.Siz

		// Symbol data
		s.P = r.Data(i)
		s.Attr.Set(sym.AttrReadOnly, r.ReadOnly())

		// Relocs
		relocs := l.relocs(r, i)
		rslice = relocs.ReadAll(rslice)
		batch := l.relocBatch
		s.R = batch[:relocs.Count:relocs.Count]
		l.relocBatch = batch[relocs.Count:]
		for j := range s.R {
			r := rslice[j]
			rs := r.Sym
			sz := r.Size
			rt := r.Type
			if rt == objabi.R_METHODOFF {
				if l.Reachable.Has(rs) {
					rt = objabi.R_ADDROFF
				} else {
					sz = 0
					rs = 0
				}
			}
			if rt == objabi.R_WEAKADDROFF && !l.Reachable.Has(rs) {
				rs = 0
				sz = 0
			}
			if rs != 0 && l.Syms[rs] != nil && l.Syms[rs].Type == sym.SABIALIAS {
				rsrelocs := l.Relocs(rs)
				rs = rsrelocs.At(0).Sym
			}
			s.R[j] = sym.Reloc{
				Off:  r.Off,
				Siz:  sz,
				Type: rt,
				Add:  r.Add,
				Sym:  l.Syms[rs],
			}
		}

		// Aux symbol info
		isym := -1
		naux := r.NAux(i)
		for j := 0; j < naux; j++ {
			a := goobj2.Aux{}
			a.Read(r.Reader, r.AuxOff(i, j))
			switch a.Type {
			case goobj2.AuxGotype:
				typ := resolveSymRef(a.Sym)
				if typ != nil {
					s.Gotype = typ
				}
			case goobj2.AuxFuncdata:
				fdsyms = append(fdsyms, resolveSymRef(a.Sym))
			case goobj2.AuxFuncInfo:
				if a.Sym.PkgIdx != goobj2.PkgIdxSelf {
					panic("funcinfo symbol not defined in current package")
				}
				isym = int(a.Sym.SymIdx)
			case goobj2.AuxDwarfInfo, goobj2.AuxDwarfLoc, goobj2.AuxDwarfRanges, goobj2.AuxDwarfLines:
				// ignored for now
			default:
				panic("unknown aux type")
			}
		}

		s.File = r.pkgprefix[:len(r.pkgprefix)-1]
		if dupok {
			s.Attr |= sym.AttrDuplicateOK
		}
		if s.Size < int64(size) {
			s.Size = int64(size)
		}
		s.Attr.Set(sym.AttrLocal, local)
		s.Attr.Set(sym.AttrMakeTypelink, makeTypelink)

		if s.Type == sym.SDWARFINFO {
			// For DWARF symbols, replace `"".` to actual package prefix
			// in the symbol content.
			// TODO: maybe we should do this in the compiler and get rid
			// of this.
			patchDWARFName(s, r)
		}

		if s.Type != sym.STEXT {
			continue
		}

		if isym == -1 {
			continue
		}

		// Record function sym and associated info for additional
		// processing in the loop below.
		fwis := funcInfoSym{s: s, isym: isym, osym: osym}
		funcs = append(funcs, fwis)

		// Read the goobj2.FuncInfo for this text symbol so that we can
		// collect allocation counts. We'll read it again in the loop
		// below.
		b := r.Data(isym)
		info := goobj2.FuncInfo{}
		info.Read(b)
		funcAllocCounts.symPtr += uint32(len(info.File))
		funcAllocCounts.pcData += uint32(len(info.Pcdata))
		funcAllocCounts.inlCall += uint32(len(info.InlTree))
		funcAllocCounts.fdOff += uint32(len(info.Funcdataoff))
	}

	// At this point we can do batch allocation of the sym.FuncInfo's,
	// along with the slices of sub-objects they use.
	fiBatch := make([]sym.FuncInfo, len(funcs))
	inlCallBatch := make([]sym.InlinedCall, funcAllocCounts.inlCall)
	symPtrBatch := make([]*sym.Symbol, funcAllocCounts.symPtr)
	pcDataBatch := make([]sym.Pcdata, funcAllocCounts.pcData)
	fdOffBatch := make([]int64, funcAllocCounts.fdOff)

	// Populate FuncInfo contents for func symbols.
	for fi := 0; fi < len(funcs); fi++ {
		s := funcs[fi].s
		isym := funcs[fi].isym
		osym := funcs[fi].osym

		s.FuncInfo = &fiBatch[0]
		fiBatch = fiBatch[1:]

		b := r.Data(isym)
		info := goobj2.FuncInfo{}
		info.Read(b)

		if info.NoSplit != 0 {
			s.Attr |= sym.AttrNoSplit
		}
		if osym.ReflectMethod() {
			s.Attr |= sym.AttrReflectMethod
		}
		if r.Flags()&goobj2.ObjFlagShared != 0 {
			s.Attr |= sym.AttrShared
		}
		if osym.TopFrame() {
			s.Attr |= sym.AttrTopFrame
		}

		pc := s.FuncInfo

		if len(info.Funcdataoff) != 0 {
			nfd := len(info.Funcdataoff)
			pc.Funcdata = fdsyms[:nfd:nfd]
			fdsyms = fdsyms[nfd:]
		}

		info.Pcdata = append(info.Pcdata, info.PcdataEnd) // for the ease of knowing where it ends
		pc.Args = int32(info.Args)
		pc.Locals = int32(info.Locals)

		npc := len(info.Pcdata) - 1 // -1 as we appended one above
		pc.Pcdata = pcDataBatch[:npc:npc]
		pcDataBatch = pcDataBatch[npc:]

		nfd := len(info.Funcdataoff)
		pc.Funcdataoff = fdOffBatch[:nfd:nfd]
		fdOffBatch = fdOffBatch[nfd:]

		nsp := len(info.File)
		pc.File = symPtrBatch[:nsp:nsp]
		symPtrBatch = symPtrBatch[nsp:]

		nic := len(info.InlTree)
		pc.InlTree = inlCallBatch[:nic:nic]
		inlCallBatch = inlCallBatch[nic:]

		pc.Pcsp.P = r.BytesAt(pcdataBase+info.Pcsp, int(info.Pcfile-info.Pcsp))
		pc.Pcfile.P = r.BytesAt(pcdataBase+info.Pcfile, int(info.Pcline-info.Pcfile))
		pc.Pcline.P = r.BytesAt(pcdataBase+info.Pcline, int(info.Pcinline-info.Pcline))
		pc.Pcinline.P = r.BytesAt(pcdataBase+info.Pcinline, int(info.Pcdata[0]-info.Pcinline))
		for k := range pc.Pcdata {
			pc.Pcdata[k].P = r.BytesAt(pcdataBase+info.Pcdata[k], int(info.Pcdata[k+1]-info.Pcdata[k]))
		}
		for k := range pc.Funcdataoff {
			pc.Funcdataoff[k] = int64(info.Funcdataoff[k])
		}
		for k := range pc.File {
			pc.File[k] = resolveSymRef(info.File[k])
		}
		for k := range pc.InlTree {
			inl := &info.InlTree[k]
			pc.InlTree[k] = sym.InlinedCall{
				Parent:   inl.Parent,
				File:     resolveSymRef(inl.File),
				Line:     inl.Line,
				Func:     l.SymName(l.resolve(r, inl.Func)),
				ParentPC: inl.ParentPC,
			}
		}

		dupok := osym.Dupok()
		if !dupok {
			if s.Attr.OnList() {
				log.Fatalf("symbol %s listed multiple times", s.Name)
			}
			s.Attr.Set(sym.AttrOnList, true)
			lib.Textp = append(lib.Textp, s)
		} else {
			// there may be a dup in another package
			// put into a temp list and add to text later
			lib.DupTextSyms = append(lib.DupTextSyms, s)
		}
	}
}

var emptyPkg = []byte(`"".`)

func patchDWARFName1(p []byte, r *oReader) ([]byte, int) {
	// This is kind of ugly. Really the package name should not
	// even be included here.
	if len(p) < 1 || p[0] != dwarf.DW_ABRV_FUNCTION {
		return p, -1
	}
	e := bytes.IndexByte(p, 0)
	if e == -1 {
		return p, -1
	}
	if !bytes.Contains(p[:e], emptyPkg) {
		return p, -1
	}
	pkgprefix := []byte(r.pkgprefix)
	patched := bytes.Replace(p[:e], emptyPkg, pkgprefix, -1)
	return append(patched, p[e:]...), e
}

func patchDWARFName(s *sym.Symbol, r *oReader) {
	patched, e := patchDWARFName1(s.P, r)
	if e == -1 {
		return
	}
	s.P = patched
	s.Attr.Set(sym.AttrReadOnly, false)
	delta := int64(len(s.P)) - s.Size
	s.Size = int64(len(s.P))
	for i := range s.R {
		r := &s.R[i]
		if r.Off > int32(e) {
			r.Off += int32(delta)
		}
	}
}

// For debugging.
func (l *Loader) Dump() {
	fmt.Println("objs")
	for _, obj := range l.objs {
		if obj.r != nil {
			fmt.Println(obj.i, obj.r.unit.Lib)
		}
	}
	fmt.Println("extStart:", l.extStart)
	fmt.Println("syms")
	for i, s := range l.Syms {
		if i == 0 {
			continue
		}
		if s != nil {
			fmt.Println(i, s, s.Type)
		} else {
			fmt.Println(i, l.SymName(Sym(i)), "<not loaded>")
		}
	}
	fmt.Println("overwrite:", l.overwrite)
	fmt.Println("symsByName")
	for name, i := range l.symsByName[0] {
		fmt.Println(i, name, 0)
	}
	for name, i := range l.symsByName[1] {
		fmt.Println(i, name, 1)
	}
}