Updated some documentation.

internal/console/source_linux_test.go

@@ -21,6 +21,7 @@ package console
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -28,6 +29,122 @@ import (
 	"testing"
 )
 
+func TestSourceWaitsForConsoleOwner(t *testing.T) {
+	for _, terminal := range []int{2, 15} {
+		t.Run(fmt.Sprint(terminal), func(t *testing.T) {
+			root := t.TempDir()
+			activePath := filepath.Join(root, "sys/devices/virtual/tty/tty0/active")
+			if err := os.MkdirAll(filepath.Dir(activePath), 0700); err != nil {
+				t.Fatal(err)
+			}
+			if err := os.WriteFile(activePath, fmt.Appendf(nil, "tty%d\n", terminal), 0600); err != nil {
+				t.Fatal(err)
+			}
+			// Other occupied consoles (including tty1) must not make this one
+			// appear occupied. There are deliberately no target device files yet.
+			mask := uint16(3)
+			stateCalls := 0
+			source := &Source{
+				root: root,
+				usage: func(path string) (uint16, error) {
+					if path != filepath.Join(root, "dev/tty1") {
+						t.Fatalf("usage query opened target or foreground alias: %s", path)
+					}
+					return mask, nil
+				},
+				state: func(path string) (bool, bool, bool, error) {
+					stateCalls++
+					if mask&(uint16(1)<<uint(terminal)) == 0 {
+						t.Fatal("opened unused console")
+					}
+					if path != filepath.Join(root, "dev", fmt.Sprintf("tty%d", terminal)) {
+						t.Fatal("queried wrong console", path)
+					}
+					return true, true, true, nil
+				},
+			}
+			for range 2 {
+				if number, active, _, err := source.State(); err != nil || active || number != terminal {
+					t.Fatal("unused console accepted input", number, active, err)
+				}
+				if snapshot, err := source.Read(); err != nil || snapshot.Active || snapshot.Terminal != terminal || len(snapshot.Cells) != 0 {
+					t.Fatal("unused console read screen devices", snapshot, err)
+				}
+			}
+			if stateCalls != 0 {
+				t.Fatal("probed unused console", stateCalls)
+			}
+			if err := os.Mkdir(filepath.Join(root, "dev"), 0700); err != nil {
+				t.Fatal(err)
+			}
+			text := "login: "
+			attributes := append([]byte{1, byte(len(text)), 0, 0}, make([]byte, len(text)*2)...)
+			if err := os.WriteFile(filepath.Join(root, "dev", fmt.Sprintf("vcsa%d", terminal)), attributes, 0600); err != nil {
+				t.Fatal(err)
+			}
+			var data []byte
+			for _, value := range text {
+				data = binary.NativeEndian.AppendUint32(data, uint32(value))
+			}
+			if err := os.WriteFile(filepath.Join(root, "dev", fmt.Sprintf("vcsu%d", terminal)), data, 0600); err != nil {
+				t.Fatal(err)
+			}
+			// A login prompt is enough; there is no authenticated user/session.
+			mask |= uint16(1) << uint(terminal)
+			if number, active, numLock, err := source.State(); err != nil || !active || !numLock || number != terminal {
+				t.Fatal("login prompt did not activate input", number, active, numLock, err)
+			}
+			if snapshot, err := source.Read(); err != nil || !snapshot.Active || string(snapshot.Cells) != text || !snapshot.NumLock || !snapshot.CapsLock {
+				t.Fatal("login prompt was not readable", snapshot, err)
+			}
+			mask = 3
+			if _, active, _, err := source.State(); err != nil || active {
+				t.Fatal("console owner disappeared but input stayed active", active, err)
+			}
+			problem := errors.New("console usage unavailable")
+			source.usage = func(string) (uint16, error) { return 0, problem }
+			if _, active, _, err := source.State(); !errors.Is(err, problem) || active {
+				t.Fatal("usage failure permitted a target probe", active, err)
+			}
+			source.Configure_ignored_vts([]int{terminal})
+			if _, active, _, err := source.State(); err != nil || active {
+				t.Fatal("ignored console queried usage", active, err)
+			}
+		})
+	}
+}
+
+func TestSourcePreservesBootAndHighConsoleProbes(t *testing.T) {
+	for _, terminal := range []int{1, 16, 63} {
+		t.Run(fmt.Sprint(terminal), func(t *testing.T) {
+			root := t.TempDir()
+			activePath := filepath.Join(root, "sys/devices/virtual/tty/tty0/active")
+			if err := os.MkdirAll(filepath.Dir(activePath), 0700); err != nil {
+				t.Fatal(err)
+			}
+			if err := os.WriteFile(activePath, fmt.Appendf(nil, "tty%d\n", terminal), 0600); err != nil {
+				t.Fatal(err)
+			}
+			source := &Source{
+				root: root,
+				usage: func(string) (uint16, error) {
+					t.Fatal("boot/high console gated on truncated bitmap")
+					return 0, nil
+				},
+				state: func(path string) (bool, bool, bool, error) {
+					if path != filepath.Join(root, "dev", fmt.Sprintf("tty%d", terminal)) {
+						t.Fatal("queried wrong console", path)
+					}
+					return true, false, false, nil
+				},
+			}
+			if number, active, _, err := source.State(); err != nil || !active || number != terminal {
+				t.Fatal("boot/high console lost input", number, active, err)
+			}
+		})
+	}
+}
+
 func TestSourceRetriesUnicodeSizeChange(t *testing.T) {
 	for _, cols := range []int{1, 3} {
 		t.Run(fmt.Sprint(cols), func(t *testing.T) {