Reinstate locks around uvm_fault calls from upageflttrap and kpageflttrap

on i386.  This is a backout of revision 1.152.

Kernel crash with messages printed concurrently from multiple CPUs
occasionally seen during ports build:

"WARNING: SPL NOT LOWERED ON TRAP EXIT"

and these panics

ddb{1}> sh panic
cpu1: uvm_fault(0xd470a0a0, 0xcf9b7000, 0, 1) -> e
cpu3: kernel diagnostic assertion "!_kernel_lock_held()" failed: file "/usr/src/sys/uvm/uvm_map.c", line 2707

diff --git a/sys/arch/i386/i386/trap.c b/sys/arch/i386/i386/trap.c
index 35bd673..e97d092 100644 (file)
--- a/sys/arch/i386/i386/trap.c
+++ b/sys/arch/i386/i386/trap.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: trap.c,v 1.153 2021/05/16 15:10:19 deraadt Exp $      */
+/*     $OpenBSD: trap.c,v 1.154 2021/06/20 10:58:36 sthen Exp $        */
 /*     $NetBSD: trap.c,v 1.95 1996/05/05 06:50:02 mycroft Exp $        */
 
 /*-
@@ -126,7 +126,10 @@ upageflttrap(struct trapframe *frame, uint32_t cr2)
        union sigval sv;
        int signal, sicode, error;
 
+       KERNEL_LOCK();
        error = uvm_fault(&p->p_vmspace->vm_map, va, 0, access_type);
+       KERNEL_UNLOCK();
+
        if (error == 0) {
                uvm_grow(p, va);
                return 1;
@@ -200,7 +203,9 @@ kpageflttrap(struct trapframe *frame, uint32_t cr2)
        if (curcpu()->ci_inatomic == 0 || map == kernel_map) {
                onfault = pcb->pcb_onfault;
                pcb->pcb_onfault = NULL;
+               KERNEL_LOCK();
                error = uvm_fault(map, va, 0, access_type);
+               KERNEL_UNLOCK();
                pcb->pcb_onfault = onfault;
 
                if (error == 0 && map != kernel_map)