Implement command IPC_INFO for semctl.

PiperOrigin-RevId: 345589628

pkg/abi/linux/sem.go

@@ -41,6 +41,12 @@ const (
 	SEMMNS = SEMMNI * SEMMSL
 	SEMOPM = 500
 	SEMVMX = 32767
+	SEMAEM = SEMVMX
+
+	// followings are unused in kernel
+	SEMUME = SEMOPM
+	SEMMNU = SEMMNS
+	SEMMAP = SEMMNS
 )
 
 const SEM_UNDO = 0x1000
@@ -53,3 +59,21 @@ type Sembuf struct {
 	SemOp  int16
 	SemFlg int16
 }
+
+// SemInfo is equivalent to struct seminfo.
+//
+// Source: include/uapi/linux/sem.h
+//
+// +marshal
+type SemInfo struct {
+	SemMap uint32
+	SemMni uint32
+	SemMns uint32
+	SemMnu uint32
+	SemMsl uint32
+	SemOpm uint32
+	SemUme uint32
+	SemUsz uint32
+	SemVmx uint32
+	SemAem uint32
+}

pkg/sentry/kernel/semaphore/semaphore.go

@@ -176,6 +176,22 @@ func (r *Registry) FindOrCreate(ctx context.Context, key, nsems int32, mode linu
 	return r.newSet(ctx, key, owner, owner, perms, nsems)
 }
 
+// IPCInfo returns information about system-wide semaphore limits and parameters.
+func (r *Registry) IPCInfo() *linux.SemInfo {
+	return &linux.SemInfo{
+		SemMap: linux.SEMMAP,
+		SemMni: linux.SEMMNI,
+		SemMns: linux.SEMMNS,
+		SemMnu: linux.SEMMNU,
+		SemMsl: linux.SEMMSL,
+		SemOpm: linux.SEMOPM,
+		SemUme: linux.SEMUME,
+		SemUsz: 0, // SemUsz not supported.
+		SemVmx: linux.SEMVMX,
+		SemAem: linux.SEMAEM,
+	}
+}
+
 // RemoveID removes set with give 'id' from the registry and marks the set as
 // dead. All waiters will be awakened and fail.
 func (r *Registry) RemoveID(id int32, creds *auth.Credentials) error {

pkg/sentry/syscalls/linux/linux64.go

@@ -118,7 +118,7 @@ var AMD64 = &kernel.SyscallTable{
 		63:  syscalls.Supported("uname", Uname),
 		64:  syscalls.Supported("semget", Semget),
 		65:  syscalls.PartiallySupported("semop", Semop, "Option SEM_UNDO not supported.", nil),
-		66:  syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
+		66:  syscalls.PartiallySupported("semctl", Semctl, "Options SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
 		67:  syscalls.Supported("shmdt", Shmdt),
 		68:  syscalls.ErrorWithEvent("msgget", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
 		69:  syscalls.ErrorWithEvent("msgsnd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}), // TODO(b/29354921)
@@ -619,7 +619,7 @@ var ARM64 = &kernel.SyscallTable{
 		188: syscalls.ErrorWithEvent("msgrcv", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}),          // TODO(b/29354921)
 		189: syscalls.ErrorWithEvent("msgsnd", syserror.ENOSYS, "", []string{"gvisor.dev/issue/135"}),          // TODO(b/29354921)
 		190: syscalls.Supported("semget", Semget),
-		191: syscalls.PartiallySupported("semctl", Semctl, "Options IPC_INFO, SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
+		191: syscalls.PartiallySupported("semctl", Semctl, "Options SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
 		192: syscalls.ErrorWithEvent("semtimedop", syserror.ENOSYS, "", []string{"gvisor.dev/issue/137"}),
 		193: syscalls.PartiallySupported("semop", Semop, "Option SEM_UNDO not supported.", nil),
 		194: syscalls.PartiallySupported("shmget", Shmget, "Option SHM_HUGETLB is not supported.", nil),

pkg/sentry/syscalls/linux/sys_sem.go

@@ -146,8 +146,15 @@ func Semctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 		v, err := getNCnt(t, id, num)
 		return uintptr(v), nil, err
 
-	case linux.IPC_INFO,
-		linux.SEM_INFO,
+	case linux.IPC_INFO:
+		buf := args[3].Pointer()
+		r := t.IPCNamespace().SemaphoreRegistry()
+		info := r.IPCInfo()
+		_, err := info.CopyOut(t, buf)
+		// TODO(gvisor.dev/issue/137): Return the index of the highest used entry.
+		return 0, nil, err
+
+	case linux.SEM_INFO,
 		linux.SEM_STAT,
 		linux.SEM_STAT_ANY:
 

test/syscalls/linux/semaphore.cc

@@ -773,6 +773,21 @@ TEST(SemaphoreTest, SemopGetncntOnSignal_NoRandomSave) {
   EXPECT_EQ(semctl(sem.get(), 0, GETNCNT), 0);
 }
 
+TEST(SemaphoreTest, IpcInfo) {
+  struct seminfo info;
+  ASSERT_THAT(semctl(0, 0, IPC_INFO, &info), SyscallSucceeds());
+
+  EXPECT_EQ(info.semmap, 1024000000);
+  EXPECT_EQ(info.semmni, 32000);
+  EXPECT_EQ(info.semmns, 1024000000);
+  EXPECT_EQ(info.semmnu, 1024000000);
+  EXPECT_EQ(info.semmsl, 32000);
+  EXPECT_EQ(info.semopm, 500);
+  EXPECT_EQ(info.semume, 500);
+  EXPECT_EQ(info.semvmx, 32767);
+  EXPECT_EQ(info.semaem, 32767);
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor