- Add a kern_semctl() helper function for __semctl(). It accepts a pointer

  to a copied-in copy of the 'union semun' and a uioseg to indicate which
  memory space the 'buf' pointer of the union points to.  This is then used
  in linux_semctl() and svr4_sys_semctl() to eliminate use of the stackgap.
- Mark linux_ipc() and svr4_sys_semsys() MPSAFE.

3 files changed, 60 insertions, 121 deletions

diff --git a/sys/compat/linux/linux_ipc.c b/sys/compat/linux/linux_ipc.c
index 0989847..2e6dabf 100644
--- a/sys/compat/linux/linux_ipc.c
+++ b/sys/compat/linux/linux_ipc.c
@@ -491,69 +491,56 @@ int
 linux_semctl(struct thread *td, struct linux_semctl_args *args)
 {
 	struct l_semid_ds linux_semid;
-	struct __semctl_args /* {
-		int		semid;
-		int		semnum;
-		int		cmd;
-		union semun	*arg;
-	} */ bsd_args;
 	struct l_seminfo linux_seminfo;
-	int error;
-	union semun *unptr;
-	caddr_t sg;
-
-	sg = stackgap_init();
-
-	/* Make sure the arg parameter can be copied in. */
-	unptr = stackgap_alloc(&sg, sizeof(union semun));
-	bcopy(&args->arg, unptr, sizeof(union semun));
-
-	bsd_args.semid = args->semid;
-	bsd_args.semnum = args->semnum;
-	bsd_args.arg = unptr;
+	struct semid_ds semid;
+	union semun semun;
+	int cmd, error;
 
 	switch (args->cmd & ~LINUX_IPC_64) {
 	case LINUX_IPC_RMID:
-		bsd_args.cmd = IPC_RMID;
+		cmd = IPC_RMID;
 		break;
 	case LINUX_GETNCNT:
-		bsd_args.cmd = GETNCNT;
+		cmd = GETNCNT;
 		break;
 	case LINUX_GETPID:
-		bsd_args.cmd = GETPID;
+		cmd = GETPID;
 		break;
 	case LINUX_GETVAL:
-		bsd_args.cmd = GETVAL;
+		cmd = GETVAL;
 		break;
 	case LINUX_GETZCNT:
-		bsd_args.cmd = GETZCNT;
+		cmd = GETZCNT;
 		break;
 	case LINUX_SETVAL:
-		bsd_args.cmd = SETVAL;
+		cmd = SETVAL;
+		semun.val = args->arg.val;
 		break;
 	case LINUX_IPC_SET:
-		bsd_args.cmd = IPC_SET;
+		cmd = IPC_SET;
 		error = linux_semid_pullup(args->cmd & LINUX_IPC_64,
 		    &linux_semid, (caddr_t)PTRIN(args->arg.buf));
 		if (error)
 			return (error);
-		unptr->buf = stackgap_alloc(&sg, sizeof(struct semid_ds));
-		linux_to_bsd_semid_ds(&linux_semid, unptr->buf);
-		return __semctl(td, &bsd_args);
+		linux_to_bsd_semid_ds(&linux_semid, &semid);
+		semun.buf = &semid;
+		return kern_semctl(td, args->semid, args->semnum, cmd, &semun,
+		    UIO_SYSSPACE);
 	case LINUX_IPC_STAT:
 	case LINUX_SEM_STAT:
 		if((args->cmd & ~LINUX_IPC_64) == LINUX_IPC_STAT)
-			bsd_args.cmd = IPC_STAT;
+			cmd = IPC_STAT;
 		else
-			bsd_args.cmd = SEM_STAT;
-		unptr->buf = stackgap_alloc(&sg, sizeof(struct semid_ds));
-		error = __semctl(td, &bsd_args);
+			cmd = SEM_STAT;
+		semun.buf = &semid;
+		error = kern_semctl(td, args->semid, args->semnum, cmd, &semun,
+		    UIO_SYSSPACE);
 		if (error)
-			return error;
-		td->td_retval[0] = (bsd_args.cmd == SEM_STAT) ?
-		    IXSEQ_TO_IPCID(bsd_args.semid, unptr->buf->sem_perm) :
+			return (error);
+		td->td_retval[0] = (cmd == SEM_STAT) ?
+		    IXSEQ_TO_IPCID(args->semid, semid.sem_perm) :
 		    0;
-		bsd_to_linux_semid_ds(unptr->buf, &linux_semid);
+		bsd_to_linux_semid_ds(&semid, &linux_semid);
 		return (linux_semid_pushdown(args->cmd & LINUX_IPC_64,
 		    &linux_semid, (caddr_t)PTRIN(args->arg.buf)));
 	case LINUX_IPC_INFO:
@@ -580,7 +567,8 @@ linux_semctl(struct thread *td, struct linux_semctl_args *args)
 		  args->cmd & ~LINUX_IPC_64);
 		return EINVAL;
 	}
-	return __semctl(td, &bsd_args);
+	return kern_semctl(td, args->semid, args->semnum, cmd, &semun,
+	    UIO_USERSPACE);
 }
 
 int
diff --git a/sys/compat/svr4/svr4_ipc.c b/sys/compat/svr4/svr4_ipc.c
index 0b6acbf..9eeaf24 100644
--- a/sys/compat/svr4/svr4_ipc.c
+++ b/sys/compat/svr4/svr4_ipc.c
@@ -105,8 +105,6 @@ static void bsd_to_svr4_semid_ds(const struct semid_ds *,
 				      struct svr4_semid_ds *);
 static void svr4_to_bsd_semid_ds(const struct svr4_semid_ds *,
 				      struct semid_ds *);
-static int svr4_setsemun(caddr_t *sgp, union semun **argp,
-			      union semun *usp);
 static int svr4_semop(struct thread *, void *);
 static int svr4_semget(struct thread *, void *);
 static int svr4_semctl(struct thread *, void *);
@@ -194,16 +192,6 @@ svr4_to_bsd_semid_ds(sds, bds)
 	bds->sem_pad2 = sds->sem_pad2;
 }
 
-static int
-svr4_setsemun(sgp, argp, usp)
-	caddr_t *sgp;
-	union semun **argp;
-	union semun *usp;
-{
-	*argp = stackgap_alloc(sgp, sizeof(union semun));
-	return copyout((caddr_t)usp, *argp, sizeof(union semun));
-}
-
 struct svr4_sys_semctl_args {
 	int what;
 	int semid;
@@ -217,108 +205,71 @@ svr4_semctl(td, v)
 	struct thread *td;
 	void *v;
 {
-	int error;
 	struct svr4_sys_semctl_args *uap = v;
-	struct __semctl_args ap;
 	struct svr4_semid_ds ss;
-	struct semid_ds bs, *bsp;
-	caddr_t sg = stackgap_init();
-
-	ap.semid = uap->semid;
-	ap.semnum = uap->semnum;
+	struct semid_ds bs;
+	union semun semun;
+	int cmd, error;
 
 	switch (uap->cmd) {
 	case SVR4_SEM_GETZCNT:
+		cmd = GETZCNT;
+		break;
+
 	case SVR4_SEM_GETNCNT:
+		cmd = GETNCNT;
+		break;
+
 	case SVR4_SEM_GETPID:
+		cmd = GETPID;
+		break;
+
 	case SVR4_SEM_GETVAL:
-		switch (uap->cmd) {
-		case SVR4_SEM_GETZCNT:
-			ap.cmd = GETZCNT;
-			break;
-		case SVR4_SEM_GETNCNT:
-			ap.cmd = GETNCNT;
-			break;
-		case SVR4_SEM_GETPID:
-			ap.cmd = GETPID;
-			break;
-		case SVR4_SEM_GETVAL:
-			ap.cmd = GETVAL;
-			break;
-		}
-		return __semctl(td, &ap);
+		cmd = GETVAL;
+		break;
 
 	case SVR4_SEM_SETVAL:
-		error = svr4_setsemun(&sg, &ap.arg, &uap->arg);
-		if (error)
-			return error;
-		ap.cmd = SETVAL;
-		return __semctl(td, &ap);
+		cmd = SETVAL;
+		break;
 
 	case SVR4_SEM_GETALL:
-		error = svr4_setsemun(&sg, &ap.arg, &uap->arg);
-		if (error)
-			return error;
-		ap.cmd = GETVAL;
-		return __semctl(td, &ap);
+		cmd = GETVAL;
+		break;
 
 	case SVR4_SEM_SETALL:
-		error = svr4_setsemun(&sg, &ap.arg, &uap->arg);
-		if (error)
-			return error;
-		ap.cmd = SETVAL;
-		return __semctl(td, &ap);
+		cmd = SETVAL;
+		break;
 
 	case SVR4_IPC_STAT:
-                ap.cmd = IPC_STAT;
-		bsp = stackgap_alloc(&sg, sizeof(bs));
-		error = svr4_setsemun(&sg, &ap.arg,
-				      (union semun *)&bsp);
+		cmd = IPC_STAT;
+		semun.buf = &bs;
+		error = kern_semctl(td, uap->semid, uap->semnum, cmd, &semun,
+		    UIO_SYSSPACE);
 		if (error)
-			return error;
-                if ((error = __semctl(td, &ap)) != 0)
-                        return error;
-		error = copyin((caddr_t)bsp, (caddr_t)&bs, sizeof(bs));
-                if (error)
                         return error;
                 bsd_to_svr4_semid_ds(&bs, &ss);
 		return copyout(&ss, uap->arg.buf, sizeof(ss));
 
 	case SVR4_IPC_SET:
-		ap.cmd = IPC_SET;
-		bsp = stackgap_alloc(&sg, sizeof(bs));
-		error = svr4_setsemun(&sg, &ap.arg,
-				      (union semun *)&bsp);
-		if (error)
-			return error;
+		cmd = IPC_SET;
 		error = copyin(uap->arg.buf, (caddr_t) &ss, sizeof ss);
                 if (error)
                         return error;
                 svr4_to_bsd_semid_ds(&ss, &bs);
-		error = copyout(&bs, bsp, sizeof(bs));
-                if (error)
-                        return error;
-		return __semctl(td, &ap);
+		semun.buf = &bs;
+		return kern_semctl(td, uap->semid, uap->semnum, cmd, &semun,
+		    UIO_SYSSPACE);
 
 	case SVR4_IPC_RMID:
-		ap.cmd = IPC_RMID;
-		bsp = stackgap_alloc(&sg, sizeof(bs));
-		error = svr4_setsemun(&sg, &ap.arg,
-				      (union semun *)&bsp);
-		if (error)
-			return error;
-		error = copyin(uap->arg.buf, &ss, sizeof ss);
-                if (error)
-                        return error;
-                svr4_to_bsd_semid_ds(&ss, &bs);
-		error = copyout(&bs, bsp, sizeof(bs));
-		if (error)
-			return error;
-		return __semctl(td, &ap);
+		cmd = IPC_RMID;
+		break;
 
 	default:
 		return EINVAL;
 	}
+
+	return kern_semctl(td, uap->semid, uap->semnum, cmd, &uap->arg,
+	    UIO_USERSPACE);
 }
 
 struct svr4_sys_semget_args {
diff --git a/sys/compat/svr4/syscalls.master b/sys/compat/svr4/syscalls.master
index 4086a36..944ec75 100644
--- a/sys/compat/svr4/syscalls.master
+++ b/sys/compat/svr4/syscalls.master
@@ -102,7 +102,7 @@
 51	AUE_NULL	UNIMPL	acct
 52	AUE_NULL	STD	{ int svr4_sys_shmsys(int what, int a2, \
 				    int a3, int a4, int a5); }
-53	AUE_NULL	STD	{ int svr4_sys_semsys(int what, int a2, \
+53	AUE_NULL	MSTD	{ int svr4_sys_semsys(int what, int a2, \
 				    int a3, int a4, int a5); }
 54	AUE_NULL	STD	{ int svr4_sys_ioctl(int fd, u_long com, \
 				    caddr_t data); }