Get rid of 88110 nmi stacks. This was a good idea, but I outsmarted myself

since it was intended to service NMI occuring in user mode, and we could
end up invoking preempt() and have another cpu start using this stack,
with interesting results.

3 files changed, 20 insertions, 50 deletions

diff --git a/sys/arch/m88k/include/cpu.h b/sys/arch/m88k/include/cpu.h
index c724487f22e..b85a7e93dad 100644
--- a/sys/arch/m88k/include/cpu.h
+++ b/sys/arch/m88k/include/cpu.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cpu.h,v 1.42 2009/02/17 21:03:59 miod Exp $ */
+/*	$OpenBSD: cpu.h,v 1.43 2009/02/21 18:35:20 miod Exp $ */
 /*
  * Copyright (c) 1996 Nivas Madhur
  * Copyright (c) 1992, 1993
@@ -114,13 +114,12 @@ struct cpu_info {
 #define	ci_pfsr_d1	 ci_cpudep3
 
 	/* 88110 fields */
-#define	ci_nmi_stack	 ci_cpudep0		/* NMI stack */
-#define	ci_ipi_arg1	 ci_cpudep1		/* Complex IPI arguments */
-#define	ci_ipi_arg2	 ci_cpudep2
-#define	ci_h_sxip	 ci_cpudep3		/* trapframe values */
-#define	ci_h_epsr	 ci_cpudep4		/* for hardclock */
-#define	ci_s_sxip	 ci_cpudep5		/* and softclock */
-#define	ci_s_epsr	 ci_cpudep6
+#define	ci_ipi_arg1	 ci_cpudep0		/* Complex IPI arguments */
+#define	ci_ipi_arg2	 ci_cpudep1
+#define	ci_h_sxip	 ci_cpudep2		/* trapframe values */
+#define	ci_h_epsr	 ci_cpudep3		/* for hardclock */
+#define	ci_s_sxip	 ci_cpudep4		/* and softclock */
+#define	ci_s_epsr	 ci_cpudep5
 
 	struct schedstate_percpu
 			 ci_schedstate;		/* scheduling state */
diff --git a/sys/arch/m88k/m88k/eh_common.S b/sys/arch/m88k/m88k/eh_common.S
index 669f0a02b12..1b48c14b9a8 100644
--- a/sys/arch/m88k/m88k/eh_common.S
+++ b/sys/arch/m88k/m88k/eh_common.S
@@ -1,4 +1,4 @@
-/*   $OpenBSD: eh_common.S,v 1.51 2009/02/16 22:55:03 miod Exp $	*/
+/*   $OpenBSD: eh_common.S,v 1.52 2009/02/21 18:35:22 miod Exp $	*/
 /*
  * Mach Operating System
  * Copyright (c) 1993-1991 Carnegie Mellon University
@@ -222,13 +222,10 @@
  *	cause other exceptions to happen, and the whole system is
  *	in a rather precarious state and so special cautions must
  * 	be taken.
- * The bit FLAG_NMI_STACK, on 88110, indicates that this exception
- *	should be handled on the NMI stack.
  */
 #define FLAG_IGNORE_DATA_EXCEPTION	0
 #define FLAG_ENABLING_FPU		1
 #define FLAG_FROM_KERNEL		2
-#define	FLAG_NMI_STACK			3
 
 /* GENeral REGister OFFset into the E.F. (exception frame) */
 #define GENREG_OFF(num)		(EF_R0 + (num) * 4)
@@ -332,7 +329,6 @@
 #ifdef M88110
 #define PREP88110(NAME, NUM, FLAG_PRECHECK) \
 	xcr	FLAGS, FLAGS, SR1			; \
-	clr	FLAGS, FLAGS, 1<FLAG_NMI_STACK>		; \
 	FLAG_PRECHECK					  \
 	/* the bsr later clobbers r1, so save now */	; \
 	stcr	r1, SR2	/* r1 now free */		; \
@@ -360,8 +356,6 @@
 #define	M88110_Data_Precheck \
 	bb1.n	FLAG_IGNORE_DATA_EXCEPTION, FLAGS, \
 	    _ASM_LABEL(m88110_ignore_data_exception);
-#define	M88110_Set_NMI_Flag \
-	set	FLAGS, FLAGS, 1<FLAG_NMI_STACK>
 
 #ifdef M88100
 /*
@@ -1605,7 +1599,7 @@ GLOBAL(m88110_fpu_handler)
 
 /* non-maskable interrupt handler (IPIs, ABORT button) */
 GLOBAL(m88110_nonmaskable)
-	PREP88110("NMI", 11, M88110_Set_NMI_Flag)
+	PREP88110("NMI", 11,)
 	or	r2, r0, r30
 	XCALL(_C_LABEL(nmi), _ASM_LABEL(check_ast))
 
@@ -1852,19 +1846,18 @@ ASLOCAL(m88110_setup_phase_one)
 	/*
 	 * If we were in the kernel when the exception occured, we have
 	 * a valid stack. Keep using it, and build the frame on it.
+	 *
+	 * Note that if this exception is an NMI, we might be currently
+	 * switching processes, and curpcb and curproc won't match. It
+	 * is nevertheless safe to use curpcb, since nmi are processed
+	 * with interrupts disabled, and we won't check for AST or soft
+	 * interrupts before returning to the cpu_switchto kernel code.
 	 */
 	bb1	FLAG_FROM_KERNEL, FLAGS, _ASM_LABEL(m88110_kernel_stack)
 
 	/*
-	 * If this is an NMI, pick the NMI stack, and build the frame
-	 * in it.
-	 */
-	bb1	FLAG_NMI_STACK, FLAGS, _ASM_LABEL(m88110_nmi_stack)
-
-	/*
-	 * Otherwise, this is a normal exception in user mode, we'll
-	 * use the PCB for the exception frame and the top of the PCB
-	 * as the stack.
+	 * Otherwise, this is an exception in user mode, we'll use the PCB
+	 * for the exception frame and the top of the PCB as the stack.
 	 */
 
 	/* compute frame address: in PCB */
@@ -1886,28 +1879,7 @@ ASLOCAL(m88110_setup_phase_one)
 
 	br	_ASM_LABEL(m88110_have_stack)
 
-ASLOCAL(m88110_nmi_stack)
-	/* NMI exception in user mode */
-
-	/* compute frame address: top of NMI stack */
-	stcr	r30,  SR3			/* save r30, now free */
-	ldcr	r30,  CPU
-	ld	r30,  r30,  CI_NMI_STACK
-	addu	r30,  r30,  (USPACE - TRAPFRAME_SIZEOF)
-
-	/* save a few registers before we lose them */
-	st	r1,   r30,  GENREG_OFF(1)	/* save prev. r1 (now free) */
-	ldcr	r1,   SR3			/* save previous r30 */
-	st	r31,  r30,  GENREG_OFF(31)
-	st	r1,   r30,  GENREG_OFF(30)
-
-	/* compute stack address: bottom of exception frame */
-	or	r31,  r30,  r0
-
-	br	_ASM_LABEL(m88110_have_stack)
-
-ASLOCAL(m88110_kernel_stack)
-	/* Exception in kernel mode */
+ASLOCAL(m88110_kernel_stack)		/* Exception in kernel mode */
 
 	/* compute stack and frame address: allocate them on current stack */
 	subu	r31,  r31,  TRAPFRAME_SIZEOF	/* r31 now our E.F. */
diff --git a/sys/arch/m88k/m88k/genassym.cf b/sys/arch/m88k/m88k/genassym.cf
index 05563cb829e..a06a498bffb 100644
--- a/sys/arch/m88k/m88k/genassym.cf
+++ b/sys/arch/m88k/m88k/genassym.cf
@@ -1,4 +1,4 @@
-#	$OpenBSD: genassym.cf,v 1.18 2009/02/08 21:40:58 miod Exp $
+#	$OpenBSD: genassym.cf,v 1.19 2009/02/21 18:35:22 miod Exp $
 #
 # Copyright (c) 1982, 1990 The Regents of the University of California.
 # All rights reserved.
@@ -28,7 +28,7 @@
 # SUCH DAMAGE.
 #
 #	@(#)genassym.c	7.8 (Berkeley) 5/7/91
-#	$Id: genassym.cf,v 1.18 2009/02/08 21:40:58 miod Exp $
+#	$Id: genassym.cf,v 1.19 2009/02/21 18:35:22 miod Exp $
 #
 
 include <sys/param.h>
@@ -69,7 +69,6 @@ member	ci_pfsr_d0
 member	ci_pfsr_d1
 member	ci_want_resched
 member	ci_softintr
-member	ci_nmi_stack
 
 # pcb fields
 struct	pcb