From 3772e814e0ead154912b1426b780015a463af85c Mon Sep 17 00:00:00 2001
From: cheloha <cheloha@openbsd.org>
Date: Wed, 12 Jul 2023 18:40:06 +0000
Subject: [PATCH] GPROF: sleep_state: disable _mcount() across suspend/resume

Something in the amd64 resume path doesn't agree with _mcount(), so
suspend/resume always fails if gmoninit is non-zero.  It would be nice
if GPROF kernels didn't crash during resume.

In sleep_state(), (1) clear gmoninit after sched_stop_secondary_cpus()
so the primary CPU isn't racing sysctl(2) on another CPU, and (2)
restore gmoninit just after resume_mp() so the secondary CPUs are out
of cpu_hatch() and away from whatever is causing the crash before
_mcount() is reenabled.

Lots of input from claudio@, deraadt@, and kettenis@.

Thread 1: https://marc.info/?l=openbsd-tech&m=168721453821801&w=2
Thread 2: https://marc.info/?l=openbsd-tech&m=168892518722935&w=2

ok kettenis@ deraadt@
---
 sys/kern/subr_suspend.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/sys/kern/subr_suspend.c b/sys/kern/subr_suspend.c
index 833c918d9f0..1b4f4062918 100644
--- a/sys/kern/subr_suspend.c
+++ b/sys/kern/subr_suspend.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: subr_suspend.c,v 1.15 2023/07/02 19:02:27 cheloha Exp $ */
+/* $OpenBSD: subr_suspend.c,v 1.16 2023/07/12 18:40:06 cheloha Exp $ */
 /*
  * Copyright (c) 2005 Thorsten Lockert <tholo@sigmasoft.com>
  * Copyright (c) 2005 Jordan Hargrave <jordan@openbsd.org>
@@ -26,6 +26,9 @@
 #include <sys/mount.h>
 #include <sys/syscallargs.h>
 #include <dev/wscons/wsdisplayvar.h>
+#ifdef GPROF
+#include <sys/gmon.h>
+#endif
 #ifdef HIBERNATE
 #include <sys/hibernate.h>
 #endif
@@ -49,6 +52,9 @@ sleep_state(void *v, int sleepmode)
 	extern int perflevel;
 	size_t rndbuflen;
 	char *rndbuf;
+#ifdef GPROF
+	int gmon_state;
+#endif
 #if NSOFTRAID > 0
 	extern void sr_quiesce(void);
 #endif
@@ -100,6 +106,12 @@ top:
 #ifdef MULTIPROCESSOR
 	sched_stop_secondary_cpus();
 	KASSERT(CPU_IS_PRIMARY(curcpu()));
+#endif
+#ifdef GPROF
+	gmon_state = gmoninit;
+	gmoninit = 0;
+#endif
+#ifdef MULTIPROCESSOR
 	sleep_mp();
 #endif
 
@@ -172,6 +184,11 @@ fail_suspend:
 	resume_randomness(rndbuf, rndbuflen);
 #ifdef MULTIPROCESSOR
 	resume_mp();
+#endif
+#ifdef GPROF
+	gmoninit = gmon_state;
+#endif
+#ifdef MULTIPROCESSOR
 	sched_start_secondary_cpus();
 #endif
 	vfs_stall(curproc, 0);
-- 
2.20.1