8 files changed, 39 insertions, 5 deletions
diff --git a/pkg/sentry/fs/tty/line_discipline.go b/pkg/sentry/fs/tty/line_discipline.go
index 12b1c6097..2e9dd2d55 100644
--- a/pkg/sentry/fs/tty/line_discipline.go
+++ b/pkg/sentry/fs/tty/line_discipline.go
@@ -27,6 +27,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 const (
 	// canonMaxBytes is the number of bytes that fit into a single line of
 	// terminal input in canonical mode. This corresponds to N_TTY_BUF_SIZE
@@ -443,3 +445,5 @@ func (l *lineDiscipline) peek(b []byte) int {
 	}
 	return size
 }
+
+// LINT.ThenChange(../../fsimpl/devpts/line_discipline.go)
diff --git a/pkg/sentry/fs/tty/master.go b/pkg/sentry/fs/tty/master.go
index f62da49bd..fe07fa929 100644
--- a/pkg/sentry/fs/tty/master.go
+++ b/pkg/sentry/fs/tty/master.go
@@ -26,6 +26,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // masterInodeOperations are the fs.InodeOperations for the master end of the
 // Terminal (ptmx file).
 //
@@ -232,3 +234,5 @@ func maybeEmitUnimplementedEvent(ctx context.Context, cmd uint32) {
 		unimpl.EmitUnimplementedEvent(ctx)
 	}
 }
+
+// LINT.ThenChange(../../fsimpl/devpts/master.go)
diff --git a/pkg/sentry/fs/tty/queue.go b/pkg/sentry/fs/tty/queue.go
index 1ca79c0b2..ceabb9b1e 100644
--- a/pkg/sentry/fs/tty/queue.go
+++ b/pkg/sentry/fs/tty/queue.go
@@ -25,6 +25,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // waitBufMaxBytes is the maximum size of a wait buffer. It is based on
 // TTYB_DEFAULT_MEM_LIMIT.
 const waitBufMaxBytes = 131072
@@ -234,3 +236,5 @@ func (q *queue) waitBufAppend(b []byte) {
 	q.waitBuf = append(q.waitBuf, b)
 	q.waitBufLen += uint64(len(b))
 }
+
+// LINT.ThenChange(../../fsimpl/devpts/queue.go)
diff --git a/pkg/sentry/fs/tty/slave.go b/pkg/sentry/fs/tty/slave.go
index 6a2dbc576..9871f6fc6 100644
--- a/pkg/sentry/fs/tty/slave.go
+++ b/pkg/sentry/fs/tty/slave.go
@@ -25,6 +25,8 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// LINT.IfChange
+
 // slaveInodeOperations are the fs.InodeOperations for the slave end of the
 // Terminal (pts file).
 //
@@ -172,3 +174,5 @@ func (sf *slaveFileOperations) Ioctl(ctx context.Context, _ *fs.File, io usermem
 		return 0, syserror.ENOTTY
 	}
 }
+
+// LINT.ThenChange(../../fsimpl/devpts/slave.go)
diff --git a/pkg/sentry/fs/tty/terminal.go b/pkg/sentry/fs/tty/terminal.go
index 5883f26db..ddcccf4da 100644
--- a/pkg/sentry/fs/tty/terminal.go
+++ b/pkg/sentry/fs/tty/terminal.go
@@ -23,6 +23,8 @@ import (
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
+// LINT.IfChange
+
 // Terminal is a pseudoterminal.
 //
 // +stateify savable
@@ -126,3 +128,5 @@ func (tm *Terminal) tty(isMaster bool) *kernel.TTY {
 	}
 	return tm.slaveKTTY
 }
+
+// LINT.ThenChange(../../fsimpl/devpts/terminal.go)
diff --git a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
index 64f1b142c..142ee53b0 100755
--- a/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
+++ b/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go
@@ -163,16 +163,25 @@ func (a *Accessor) CreateDeviceFile(ctx context.Context, pathname string, kind v
 func (a *Accessor) UserspaceInit(ctx context.Context) error {
 	actx := a.wrapContext(ctx)
 
-	// systemd: src/shared/dev-setup.c:dev_setup()
+	// Initialize symlinks.
 	for _, symlink := range []struct {
 		source string
 		target string
 	}{
-		// /proc/kcore is not implemented.
+		// systemd: src/shared/dev-setup.c:dev_setup()
 		{source: "fd", target: "/proc/self/fd"},
 		{source: "stdin", target: "/proc/self/fd/0"},
 		{source: "stdout", target: "/proc/self/fd/1"},
 		{source: "stderr", target: "/proc/self/fd/2"},
+		// /proc/kcore is not implemented.
+
+		// Linux implements /dev/ptmx as a device node, but advises
+		// container implementations to create /dev/ptmx as a symlink
+		// to pts/ptmx (Documentation/filesystems/devpts.txt). Systemd
+		// follows this advice (src/nspawn/nspawn.c:setup_pts()), while
+		// LXC tries to create a bind mount and falls back to a symlink
+		// (src/lxc/conf.c:lxc_setup_devpts()).
+		{source: "ptmx", target: "pts/ptmx"},
 	} {
 		if err := a.vfsObj.SymlinkAt(actx, a.creds, a.pathOperationAt(symlink.source), symlink.target); err != nil {
 			return fmt.Errorf("failed to create symlink %q => %q: %v", symlink.source, symlink.target, err)
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 3164d022c..1d46dba25 100755
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -391,7 +391,7 @@ func (fs *Filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 	// O_NOFOLLOW have no effect here (they're handled by VFS by setting
 	// appropriate bits in rp), but are returned by
 	// FileDescriptionImpl.StatusFlags().
-	opts.Flags &= linux.O_ACCMODE | linux.O_CREAT | linux.O_EXCL | linux.O_TRUNC | linux.O_DIRECTORY | linux.O_NOFOLLOW
+	opts.Flags &= linux.O_ACCMODE | linux.O_CREAT | linux.O_EXCL | linux.O_TRUNC | linux.O_DIRECTORY | linux.O_NOFOLLOW | linux.O_NONBLOCK
 	ats := vfs.AccessTypesForOpenFlags(&opts)
 
 	// Do not create new file.
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index 9f526359e..a946645f6 100755
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -216,6 +216,11 @@ func (a *InodeAttrs) Init(creds *auth.Credentials, ino uint64, mode linux.FileMo
 	atomic.StoreUint32(&a.nlink, nlink)
 }
 
+// Ino returns the inode id.
+func (a *InodeAttrs) Ino() uint64 {
+	return atomic.LoadUint64(&a.ino)
+}
+
 // Mode implements Inode.Mode.
 func (a *InodeAttrs) Mode() linux.FileMode {
 	return linux.FileMode(atomic.LoadUint32(&a.mode))
@@ -359,8 +364,8 @@ func (o *OrderedChildren) Destroy() {
 // cache. Populate returns the number of directories inserted, which the caller
 // may use to update the link count for the parent directory.
 //
-// Precondition: d.Impl() must be a kernfs Dentry. d must represent a directory
-// inode. children must not contain any conflicting entries already in o.
+// Precondition: d must represent a directory inode. children must not contain
+// any conflicting entries already in o.
 func (o *OrderedChildren) Populate(d *Dentry, children map[string]*Dentry) uint32 {
 	var links uint32
 	for name, child := range children {