4 files changed, 34 insertions, 32 deletions
diff --git a/pkg/sentry/fs/sys/BUILD b/pkg/sentry/fs/sys/BUILD
index 5ba23d5da..7de928e16 100644
--- a/pkg/sentry/fs/sys/BUILD
+++ b/pkg/sentry/fs/sys/BUILD
@@ -13,12 +13,13 @@ go_library(
     importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/fs/sys",
     visibility = ["//pkg/sentry:internal"],
     deps = [
+        "//pkg/abi/linux",
         "//pkg/sentry/context",
         "//pkg/sentry/device",
         "//pkg/sentry/fs",
+        "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/fs/ramfs",
         "//pkg/sentry/kernel",
         "//pkg/sentry/usermem",
-        "//pkg/syserror",
     ],
 )
diff --git a/pkg/sentry/fs/sys/devices.go b/pkg/sentry/fs/sys/devices.go
index e64aa0edc..8b728a4e4 100644
--- a/pkg/sentry/fs/sys/devices.go
+++ b/pkg/sentry/fs/sys/devices.go
@@ -16,43 +16,50 @@ package sys
 
 import (
 	"fmt"
-	"io"
 
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
-	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
-	"gvisor.googlesource.com/gvisor/pkg/syserror"
 )
 
 // +stateify savable
 type cpunum struct {
-	ramfs.Entry
+	fsutil.InodeGenericChecker       `state:"nosave"`
+	fsutil.InodeNoExtendedAttributes `state:"nosave"`
+	fsutil.InodeNoopRelease          `state:"nosave"`
+	fsutil.InodeNoopWriteOut         `state:"nosave"`
+	fsutil.InodeNotDirectory         `state:"nosave"`
+	fsutil.InodeNotMappable          `state:"nosave"`
+	fsutil.InodeNotSocket            `state:"nosave"`
+	fsutil.InodeNotSymlink           `state:"nosave"`
+	fsutil.InodeNotVirtual           `state:"nosave"`
+	fsutil.InodeNotTruncatable       `state:"nosave"`
+
+	fsutil.InodeSimpleAttributes
+	fsutil.InodeStaticFileGetter
+
+	// k is the system kernel.
+	k *kernel.Kernel
 }
 
-func (c *cpunum) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
-	if offset < 0 {
-		return 0, syserror.EINVAL
-	}
+var _ fs.InodeOperations = (*cpunum)(nil)
 
+func newPossible(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
+	var maxCore uint
 	k := kernel.KernelFromContext(ctx)
-	if k == nil {
-		return 0, io.EOF
+	if k != nil {
+		maxCore = k.ApplicationCores() - 1
 	}
+	contents := []byte(fmt.Sprintf("0-%d\n", maxCore))
 
-	str := []byte(fmt.Sprintf("0-%d\n", k.ApplicationCores()-1))
-	if offset >= int64(len(str)) {
-		return 0, io.EOF
+	c := &cpunum{
+		InodeSimpleAttributes: fsutil.NewInodeSimpleAttributes(ctx, fs.RootOwner, fs.FilePermsFromMode(0444), linux.SYSFS_MAGIC),
+		InodeStaticFileGetter: fsutil.InodeStaticFileGetter{
+			Contents: contents,
+		},
 	}
-
-	n, err := dst.CopyOut(ctx, str[offset:])
-	return int64(n), err
-}
-
-func newPossible(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
-	c := &cpunum{}
-	c.InitEntry(ctx, fs.RootOwner, fs.FilePermsFromMode(0444))
 	return newFile(c, msrc)
 }
 
diff --git a/pkg/sentry/fs/sys/fs.go b/pkg/sentry/fs/sys/fs.go
index 5ce33f87f..301fef038 100644
--- a/pkg/sentry/fs/sys/fs.go
+++ b/pkg/sentry/fs/sys/fs.go
@@ -24,6 +24,8 @@ import (
 // +stateify savable
 type filesystem struct{}
 
+var _ fs.Filesystem = (*filesystem)(nil)
+
 func init() {
 	fs.RegisterFilesystem(&filesystem{})
 }
diff --git a/pkg/sentry/fs/sys/sys.go b/pkg/sentry/fs/sys/sys.go
index 7cc1942c7..c5b56fe69 100644
--- a/pkg/sentry/fs/sys/sys.go
+++ b/pkg/sentry/fs/sys/sys.go
@@ -22,13 +22,6 @@ import (
 	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
 )
 
-// sys is a root sys node.
-//
-// +stateify savable
-type sys struct {
-	ramfs.Dir
-}
-
 func newFile(node fs.InodeOperations, msrc *fs.MountSource) *fs.Inode {
 	sattr := fs.StableAttr{
 		DeviceID:  sysfsDevice.DeviceID(),
@@ -40,8 +33,7 @@ func newFile(node fs.InodeOperations, msrc *fs.MountSource) *fs.Inode {
 }
 
 func newDir(ctx context.Context, msrc *fs.MountSource, contents map[string]*fs.Inode) *fs.Inode {
-	d := &sys{}
-	d.InitDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
+	d := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
 	return fs.NewInode(d, msrc, fs.StableAttr{
 		DeviceID:  sysfsDevice.DeviceID(),
 		InodeID:   sysfsDevice.NextIno(),