From 0210029b617674d420e55dba5931baf0ea7b0e93 Mon Sep 17 00:00:00 2001
From: Martin Pieuchot <mpi@cvs.openbsd.org>
Date: Tue, 20 Mar 2018 15:45:33 +0000
Subject: Do not panic from ddb(4) when a lock requirement isn't fulfilled.

Extend the logic already present for panic() to any DDB-related
operation such that if ddb(4) is entered because of a fault or
other trap it is still possible to call 'boot reboot'.

While here stop printing splassert() messages as well, to not fill
the buffer.

ok visa@, deraadt@
---
 sys/arch/alpha/alpha/db_interface.c     |  4 +---
 sys/arch/amd64/amd64/db_interface.c     |  3 +--
 sys/arch/arm/arm/db_interface.c         |  4 +---
 sys/arch/arm64/arm64/db_interface.c     |  4 +---
 sys/arch/hppa/hppa/db_interface.c       |  3 +--
 sys/arch/i386/i386/db_interface.c       |  3 +--
 sys/arch/mips64/mips64/db_machdep.c     |  3 +--
 sys/arch/powerpc/ddb/db_interface.c     |  5 +----
 sys/arch/sh/sh/db_interface.c           |  4 +---
 sys/arch/sparc64/sparc64/db_interface.c |  4 +---
 sys/kern/init_main.c                    |  3 ++-
 sys/kern/kern_lock.c                    |  4 ++--
 sys/kern/kern_rwlock.c                  | 10 +++++-----
 sys/kern/subr_prf.c                     |  4 +++-
 sys/sys/systm.h                         |  3 ++-
 15 files changed, 24 insertions(+), 37 deletions(-)

diff --git a/sys/arch/alpha/alpha/db_interface.c b/sys/arch/alpha/alpha/db_interface.c
index 9249bf3a9a3..a91a63bbabd 100644
--- a/sys/arch/alpha/alpha/db_interface.c
+++ b/sys/arch/alpha/alpha/db_interface.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: db_interface.c,v 1.23 2017/04/30 16:45:45 mpi Exp $ */
+/* $OpenBSD: db_interface.c,v 1.24 2018/03/20 15:45:32 mpi Exp $ */
 /* $NetBSD: db_interface.c,v 1.8 1999/10/12 17:08:57 jdolecek Exp $ */
 
 /* 
@@ -92,8 +92,6 @@ struct db_command db_machine_command_table[] = {
 	{ NULL,		NULL,		0,	NULL }
 };
 
-int	db_active = 0;
-
 struct db_variable db_regs[] = {
 	{	"v0",	&ddb_regs.tf_regs[FRAME_V0],	FCN_NULL	},
 	{	"t0",	&ddb_regs.tf_regs[FRAME_T0],	FCN_NULL	},
diff --git a/sys/arch/amd64/amd64/db_interface.c b/sys/arch/amd64/amd64/db_interface.c
index a8931294d51..70e7ac718dd 100644
--- a/sys/arch/amd64/amd64/db_interface.c
+++ b/sys/arch/amd64/amd64/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.29 2017/07/19 14:34:10 kettenis Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.30 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.1 2003/04/26 18:39:27 fvdl Exp $	*/
 
 /*
@@ -78,7 +78,6 @@ boolean_t	 db_switch_cpu;
 long		 db_switch_to_cpu;
 #endif
 
-int	db_active;
 db_regs_t ddb_regs;
 
 void db_printtrap(int, int);
diff --git a/sys/arch/arm/arm/db_interface.c b/sys/arch/arm/arm/db_interface.c
index 322eb123bf6..8534dda55c4 100644
--- a/sys/arch/arm/arm/db_interface.c
+++ b/sys/arch/arm/arm/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.12 2017/04/30 16:45:45 mpi Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.13 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.34 2003/10/26 23:11:15 chris Exp $	*/
 
 /* 
@@ -92,8 +92,6 @@ extern label_t       *db_recover;
 
 struct db_variable * db_eregs = db_regs + nitems(db_regs);
 
-int	db_active = 0;
-
 int
 db_access_und_sp(struct db_variable *vp, db_expr_t *valp, int rw)
 {
diff --git a/sys/arch/arm64/arm64/db_interface.c b/sys/arch/arm64/arm64/db_interface.c
index 64675c08f8b..d615be12497 100644
--- a/sys/arch/arm64/arm64/db_interface.c
+++ b/sys/arch/arm64/arm64/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.4 2018/01/30 15:46:12 kettenis Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.5 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.34 2003/10/26 23:11:15 chris Exp $	*/
 
 /*
@@ -122,8 +122,6 @@ extern label_t       *db_recover;
 
 struct db_variable * db_eregs = db_regs + nitems(db_regs);
 
-int	db_active = 0;
-
 #ifdef DDB
 /*
  *  kdb_trap - field a TRACE or BPT trap
diff --git a/sys/arch/hppa/hppa/db_interface.c b/sys/arch/hppa/hppa/db_interface.c
index 89c03345f90..33c3bf093fc 100644
--- a/sys/arch/hppa/hppa/db_interface.c
+++ b/sys/arch/hppa/hppa/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.42 2017/11/03 11:29:46 jasper Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.43 2018/03/20 15:45:32 mpi Exp $	*/
 
 /*
  * Copyright (c) 1999-2003 Michael Shalayeff
@@ -122,7 +122,6 @@ struct db_variable db_regs[] = {
 	{ "cr30",  (long *)&ddb_regs.tf_cr30,  FCN_NULL },
 };
 struct db_variable *db_eregs = db_regs + nitems(db_regs);
-int db_active = 0;
 
 void
 db_enter(void)
diff --git a/sys/arch/i386/i386/db_interface.c b/sys/arch/i386/i386/db_interface.c
index 8de52b0fc68..5791d6a69e6 100644
--- a/sys/arch/i386/i386/db_interface.c
+++ b/sys/arch/i386/i386/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.37 2018/03/13 13:51:05 bluhm Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.38 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.22 1996/05/03 19:42:00 christos Exp $	*/
 
 /*
@@ -72,7 +72,6 @@ long		 db_switch_to_cpu;
 #endif
 
 db_regs_t	ddb_regs;
-int	db_active = 0;
 
 void kdbprinttrap(int, int);
 void db_sysregs_cmd(db_expr_t, int, db_expr_t, char *);
diff --git a/sys/arch/mips64/mips64/db_machdep.c b/sys/arch/mips64/mips64/db_machdep.c
index 1c620160023..91f479b99b7 100644
--- a/sys/arch/mips64/mips64/db_machdep.c
+++ b/sys/arch/mips64/mips64/db_machdep.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_machdep.c,v 1.48 2017/08/26 15:21:48 visa Exp $ */
+/*	$OpenBSD: db_machdep.c,v 1.49 2018/03/20 15:45:32 mpi Exp $ */
 
 /*
  * Copyright (c) 1998-2003 Opsycon AB (www.opsycon.se)
@@ -76,7 +76,6 @@ boolean_t        db_switch_cpu;
 long             db_switch_to_cpu;
 #endif
 
-int   db_active = 0;
 db_regs_t ddb_regs;
 
 #ifdef MULTIPROCESSOR
diff --git a/sys/arch/powerpc/ddb/db_interface.c b/sys/arch/powerpc/ddb/db_interface.c
index e00cf2a8b86..6440539219e 100644
--- a/sys/arch/powerpc/ddb/db_interface.c
+++ b/sys/arch/powerpc/ddb/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.3 2017/04/30 16:45:45 mpi Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.4 2018/03/20 15:45:32 mpi Exp $	*/
 /*      $NetBSD: db_interface.c,v 1.12 2001/07/22 11:29:46 wiz Exp $ */
 
 /*
@@ -50,7 +50,6 @@ boolean_t        db_switch_cpu;
 long             db_switch_to_cpu;
 #endif
 
-int db_active;
 extern db_regs_t ddb_regs;
 
 #ifdef MULTIPROCESSOR
@@ -60,8 +59,6 @@ void db_stopproc_cmd(db_expr_t, int, db_expr_t, char *);
 void db_ddbproc_cmd(db_expr_t, int, db_expr_t, char *);
 #endif
 
-int db_active = 0;
-
 int db_trap_glue(struct trapframe *frame); /* called from locore */
 
 void
diff --git a/sys/arch/sh/sh/db_interface.c b/sys/arch/sh/sh/db_interface.c
index ca60506f1a8..423259dd046 100644
--- a/sys/arch/sh/sh/db_interface.c
+++ b/sys/arch/sh/sh/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.10 2017/04/30 16:45:45 mpi Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.11 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.37 2006/09/06 00:11:49 uwe Exp $	*/
 
 /*-
@@ -83,8 +83,6 @@ struct db_command db_machine_command_table[] = {
 	{ NULL }
 };
 
-int db_active;
-
 void
 db_machine_init(void)
 {
diff --git a/sys/arch/sparc64/sparc64/db_interface.c b/sys/arch/sparc64/sparc64/db_interface.c
index c62b7c330ea..9c8a91149a4 100644
--- a/sys/arch/sparc64/sparc64/db_interface.c
+++ b/sys/arch/sparc64/sparc64/db_interface.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: db_interface.c,v 1.49 2017/12/03 10:55:50 mpi Exp $	*/
+/*	$OpenBSD: db_interface.c,v 1.50 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: db_interface.c,v 1.61 2001/07/31 06:55:47 eeh Exp $ */
 
 /*
@@ -197,8 +197,6 @@ struct db_variable *db_eregs = db_regs + nitems(db_regs);
 
 extern label_t	*db_recover;
 
-int	db_active = 0;
-
 extern char *trap_type[];
 
 void kdb_kbd_trap(struct trapframe64 *);
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 29cd5b2f661..17bff8830fb 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init_main.c,v 1.274 2018/02/28 18:47:33 patrick Exp $	*/
+/*	$OpenBSD: init_main.c,v 1.275 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: init_main.c,v 1.84.4.1 1996/06/02 09:08:06 mrg Exp $	*/
 
 /*
@@ -124,6 +124,7 @@ extern	struct user *proc0paddr;
 struct	vnode *rootvp, *swapdev_vp;
 int	boothowto;
 struct	timespec boottime;
+int	db_active = 0;
 int	ncpus =  1;
 int	ncpusfound = 1;			/* number of cpus we find */
 volatile int start_init_exec;		/* semaphore for start_init() */
diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 2d79db04ed7..f108c7393e9 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_lock.c,v 1.59 2018/02/19 09:18:00 mpi Exp $	*/
+/*	$OpenBSD: kern_lock.c,v 1.60 2018/03/20 15:45:32 mpi Exp $	*/
 
 /*
  * Copyright (c) 2017 Visa Hankala
@@ -79,7 +79,7 @@ _kernel_unlock(void)
 int
 _kernel_lock_held(void)
 {
-	if (panicstr)
+	if (panicstr || db_active)
 		return 1;
 	return (__mp_lock_held(&kernel_lock, curcpu()));
 }
diff --git a/sys/kern/kern_rwlock.c b/sys/kern/kern_rwlock.c
index 88228a224a1..1bde7064757 100644
--- a/sys/kern/kern_rwlock.c
+++ b/sys/kern/kern_rwlock.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_rwlock.c,v 1.33 2017/12/18 10:05:43 mpi Exp $	*/
+/*	$OpenBSD: kern_rwlock.c,v 1.34 2018/03/20 15:45:32 mpi Exp $	*/
 
 /*
  * Copyright (c) 2002, 2003 Artur Grabowski <art@openbsd.org>
@@ -236,8 +236,8 @@ retry:
 		unsigned long set = o | op->wait_set;
 		int do_sleep;
 
-		/* Avoid deadlocks after panic */
-		if (panicstr)
+		/* Avoid deadlocks after panic or in DDB */
+		if (panicstr || db_active)
 			return (0);
 
 		rw_enter_diag(rwl, flags);
@@ -287,8 +287,8 @@ _rw_exit(struct rwlock *rwl LOCK_FL_VARS)
 	int wrlock = owner & RWLOCK_WRLOCK;
 	unsigned long set;
 
-	/* Avoid deadlocks after panic */
-	if (panicstr)
+	/* Avoid deadlocks after panic or in DDB */
+	if (panicstr || db_active)
 		return;
 
 	if (wrlock)
diff --git a/sys/kern/subr_prf.c b/sys/kern/subr_prf.c
index 3572e809d09..c75e2a88769 100644
--- a/sys/kern/subr_prf.c
+++ b/sys/kern/subr_prf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_prf.c,v 1.93 2018/01/05 11:10:25 pirofti Exp $	*/
+/*	$OpenBSD: subr_prf.c,v 1.94 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: subr_prf.c,v 1.45 1997/10/24 18:14:25 chuck Exp $	*/
 
 /*-
@@ -216,6 +216,8 @@ panic(const char *fmt, ...)
 void
 splassert_fail(int wantipl, int haveipl, const char *func)
 {
+	if (panicstr || db_active)
+		return;
 
 	printf("splassert: %s: want %d have %d\n", func, wantipl, haveipl);
 	switch (splassert_ctl) {
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 93ddae25307..7c14c9bd5f3 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: systm.h,v 1.138 2018/02/08 09:27:44 mortimer Exp $	*/
+/*	$OpenBSD: systm.h,v 1.139 2018/03/20 15:45:32 mpi Exp $	*/
 /*	$NetBSD: systm.h,v 1.50 1996/06/09 04:55:09 briggs Exp $	*/
 
 /*-
@@ -79,6 +79,7 @@ extern const char ostype[];
 extern const char osversion[];
 extern const char osrelease[];
 extern int cold;		/* cold start flag initialized in locore */
+extern int db_active;		/* running currently inside ddb(4) */
 
 extern int ncpus;		/* number of CPUs used */
 extern int ncpusfound;		/* number of CPUs found */
-- 
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