Get /bin/true to run on VFS2

Included:
- loader_test.go RunTest and TestStartSignal VFS2
- container_test.go TestAppExitStatus on VFS2
- experimental flag added to runsc to turn on VFS2

Note: shared mounts are not yet supported.
PiperOrigin-RevId: 307070753

1 files changed, 33 insertions, 0 deletions

diff --git a/runsc/boot/fds.go b/runsc/boot/fds.go
index 5314b0f2a..7e49f6f9f 100644
--- a/runsc/boot/fds.go
+++ b/runsc/boot/fds.go
@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/host"
+	vfshost "gvisor.dev/gvisor/pkg/sentry/fsimpl/host"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 )
 
@@ -31,6 +32,10 @@ func createFDTable(ctx context.Context, console bool, stdioFDs []int) (*kernel.F
 		return nil, fmt.Errorf("stdioFDs should contain exactly 3 FDs (stdin, stdout, and stderr), but %d FDs received", len(stdioFDs))
 	}
 
+	if kernel.VFS2Enabled {
+		return createFDTableVFS2(ctx, console, stdioFDs)
+	}
+
 	k := kernel.KernelFromContext(ctx)
 	fdTable := k.NewFDTable()
 	defer fdTable.DecRef()
@@ -78,3 +83,31 @@ func createFDTable(ctx context.Context, console bool, stdioFDs []int) (*kernel.F
 	fdTable.IncRef()
 	return fdTable, nil
 }
+
+func createFDTableVFS2(ctx context.Context, console bool, stdioFDs []int) (*kernel.FDTable, error) {
+	k := kernel.KernelFromContext(ctx)
+	fdTable := k.NewFDTable()
+	defer fdTable.DecRef()
+
+	hostMount, err := vfshost.NewMount(k.VFS())
+	if err != nil {
+		return nil, fmt.Errorf("creating host mount: %w", err)
+	}
+
+	for appFD, hostFD := range stdioFDs {
+		// TODO(gvisor.dev/issue/1482): Add TTY support.
+		appFile, err := vfshost.ImportFD(hostMount, hostFD, false)
+		if err != nil {
+			return nil, err
+		}
+
+		if err := fdTable.NewFDAtVFS2(ctx, int32(appFD), appFile, kernel.FDFlags{}); err != nil {
+			appFile.DecRef()
+			return nil, err
+		}
+		appFile.DecRef()
+	}
+
+	fdTable.IncRef()
+	return fdTable, nil
+}