Add option EXCEPTION_TRACING, which enables KTR-like functionality

for processor interruptions. This is especially useful to track
unexpected nested TLB faults.

Approved by: re (blanket)

sys/conf/options.ia64

@@ -11,6 +11,8 @@ UWX_TRACE_ENABLE	opt_global.h
 
 COMPAT_IA32		opt_compat.h
 
+EXCEPTION_TRACING	opt_xtrace.h
+
 VGA_ALT_SEQACCESS	opt_vga.h
 VGA_DEBUG		opt_vga.h
 VGA_NO_FONT_LOADING	opt_vga.h

sys/ia64/ia64/db_machdep.c

@@ -29,6 +29,8 @@
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
+#include <opt_xtrace.h>
+
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/cons.h>
@@ -604,3 +606,29 @@ stack_save(struct stack *st)
 	 * Can unw_create* sleep?
 	 */
 }
+
+#ifdef EXCEPTION_TRACING
+
+extern long xtrace[];
+extern long *xhead;
+
+DB_COMMAND(xtrace, db_xtrace)
+{
+	long *p;
+
+	p = (*xhead == 0) ? xtrace : xhead;
+
+	db_printf("ITC\t\t IVT\t\t  IIP\t\t   IFA\t\t    ISR\n");
+	if (*p == 0)
+		return;
+
+	do {
+		db_printf("%016lx %016lx %016lx %016lx %016lx\n", p[0], p[1],
+		    p[2], p[3], p[4]);
+		p += 5;
+		if (p == (void *)&xhead)
+			p = xtrace;
+	} while (p != xhead);
+}
+
+#endif

sys/ia64/ia64/exception.S

@@ -28,6 +28,8 @@
 #include <machine/asm.h>
 __FBSDID("$FreeBSD$");
 
+#include <opt_xtrace.h>
+
 #include <machine/pte.h>
 #include <assym.s>
 
@@ -38,6 +40,59 @@ __FBSDID("$FreeBSD$");
  * ar.k4 = PCPU data
  */
 
+#ifdef EXCEPTION_TRACING
+
+	.data
+	.global xtrace, xhead
+xtrace:	.space	1024*5*8
+xhead:	data8	xtrace
+
+#define	XTRACE(offset)				\
+{	.mmi ;					\
+	mov	r24=ar.itc ;			\
+	mov	r25=cr.iip ;			\
+	mov	r27=offset ;			\
+} ;						\
+{	.mlx ;					\
+	mov	r28=cr.ifa ;			\
+	movl	r29=xhead ;;			\
+} ;						\
+{	.mmi ;					\
+	ld8	r29=[r29] ;;			\
+	st8	[r29]=r24,8 ;			\
+	nop	0 ;;				\
+} ;						\
+{	.mmi ;					\
+	st8	[r29]=r27,8 ;;			\
+	mov	r24=cr.isr ;			\
+	add	r27=8,r29 ;;			\
+} ;						\
+{	.mmi ;					\
+	st8	[r29]=r25,16 ;;			\
+	st8	[r27]=r28,16 ;			\
+	mov	r25=pr ;;			\
+} ;						\
+{	.mlx ;					\
+	st8	[r29]=r24 ;			\
+	movl	r28=xhead ;;			\
+} ;						\
+{	.mii ;					\
+	cmp.eq	p15,p0=r27,r28 ;		\
+	addl	r29=1024*5*8,r0 ;;		\
+(p15)	sub	r27=r28,r29 ;;			\
+} ;						\
+{	.mib ;					\
+	st8	[r28]=r27 ;			\
+	mov	pr=r25,0x1ffff ;		\
+	nop	0 ;;				\
+}
+
+#else
+
+#define	XTRACE(offset)
+
+#endif
+
 	.text
 
 /*
@@ -606,7 +661,8 @@ END(exception_restore)
 	.unwabi	@svr4, 'I';			\
 	.save	rp, r0;				\
 	.body;					\
-ivt_##name:
+ivt_##name:					\
+	XTRACE(offset)
 
 #define	IVT_END(name)				\
 	.endp	ivt_##name