//pkg/state fixes for VFS2.

- When encodeState.resolve() determines that the resolved reflect.Value is
  contained by a previously-resolved object, set wire.Ref.Type to the
  containing object's type (existing.obj.Type()) rather than the contained
  value's type (obj.Type()).

- When encodeState.resolve() determines that the resolved reflect.Value
  contains a previously-resolved object, handle cases where the new object
  contains *multiple* previously-resolved objects. (This may cause
  previously-allocated object IDs to become unused; to facilitate this, change
  encodeState.pending to a map, and change the wire format to prefix each
  object with its object ID.)

- Add encodeState.encodedStructs to avoid redundant encoding of structs, since
  deduplication of objects via encodeState.resolve() doesn't work for objects
  instantiated by StateSave() and passed to SaveValue() (i.e. fields tagged
  `state:".(whatever)"`).

- Make unexported array fields deserializable via slices that refer to them by
  casting away their unexportedness in decodeState.decodeObject().

Updates #1663

PiperOrigin-RevId: 338727687

2 files changed, 63 insertions, 6 deletions

diff --git a/pkg/state/tests/struct.go b/pkg/state/tests/struct.go
index bd2c2b399..69143d194 100644
--- a/pkg/state/tests/struct.go
+++ b/pkg/state/tests/struct.go
@@ -54,12 +54,47 @@ type outerArray struct {
 }
 
 // +stateify savable
+type outerSlice struct {
+	inner []inner
+}
+
+// +stateify savable
 type inner struct {
 	v int64
 }
 
 // +stateify savable
+type outerFieldValue struct {
+	inner innerFieldValue
+}
+
+// +stateify savable
+type innerFieldValue struct {
+	v int64 `state:".(*savedFieldValue)"`
+}
+
+// +stateify savable
+type savedFieldValue struct {
+	v int64
+}
+
+func (ifv *innerFieldValue) saveV() *savedFieldValue {
+	return &savedFieldValue{ifv.v}
+}
+
+func (ifv *innerFieldValue) loadV(sfv *savedFieldValue) {
+	ifv.v = sfv.v
+}
+
+// +stateify savable
 type system struct {
 	v1 interface{}
 	v2 interface{}
 }
+
+// +stateify savable
+type system3 struct {
+	v1 interface{}
+	v2 interface{}
+	v3 interface{}
+}
diff --git a/pkg/state/tests/struct_test.go b/pkg/state/tests/struct_test.go
index de9d17aa7..c91c2c032 100644
--- a/pkg/state/tests/struct_test.go
+++ b/pkg/state/tests/struct_test.go
@@ -15,6 +15,7 @@
 package tests
 
 import (
+	"math/rand"
 	"testing"
 
 	"gvisor.dev/gvisor/pkg/state"
@@ -67,12 +68,23 @@ func TestRegisterTypeOnlyStruct(t *testing.T) {
 }
 
 func TestEmbeddedPointers(t *testing.T) {
-	var (
-		ofs outerSame
-		of1 outerFieldFirst
-		of2 outerFieldSecond
-		oa  outerArray
-	)
+	// Give each int64 a random value to prevent Go from using
+	// runtime.staticuint64s, which confounds tests for struct duplication.
+	magic := func() int64 {
+		for {
+			n := rand.Int63()
+			if n < 0 || n > 255 {
+				return n
+			}
+		}
+	}
+
+	ofs := outerSame{inner{magic()}}
+	of1 := outerFieldFirst{inner{magic()}, magic()}
+	of2 := outerFieldSecond{magic(), inner{magic()}}
+	oa := outerArray{[2]inner{{magic()}, {magic()}}}
+	osl := outerSlice{oa.inner[:]}
+	ofv := outerFieldValue{innerFieldValue{magic()}}
 
 	runTestCases(t, false, "embedded-pointers", []interface{}{
 		system{&ofs, &ofs.inner},
@@ -85,5 +97,15 @@ func TestEmbeddedPointers(t *testing.T) {
 		system{&oa, &oa.inner[1]},
 		system{&oa.inner[0], &oa},
 		system{&oa.inner[1], &oa},
+		system3{&oa, &oa.inner[0], &oa.inner[1]},
+		system3{&oa, &oa.inner[1], &oa.inner[0]},
+		system3{&oa.inner[0], &oa, &oa.inner[1]},
+		system3{&oa.inner[1], &oa, &oa.inner[0]},
+		system3{&oa.inner[0], &oa.inner[1], &oa},
+		system3{&oa.inner[1], &oa.inner[0], &oa},
+		system{&oa, &osl},
+		system{&osl, &oa},
+		system{&ofv, &ofv.inner},
+		system{&ofv.inner, &ofv},
 	})
 }