1 files changed, 293 insertions, 0 deletions
diff --git a/src/cmd/link/internal/ld/decodesym.go b/src/cmd/link/internal/ld/decodesym.go
new file mode 100644
index 0000000..fc179fc
--- /dev/null
+++ b/src/cmd/link/internal/ld/decodesym.go
@@ -0,0 +1,293 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ld
+
+import (
+	"cmd/internal/objabi"
+	"cmd/internal/sys"
+	"cmd/link/internal/loader"
+	"cmd/link/internal/sym"
+	"debug/elf"
+	"log"
+)
+
+// Decoding the type.* symbols.	 This has to be in sync with
+// ../../runtime/type.go, or more specifically, with what
+// cmd/compile/internal/gc/reflect.go stuffs in these.
+
+// tflag is documented in reflect/type.go.
+//
+// tflag values must be kept in sync with copies in:
+//	cmd/compile/internal/gc/reflect.go
+//	cmd/link/internal/ld/decodesym.go
+//	reflect/type.go
+//	runtime/type.go
+const (
+	tflagUncommon  = 1 << 0
+	tflagExtraStar = 1 << 1
+)
+
+func decodeInuxi(arch *sys.Arch, p []byte, sz int) uint64 {
+	switch sz {
+	case 2:
+		return uint64(arch.ByteOrder.Uint16(p))
+	case 4:
+		return uint64(arch.ByteOrder.Uint32(p))
+	case 8:
+		return arch.ByteOrder.Uint64(p)
+	default:
+		Exitf("dwarf: decode inuxi %d", sz)
+		panic("unreachable")
+	}
+}
+
+func commonsize(arch *sys.Arch) int      { return 4*arch.PtrSize + 8 + 8 } // runtime._type
+func structfieldSize(arch *sys.Arch) int { return 3 * arch.PtrSize }       // runtime.structfield
+func uncommonSize() int                  { return 4 + 2 + 2 + 4 + 4 }      // runtime.uncommontype
+
+// Type.commonType.kind
+func decodetypeKind(arch *sys.Arch, p []byte) uint8 {
+	return p[2*arch.PtrSize+7] & objabi.KindMask //  0x13 / 0x1f
+}
+
+// Type.commonType.kind
+func decodetypeUsegcprog(arch *sys.Arch, p []byte) uint8 {
+	return p[2*arch.PtrSize+7] & objabi.KindGCProg //  0x13 / 0x1f
+}
+
+// Type.commonType.size
+func decodetypeSize(arch *sys.Arch, p []byte) int64 {
+	return int64(decodeInuxi(arch, p, arch.PtrSize)) // 0x8 / 0x10
+}
+
+// Type.commonType.ptrdata
+func decodetypePtrdata(arch *sys.Arch, p []byte) int64 {
+	return int64(decodeInuxi(arch, p[arch.PtrSize:], arch.PtrSize)) // 0x8 / 0x10
+}
+
+// Type.commonType.tflag
+func decodetypeHasUncommon(arch *sys.Arch, p []byte) bool {
+	return p[2*arch.PtrSize+4]&tflagUncommon != 0
+}
+
+// Type.FuncType.dotdotdot
+func decodetypeFuncDotdotdot(arch *sys.Arch, p []byte) bool {
+	return uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2))&(1<<15) != 0
+}
+
+// Type.FuncType.inCount
+func decodetypeFuncInCount(arch *sys.Arch, p []byte) int {
+	return int(decodeInuxi(arch, p[commonsize(arch):], 2))
+}
+
+func decodetypeFuncOutCount(arch *sys.Arch, p []byte) int {
+	return int(uint16(decodeInuxi(arch, p[commonsize(arch)+2:], 2)) & (1<<15 - 1))
+}
+
+// InterfaceType.methods.length
+func decodetypeIfaceMethodCount(arch *sys.Arch, p []byte) int64 {
+	return int64(decodeInuxi(arch, p[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
+}
+
+// Matches runtime/typekind.go and reflect.Kind.
+const (
+	kindArray     = 17
+	kindChan      = 18
+	kindFunc      = 19
+	kindInterface = 20
+	kindMap       = 21
+	kindPtr       = 22
+	kindSlice     = 23
+	kindStruct    = 25
+	kindMask      = (1 << 5) - 1
+)
+
+func decodeReloc(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Reloc {
+	for j := 0; j < relocs.Count(); j++ {
+		rel := relocs.At(j)
+		if rel.Off() == off {
+			return rel
+		}
+	}
+	return loader.Reloc{}
+}
+
+func decodeRelocSym(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int32) loader.Sym {
+	return decodeReloc(ldr, symIdx, relocs, off).Sym()
+}
+
+// decodetypeName decodes the name from a reflect.name.
+func decodetypeName(ldr *loader.Loader, symIdx loader.Sym, relocs *loader.Relocs, off int) string {
+	r := decodeRelocSym(ldr, symIdx, relocs, int32(off))
+	if r == 0 {
+		return ""
+	}
+
+	data := ldr.Data(r)
+	namelen := int(uint16(data[1])<<8 | uint16(data[2]))
+	return string(data[3 : 3+namelen])
+}
+
+func decodetypeFuncInType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
+	uadd := commonsize(arch) + 4
+	if arch.PtrSize == 8 {
+		uadd += 4
+	}
+	if decodetypeHasUncommon(arch, ldr.Data(symIdx)) {
+		uadd += uncommonSize()
+	}
+	return decodeRelocSym(ldr, symIdx, relocs, int32(uadd+i*arch.PtrSize))
+}
+
+func decodetypeFuncOutType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, relocs *loader.Relocs, i int) loader.Sym {
+	return decodetypeFuncInType(ldr, arch, symIdx, relocs, i+decodetypeFuncInCount(arch, ldr.Data(symIdx)))
+}
+
+func decodetypeArrayElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) // 0x1c / 0x30
+}
+
+func decodetypeArrayLen(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) int64 {
+	data := ldr.Data(symIdx)
+	return int64(decodeInuxi(arch, data[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
+}
+
+func decodetypeChanElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) // 0x1c / 0x30
+}
+
+func decodetypeMapKey(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) // 0x1c / 0x30
+}
+
+func decodetypeMapValue(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))+int32(arch.PtrSize)) // 0x20 / 0x38
+}
+
+func decodetypePtrElem(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) loader.Sym {
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(commonsize(arch))) // 0x1c / 0x30
+}
+
+func decodetypeStructFieldCount(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) int {
+	data := ldr.Data(symIdx)
+	return int(decodeInuxi(arch, data[commonsize(arch)+2*arch.PtrSize:], arch.PtrSize))
+}
+
+func decodetypeStructFieldArrayOff(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) int {
+	data := ldr.Data(symIdx)
+	off := commonsize(arch) + 4*arch.PtrSize
+	if decodetypeHasUncommon(arch, data) {
+		off += uncommonSize()
+	}
+	off += i * structfieldSize(arch)
+	return off
+}
+
+func decodetypeStructFieldName(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) string {
+	off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
+	relocs := ldr.Relocs(symIdx)
+	return decodetypeName(ldr, symIdx, &relocs, off)
+}
+
+func decodetypeStructFieldType(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) loader.Sym {
+	off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
+	relocs := ldr.Relocs(symIdx)
+	return decodeRelocSym(ldr, symIdx, &relocs, int32(off+arch.PtrSize))
+}
+
+func decodetypeStructFieldOffsAnon(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym, i int) int64 {
+	off := decodetypeStructFieldArrayOff(ldr, arch, symIdx, i)
+	data := ldr.Data(symIdx)
+	return int64(decodeInuxi(arch, data[off+2*arch.PtrSize:], arch.PtrSize))
+}
+
+// decodetypeStr returns the contents of an rtype's str field (a nameOff).
+func decodetypeStr(ldr *loader.Loader, arch *sys.Arch, symIdx loader.Sym) string {
+	relocs := ldr.Relocs(symIdx)
+	str := decodetypeName(ldr, symIdx, &relocs, 4*arch.PtrSize+8)
+	data := ldr.Data(symIdx)
+	if data[2*arch.PtrSize+4]&tflagExtraStar != 0 {
+		return str[1:]
+	}
+	return str
+}
+
+func decodetypeGcmask(ctxt *Link, s loader.Sym) []byte {
+	if ctxt.loader.SymType(s) == sym.SDYNIMPORT {
+		symData := ctxt.loader.Data(s)
+		addr := decodetypeGcprogShlib(ctxt, symData)
+		ptrdata := decodetypePtrdata(ctxt.Arch, symData)
+		sect := findShlibSection(ctxt, ctxt.loader.SymPkg(s), addr)
+		if sect != nil {
+			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", ctxt.loader.SymName(s))
+		return nil
+	}
+	relocs := ctxt.loader.Relocs(s)
+	mask := decodeRelocSym(ctxt.loader, s, &relocs, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize))
+	return ctxt.loader.Data(mask)
+}
+
+// Type.commonType.gc
+func decodetypeGcprog(ctxt *Link, s loader.Sym) []byte {
+	if ctxt.loader.SymType(s) == sym.SDYNIMPORT {
+		symData := ctxt.loader.Data(s)
+		addr := decodetypeGcprogShlib(ctxt, symData)
+		sect := findShlibSection(ctxt, ctxt.loader.SymPkg(s), addr)
+		if sect != nil {
+			// A gcprog is a 4-byte uint32 indicating length, followed by
+			// the actual program.
+			progsize := make([]byte, 4)
+			_, err := sect.ReadAt(progsize, int64(addr-sect.Addr))
+			if err != nil {
+				log.Fatal(err)
+			}
+			progbytes := make([]byte, ctxt.Arch.ByteOrder.Uint32(progsize))
+			_, err = sect.ReadAt(progbytes, int64(addr-sect.Addr+4))
+			if err != nil {
+				log.Fatal(err)
+			}
+			return append(progsize, progbytes...)
+		}
+		Exitf("cannot find gcmask for %s", ctxt.loader.SymName(s))
+		return nil
+	}
+	relocs := ctxt.loader.Relocs(s)
+	rs := decodeRelocSym(ctxt.loader, s, &relocs, 2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize))
+	return ctxt.loader.Data(rs)
+}
+
+// Find the elf.Section of a given shared library that contains a given address.
+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[1:] { // skip the NULL section
+				if sect.Addr <= addr && addr < sect.Addr+sect.Size {
+					return sect
+				}
+			}
+		}
+	}
+	return nil
+}
+
+func decodetypeGcprogShlib(ctxt *Link, data []byte) uint64 {
+	return decodeInuxi(ctxt.Arch, data[2*int32(ctxt.Arch.PtrSize)+8+1*int32(ctxt.Arch.PtrSize):], ctxt.Arch.PtrSize)
+}