Provide better message when memfd_create fails with ENOSYS

Updates #100

PiperOrigin-RevId: 213414821
Change-Id: I90c2e6c18c54a6afcd7ad6f409f670aa31577d37

2 files changed, 6 insertions, 0 deletions

diff --git a/pkg/sentry/platform/filemem/filemem.go b/pkg/sentry/platform/filemem/filemem.go
index feb020ef8..f278c8d63 100644
--- a/pkg/sentry/platform/filemem/filemem.go
+++ b/pkg/sentry/platform/filemem/filemem.go
@@ -233,6 +233,9 @@ func newFromFile(file *os.File) (*FileMem, error) {
 func New(name string) (*FileMem, error) {
 	fd, err := memutil.CreateMemFD(name, 0)
 	if err != nil {
+		if e, ok := err.(syscall.Errno); ok && e == syscall.ENOSYS {
+			return nil, fmt.Errorf("memfd_create(2) is not implemented. Check that you have Linux 3.17 or higher")
+		}
 		return nil, err
 	}
 	return newFromFile(os.NewFile(uintptr(fd), name))
diff --git a/pkg/sentry/usage/memory.go b/pkg/sentry/usage/memory.go
index f13a77779..92a478d85 100644
--- a/pkg/sentry/usage/memory.go
+++ b/pkg/sentry/usage/memory.go
@@ -122,6 +122,9 @@ func Init() error {
 	const name = "memory-usage"
 	fd, err := memutil.CreateMemFD(name, 0)
 	if err != nil {
+		if e, ok := err.(syscall.Errno); ok && e == syscall.ENOSYS {
+			return fmt.Errorf("memfd_create(2) is not implemented. Check that you have Linux 3.17 or higher")
+		}
 		return fmt.Errorf("error creating usage file: %v", err)
 	}
 	file := os.NewFile(uintptr(fd), name)