pkg/proc: pad variable mem in extractVarInfoFromEntry (#3365)

* pkg/proc: pad variable mem in extractVarInfoFromEntry

On 64 bit system, the byte size of the following struct is 16:
    type myStruct struct {
       a int
       b uint32
    }
But extractVarInfoFromEntry only allocates a mem of 12 bytes for it.
When calling method of this struct with the "call" command, it will
result in this error:
    write out of bounds

This patch extends the mem by adding padding bytes to the end of the
mem.

Fixes #3364.

* move the padding logic into newCompositeMemory

_fixtures/fncall.go

@@ -199,6 +199,15 @@ func (i Issue2698) String() string {
 	return fmt.Sprintf("%d %d %d %d", i.a, i.b, i.c, i.d)
 }
 
+type Issue3364 struct {
+	a int
+	b uint32
+}
+
+func (i Issue3364) String() string {
+	return fmt.Sprintf("%d %d", i.a, i.b)
+}
+
 func main() {
 	one, two := 1, 2
 	intslice := []int{1, 2, 3}
@@ -222,6 +231,10 @@ func main() {
 		c: 3,
 		d: 4,
 	}
+	issue3364 := Issue3364{
+		a: 1,
+		b: 2,
+	}
 
 	fn2clos := makeclos(pa)
 	fn2glob := call1
@@ -241,5 +254,5 @@ func main() {
 	d.Method()
 	d.Base.Method()
 	x.CallMe()
-	fmt.Println(one, two, zero, call, call0, call2, callexit, callpanic, callbreak, callstacktrace, stringsJoin, intslice, stringslice, comma, a.VRcvr, a.PRcvr, pa, vable_a, vable_pa, pable_pa, fn2clos, fn2glob, fn2valmeth, fn2ptrmeth, fn2nil, ga, escapeArg, a2, square, intcallpanic, onetwothree, curriedAdd, getAStruct, getAStructPtr, getVRcvrableFromAStruct, getPRcvrableFromAStructPtr, getVRcvrableFromAStructPtr, pa2, noreturncall, str, d, x, x2.CallMe(5), longstrs, regabistacktest, regabistacktest2, issue2698.String(), regabistacktest3, rast3, floatsum, ref)
+	fmt.Println(one, two, zero, call, call0, call2, callexit, callpanic, callbreak, callstacktrace, stringsJoin, intslice, stringslice, comma, a.VRcvr, a.PRcvr, pa, vable_a, vable_pa, pable_pa, fn2clos, fn2glob, fn2valmeth, fn2ptrmeth, fn2nil, ga, escapeArg, a2, square, intcallpanic, onetwothree, curriedAdd, getAStruct, getAStructPtr, getVRcvrableFromAStruct, getPRcvrableFromAStructPtr, getVRcvrableFromAStructPtr, pa2, noreturncall, str, d, x, x2.CallMe(5), longstrs, regabistacktest, regabistacktest2, issue2698.String(), issue3364.String(), regabistacktest3, rast3, floatsum, ref)
 }

pkg/proc/dwarf_export_test.go

@@ -20,7 +20,7 @@ func NewCompositeMemory(p *Target, pieces []op.Piece, base uint64) (*compositeMe
 	dwarfregs := arch.RegistersToDwarfRegisters(0, regs)
 	dwarfregs.ChangeFunc = p.CurrentThread().SetReg
 
-	mem, err := newCompositeMemory(p.Memory(), arch, *dwarfregs, pieces)
+	mem, err := newCompositeMemory(p.Memory(), arch, *dwarfregs, pieces, 0)
 	if mem != nil {
 		mem.base = base
 	}

pkg/proc/mem.go

@@ -98,17 +98,17 @@ type compositeMemory struct {
 
 // CreateCompositeMemory created a new composite memory type using the provided MemoryReadWriter as the
 // underlying memory buffer.
-func CreateCompositeMemory(mem MemoryReadWriter, arch *Arch, regs op.DwarfRegisters, pieces []op.Piece) (*compositeMemory, error) {
+func CreateCompositeMemory(mem MemoryReadWriter, arch *Arch, regs op.DwarfRegisters, pieces []op.Piece, size int64) (*compositeMemory, error) {
 	// This is basically a small wrapper to avoid having to change all callers
 	// of newCompositeMemory since it existed first.
-	cm, err := newCompositeMemory(mem, arch, regs, pieces)
+	cm, err := newCompositeMemory(mem, arch, regs, pieces, size)
 	if cm != nil {
 		cm.base = fakeAddressUnresolv
 	}
 	return cm, err
 }
 
-func newCompositeMemory(mem MemoryReadWriter, arch *Arch, regs op.DwarfRegisters, pieces []op.Piece) (*compositeMemory, error) {
+func newCompositeMemory(mem MemoryReadWriter, arch *Arch, regs op.DwarfRegisters, pieces []op.Piece, size int64) (*compositeMemory, error) {
 	cmem := &compositeMemory{realmem: mem, arch: arch, regs: regs, pieces: pieces, data: []byte{}}
 	for i := range pieces {
 		piece := &pieces[i]
@@ -147,6 +147,11 @@ func newCompositeMemory(mem MemoryReadWriter, arch *Arch, regs op.DwarfRegisters
 			panic("unsupported piece kind")
 		}
 	}
+	paddingBytes := int(size) - len(cmem.data)
+	if paddingBytes > 0 && paddingBytes < arch.ptrSize {
+		padding := make([]byte, paddingBytes)
+		cmem.data = append(cmem.data, padding...)
+	}
 	return cmem, nil
 }
 

pkg/proc/target.go

@@ -454,7 +454,7 @@ func (t *Target) GetBufferedTracepoints() []*UProbeTraceResult {
 		v.Kind = ip.Kind
 
 		cachedMem := CreateLoadedCachedMemory(ip.Data)
-		compMem, _ := CreateCompositeMemory(cachedMem, t.BinInfo().Arch, op.DwarfRegisters{}, ip.Pieces)
+		compMem, _ := CreateCompositeMemory(cachedMem, t.BinInfo().Arch, op.DwarfRegisters{}, ip.Pieces, ip.RealType.Common().ByteSize)
 		v.mem = compMem
 
 		// Load the value here so that we don't have to export
@@ -506,7 +506,7 @@ const (
 // This caching is primarily done so that registerized variables don't get a
 // different address every time they are evaluated, which would be confusing
 // and leak memory.
-func (t *Target) newCompositeMemory(mem MemoryReadWriter, regs op.DwarfRegisters, pieces []op.Piece, descr *locationExpr) (int64, *compositeMemory, error) {
+func (t *Target) newCompositeMemory(mem MemoryReadWriter, regs op.DwarfRegisters, pieces []op.Piece, descr *locationExpr, size int64) (int64, *compositeMemory, error) {
 	var key string
 	if regs.CFA != 0 && len(pieces) > 0 {
 		// key is created by concatenating the location expression with the CFA,
@@ -521,7 +521,7 @@ func (t *Target) newCompositeMemory(mem MemoryReadWriter, regs op.DwarfRegisters
 		}
 	}
 
-	cmem, err := newCompositeMemory(mem, t.BinInfo().Arch, regs, pieces)
+	cmem, err := newCompositeMemory(mem, t.BinInfo().Arch, regs, pieces, size)
 	if err != nil {
 		return 0, cmem, err
 	}

pkg/proc/variables.go

@@ -1198,9 +1198,9 @@ func extractVarInfoFromEntry(tgt *Target, bi *BinaryInfo, image *Image, regs op.
 	if pieces != nil {
 		var cmem *compositeMemory
 		if tgt != nil {
-			addr, cmem, err = tgt.newCompositeMemory(mem, regs, pieces, descr)
+			addr, cmem, err = tgt.newCompositeMemory(mem, regs, pieces, descr, t.Common().ByteSize)
 		} else {
-			cmem, err = newCompositeMemory(mem, bi.Arch, regs, pieces)
+			cmem, err = newCompositeMemory(mem, bi.Arch, regs, pieces, t.Common().ByteSize)
 			if cmem != nil {
 				cmem.base = fakeAddressUnresolv
 				addr = int64(cmem.base)

pkg/proc/variables_test.go

@@ -1267,6 +1267,7 @@ func TestCallFunction(t *testing.T) {
 		{`regabistacktest("one", "two", "three", "four", "five", 4)`, []string{`:string:"onetwo"`, `:string:"twothree"`, `:string:"threefour"`, `:string:"fourfive"`, `:string:"fiveone"`, ":uint8:8"}, nil},
 		{`regabistacktest2(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)`, []string{":int:3", ":int:5", ":int:7", ":int:9", ":int:11", ":int:13", ":int:15", ":int:17", ":int:19", ":int:11"}, nil},
 		{`issue2698.String()`, []string{`:string:"1 2 3 4"`}, nil},
+		{`issue3364.String()`, []string{`:string:"1 2"`}, nil},
 		{`regabistacktest3(rast3, 5)`, []string{`:[10]string:[10]string ["onetwo","twothree","threefour","fourfive","fivesix","sixseven","sevenheight","heightnine","nineten","tenone"]`, ":uint8:15"}, nil},
 		{`floatsum(1, 2)`, []string{":float64:3"}, nil},
 	}