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

4 files changed, 38 insertions, 13 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
+}