pkg,service: add cmd `examinemem`(`x`) for examining memory. (#1814)

According to #1800 #1584 #1038, `dlv` should enable the user to dive into
memory. User can print binary data in specific memory address range.
But not support for sepecific variable name or structures temporarily.(Because
I have no idea that modify `print` command.)

Close #1584.

Documentation/cli/README.md

@@ -24,6 +24,7 @@ Command | Description
 [disassemble](#disassemble) | Disassembler.
 [down](#down) | Move the current frame down.
 [edit](#edit) | Open where you are in $DELVE_EDITOR or $EDITOR
+[examinemem](#examinemem) | Examine memory:
 [exit](#exit) | Exit the debugger.
 [frame](#frame) | Set the current frame, or execute command on a different frame.
 [funcs](#funcs) | Print list of functions.
@@ -210,6 +211,18 @@ If locspec is omitted edit will open the current source file in the editor, othe
 
 Aliases: ed
 
+## examinemem
+Examine memory:
+
+    examinemem [-fmt <format>] [-len <length>] <address>
+
+Format represents the data format and the value is one of this list (default hex): oct(octal), hex(hexadecimal), dec(decimal), bin(binary).
+Length is the number of bytes (default 1) and must be less than or equal to 1000.
+Address is the memory location of the target to examine.
+For example:  x -fmt hex -len 20 0xc00008af38
+
+Aliases: x
+
 ## exit
 Exit the debugger.
 		

Documentation/cli/starlark.md

@@ -29,6 +29,7 @@ create_breakpoint(Breakpoint) | Equivalent to API call [CreateBreakpoint](https:
 detach(Kill) | Equivalent to API call [Detach](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Detach)
 disassemble(Scope, StartPC, EndPC, Flavour) | Equivalent to API call [Disassemble](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Disassemble)
 eval(Scope, Expr, Cfg) | Equivalent to API call [Eval](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.Eval)
+examine_memory(Address, Length) | Equivalent to API call [ExamineMemory](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.ExamineMemory)
 find_location(Scope, Loc, IncludeNonExecutableLines) | Equivalent to API call [FindLocation](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.FindLocation)
 function_return_locations(FnName) | Equivalent to API call [FunctionReturnLocations](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.FunctionReturnLocations)
 get_breakpoint(Id, Name) | Equivalent to API call [GetBreakpoint](https://godoc.org/github.com/go-delve/delve/service/rpc2#RPCServer.GetBreakpoint)

_fixtures/examinememory.go

+package main
+
+import (
+	"fmt"
+	"unsafe"
+)
+
+func main() {
+	l := int(51)
+	bs := make([]byte, l)
+	for i := 0; i < l; i++ {
+		bs[i] = byte(i + int(10))
+	}
+
+	bsp := (*byte)(unsafe.Pointer(&bs[0]))
+
+	bspUintptr := uintptr(unsafe.Pointer(bsp))
+
+	fmt.Printf("%#x\n", bspUintptr)
+	_ = *bsp
+
+	bs[0] = 255
+
+	_ = *bsp
+}

pkg/terminal/command.go

@@ -7,6 +7,10 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
+	"github.com/cosiner/argv"
+	"github.com/go-delve/delve/service"
+	"github.com/go-delve/delve/service/api"
+	"github.com/go-delve/delve/service/debugger"
 	"go/parser"
 	"go/scanner"
 	"io"
@@ -20,11 +24,6 @@ import (
 	"strconv"
 	"strings"
 	"text/tabwriter"
-
-	"github.com/cosiner/argv"
-	"github.com/go-delve/delve/service"
-	"github.com/go-delve/delve/service/api"
-	"github.com/go-delve/delve/service/debugger"
 )
 
 const optimizedFunctionWarning = "Warning: debugging optimized function"
@@ -368,6 +367,15 @@ Defines <alias> as an alias to <command> or removes an alias.`},
 	
 If locspec is omitted edit will open the current source file in the editor, otherwise it will open the specified location.`},
 		{aliases: []string{"libraries"}, cmdFn: libraries, helpMsg: `List loaded dynamic libraries`},
+
+		{aliases: []string{"examinemem", "x"}, cmdFn: examineMemoryCmd, helpMsg: `Examine memory:
+
+    examinemem [-fmt <format>] [-len <length>] <address>
+
+Format represents the data format and the value is one of this list (default hex): oct(octal), hex(hexadecimal), dec(decimal), bin(binary).
+Length is the number of bytes (default 1) and must be less than or equal to 1000.
+Address is the memory location of the target to examine.
+For example:  x -fmt hex -len 20 0xc00008af38`},
 	}
 
 	if client == nil || client.Recorded() {
@@ -1349,6 +1357,81 @@ func edit(t *Term, ctx callContext, args string) error {
 	return cmd.Run()
 }
 
+func examineMemoryCmd(t *Term, ctx callContext, args string) error {
+	v := strings.FieldsFunc(args, func(c rune) bool {
+		return c == ' '
+	})
+
+	var (
+		address int64
+		err     error
+		ok      bool
+	)
+
+	// Default value
+	priFmt := byte('x')
+	length := 1
+
+	for i := 0; i < len(v); i++ {
+		switch v[i] {
+		case "-fmt":
+			i++
+			if i >= len(v) {
+				return fmt.Errorf("expected argument after -fmt")
+			}
+			fmtMapToPriFmt := map[string]byte{
+				"oct":         'o',
+				"octal":       'o',
+				"hex":         'x',
+				"hexadecimal": 'x',
+				"dec":         'd',
+				"decimal":     'd',
+				"bin":         'b',
+				"binary":      'b',
+			}
+			priFmt, ok = fmtMapToPriFmt[v[i]]
+			if !ok {
+				return fmt.Errorf("%q is not a valid format", v[i])
+			}
+		case "-len":
+			i++
+			if i >= len(v) {
+				return fmt.Errorf("expected argument after -len")
+			}
+			var err error
+			length, err = strconv.Atoi(v[i])
+			if err != nil || length <= 0 {
+				return fmt.Errorf("len must be an positive integer")
+			}
+			// TODO, maybe configured by user.
+			if length > 1000 {
+				return fmt.Errorf("len must be less than or equal to 1000")
+			}
+		default:
+			if i != len(v)-1 {
+				return fmt.Errorf("unknown option %q", v[i])
+			}
+			// TODO, maybe we can support expression.
+			address, err = strconv.ParseInt(v[len(v)-1], 0, 64)
+			if err != nil {
+				return fmt.Errorf("convert address into uintptr type failed, %s", err)
+			}
+		}
+	}
+
+	if address == 0 {
+		return fmt.Errorf("no address specified")
+	}
+
+	memArea, err := t.client.ExamineMemory(uintptr(address), length)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(api.PrettyExamineMemory(uintptr(address), memArea, priFmt))
+	return nil
+}
+
 func printVar(t *Term, ctx callContext, args string) error {
 	if len(args) == 0 {
 		return fmt.Errorf("not enough arguments")

pkg/terminal/command_test.go

@@ -993,3 +993,42 @@ func TestIssue1598(t *testing.T) {
 		}
 	})
 }
+
+func TestExamineMemoryCmd(t *testing.T) {
+	withTestTerminal("examinememory", t, func(term *FakeTerminal) {
+		term.MustExec("break examinememory.go:19")
+		term.MustExec("break examinememory.go:24")
+		term.MustExec("continue")
+
+		addressStr := strings.TrimSpace(term.MustExec("p bspUintptr"))
+		address, err := strconv.ParseInt(addressStr, 0, 64)
+		if err != nil {
+			t.Fatalf("could convert %s into int64, err %s", addressStr, err)
+		}
+
+		res := term.MustExec("examinemem  -len 52 -fmt hex " + addressStr)
+		t.Logf("the result of examining memory \n%s", res)
+		// check first line
+		firstLine := fmt.Sprintf("%#x:    0xa     0xb     0xc     0xd     0xe     0xf     0x10    0x11", address)
+		if !strings.Contains(res, firstLine) {
+			t.Fatalf("expected first line: %s", firstLine)
+		}
+
+		// check last line
+		lastLine := fmt.Sprintf("%#x:    0x3a    0x3b    0x3c    0x0", address+6*8)
+		if !strings.Contains(res, lastLine) {
+			t.Fatalf("expected last line: %s", lastLine)
+		}
+
+		// second examining memory
+		term.MustExec("continue")
+		res = term.MustExec("x -len 52 -fmt bin " + addressStr)
+		t.Logf("the second result of examining memory result \n%s", res)
+
+		// check first line
+		firstLine = fmt.Sprintf("%#x:    11111111    00001011    00001100    00001101", address)
+		if !strings.Contains(res, firstLine) {
+			t.Fatalf("expected first line: %s", firstLine)
+		}
+	})
+}

pkg/terminal/starbind/starlark_mapping.go

@@ -450,6 +450,44 @@ func (env *Env) starlarkPredeclare() starlark.StringDict {
 		}
 		return env.interfaceToStarlarkValue(rpcRet), nil
 	})
+	r["examine_memory"] = starlark.NewBuiltin("examine_memory", func(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
+		if err := isCancelled(thread); err != nil {
+			return starlark.None, decorateError(thread, err)
+		}
+		var rpcArgs rpc2.ExamineMemoryIn
+		var rpcRet rpc2.ExaminedMemoryOut
+		if len(args) > 0 && args[0] != starlark.None {
+			err := unmarshalStarlarkValue(args[0], &rpcArgs.Address, "Address")
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		if len(args) > 1 && args[1] != starlark.None {
+			err := unmarshalStarlarkValue(args[1], &rpcArgs.Length, "Length")
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		for _, kv := range kwargs {
+			var err error
+			switch kv[0].(starlark.String) {
+			case "Address":
+				err = unmarshalStarlarkValue(kv[1], &rpcArgs.Address, "Address")
+			case "Length":
+				err = unmarshalStarlarkValue(kv[1], &rpcArgs.Length, "Length")
+			default:
+				err = fmt.Errorf("unknown argument %q", kv[0])
+			}
+			if err != nil {
+				return starlark.None, decorateError(thread, err)
+			}
+		}
+		err := env.ctx.Client().CallAPI("ExamineMemory", &rpcArgs, &rpcRet)
+		if err != nil {
+			return starlark.None, err
+		}
+		return env.interfaceToStarlarkValue(rpcRet), nil
+	})
 	r["find_location"] = starlark.NewBuiltin("find_location", func(thread *starlark.Thread, _ *starlark.Builtin, args starlark.Tuple, kwargs []starlark.Tuple) (starlark.Value, error) {
 		if err := isCancelled(thread); err != nil {
 			return starlark.None, decorateError(thread, err)

service/api/prettyprint.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"reflect"
+	"strconv"
 	"strings"
 )
 
@@ -354,3 +355,53 @@ func (v *Variable) writeSliceOrArrayTo(buf io.Writer, newlines bool, indent stri
 
 	fmt.Fprint(buf, "]")
 }
+
+func PrettyExamineMemory(address uintptr, memArea []byte, format byte) string {
+	cols := 8
+	// Avoid emitting rows that are too long when using binary format
+	if format == 'b' {
+		cols = 4
+	}
+
+	l := len(memArea)
+	rows := l / cols
+	if l%cols != 0 {
+		rows++
+	}
+
+	var colFormat string
+	// Leading zero and occupy 8 for binary
+	if format == 'b' {
+		colFormat = "    %#08b"
+	} else {
+		var maxColCharNum int
+		for i := 0; i < rows; i++ {
+			for j := 0; j < cols && i*cols+j < l; j++ {
+				curColCharNum := len(fmt.Sprintf("%#"+string(format), memArea[i*cols+j]))
+				if curColCharNum > maxColCharNum {
+					maxColCharNum = curColCharNum
+				}
+			}
+		}
+		colFormat = "    %#-" + strconv.Itoa(maxColCharNum) + string(format)
+	}
+
+	lines := ""
+	for i := 0; i < rows; i++ {
+		lines += fmt.Sprintf("%#x:", address)
+		for j := 0; j < cols && i*cols+j < l; j++ {
+			curOutput := fmt.Sprintf(colFormat, memArea[i*cols+j])
+
+			// Diffrent versions of golang output differently if binary.
+			// See https://ci.appveyor.com/project/derekparker/delve-facy3/builds/30179356.
+			// Remove prefix `0b` if binary in some versions of golang because it is not graceful.
+			if format == 'b' && strings.Contains(curOutput, "0b") {
+				curOutput = "    " + curOutput[6:]
+			}
+			lines += curOutput
+		}
+		lines += "\n"
+		address += uintptr(cols)
+	}
+	return lines
+}

service/client.go

@@ -147,6 +147,11 @@ type Client interface {
 	// ListDynamicLibraries returns a list of loaded dynamic libraries.
 	ListDynamicLibraries() ([]api.Image, error)
 
+	// ExamineMemory returns the raw memory stored at the given address.
+	// The amount of data to be read is specified by length which must be less than or equal to 1000.
+	// This function will return an error if it reads less than `length` bytes.
+	ExamineMemory(address uintptr, length int) ([]byte, error)
+
 	// Disconnect closes the connection to the server without sending a Detach request first.
 	// If cont is true a continue command will be sent instead.
 	Disconnect(cont bool) error

service/debugger/debugger.go

@@ -1313,6 +1313,25 @@ func (d *Debugger) ListDynamicLibraries() []api.Image {
 	return r
 }
 
+// ExamineMemory returns the raw memory stored at the given address.
+// The amount of data to be read is specified by length.
+// This function will return an error if it reads less than `length` bytes.
+func (d *Debugger) ExamineMemory(address uintptr, length int) ([]byte, error) {
+	d.processMutex.Lock()
+	defer d.processMutex.Unlock()
+
+	thread := d.target.CurrentThread()
+	data := make([]byte, length)
+	n, err := thread.ReadMemory(data, address)
+	if err != nil {
+		return nil, err
+	}
+	if length != n {
+		return nil, errors.New("the specific range has exceeded readable area")
+	}
+	return data, nil
+}
+
 func (d *Debugger) GetVersion(out *api.GetVersionOut) error {
 	if d.config.CoreFile != "" {
 		if d.config.Backend == "rr" {

service/rpc2/client.go

@@ -413,6 +413,17 @@ func (c *RPCClient) ListDynamicLibraries() ([]api.Image, error) {
 	return out.List, nil
 }
 
+func (c *RPCClient) ExamineMemory(address uintptr, count int) ([]byte, error) {
+	out := &ExaminedMemoryOut{}
+
+	err := c.call("ExamineMemory", ExamineMemoryIn{Length: count, Address: address}, out)
+	if err != nil {
+		return nil, err
+	}
+
+	return out.Mem, nil
+}
+
 func (c *RPCClient) call(method string, args, reply interface{}) error {
 	return c.client.Call("RPCServer."+method, args, reply)
 }

service/rpc2/server.go

@@ -751,3 +751,27 @@ func (s *RPCServer) ListPackagesBuildInfo(in ListPackagesBuildInfoIn, out *ListP
 	out.List = s.debugger.ListPackagesBuildInfo(in.IncludeFiles)
 	return nil
 }
+
+// ExamineMemoryIn holds the arguments of ExamineMemory
+type ExamineMemoryIn struct {
+	Address uintptr
+	Length  int
+}
+
+// ExaminedMemoryOut holds the return values of ExamineMemory
+type ExaminedMemoryOut struct {
+	Mem []byte
+}
+
+func (s *RPCServer) ExamineMemory(arg ExamineMemoryIn, out *ExaminedMemoryOut) error {
+	if arg.Length > 1000 {
+		return fmt.Errorf("len must be less than or equal to 1000")
+	}
+	Mem, err := s.debugger.ExamineMemory(arg.Address, arg.Length)
+	if err != nil {
+		return err
+	}
+
+	out.Mem = Mem
+	return nil
+}