Implement TTY field in control.Processes().

Threadgroups already know their TTY (if they have one), which now contains the
TTY Index, and is returned in the Processes() call.

PiperOrigin-RevId: 284263850

7 files changed, 173 insertions, 14 deletions

diff --git a/pkg/sentry/control/proc.go b/pkg/sentry/control/proc.go
index c35faeb4c..a6f90b2bb 100644
--- a/pkg/sentry/control/proc.go
+++ b/pkg/sentry/control/proc.go
@@ -268,7 +268,6 @@ func (proc *Proc) Ps(args *PsArgs, out *string) error {
 }
 
 // Process contains information about a single process in a Sandbox.
-// TODO(b/117881927): Implement TTY field.
 type Process struct {
 	UID auth.KUID       `json:"uid"`
 	PID kernel.ThreadID `json:"pid"`
@@ -276,6 +275,9 @@ type Process struct {
 	PPID kernel.ThreadID `json:"ppid"`
 	// Processor utilization
 	C int32 `json:"c"`
+	// TTY name of the process. Will be of the form "pts/N" if there is a
+	// TTY, or "?" if there is not.
+	TTY string `json:"tty"`
 	// Start time
 	STime string `json:"stime"`
 	// CPU time
@@ -285,18 +287,19 @@ type Process struct {
 }
 
 // ProcessListToTable prints a table with the following format:
-// UID       PID       PPID      C         STIME     TIME       CMD
-// 0         1         0         0         14:04     505262ns   tail
+// UID       PID       PPID      C         TTY		STIME     TIME       CMD
+// 0         1         0         0         pty/4	14:04     505262ns   tail
 func ProcessListToTable(pl []*Process) string {
 	var buf bytes.Buffer
 	tw := tabwriter.NewWriter(&buf, 10, 1, 3, ' ', 0)
-	fmt.Fprint(tw, "UID\tPID\tPPID\tC\tSTIME\tTIME\tCMD")
+	fmt.Fprint(tw, "UID\tPID\tPPID\tC\tTTY\tSTIME\tTIME\tCMD")
 	for _, d := range pl {
-		fmt.Fprintf(tw, "\n%d\t%d\t%d\t%d\t%s\t%s\t%s",
+		fmt.Fprintf(tw, "\n%d\t%d\t%d\t%d\t%s\t%s\t%s\t%s",
 			d.UID,
 			d.PID,
 			d.PPID,
 			d.C,
+			d.TTY,
 			d.STime,
 			d.Time,
 			d.Cmd)
@@ -347,7 +350,7 @@ func Processes(k *kernel.Kernel, containerID string, out *[]*Process) error {
 		if p := tg.Leader().Parent(); p != nil {
 			ppid = p.PIDNamespace().IDOfThreadGroup(p.ThreadGroup())
 		}
-		*out = append(*out, &Process{
+		p := Process{
 			UID:   tg.Leader().Credentials().EffectiveKUID,
 			PID:   pid,
 			PPID:  ppid,
@@ -355,7 +358,9 @@ func Processes(k *kernel.Kernel, containerID string, out *[]*Process) error {
 			C:     percentCPU(tg.CPUStats(), tg.Leader().StartTime(), now),
 			Time:  tg.CPUStats().SysTime.String(),
 			Cmd:   tg.Leader().Name(),
-		})
+			TTY:   ttyName(tg.TTY()),
+		}
+		*out = append(*out, &p)
 	}
 	sort.Slice(*out, func(i, j int) bool { return (*out)[i].PID < (*out)[j].PID })
 	return nil
@@ -395,3 +400,10 @@ func percentCPU(stats usage.CPUStats, startTime, now ktime.Time) int32 {
 	}
 	return int32(percentCPU)
 }
+
+func ttyName(tty *kernel.TTY) string {
+	if tty == nil {
+		return "?"
+	}
+	return fmt.Sprintf("pts/%d", tty.Index)
+}
diff --git a/pkg/sentry/control/proc_test.go b/pkg/sentry/control/proc_test.go
index d8ada2694..0a88459b2 100644
--- a/pkg/sentry/control/proc_test.go
+++ b/pkg/sentry/control/proc_test.go
@@ -34,7 +34,7 @@ func TestProcessListTable(t *testing.T) {
 	}{
 		{
 			pl:       []*Process{},
-			expected: "UID       PID       PPID      C         STIME     TIME      CMD",
+			expected: "UID       PID       PPID      C         TTY       STIME     TIME      CMD",
 		},
 		{
 			pl: []*Process{
@@ -43,6 +43,7 @@ func TestProcessListTable(t *testing.T) {
 					PID:   0,
 					PPID:  0,
 					C:     0,
+					TTY:   "?",
 					STime: "0",
 					Time:  "0",
 					Cmd:   "zero",
@@ -52,14 +53,15 @@ func TestProcessListTable(t *testing.T) {
 					PID:   1,
 					PPID:  1,
 					C:     1,
+					TTY:   "pts/4",
 					STime: "1",
 					Time:  "1",
 					Cmd:   "one",
 				},
 			},
-			expected: `UID       PID       PPID      C         STIME     TIME      CMD
-0         0         0         0         0         0         zero
-1         1         1         1         1         1         one`,
+			expected: `UID       PID       PPID      C         TTY       STIME     TIME      CMD
+0         0         0         0         ?         0         0         zero
+1         1         1         1         pts/4     1         1         one`,
 		},
 	}
 
diff --git a/pkg/sentry/fs/tty/terminal.go b/pkg/sentry/fs/tty/terminal.go
index ff8138820..917f90cc0 100644
--- a/pkg/sentry/fs/tty/terminal.go
+++ b/pkg/sentry/fs/tty/terminal.go
@@ -53,8 +53,8 @@ func newTerminal(ctx context.Context, d *dirInodeOperations, n uint32) *Terminal
 		d:          d,
 		n:          n,
 		ld:         newLineDiscipline(termios),
-		masterKTTY: &kernel.TTY{},
-		slaveKTTY:  &kernel.TTY{},
+		masterKTTY: &kernel.TTY{Index: n},
+		slaveKTTY:  &kernel.TTY{Index: n},
 	}
 	t.EnableLeakCheck("tty.Terminal")
 	return &t
diff --git a/pkg/sentry/kernel/tty.go b/pkg/sentry/kernel/tty.go
index 34f84487a..048de26dc 100644
--- a/pkg/sentry/kernel/tty.go
+++ b/pkg/sentry/kernel/tty.go
@@ -21,8 +21,19 @@ import "sync"
 //
 // +stateify savable
 type TTY struct {
+	// Index is the terminal index. It is immutable.
+	Index uint32
+
 	mu sync.Mutex `state:"nosave"`
 
 	// tg is protected by mu.
 	tg *ThreadGroup
 }
+
+// TTY returns the thread group's controlling terminal. If nil, there is no
+// controlling terminal.
+func (tg *ThreadGroup) TTY() *TTY {
+	tg.signalHandlers.mu.Lock()
+	defer tg.signalHandlers.mu.Unlock()
+	return tg.tty
+}
diff --git a/runsc/container/container_test.go b/runsc/container/container_test.go
index 07eacaac0..1d06f2780 100644
--- a/runsc/container/container_test.go
+++ b/runsc/container/container_test.go
@@ -98,10 +98,14 @@ func procListsEqual(got, want []*control.Process) bool {
 	for i := range got {
 		pd1 := got[i]
 		pd2 := want[i]
-		// Zero out unimplemented and timing dependant fields.
+		// Zero out timing dependant fields.
 		pd1.Time = ""
 		pd1.STime = ""
 		pd1.C = 0
+		// Ignore TTY field too, since it's not relevant in the cases
+		// where we use this method. Tests that care about the TTY
+		// field should check for it themselves.
+		pd1.TTY = ""
 		if *pd1 != *pd2 {
 			return false
 		}
@@ -2112,6 +2116,95 @@ func TestOverlayfsStaleRead(t *testing.T) {
 	}
 }
 
+// TestTTYField checks TTY field returned by container.Processes().
+func TestTTYField(t *testing.T) {
+	stop := testutil.StartReaper()
+	defer stop()
+
+	testApp, err := testutil.FindFile("runsc/container/test_app/test_app")
+	if err != nil {
+		t.Fatal("error finding test_app:", err)
+	}
+
+	testCases := []struct {
+		name         string
+		useTTY       bool
+		wantTTYField string
+	}{
+		{
+			name:         "no tty",
+			useTTY:       false,
+			wantTTYField: "?",
+		},
+		{
+			name:         "tty used",
+			useTTY:       true,
+			wantTTYField: "pts/0",
+		},
+	}
+
+	for _, test := range testCases {
+		t.Run(test.name, func(t *testing.T) {
+			conf := testutil.TestConfig()
+
+			// We will run /bin/sleep, possibly with an open TTY.
+			cmd := []string{"/bin/sleep", "10000"}
+			if test.useTTY {
+				// Run inside the "pty-runner".
+				cmd = append([]string{testApp, "pty-runner"}, cmd...)
+			}
+
+			spec := testutil.NewSpecWithArgs(cmd...)
+			rootDir, bundleDir, err := testutil.SetupContainer(spec, conf)
+			if err != nil {
+				t.Fatalf("error setting up container: %v", err)
+			}
+			defer os.RemoveAll(rootDir)
+			defer os.RemoveAll(bundleDir)
+
+			// Create and start the container.
+			args := Args{
+				ID:        testutil.UniqueContainerID(),
+				Spec:      spec,
+				BundleDir: bundleDir,
+			}
+			c, err := New(conf, args)
+			if err != nil {
+				t.Fatalf("error creating container: %v", err)
+			}
+			defer c.Destroy()
+			if err := c.Start(conf); err != nil {
+				t.Fatalf("error starting container: %v", err)
+			}
+
+			// Wait for sleep to be running, and check the TTY
+			// field.
+			var gotTTYField string
+			cb := func() error {
+				ps, err := c.Processes()
+				if err != nil {
+					err = fmt.Errorf("error getting process data from container: %v", err)
+					return &backoff.PermanentError{Err: err}
+				}
+				for _, p := range ps {
+					if strings.Contains(p.Cmd, "sleep") {
+						gotTTYField = p.TTY
+						return nil
+					}
+				}
+				return fmt.Errorf("sleep not running")
+			}
+			if err := testutil.Poll(cb, 30*time.Second); err != nil {
+				t.Fatalf("error waiting for sleep process: %v", err)
+			}
+
+			if gotTTYField != test.wantTTYField {
+				t.Errorf("tty field got %q, want %q", gotTTYField, test.wantTTYField)
+			}
+		})
+	}
+}
+
 // executeSync synchronously executes a new process.
 func (cont *Container) executeSync(args *control.ExecArgs) (syscall.WaitStatus, error) {
 	pid, err := cont.Execute(args)
diff --git a/runsc/container/test_app/BUILD b/runsc/container/test_app/BUILD
index 9bf9e6e9d..bfd338bb6 100644
--- a/runsc/container/test_app/BUILD
+++ b/runsc/container/test_app/BUILD
@@ -15,5 +15,6 @@ go_binary(
         "//pkg/unet",
         "//runsc/testutil",
         "@com_github_google_subcommands//:go_default_library",
+        "@com_github_kr_pty//:go_default_library",
     ],
 )
diff --git a/runsc/container/test_app/test_app.go b/runsc/container/test_app/test_app.go
index 913d781c6..a1c8a741a 100644
--- a/runsc/container/test_app/test_app.go
+++ b/runsc/container/test_app/test_app.go
@@ -19,6 +19,7 @@ package main
 import (
 	"context"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"log"
 	"net"
@@ -31,6 +32,7 @@ import (
 
 	"flag"
 	"github.com/google/subcommands"
+	"github.com/kr/pty"
 	"gvisor.dev/gvisor/runsc/testutil"
 )
 
@@ -41,6 +43,7 @@ func main() {
 	subcommands.Register(new(fdReceiver), "")
 	subcommands.Register(new(fdSender), "")
 	subcommands.Register(new(forkBomb), "")
+	subcommands.Register(new(ptyRunner), "")
 	subcommands.Register(new(reaper), "")
 	subcommands.Register(new(syscall), "")
 	subcommands.Register(new(taskTree), "")
@@ -352,3 +355,40 @@ func (c *capability) Execute(ctx context.Context, f *flag.FlagSet, args ...inter
 
 	return subcommands.ExitSuccess
 }
+
+type ptyRunner struct{}
+
+// Name implements subcommands.Command.
+func (*ptyRunner) Name() string {
+	return "pty-runner"
+}
+
+// Synopsis implements subcommands.Command.
+func (*ptyRunner) Synopsis() string {
+	return "runs the given command with an open pty terminal"
+}
+
+// Usage implements subcommands.Command.
+func (*ptyRunner) Usage() string {
+	return "pty-runner [command]"
+}
+
+// SetFlags implements subcommands.Command.SetFlags.
+func (*ptyRunner) SetFlags(f *flag.FlagSet) {}
+
+// Execute implements subcommands.Command.
+func (*ptyRunner) Execute(_ context.Context, fs *flag.FlagSet, _ ...interface{}) subcommands.ExitStatus {
+	c := exec.Command(fs.Args()[0], fs.Args()[1:]...)
+	f, err := pty.Start(c)
+	if err != nil {
+		fmt.Printf("pty.Start failed: %v", err)
+		return subcommands.ExitFailure
+	}
+	defer f.Close()
+
+	// Copy stdout from the command to keep this process alive until the
+	// subprocess exits.
+	io.Copy(os.Stdout, f)
+
+	return subcommands.ExitSuccess
+}