proc: Use MemoryReader inside memoryReadWriter

pkg/proc/core.go

@@ -9,15 +9,6 @@ import (
 	"sync"
 )
 
-// MemoryReader is like io.ReaderAt, but the offset is a uintptr so that it
-// can address all of 64-bit memory.
-// Redundant with memoryReadWriter but more easily suited to working with
-// the standard io package.
-type MemoryReader interface {
-	// ReadMemory is just like io.ReaderAt.ReadAt.
-	ReadMemory(buf []byte, addr uintptr) (n int, err error)
-}
-
 // A SplicedMemory represents a memory space formed from multiple regions,
 // each of which may override previously regions. For example, in the following
 // core, the program text was loaded at 0x400000:
@@ -203,13 +194,12 @@ func (p *CoreProcess) BinInfo() *BinaryInfo {
 	return &p.bi
 }
 
-func (thread *CoreThread) readMemory(addr uintptr, size int) (data []byte, err error) {
-	data = make([]byte, size)
-	n, err := thread.p.core.ReadMemory(data, addr)
+func (thread *CoreThread) ReadMemory(data []byte, addr uintptr) (n int, err error) {
+	n, err = thread.p.core.ReadMemory(data, addr)
 	if err == nil && n != len(data) {
 		err = ErrShortRead
 	}
-	return data, err
+	return n, err
 }
 
 func (thread *CoreThread) writeMemory(addr uintptr, data []byte) (int, error) {

pkg/proc/disasm.go

@@ -45,7 +45,8 @@ func Disassemble(dbp DisassembleInfo, g *G, startPC, endPC uint64) ([]AsmInstruc
 }
 
 func disassemble(memrw memoryReadWriter, regs Registers, breakpoints map[uint64]*Breakpoint, bi *BinaryInfo, startPC, endPC uint64) ([]AsmInstruction, error) {
-	mem, err := memrw.readMemory(uintptr(startPC), int(endPC-startPC))
+	mem := make([]byte, int(endPC-startPC))
+	_, err := memrw.ReadMemory(mem, uintptr(startPC))
 	if err != nil {
 		return nil, err
 	}

pkg/proc/disasm_amd64.go

@@ -96,7 +96,8 @@ func resolveCallArg(inst *ArchInst, currentGoroutine bool, regs Registers, mem m
 		}
 		addr := uintptr(int64(base) + int64(index*uint64(arg.Scale)) + arg.Disp)
 		//TODO: should this always be 64 bits instead of inst.MemBytes?
-		pcbytes, err := mem.readMemory(addr, inst.MemBytes)
+		pcbytes := make([]byte, inst.MemBytes)
+		_, err := mem.ReadMemory(pcbytes, addr)
 		if err != nil {
 			return nil
 		}

pkg/proc/gdbserver.go

@@ -841,8 +841,12 @@ func (p *GdbserverProcess) setCurrentBreakpoints() error {
 	return nil
 }
 
-func (t *GdbserverThread) readMemory(addr uintptr, size int) (data []byte, err error) {
-	return t.p.conn.readMemory(addr, size)
+func (t *GdbserverThread) ReadMemory(data []byte, addr uintptr) (n int, err error) {
+	err = t.p.conn.readMemory(data, addr)
+	if err != nil {
+		return 0, err
+	}
+	return len(data), nil
 }
 
 func (t *GdbserverThread) writeMemory(addr uintptr, data []byte) (written int, err error) {
@@ -1028,7 +1032,8 @@ func (t *GdbserverThread) reloadGAtPC() error {
 		}
 	}
 
-	savedcode, err := t.readMemory(uintptr(pc), len(movinstr))
+	savedcode := make([]byte, len(movinstr))
+	_, err := t.ReadMemory(savedcode, uintptr(pc))
 	if err != nil {
 		return err
 	}

pkg/proc/gdbserver_conn.go

@@ -778,8 +778,9 @@ func (conn *gdbConn) appendThreadSelector(threadID string) {
 }
 
 // executes 'm' (read memory) command
-func (conn *gdbConn) readMemory(addr uintptr, size int) (data []byte, err error) {
-	data = make([]byte, 0, size)
+func (conn *gdbConn) readMemory(data []byte, addr uintptr) error {
+	size := len(data)
+	data = data[:0]
 
 	for size > 0 {
 		conn.outbuf.Reset()
@@ -794,7 +795,7 @@ func (conn *gdbConn) readMemory(addr uintptr, size int) (data []byte, err error)
 		fmt.Fprintf(&conn.outbuf, "$m%x,%x", addr+uintptr(len(data)), sz)
 		resp, err := conn.exec(conn.outbuf.Bytes(), "memory read")
 		if err != nil {
-			return nil, err
+			return err
 		}
 
 		for i := 0; i < len(resp); i += 2 {
@@ -802,7 +803,7 @@ func (conn *gdbConn) readMemory(addr uintptr, size int) (data []byte, err error)
 			data = append(data, uint8(n))
 		}
 	}
-	return data, nil
+	return nil
 }
 
 // executes 'M' (write memory) command

pkg/proc/mem.go

@@ -2,8 +2,17 @@ package proc
 
 const cacheEnabled = true
 
+// MemoryReader is like io.ReaderAt, but the offset is a uintptr so that it
+// can address all of 64-bit memory.
+// Redundant with memoryReadWriter but more easily suited to working with
+// the standard io package.
+type MemoryReader interface {
+	// ReadMemory is just like io.ReaderAt.ReadAt.
+	ReadMemory(buf []byte, addr uintptr) (n int, err error)
+}
+
 type memoryReadWriter interface {
-	readMemory(addr uintptr, size int) (data []byte, err error)
+	MemoryReader
 	writeMemory(addr uintptr, data []byte) (written int, err error)
 }
 
@@ -17,14 +26,13 @@ func (m *memCache) contains(addr uintptr, size int) bool {
 	return addr >= m.cacheAddr && addr <= (m.cacheAddr+uintptr(len(m.cache)-size))
 }
 
-func (m *memCache) readMemory(addr uintptr, size int) (data []byte, err error) {
-	if m.contains(addr, size) {
-		d := make([]byte, size)
-		copy(d, m.cache[addr-m.cacheAddr:])
-		return d, nil
+func (m *memCache) ReadMemory(data []byte, addr uintptr) (n int, err error) {
+	if m.contains(addr, len(data)) {
+		copy(data, m.cache[addr-m.cacheAddr:])
+		return len(data), nil
 	}
 
-	return m.mem.readMemory(addr, size)
+	return m.mem.ReadMemory(data, addr)
 }
 
 func (m *memCache) writeMemory(addr uintptr, data []byte) (written int, err error) {
@@ -42,14 +50,16 @@ func cacheMemory(mem memoryReadWriter, addr uintptr, size int) memoryReadWriter
 		if cacheMem.contains(addr, size) {
 			return mem
 		} else {
-			cache, err := cacheMem.mem.readMemory(addr, size)
+			cache := make([]byte, size)
+			_, err := cacheMem.mem.ReadMemory(cache, addr)
 			if err != nil {
 				return mem
 			}
 			return &memCache{addr, cache, mem}
 		}
 	}
-	cache, err := mem.readMemory(addr, size)
+	cache := make([]byte, size)
+	_, err := mem.ReadMemory(cache, addr)
 	if err != nil {
 		return mem
 	}

pkg/proc/moduledata.go

@@ -142,7 +142,8 @@ const (
 
 func loadName(bi *BinaryInfo, addr uintptr, mem memoryReadWriter) (name, tag string, pkgpathoff int32, err error) {
 	off := addr
-	namedata, err := mem.readMemory(off, 3)
+	namedata := make([]byte, 3)
+	_, err = mem.ReadMemory(namedata, off)
 	off += 3
 	if err != nil {
 		return "", "", 0, err
@@ -150,7 +151,8 @@ func loadName(bi *BinaryInfo, addr uintptr, mem memoryReadWriter) (name, tag str
 
 	namelen := uint16(namedata[1]<<8) | uint16(namedata[2])
 
-	rawstr, err := mem.readMemory(off, int(namelen))
+	rawstr := make([]byte, int(namelen))
+	_, err = mem.ReadMemory(rawstr, off)
 	off += uintptr(namelen)
 	if err != nil {
 		return "", "", 0, err
@@ -159,14 +161,16 @@ func loadName(bi *BinaryInfo, addr uintptr, mem memoryReadWriter) (name, tag str
 	name = string(rawstr)
 
 	if namedata[0]&nameflagHasTag != 0 {
-		taglendata, err := mem.readMemory(off, 2)
+		taglendata := make([]byte, 2)
+		_, err = mem.ReadMemory(taglendata, off)
 		off += 2
 		if err != nil {
 			return "", "", 0, err
 		}
 		taglen := uint16(taglendata[0]<<8) | uint16(taglendata[1])
 
-		rawstr, err := mem.readMemory(off, int(taglen))
+		rawstr := make([]byte, int(taglen))
+		_, err = mem.ReadMemory(rawstr, off)
 		off += uintptr(taglen)
 		if err != nil {
 			return "", "", 0, err
@@ -176,7 +180,8 @@ func loadName(bi *BinaryInfo, addr uintptr, mem memoryReadWriter) (name, tag str
 	}
 
 	if namedata[0]&nameflagHasPkg != 0 {
-		pkgdata, err := mem.readMemory(off, 4)
+		pkgdata := make([]byte, 4)
+		_, err = mem.ReadMemory(pkgdata, off)
 		if err != nil {
 			return "", "", 0, err
 		}

pkg/proc/proc.go

@@ -282,7 +282,8 @@ func (dbp *Process) SetBreakpoint(addr uint64, kind BreakpointKind, cond ast.Exp
 	}
 
 	thread := dbp.threads[tid]
-	originalData, err := thread.readMemory(uintptr(addr), dbp.bi.arch.BreakpointSize())
+	originalData := make([]byte, dbp.bi.arch.BreakpointSize())
+	_, err := thread.ReadMemory(originalData, uintptr(addr))
 	if err != nil {
 		return nil, err
 	}
@@ -707,7 +708,8 @@ func GoroutinesInfo(dbp EvalScopeConvertible) ([]*G, error) {
 	if err != nil {
 		return nil, err
 	}
-	allglenBytes, err := dbp.CurrentThread().readMemory(uintptr(addr), 8)
+	allglenBytes := make([]byte, 8)
+	_, err = dbp.CurrentThread().ReadMemory(allglenBytes, uintptr(addr))
 	if err != nil {
 		return nil, err
 	}
@@ -722,7 +724,8 @@ func GoroutinesInfo(dbp EvalScopeConvertible) ([]*G, error) {
 			return nil, err
 		}
 	}
-	faddr, err := dbp.CurrentThread().readMemory(uintptr(allgentryaddr), dbp.BinInfo().arch.PtrSize())
+	faddr := make([]byte, dbp.BinInfo().arch.PtrSize())
+	_, err = dbp.CurrentThread().ReadMemory(faddr, uintptr(allgentryaddr))
 	allgptr := binary.LittleEndian.Uint64(faddr)
 
 	for i := uint64(0); i < allglen; i++ {

pkg/proc/proc_test.go

@@ -135,7 +135,9 @@ func getRegisters(p IProcess, t *testing.T) Registers {
 }
 
 func dataAtAddr(thread memoryReadWriter, addr uint64) ([]byte, error) {
-	return thread.readMemory(uintptr(addr), 1)
+	data := make([]byte, 1)
+	_, err := thread.ReadMemory(data, uintptr(addr))
+	return data, err
 }
 
 func assertNoError(err error, t testing.TB, s string) {

pkg/proc/proc_windows.go

@@ -330,7 +330,8 @@ func (dbp *Process) waitForDebugEvent(flags waitForDebugEventFlags) (threadID, e
 				// this exception anymore.
 				atbp := true
 				if thread, found := dbp.threads[tid]; found {
-					if data, err := thread.readMemory(exception.ExceptionRecord.ExceptionAddress, dbp.bi.arch.BreakpointSize()); err == nil {
+					data := make([]byte, dbp.bi.arch.BreakpointSize())
+					if _, err := thread.ReadMemory(data, exception.ExceptionRecord.ExceptionAddress); err == nil {
 						instr := dbp.bi.arch.BreakpointInstruction()
 						for i := range instr {
 							if data[i] != instr[i] {

pkg/proc/threads.go

@@ -385,7 +385,8 @@ func getGVariable(thread IThread) (*Variable, error) {
 
 	gaddr, hasgaddr := regs.GAddr()
 	if !hasgaddr {
-		gaddrbs, err := thread.readMemory(uintptr(regs.TLS()+arch.GStructOffset()), arch.PtrSize())
+		gaddrbs := make([]byte, arch.PtrSize())
+		_, err := thread.ReadMemory(gaddrbs, uintptr(regs.TLS()+arch.GStructOffset()))
 		if err != nil {
 			return nil, err
 		}

pkg/proc/threads_darwin.go

@@ -119,20 +119,19 @@ func (t *Thread) writeMemory(addr uintptr, data []byte) (int, error) {
 	return len(data), nil
 }
 
-func (t *Thread) readMemory(addr uintptr, size int) ([]byte, error) {
-	if size == 0 {
-		return nil, nil
+func (t *Thread) ReadMemory(buf []byte, addr uintptr) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
 	}
 	var (
-		buf    = make([]byte, size)
 		vmData = unsafe.Pointer(&buf[0])
 		vmAddr = C.mach_vm_address_t(addr)
-		length = C.mach_msg_type_number_t(size)
+		length = C.mach_msg_type_number_t(len(buf))
 	)
 
 	ret := C.read_memory(t.dbp.os.task, vmAddr, vmData, length)
 	if ret < 0 {
-		return nil, fmt.Errorf("could not read memory")
+		return 0, fmt.Errorf("could not read memory")
 	}
-	return buf, nil
+	return len(buf), nil
 }

pkg/proc/threads_linux.go

@@ -102,11 +102,10 @@ func (t *Thread) writeMemory(addr uintptr, data []byte) (written int, err error)
 	return
 }
 
-func (t *Thread) readMemory(addr uintptr, size int) (data []byte, err error) {
-	if size == 0 {
+func (t *Thread) ReadMemory(data []byte, addr uintptr) (n int, err error) {
+	if len(data) == 0 {
 		return
 	}
-	data = make([]byte, size)
 	t.dbp.execPtraceFunc(func() { _, err = sys.PtracePeekData(t.ID, addr, data) })
 	return
 }

pkg/proc/threads_windows.go

@@ -138,15 +138,14 @@ func (t *Thread) writeMemory(addr uintptr, data []byte) (int, error) {
 	return int(count), nil
 }
 
-func (t *Thread) readMemory(addr uintptr, size int) ([]byte, error) {
-	if size == 0 {
-		return nil, nil
+func (t *Thread) ReadMemory(buf []byte, addr uintptr) (int, error) {
+	if len(buf) == 0 {
+		return 0, nil
 	}
 	var count uintptr
-	buf := make([]byte, size)
-	err := _ReadProcessMemory(t.dbp.os.hProcess, addr, &buf[0], uintptr(size), &count)
-	if err != nil {
-		return nil, err
+	err := _ReadProcessMemory(t.dbp.os.hProcess, addr, &buf[0], uintptr(len(buf)), &count)
+	if err == nil && count != uintptr(len(buf)) {
+		err = ErrShortRead
 	}
-	return buf[:count], nil
+	return int(count), err
 }

pkg/proc/variables.go

@@ -367,7 +367,8 @@ func (gvar *Variable) parseG() (*G, error) {
 	_, deref := gvar.RealType.(*dwarf.PtrType)
 
 	if deref {
-		gaddrbytes, err := mem.readMemory(uintptr(gaddr), gvar.bi.arch.PtrSize())
+		gaddrbytes := make([]byte, gvar.bi.arch.PtrSize())
+		_, err := mem.ReadMemory(gaddrbytes, uintptr(gaddr))
 		if err != nil {
 			return nil, fmt.Errorf("error derefing *G %s", err)
 		}
@@ -886,7 +887,8 @@ func (v *Variable) loadValueInternal(recurseLevel int, cfg LoadConfig) {
 		v.Value = constant.MakeUint64(val)
 
 	case reflect.Bool:
-		val, err := v.mem.readMemory(v.Addr, 1)
+		val := make([]byte, 1)
+		_, err := v.mem.ReadMemory(val, v.Addr)
 		v.Unreadable = err
 		if err == nil {
 			v.Value = constant.MakeBool(val[0] != 0)
@@ -946,7 +948,8 @@ func readStringInfo(mem memoryReadWriter, arch Arch, addr uintptr) (uintptr, int
 	mem = cacheMemory(mem, addr, arch.PtrSize()*2)
 
 	// read len
-	val, err := mem.readMemory(addr+uintptr(arch.PtrSize()), arch.PtrSize())
+	val := make([]byte, arch.PtrSize())
+	_, err := mem.ReadMemory(val, addr+uintptr(arch.PtrSize()))
 	if err != nil {
 		return 0, 0, fmt.Errorf("could not read string len %s", err)
 	}
@@ -956,7 +959,7 @@ func readStringInfo(mem memoryReadWriter, arch Arch, addr uintptr) (uintptr, int
 	}
 
 	// read addr
-	val, err = mem.readMemory(addr, arch.PtrSize())
+	_, err = mem.ReadMemory(val, addr)
 	if err != nil {
 		return 0, 0, fmt.Errorf("could not read string pointer %s", err)
 	}
@@ -974,7 +977,8 @@ func readStringValue(mem memoryReadWriter, addr uintptr, strlen int64, cfg LoadC
 		count = int64(cfg.MaxStringLen)
 	}
 
-	val, err := mem.readMemory(addr, int(count))
+	val := make([]byte, int(count))
+	_, err := mem.ReadMemory(val, addr)
 	if err != nil {
 		return "", fmt.Errorf("could not read string at %#v due to %s", addr, err)
 	}
@@ -1102,7 +1106,8 @@ func (v *Variable) writeComplex(real, imag float64, size int64) error {
 func readIntRaw(mem memoryReadWriter, addr uintptr, size int64) (int64, error) {
 	var n int64
 
-	val, err := mem.readMemory(addr, int(size))
+	val := make([]byte, int(size))
+	_, err := mem.ReadMemory(val, addr)
 	if err != nil {
 		return 0, err
 	}
@@ -1142,7 +1147,8 @@ func (v *Variable) writeUint(value uint64, size int64) error {
 func readUintRaw(mem memoryReadWriter, addr uintptr, size int64) (uint64, error) {
 	var n uint64
 
-	val, err := mem.readMemory(addr, int(size))
+	val := make([]byte, int(size))
+	_, err := mem.ReadMemory(val, addr)
 	if err != nil {
 		return 0, err
 	}
@@ -1162,7 +1168,8 @@ func readUintRaw(mem memoryReadWriter, addr uintptr, size int64) (uint64, error)
 }
 
 func (v *Variable) readFloatRaw(size int64) (float64, error) {
-	val, err := v.mem.readMemory(v.Addr, int(size))
+	val := make([]byte, int(size))
+	_, err := v.mem.ReadMemory(val, v.Addr)
 	if err != nil {
 		return 0.0, err
 	}
@@ -1206,7 +1213,8 @@ func (v *Variable) writeBool(value bool) error {
 }
 
 func (v *Variable) readFunctionPtr() {
-	val, err := v.mem.readMemory(v.Addr, v.bi.arch.PtrSize())
+	val := make([]byte, v.bi.arch.PtrSize())
+	_, err := v.mem.ReadMemory(val, v.Addr)
 	if err != nil {
 		v.Unreadable = err
 		return
@@ -1220,7 +1228,7 @@ func (v *Variable) readFunctionPtr() {
 		return
 	}
 
-	val, err = v.mem.readMemory(fnaddr, v.bi.arch.PtrSize())
+	_, err = v.mem.ReadMemory(val, fnaddr)
 	if err != nil {
 		v.Unreadable = err
 		return