Split out kernel side of msgctl(2) into two parts: the first that pops data

from the userland and pushes results back and the second which does
actual processing. Use the latter to eliminate stackgap in the linux wrapper
of that syscall.

MFC after:      2 weeks

1 files changed, 10 insertions, 17 deletions

diff --git a/sys/compat/linux/linux_ipc.c b/sys/compat/linux/linux_ipc.c
index 662669d..8fc33878 100644
--- a/sys/compat/linux/linux_ipc.c
+++ b/sys/compat/linux/linux_ipc.c
@@ -634,33 +634,26 @@ linux_msgget(struct thread *td, struct linux_msgget_args *args)
 int
 linux_msgctl(struct thread *td, struct linux_msgctl_args *args)
 {
-    struct msgctl_args /* {
-	int     msqid;
-	int     cmd;
-	struct	msqid_ds *buf;
-    } */ bsd_args;
-    int error;
+    int error, bsd_cmd;
     struct l_msqid_ds linux_msqid;
-    caddr_t sg = stackgap_init();
+    struct msqid_ds bsd_msqid;
+    struct msqid_ds *bsd_msqptr;
 
     error = linux_msqid_pullup(args->cmd & LINUX_IPC_64,
       &linux_msqid, (caddr_t)PTRIN(args->buf));
     if (error != 0)
 	return (error);
-    bsd_args.buf = (struct msqid_ds*)stackgap_alloc(&sg,
-      sizeof(struct l_msqid_ds));
-    bsd_args.msqid = args->msqid;
-    bsd_args.cmd = args->cmd & ~LINUX_IPC_64;
-    if (bsd_args.cmd == LINUX_IPC_SET)
-	linux_to_bsd_msqid_ds(&linux_msqid, bsd_args.buf);
+    bsd_cmd = args->cmd & ~LINUX_IPC_64;
+    if (bsd_cmd == LINUX_IPC_SET)
+	linux_to_bsd_msqid_ds(&linux_msqid, &bsd_msqid);
 
-    error = msgctl(td, &bsd_args);
+    error = kern_msgctl(td, args->msqid, bsd_cmd, &bsd_msqid, &bsd_msqptr);
     if (error != 0)
-	if (bsd_args.cmd != LINUX_IPC_RMID || error != EINVAL)
+	if (bsd_cmd != LINUX_IPC_RMID || error != EINVAL)
 	    return (error);
 
-    if (bsd_args.cmd == LINUX_IPC_STAT) {
-	bsd_to_linux_msqid_ds(bsd_args.buf, &linux_msqid);
+    if (bsd_cmd == LINUX_IPC_STAT) {
+	bsd_to_linux_msqid_ds(bsd_msqptr, &linux_msqid);
 	return (linux_msqid_pushdown(args->cmd & LINUX_IPC_64,
 	  &linux_msqid, (caddr_t)PTRIN(args->buf)));
     }