[src/trunk]: src/sys/arch/x86/x86 Add splhigh() around the FPU code, we don't...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/768645dd9c8d
branches:  trunk
changeset: 320628:768645dd9c8d
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Jul 14 14:46:41 2018 +0000

description:
Add splhigh() around the FPU code, we don't want to be preempted in the
middle, this could corrupt the FPU state and trigger undefined behavior.

Intentionally use splhigh and not kpreempt_disable, to match the generic
x86 FPU code.

Compile-tested only (I don't have VIA).

Found by Maya almost a year ago.

diffstat:

 sys/arch/x86/x86/via_padlock.c |  17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

diffs (47 lines):

diff -r ac316d250382 -r 768645dd9c8d sys/arch/x86/x86/via_padlock.c
--- a/sys/arch/x86/x86/via_padlock.c    Sat Jul 14 14:34:32 2018 +0000
+++ b/sys/arch/x86/x86/via_padlock.c    Sat Jul 14 14:46:41 2018 +0000
@@ -1,5 +1,5 @@
 /*     $OpenBSD: via.c,v 1.8 2006/11/17 07:47:56 tom Exp $     */
-/*     $NetBSD: via_padlock.c,v 1.25 2016/02/27 00:54:59 tls Exp $ */
+/*     $NetBSD: via_padlock.c,v 1.26 2018/07/14 14:46:41 maxv Exp $ */
 
 /*-
  * Copyright (c) 2003 Jason Wright
@@ -20,7 +20,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: via_padlock.c,v 1.25 2016/02/27 00:54:59 tls Exp $");
+__KERNEL_RCSID(0, "$NetBSD: via_padlock.c,v 1.26 2018/07/14 14:46:41 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -332,10 +332,13 @@
 via_padlock_cbc(void *cw, void *src, void *dst, void *key, int rep,
     void *iv)
 {
-       unsigned int creg0;
+       unsigned int cr0;
+       int s;
 
-       creg0 = rcr0();         /* Permit access to SIMD/FPU path */
-       lcr0(creg0 & ~(CR0_EM|CR0_TS));
+       s = splhigh();
+
+       cr0 = rcr0();           /* Permit access to SIMD/FPU path */
+       lcr0(cr0 & ~(CR0_EM|CR0_TS));
 
        /* Do the deed */
        __asm __volatile("pushfl; popfl");      /* force key reload */
@@ -343,7 +346,9 @@
                        : "a" (iv), "b" (key), "c" (rep), "d" (cw), "S" (src), "D" (dst)
                        : "memory", "cc");
 
-       lcr0(creg0);
+       lcr0(cr0);
+
+       splx(s);
 }
 
 int