From 3da80d3a0e4fffb41478141e752c945daf69aeaf Mon Sep 17 00:00:00 2001
From: Marius Strobl <marius@FreeBSD.org>
Date: Wed, 7 Jan 2009 21:25:44 +0000
Subject: [PATCH] Check the return values of contigmalloc(9) as well as
 bus_dma(9) functions and stop attaching of dcons(4) and dcons_crom(4) if they
 indicate failure. This fixes a panic seen on sparc64 machines with no free
 physical memory in the requested 32-bit region but still doesn't make
 dcons(4)/dcons_crom(4) these work. I think the latter can be fixed by simply
 specifying ~0UL as the upper limit for contigmalloc(9) and letting the bounce
 pages and the IOMMU respectively handle limitations of the DMA engine. I
 didn't want to change that without the consensus of simokawa@ though, who
 unfortunately didn't reply so far.

MFC after:	1 week
---
 sys/dev/dcons/dcons_crom.c | 15 ++++++++++++---
 sys/dev/dcons/dcons_os.c   | 18 +++++++++++-------
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/sys/dev/dcons/dcons_crom.c b/sys/dev/dcons/dcons_crom.c
index 0b2b707fcde..ee263e95ac7 100644
--- a/sys/dev/dcons/dcons_crom.c
+++ b/sys/dev/dcons/dcons_crom.c
@@ -205,7 +205,10 @@ dcons_crom_attach(device_t dev)
 	return (-1);
 #else
 	struct dcons_crom_softc *sc;
+	int error;
 
+	if (dcons_conf->buf == NULL)
+		return (ENXIO);
         sc = (struct dcons_crom_softc *) device_get_softc(dev);
 	sc->fd.fc = device_get_ivars(dev);
 	sc->fd.dev = dev;
@@ -213,7 +216,7 @@ dcons_crom_attach(device_t dev)
 	sc->fd.post_busreset = (void *) dcons_crom_post_busreset;
 
 	/* map dcons buffer */
-	bus_dma_tag_create(
+	error = bus_dma_tag_create(
 		/*parent*/ sc->fd.fc->dmat,
 		/*alignment*/ sizeof(u_int32_t),
 		/*boundary*/ 0,
@@ -229,10 +232,16 @@ dcons_crom_attach(device_t dev)
 		/*lockarg*/&Giant,
 #endif
 		&sc->dma_tag);
-	bus_dmamap_create(sc->dma_tag, BUS_DMA_COHERENT, &sc->dma_map);
-	bus_dmamap_load(sc->dma_tag, sc->dma_map,
+	if (error != 0)
+		return (error);
+	error = bus_dmamap_create(sc->dma_tag, BUS_DMA_COHERENT, &sc->dma_map);
+	if (error != 0)
+		return (error);
+	error = bus_dmamap_load(sc->dma_tag, sc->dma_map,
 	    (void *)dcons_conf->buf, dcons_conf->size,
 	    dmamap_cb, sc, 0);
+	if (error != 0)
+		return (error);
 	sc->ehand = EVENTHANDLER_REGISTER(dcons_poll, dcons_crom_poll,
 			 (void *)sc, 0);
 	return (0);
diff --git a/sys/dev/dcons/dcons_os.c b/sys/dev/dcons/dcons_os.c
index 466f7a0f676..f4d4181b9a6 100644
--- a/sys/dev/dcons/dcons_os.c
+++ b/sys/dev/dcons/dcons_os.c
@@ -336,6 +336,8 @@ dcons_drv_init(int stage)
 		 */ 
 		dg.buf = (struct dcons_buf *) contigmalloc(dg.size,
 			M_DEVBUF, 0, 0x10000, 0xffffffff, PAGE_SIZE, 0ul);
+		if (dg.buf == NULL)
+			return (-1);
 		dcons_init(dg.buf, dg.size, sc);
 	}
 
@@ -400,8 +402,8 @@ dcons_modevent(module_t mode, int type, void *data)
 	switch (type) {
 	case MOD_LOAD:
 		ret = dcons_drv_init(1);
-		dcons_attach();
 		if (ret == 0) {
+			dcons_attach();
 			dcons_cnprobe(&dcons_consdev);
 			dcons_cninit(&dcons_consdev);
 			cnadd(&dcons_consdev);
@@ -409,13 +411,15 @@ dcons_modevent(module_t mode, int type, void *data)
 		break;
 	case MOD_UNLOAD:
 		printf("dcons: unload\n");
-		callout_stop(&dcons_callout);
-		cnremove(&dcons_consdev);
-		dcons_detach(DCONS_CON);
-		dcons_detach(DCONS_GDB);
-		dg.buf->magic = 0;
+		if (drv_init == 1) {
+			callout_stop(&dcons_callout);
+			cnremove(&dcons_consdev);
+			dcons_detach(DCONS_CON);
+			dcons_detach(DCONS_GDB);
+			dg.buf->magic = 0;
 
-		contigfree(dg.buf, DCONS_BUF_SIZE, M_DEVBUF);
+			contigfree(dg.buf, DCONS_BUF_SIZE, M_DEVBUF);
+		}
 
 		break;
 	case MOD_SHUTDOWN: