Port imported TTY fds to vfs2.

Refactor fs/host.TTYFileOperations so that the relevant functionality can be
shared with VFS2 (fsimpl/host.ttyFD).

Incorporate host.defaultFileFD into the default host.fileDescription. This way,
there is no need for a separate default_file.go. As in vfs1, the TTY file
implementation can be built on top of this default and override operations as
necessary (PRead/Read/PWrite/Write, Release, Ioctl).

Note that these changes still need to be plumbed into runsc, which refers to
imported TTYs in control/proc.go:ExecAsync.

Updates #1672.

PiperOrigin-RevId: 301718157

3 files changed, 13 insertions, 4 deletions

diff --git a/pkg/sentry/fs/host/ioctl_unsafe.go b/pkg/sentry/fs/host/ioctl_unsafe.go
index 271582e54..150ac8e19 100644
--- a/pkg/sentry/fs/host/ioctl_unsafe.go
+++ b/pkg/sentry/fs/host/ioctl_unsafe.go
@@ -21,6 +21,8 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 )
 
+// LINT.IfChange
+
 func ioctlGetTermios(fd int) (*linux.Termios, error) {
 	var t linux.Termios
 	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), linux.TCGETS, uintptr(unsafe.Pointer(&t)))
@@ -54,3 +56,5 @@ func ioctlSetWinsize(fd int, w *linux.Winsize) error {
 	}
 	return nil
 }
+
+// LINT.ThenChange(../../fsimpl/host/ioctl_unsafe.go)
diff --git a/pkg/sentry/fs/host/tty.go b/pkg/sentry/fs/host/tty.go
index 3f218b4a7..cb91355ab 100644
--- a/pkg/sentry/fs/host/tty.go
+++ b/pkg/sentry/fs/host/tty.go
@@ -26,6 +26,8 @@ import (
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
+// LINT.IfChange
+
 // TTYFileOperations implements fs.FileOperations for a host file descriptor
 // that wraps a TTY FD.
 //
@@ -43,6 +45,7 @@ type TTYFileOperations struct {
 	// connected to this TTY.
 	fgProcessGroup *kernel.ProcessGroup
 
+	// termios contains the terminal attributes for this TTY.
 	termios linux.KernelTermios
 }
 
@@ -357,3 +360,5 @@ func (t *TTYFileOperations) checkChange(ctx context.Context, sig linux.Signal) e
 	_ = pg.SendSignal(kernel.SignalInfoPriv(sig))
 	return kernel.ERESTARTSYS
 }
+
+// LINT.ThenChange(../../fsimpl/host/tty.go)
diff --git a/pkg/sentry/fs/host/util.go b/pkg/sentry/fs/host/util.go
index 388108fdf..1b0356930 100644
--- a/pkg/sentry/fs/host/util.go
+++ b/pkg/sentry/fs/host/util.go
@@ -23,7 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/device"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/time"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
 
@@ -80,9 +80,9 @@ func unstableAttr(s *syscall.Stat_t) fs.UnstableAttr {
 		Usage:            s.Blocks * 512,
 		Perms:            fs.FilePermsFromMode(linux.FileMode(s.Mode)),
 		Owner:            owner(s),
-		AccessTime:       time.FromUnix(s.Atim.Sec, s.Atim.Nsec),
-		ModificationTime: time.FromUnix(s.Mtim.Sec, s.Mtim.Nsec),
-		StatusChangeTime: time.FromUnix(s.Ctim.Sec, s.Ctim.Nsec),
+		AccessTime:       ktime.FromUnix(s.Atim.Sec, s.Atim.Nsec),
+		ModificationTime: ktime.FromUnix(s.Mtim.Sec, s.Mtim.Nsec),
+		StatusChangeTime: ktime.FromUnix(s.Ctim.Sec, s.Ctim.Nsec),
 		Links:            uint64(s.Nlink),
 	}
 }