Kernel stack can be swapped. This means that stuff that's on the stack

should never be referenced outside the context of the process to which
this stack belongs unless we do the PHOLD/PRELE dance. Loads of code
doesn't follow the rules here. Instead of trying to track down all
offenders and fix this hairy situation, it makes much more sense
to not swap kernel stacks.

From art@, tested by many some time ago.

1 files changed, 3 insertions, 16 deletions

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index a68f5b09815..3c8d6f3c011 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_fork.c,v 1.84 2006/04/30 15:37:07 kettenis Exp $	*/
+/*	$OpenBSD: kern_fork.c,v 1.85 2006/11/29 12:24:17 miod Exp $	*/
 /*	$NetBSD: kern_fork.c,v 1.29 1996/02/09 18:59:34 christos Exp $	*/
 
 /*
@@ -191,10 +191,7 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 		return (EAGAIN);
 	}
 
-	/*
-	 * Allocate a pcb and kernel stack for the process
-	 */
-	uaddr = uvm_km_valloc_align(kernel_map, USPACE, USPACE_ALIGN);
+	uaddr = uvm_km_alloc1(kernel_map, USPACE, USPACE_ALIGN, 1);
 	if (uaddr == 0) {
 		chgproccnt(uid, -1);
 		nprocs--;
@@ -237,7 +234,7 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 	 * Increase reference counts on shared objects.
 	 * The p_stats and p_sigacts substructs are set in vm_fork.
 	 */
-	p2->p_flag = P_INMEM;
+	p2->p_flag = 0;
 	p2->p_emul = p1->p_emul;
 	if (p1->p_flag & P_PROFIL)
 		startprofclock(p2);
@@ -331,11 +328,6 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 	 */
 	if (p2->p_emul->e_proc_fork)
 		(*p2->p_emul->e_proc_fork)(p2, p1);
-	/*
-	 * This begins the section where we must prevent the parent
-	 * from being swapped.
-	 */
-	PHOLD(p1);
 
 	p2->p_addr = (struct user *)uaddr;
 
@@ -407,11 +399,6 @@ fork1(struct proc *p1, int exitsig, int flags, void *stack, size_t stacksize,
 	SCHED_UNLOCK(s);
 
 	/*
-	 * Now can be swapped.
-	 */
-	PRELE(p1);
-
-	/*
 	 * Notify any interested parties about the new process.
 	 */
 	KNOTE(&p1->p_klist, NOTE_FORK | p2->p_pid);