diff --git a/sys/arch/alpha/common/sgmap_typedep.c b/sys/arch/alpha/common/sgmap_typedep.c
index 312ecdba13e4..510606c6060b 100644
--- a/sys/arch/alpha/common/sgmap_typedep.c
+++ b/sys/arch/alpha/common/sgmap_typedep.c
@@ -1,4 +1,4 @@
-/* $NetBSD: sgmap_typedep.c,v 1.3 1997/09/02 20:11:24 thorpej Exp $ */
+/* $NetBSD: sgmap_typedep.c,v 1.4 1997/09/05 02:21:49 thorpej Exp $ */
 
 /*-
  * Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -37,7 +37,21 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-__KERNEL_RCSID(0, "$NetBSD: sgmap_typedep.c,v 1.3 1997/09/02 20:11:24 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sgmap_typedep.c,v 1.4 1997/09/05 02:21:49 thorpej Exp $");
+
+#ifdef SGMAP_LOG
+
+#ifndef SGMAP_LOGSIZE
+#define	SGMAP_LOGSIZE	4096
+#endif
+
+struct sgmap_log_entry	__C(SGMAP_TYPE,_log)[SGMAP_LOGSIZE];
+int			__C(SGMAP_TYPE,_log_next);
+int			__C(SGMAP_TYPE,_log_last);
+u_long			__C(SGMAP_TYPE,_log_loads);
+u_long			__C(SGMAP_TYPE,_log_unloads);
+
+#endif /* SGMAP_LOG */
 
 int
 __C(SGMAP_TYPE,_load)(t, map, buf, buflen, p, flags, sgmap)
@@ -56,15 +70,18 @@ __C(SGMAP_TYPE,_load)(t, map, buf, buflen, p, flags, sgmap)
 	bus_size_t dmalen;
 	SGMAP_PTE_TYPE *pte, *page_table = sgmap->aps_pt;
 	int pteidx, error;
-
-	if (buflen > map->_dm_size)
-		return (EINVAL);
+#ifdef SGMAP_LOG
+	struct sgmap_log_entry sl;
+#endif
 
 	/*
 	 * Make sure that on error condition we return "no valid mappings".
 	 */
 	map->dm_nsegs = 0;
 
+	if (buflen > map->_dm_size)
+		return (EINVAL);
+
 	/*
 	 * Remember the offset into the first page and the total
 	 * transfer length.
@@ -78,6 +95,16 @@ __C(SGMAP_TYPE,_load)(t, map, buf, buflen, p, flags, sgmap)
 	    dmaoffset, dmalen);
 #endif
 
+#ifdef SGMAP_LOG
+	if (panicstr == NULL) {
+		sl.sl_op = 1;
+		sl.sl_sgmap = sgmap;
+		sl.sl_origbuf = buf;
+		sl.sl_pgoffset = dmaoffset;
+		sl.sl_origlen = dmalen;
+	}
+#endif
+
 	/*
 	 * Allocate the necessary virtual address space for the
 	 * mapping.  Round the size, since we deal with whole pages.
@@ -105,6 +132,13 @@ __C(SGMAP_TYPE,_load)(t, map, buf, buflen, p, flags, sgmap)
 	    (pteidx << SGMAP_ADDR_PTEIDX_SHIFT) | dmaoffset;
 	map->dm_segs[0].ds_len = dmalen;
 
+#ifdef SGMAP_LOG
+	if (panicstr == NULL) {
+		sl.sl_sgva = a->apdc_sgva;
+		sl.sl_dmaaddr = map->dm_segs[0].ds_addr;
+	}
+#endif
+
 #ifdef SGMAP_DEBUG
 	printf("sgmap_load: wbase = 0x%lx, vpage = 0x%x, dma addr = 0x%lx\n",
 	    sgmap->aps_wbase, (pteidx << SGMAP_ADDR_PTEIDX_SHIFT),
@@ -136,6 +170,18 @@ __C(SGMAP_TYPE,_load)(t, map, buf, buflen, p, flags, sgmap)
 
 	alpha_mb();
 
+#ifdef SGMAP_LOG
+	if (panicstr == NULL) {
+		sl.sl_ptecnt = a->apdc_ptecnt;
+		bcopy(&sl, &__C(SGMAP_TYPE,_log)[__C(SGMAP_TYPE,_log_next)],
+		    sizeof(sl));
+		__C(SGMAP_TYPE,_log_last) = __C(SGMAP_TYPE,_log_next);
+		if (++__C(SGMAP_TYPE,_log_next) == SGMAP_LOGSIZE)
+			__C(SGMAP_TYPE,_log_next) = 0;
+		__C(SGMAP_TYPE,_log_loads)++;
+	}
+#endif
+
 	map->dm_nsegs = 1;
 	return (0);
 }
@@ -187,6 +233,24 @@ __C(SGMAP_TYPE,_unload)(t, map, sgmap)
 	struct alpha_sgmap_cookie *a = map->_dm_sgcookie;
 	SGMAP_PTE_TYPE *pte, *page_table = sgmap->aps_pt;
 	int ptecnt;
+#ifdef SGMAP_LOG
+	struct sgmap_log_entry *sl;
+
+	if (panicstr == NULL) {
+		sl = &__C(SGMAP_TYPE,_log)[__C(SGMAP_TYPE,_log_next)];
+
+		bzero(sl, sizeof(*sl));
+		sl->sl_op = 0;
+		sl->sl_sgmap = sgmap;
+		sl->sl_sgva = a->apdc_sgva;
+		sl->sl_dmaaddr = map->dm_segs[0].ds_addr;
+
+		__C(SGMAP_TYPE,_log_last) = __C(SGMAP_TYPE,_log_next);
+		if (++__C(SGMAP_TYPE,_log_next) == SGMAP_LOGSIZE)
+			__C(SGMAP_TYPE,_log_next) = 0;
+		__C(SGMAP_TYPE,_log_unloads)++;
+	}
+#endif
 
 	/*
 	 * Invalidate the PTEs for the mapping.
diff --git a/sys/arch/alpha/common/sgmapvar.h b/sys/arch/alpha/common/sgmapvar.h
index 8c8524a1e0dd..73971c2d67e6 100644
--- a/sys/arch/alpha/common/sgmapvar.h
+++ b/sys/arch/alpha/common/sgmapvar.h
@@ -1,4 +1,6 @@
-/* $NetBSD: sgmapvar.h,v 1.2 1997/06/07 05:29:33 thorpej Exp $ */
+/* $NetBSD: sgmapvar.h,v 1.3 1997/09/05 02:21:51 thorpej Exp $ */
+
+#define	SGMAP_LOG
 
 /*-
  * Copyright (c) 1997 The NetBSD Foundation, Inc.
@@ -74,6 +76,22 @@ struct alpha_sgmap_cookie {
 /* apdc_flags */
 #define	APDC_HAS_SGMAP		0x01	/* sgva/len are valid */
 
+#ifdef SGMAP_LOG
+/*
+ * Log entry, used for debugging SGMAPs.
+ */
+struct sgmap_log_entry {
+	int	sl_op;			/* op; 1 = load, 0 = unload */
+	struct alpha_sgmap *sl_sgmap;	/* sgmap for entry */
+	void	*sl_origbuf;		/* original buffer */
+	u_long	sl_pgoffset;		/* page offset of buffer start */
+	u_long	sl_origlen;		/* length of transfer */
+	u_long	sl_sgva;		/* sgva of transfer */
+	u_long	sl_dmaaddr;		/* dma address */
+	int	sl_ptecnt;		/* pte count */
+};
+#endif
+
 void	alpha_sgmap_init __P((bus_dma_tag_t, struct alpha_sgmap *,
 	    const char *, bus_addr_t, bus_addr_t, bus_size_t, size_t, void *));