Implement command SEM_INFO and SEM_STAT for semctl.

PiperOrigin-RevId: 347711998

4 files changed, 62 insertions, 7 deletions

diff --git a/pkg/abi/linux/sem.go b/pkg/abi/linux/sem.go
index 0adff8dff..2424884c1 100644
--- a/pkg/abi/linux/sem.go
+++ b/pkg/abi/linux/sem.go
@@ -43,10 +43,10 @@ const (
 	SEMVMX = 32767
 	SEMAEM = SEMVMX
 
-	// followings are unused in kernel
 	SEMUME = SEMOPM
 	SEMMNU = SEMMNS
 	SEMMAP = SEMMNS
+	SEMUSZ = 20
 )
 
 const SEM_UNDO = 0x1000
diff --git a/pkg/sentry/kernel/semaphore/semaphore.go b/pkg/sentry/kernel/semaphore/semaphore.go
index 3dd3953b3..db01e4a97 100644
--- a/pkg/sentry/kernel/semaphore/semaphore.go
+++ b/pkg/sentry/kernel/semaphore/semaphore.go
@@ -193,12 +193,26 @@ func (r *Registry) IPCInfo() *linux.SemInfo {
 		SemMsl: linux.SEMMSL,
 		SemOpm: linux.SEMOPM,
 		SemUme: linux.SEMUME,
-		SemUsz: 0, // SemUsz not supported.
+		SemUsz: linux.SEMUSZ,
 		SemVmx: linux.SEMVMX,
 		SemAem: linux.SEMAEM,
 	}
 }
 
+// SemInfo returns a seminfo structure containing the same information as
+// for IPC_INFO, except that SemUsz field returns the number of existing
+// semaphore sets, and SemAem field returns the number of existing semaphores.
+func (r *Registry) SemInfo() *linux.SemInfo {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	info := r.IPCInfo()
+	info.SemUsz = uint32(len(r.semaphores))
+	info.SemAem = uint32(r.totalSems())
+
+	return info
+}
+
 // HighestIndex returns the index of the highest used entry in
 // the kernel's array.
 func (r *Registry) HighestIndex() int32 {
@@ -289,6 +303,18 @@ func (r *Registry) FindByID(id int32) *Set {
 	return r.semaphores[id]
 }
 
+// FindByIndex looks up a set given an index.
+func (r *Registry) FindByIndex(index int32) *Set {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	id, present := r.indexes[index]
+	if !present {
+		return nil
+	}
+	return r.semaphores[id]
+}
+
 func (r *Registry) findByKey(key int32) *Set {
 	for _, v := range r.semaphores {
 		if v.key == key {
diff --git a/pkg/sentry/syscalls/linux/linux64.go b/pkg/sentry/syscalls/linux/linux64.go
index cff442846..b815e498f 100644
--- a/pkg/sentry/syscalls/linux/linux64.go
+++ b/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 SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
+		66:  syscalls.PartiallySupported("semctl", Semctl, "Options 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 SEM_INFO, SEM_STAT, SEM_STAT_ANY not supported.", nil),
+		191: syscalls.PartiallySupported("semctl", Semctl, "Options 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),
diff --git a/pkg/sentry/syscalls/linux/sys_sem.go b/pkg/sentry/syscalls/linux/sys_sem.go
index a62a6b3b5..1166cd7bb 100644
--- a/pkg/sentry/syscalls/linux/sys_sem.go
+++ b/pkg/sentry/syscalls/linux/sys_sem.go
@@ -155,10 +155,28 @@ func Semctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 		}
 		return uintptr(r.HighestIndex()), nil, nil
 
-	case linux.SEM_INFO,
-		linux.SEM_STAT,
-		linux.SEM_STAT_ANY:
+	case linux.SEM_INFO:
+		buf := args[3].Pointer()
+		r := t.IPCNamespace().SemaphoreRegistry()
+		info := r.SemInfo()
+		if _, err := info.CopyOut(t, buf); err != nil {
+			return 0, nil, err
+		}
+		return uintptr(r.HighestIndex()), nil, nil
 
+	case linux.SEM_STAT:
+		arg := args[3].Pointer()
+		// id is an index in SEM_STAT.
+		semid, ds, err := semStat(t, id)
+		if err != nil {
+			return 0, nil, err
+		}
+		if _, err := ds.CopyOut(t, arg); err != nil {
+			return 0, nil, err
+		}
+		return uintptr(semid), nil, err
+
+	case linux.SEM_STAT_ANY:
 		t.Kernel().EmitUnimplementedEvent(t)
 		fallthrough
 
@@ -203,6 +221,17 @@ func ipcStat(t *kernel.Task, id int32) (*linux.SemidDS, error) {
 	return set.GetStat(creds)
 }
 
+func semStat(t *kernel.Task, index int32) (int32, *linux.SemidDS, error) {
+	r := t.IPCNamespace().SemaphoreRegistry()
+	set := r.FindByIndex(index)
+	if set == nil {
+		return 0, nil, syserror.EINVAL
+	}
+	creds := auth.CredentialsFromContext(t)
+	ds, err := set.GetStat(creds)
+	return set.ID, ds, err
+}
+
 func setVal(t *kernel.Task, id int32, num int32, val int16) error {
 	r := t.IPCNamespace().SemaphoreRegistry()
 	set := r.FindByID(id)