From: cheloha <cheloha@openbsd.org>
Date: Tue, 27 Jun 2023 10:11:15 +0000 (+0000)
Subject: amd64: MCOUNT_EXIT: restore interrupts, don't unconditionally reenable them
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=08cf7c3f88334cf737af7753d1b04496aca85a86;p=openbsd

amd64: MCOUNT_EXIT: restore interrupts, don't unconditionally reenable them

This bug can cause all sorts of problems, but in particular it was
most easily reproduced as a double fault in the syscall return path on
this CPU model:

Intel(R) Core(TM) i7-8650U CPU @ 1.90GHz

Tons of help from guenther@ in narrowing down the root cause.  Fix
tweaked by guenther@.  Additional input from deraadt@ and kettenis@.

ok guenther@
---

diff --git a/sys/arch/amd64/include/profile.h b/sys/arch/amd64/include/profile.h
index 7f63b92c8f0..cee88380993 100644
--- a/sys/arch/amd64/include/profile.h
+++ b/sys/arch/amd64/include/profile.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: profile.h,v 1.5 2021/09/04 22:15:33 bluhm Exp $	*/
+/*	$OpenBSD: profile.h,v 1.6 2023/06/27 10:11:15 cheloha Exp $	*/
 /*	$NetBSD: profile.h,v 1.3 2003/11/28 23:22:45 fvdl Exp $	*/
 
 /*
@@ -72,6 +72,6 @@ __asm(" .globl __mcount		\n"			\
 
 
 #ifdef _KERNEL
-#define MCOUNT_ENTER	(void)&s; __asm__("cli");
-#define MCOUNT_EXIT	__asm__("sti");
+#define MCOUNT_ENTER	s = intr_disable()
+#define MCOUNT_EXIT	intr_restore(s)
 #endif /* _KERNEL */