BUG_ON() is a macro very very similar to assert(), and it's a really bad

idea in general to put statements with side-effects inside such a construct
(for example the BUG_ON() could be compiled away for non-debug builds).

The patch below fixes this for the drivers/xen tree.

I chose the general construct to store the respective return values in a
local var instead of an if (...) BUG(); because it looks like most of these
BUG_ON()'s need to be replaced by real error handling when going towards
production releases anyway, and then the local variable is going to be
needed anyway. (and besides the if construct tends to get unreable due to
the unlikely() etc).

Please apply.

Greetings,
   Arjan van de Ven

linux-2.6-xen-sparse/drivers/xen/balloon/balloon.c

@@ -191,12 +191,13 @@ static int increase_reservation(unsigned long nr_pages)
 	rc = HYPERVISOR_memory_op(
 		XENMEM_increase_reservation, &reservation);
 	if (rc < nr_pages) {
+		int ret;
 		/* We hit the Xen hard limit: reprobe. */
 		reservation.extent_start = mfn_list;
 		reservation.nr_extents   = rc;
-		BUG_ON(HYPERVISOR_memory_op(
-			XENMEM_decrease_reservation,
-			&reservation) != rc);
+		ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+				&reservation);
+		BUG_ON(ret != rc);
 		hard_limit = current_pages + rc - driver_pages;
 		goto out;
 	}
@@ -213,11 +214,14 @@ static int increase_reservation(unsigned long nr_pages)
 		xen_machphys_update(mfn_list[i], pfn);
             
 		/* Link back into the page tables if not highmem. */
-		if (pfn < max_low_pfn)
-			BUG_ON(HYPERVISOR_update_va_mapping(
+		if (pfn < max_low_pfn) {
+			int ret;
+			ret = HYPERVISOR_update_va_mapping(
 				(unsigned long)__va(pfn << PAGE_SHIFT),
 				pfn_pte_ma(mfn_list[i], PAGE_KERNEL),
-				0));
+				0);
+			BUG_ON(ret);
+		}
 
 		/* Relinquish the page back to the allocator. */
 		ClearPageReserved(page);
@@ -242,6 +246,7 @@ static int decrease_reservation(unsigned long nr_pages)
 	struct page   *page;
 	void          *v;
 	int            need_sleep = 0;
+	int ret;
 	struct xen_memory_reservation reservation = {
 		.address_bits = 0,
 		.extent_order = 0,
@@ -268,8 +273,9 @@ static int decrease_reservation(unsigned long nr_pages)
 		if (!PageHighMem(page)) {
 			v = phys_to_virt(pfn << PAGE_SHIFT);
 			scrub_pages(v, 1);
-			BUG_ON(HYPERVISOR_update_va_mapping(
-				(unsigned long)v, __pte_ma(0), 0));
+			ret = HYPERVISOR_update_va_mapping(
+				(unsigned long)v, __pte_ma(0), 0);
+			BUG_ON(ret);
 		}
 #ifdef CONFIG_XEN_SCRUB_PAGES
 		else {
@@ -295,8 +301,8 @@ static int decrease_reservation(unsigned long nr_pages)
 
 	reservation.extent_start = mfn_list;
 	reservation.nr_extents   = nr_pages;
-	BUG_ON(HYPERVISOR_memory_op(
-		XENMEM_decrease_reservation, &reservation) != nr_pages);
+	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+	BUG_ON(ret != nr_pages);
 
 	current_pages -= nr_pages;
 	totalram_pages = current_pages;
@@ -501,6 +507,7 @@ static int dealloc_pte_fn(
 	pte_t *pte, struct page *pte_page, unsigned long addr, void *data)
 {
 	unsigned long mfn = pte_mfn(*pte);
+	int ret;
 	struct xen_memory_reservation reservation = {
 		.extent_start = &mfn,
 		.nr_extents   = 1,
@@ -510,8 +517,8 @@ static int dealloc_pte_fn(
 	set_pte_at(&init_mm, addr, pte, __pte_ma(0));
 	phys_to_machine_mapping[__pa(addr) >> PAGE_SHIFT] =
 		INVALID_P2M_ENTRY;
-	BUG_ON(HYPERVISOR_memory_op(
-		XENMEM_decrease_reservation, &reservation) != 1);
+	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
+	BUG_ON(ret != 1);
 	return 0;
 }
 
@@ -519,6 +526,7 @@ struct page *balloon_alloc_empty_page_range(unsigned long nr_pages)
 {
 	unsigned long vstart, flags;
 	unsigned int  order = get_order(nr_pages * PAGE_SIZE);
+	int ret;
 
 	vstart = __get_free_pages(GFP_KERNEL, order);
 	if (vstart == 0)
@@ -527,8 +535,9 @@ struct page *balloon_alloc_empty_page_range(unsigned long nr_pages)
 	scrub_pages(vstart, 1 << order);
 
 	balloon_lock(flags);
-	BUG_ON(generic_page_range(
-		&init_mm, vstart, PAGE_SIZE << order, dealloc_pte_fn, NULL));
+	ret = generic_page_range(
+		&init_mm, vstart, PAGE_SIZE << order, dealloc_pte_fn, NULL);
+	BUG_ON(ret);
 	current_pages -= 1UL << order;
 	balloon_unlock(flags);
 

linux-2.6-xen-sparse/drivers/xen/blkback/blkback.c

@@ -108,6 +108,7 @@ static void fast_flush_area(int idx, int nr_pages)
 	struct gnttab_unmap_grant_ref unmap[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	unsigned int i, invcount = 0;
 	u16 handle;
+	int ret;
 
 	for (i = 0; i < nr_pages; i++) {
 		handle = pending_handle(idx, i);
@@ -120,8 +121,9 @@ static void fast_flush_area(int idx, int nr_pages)
 		invcount++;
 	}
 
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_unmap_grant_ref, unmap, invcount));
+	ret = HYPERVISOR_grant_table_op(
+		GNTTABOP_unmap_grant_ref, unmap, invcount);
+	BUG_ON(ret);
 }
 
 
@@ -338,6 +340,7 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
 	struct bio *bio = NULL, *biolist[BLKIF_MAX_SEGMENTS_PER_REQUEST];
 	int nbio = 0;
 	request_queue_t *q;
+	int ret;
 
 	/* Check that number of segments is sane. */
 	nseg = req->nr_segments;
@@ -367,8 +370,8 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
 			map[i].flags |= GNTMAP_readonly;
 	}
 
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_map_grant_ref, map, nseg));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, nseg);
+	BUG_ON(ret);
 
 	for (i = 0; i < nseg; i++) {
 		if (unlikely(map[i].handle < 0)) {
@@ -493,6 +496,7 @@ static int __init blkif_init(void)
 {
 	int i;
 	struct page *page;
+	int ret;
 
 	blkif_interface_init();
 
@@ -509,7 +513,8 @@ static int __init blkif_init(void)
 	spin_lock_init(&blkio_schedule_list_lock);
 	INIT_LIST_HEAD(&blkio_schedule_list);
 
-	BUG_ON(kernel_thread(blkio_schedule, 0, CLONE_FS | CLONE_FILES) < 0);
+	ret = kernel_thread(blkio_schedule, 0, CLONE_FS | CLONE_FILES);
+	BUG_ON(ret < 0);
 
 	blkif_xenbus_init();
 

linux-2.6-xen-sparse/drivers/xen/blkback/interface.c

@@ -31,6 +31,7 @@ blkif_t *alloc_blkif(domid_t domid)
 static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 {
 	struct gnttab_map_grant_ref op;
+	int ret;
 
 	op.host_addr = (unsigned long)blkif->blk_ring_area->addr;
 	op.flags     = GNTMAP_host_map;
@@ -38,8 +39,9 @@ static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 	op.dom       = blkif->domid;
 
 	lock_vm_area(blkif->blk_ring_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1);
 	unlock_vm_area(blkif->blk_ring_area);
+	BUG_ON(ret);
 
 	if (op.handle < 0) {
 		DPRINTK(" Grant table operation failure !\n");
@@ -55,14 +57,16 @@ static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 static void unmap_frontend_page(blkif_t *blkif)
 {
 	struct gnttab_unmap_grant_ref op;
+	int ret;
 
 	op.host_addr    = (unsigned long)blkif->blk_ring_area->addr;
 	op.handle       = blkif->shmem_handle;
 	op.dev_bus_addr = 0;
 
 	lock_vm_area(blkif->blk_ring_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1);
 	unlock_vm_area(blkif->blk_ring_area);
+	BUG_ON(ret);
 }
 
 int blkif_map(blkif_t *blkif, unsigned long shared_page, unsigned int evtchn)

linux-2.6-xen-sparse/drivers/xen/blkfront/blkfront.c

@@ -305,6 +305,7 @@ static irqreturn_t blkif_int(int irq, void *dev_id, struct pt_regs *ptregs)
 
 	for (i = info->ring.rsp_cons; i != rp; i++) {
 		unsigned long id;
+		int ret;
 
 		bret = RING_GET_RESPONSE(&info->ring, i);
 		id   = bret->id;
@@ -321,9 +322,10 @@ static irqreturn_t blkif_int(int irq, void *dev_id, struct pt_regs *ptregs)
 				DPRINTK("Bad return from blkdev data "
 					"request: %x\n", bret->status);
 
-			BUG_ON(end_that_request_first(
+			ret = end_that_request_first(
 				req, (bret->status == BLKIF_RSP_OKAY),
-				req->hard_nr_sectors));
+				req->hard_nr_sectors);
+			BUG_ON(ret);
 			end_that_request_last(req);
 			break;
 		default:

linux-2.6-xen-sparse/drivers/xen/blktap/blktap.c

@@ -413,6 +413,7 @@ static void fast_flush_area(int idx, int nr_pages)
 	unsigned int i, op = 0;
 	struct grant_handle_pair *handle;
 	unsigned long ptep;
+	int ret;
 
 	for ( i = 0; i < nr_pages; i++)
 	{
@@ -440,8 +441,8 @@ static void fast_flush_area(int idx, int nr_pages)
 		BLKTAP_INVALIDATE_HANDLE(handle);
 	}
 
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_unmap_grant_ref, unmap, op));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, op);
+	BUG_ON(ret);
 
 	if (blktap_vma != NULL)
 		zap_page_range(blktap_vma, 
@@ -673,6 +674,7 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
 	struct gnttab_map_grant_ref map[BLKIF_MAX_SEGMENTS_PER_REQUEST*2];
 	int op, ret;
 	unsigned int nseg;
+	int retval;
 
 	/* Check that number of segments is sane. */
 	nseg = req->nr_segments;
@@ -740,8 +742,8 @@ static void dispatch_rw_block_io(blkif_t *blkif, blkif_request_t *req)
 		op++;
 	}
 
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_map_grant_ref, map, op));
+	retval = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map, op);
+	BUG_ON(retval);
 
 	op = 0;
 	for (i = 0; i < (req->nr_segments*2); i += 2) {
@@ -877,7 +879,8 @@ static int __init blkif_init(void)
 	spin_lock_init(&blkio_schedule_list_lock);
 	INIT_LIST_HEAD(&blkio_schedule_list);
 
-	BUG_ON(kernel_thread(blkio_schedule, 0, CLONE_FS | CLONE_FILES) < 0);
+	i = kernel_thread(blkio_schedule, 0, CLONE_FS | CLONE_FILES);
+	BUG_ON(i<0);
 
 	blkif_xenbus_init();
 

linux-2.6-xen-sparse/drivers/xen/blktap/interface.c

@@ -31,6 +31,7 @@ blkif_t *alloc_blkif(domid_t domid)
 static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 {
 	struct gnttab_map_grant_ref op;
+	int ret;
 
 	op.host_addr = (unsigned long)blkif->blk_ring_area->addr;
 	op.flags     = GNTMAP_host_map;
@@ -38,8 +39,9 @@ static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 	op.dom       = blkif->domid;
 
 	lock_vm_area(blkif->blk_ring_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1);
 	unlock_vm_area(blkif->blk_ring_area);
+	BUG_ON(ret);
 
 	if (op.handle < 0) {
 		DPRINTK(" Grant table operation failure !\n");
@@ -55,14 +57,16 @@ static int map_frontend_page(blkif_t *blkif, unsigned long shared_page)
 static void unmap_frontend_page(blkif_t *blkif)
 {
 	struct gnttab_unmap_grant_ref op;
+	int ret;
 
 	op.host_addr    = (unsigned long)blkif->blk_ring_area->addr;
 	op.handle       = blkif->shmem_handle;
 	op.dev_bus_addr = 0;
 
 	lock_vm_area(blkif->blk_ring_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1);
 	unlock_vm_area(blkif->blk_ring_area);
+	BUG_ON(ret);
 }
 
 int blkif_map(blkif_t *blkif, unsigned long shared_page, unsigned int evtchn)

linux-2.6-xen-sparse/drivers/xen/evtchn/evtchn.c

@@ -282,6 +282,7 @@ static int evtchn_ioctl(struct inode *inode, struct file *file,
 
 	case IOCTL_EVTCHN_UNBIND: {
 		struct ioctl_evtchn_unbind unbind;
+		int ret;
 
 		rc = -EFAULT;
 		if (copy_from_user(&unbind, (void *)arg, sizeof(unbind)))
@@ -306,7 +307,8 @@ static int evtchn_ioctl(struct inode *inode, struct file *file,
 
 		op.cmd = EVTCHNOP_close;
 		op.u.close.port = unbind.port;
-		BUG_ON(HYPERVISOR_event_channel_op(&op));
+		ret = HYPERVISOR_event_channel_op(&op);
+		BUG_ON(ret);
 
 		rc = 0;
 		break;
@@ -399,6 +401,7 @@ static int evtchn_release(struct inode *inode, struct file *filp)
 
 	for (i = 0; i < NR_EVENT_CHANNELS; i++)
 	{
+		int ret;
 		if (port_user[i] != u)
 			continue;
 
@@ -407,7 +410,8 @@ static int evtchn_release(struct inode *inode, struct file *filp)
 
 		op.cmd = EVTCHNOP_close;
 		op.u.close.port = i;
-		BUG_ON(HYPERVISOR_event_channel_op(&op));
+		ret = HYPERVISOR_event_channel_op(&op);
+		BUG_ON(ret);
 	}
 
 	spin_unlock_irq(&port_user_lock);

linux-2.6-xen-sparse/drivers/xen/netback/interface.c

@@ -115,6 +115,7 @@ static int map_frontend_pages(
 	netif_t *netif, grant_ref_t tx_ring_ref, grant_ref_t rx_ring_ref)
 {
 	struct gnttab_map_grant_ref op;
+	int ret;
 
 	op.host_addr = (unsigned long)netif->comms_area->addr;
 	op.flags     = GNTMAP_host_map;
@@ -122,8 +123,9 @@ static int map_frontend_pages(
 	op.dom       = netif->domid;
     
 	lock_vm_area(netif->comms_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1);
 	unlock_vm_area(netif->comms_area);
+	BUG_ON(ret);
 
 	if (op.handle < 0) { 
 		DPRINTK(" Gnttab failure mapping tx_ring_ref!\n");
@@ -139,8 +141,9 @@ static int map_frontend_pages(
 	op.dom       = netif->domid;
 
 	lock_vm_area(netif->comms_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1);
 	unlock_vm_area(netif->comms_area);
+	BUG_ON(ret);
 
 	if (op.handle < 0) { 
 		DPRINTK(" Gnttab failure mapping rx_ring_ref!\n");
@@ -156,22 +159,25 @@ static int map_frontend_pages(
 static void unmap_frontend_pages(netif_t *netif)
 {
 	struct gnttab_unmap_grant_ref op;
+	int ret;
 
 	op.host_addr    = (unsigned long)netif->comms_area->addr;
 	op.handle       = netif->tx_shmem_handle;
 	op.dev_bus_addr = 0;
 
 	lock_vm_area(netif->comms_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1);
 	unlock_vm_area(netif->comms_area);
+	BUG_ON(ret);
 
 	op.host_addr    = (unsigned long)netif->comms_area->addr + PAGE_SIZE;
 	op.handle       = netif->rx_shmem_handle;
 	op.dev_bus_addr = 0;
 
 	lock_vm_area(netif->comms_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1);
 	unlock_vm_area(netif->comms_area);
+	BUG_ON(ret);
 }
 
 int netif_map(netif_t *netif, unsigned long tx_ring_ref,

linux-2.6-xen-sparse/drivers/xen/netback/netback.c

@@ -112,9 +112,12 @@ static void free_mfn(unsigned long mfn)
 	spin_lock_irqsave(&mfn_lock, flags);
 	if ( alloc_index != MAX_MFN_ALLOC )
 		mfn_list[alloc_index++] = mfn;
-	else
-		BUG_ON(HYPERVISOR_memory_op(XENMEM_decrease_reservation,
-					    &reservation) != 1);
+	else {
+		int ret;
+		ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
+					    &reservation);
+		BUG_ON(ret != 1);
+	}
 	spin_unlock_irqrestore(&mfn_lock, flags);
 }
 #endif
@@ -159,13 +162,15 @@ int netif_be_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	 */
 	if (skb_shared(skb) || skb_cloned(skb) || !is_xen_skb(skb)) {
 		int hlen = skb->data - skb->head;
+		int ret;
 		struct sk_buff *nskb = dev_alloc_skb(hlen + skb->len);
 		if ( unlikely(nskb == NULL) )
 			goto drop;
 		skb_reserve(nskb, hlen);
 		__skb_put(nskb, skb->len);
-		BUG_ON(skb_copy_bits(skb, -hlen, nskb->data - hlen,
-				     skb->len + hlen));
+		ret = skb_copy_bits(skb, -hlen, nskb->data - hlen,
+				     skb->len + hlen);
+		BUG_ON(ret);
 		nskb->dev = skb->dev;
 		nskb->proto_csum_valid = skb->proto_csum_valid;
 		dev_kfree_skb(skb);
@@ -218,6 +223,7 @@ static void net_rx_action(unsigned long unused)
 	struct sk_buff *skb;
 	u16 notify_list[NETIF_RX_RING_SIZE];
 	int notify_nr = 0;
+	int ret;
 
 	skb_queue_head_init(&rxq);
 
@@ -279,7 +285,8 @@ static void net_rx_action(unsigned long unused)
 	mcl++;
 
 	mcl[-2].args[MULTI_UVMFLAGS_INDEX] = UVMF_TLB_FLUSH|UVMF_ALL;
-	BUG_ON(HYPERVISOR_multicall(rx_mcl, mcl - rx_mcl) != 0);
+	ret = HYPERVISOR_multicall(rx_mcl, mcl - rx_mcl);
+	BUG_ON(ret != 0);
 
 	mcl = rx_mcl;
 	if( HYPERVISOR_grant_table_op(GNTTABOP_transfer, grant_rx_op, 
@@ -421,6 +428,7 @@ inline static void net_tx_action_dealloc(void)
 	u16 pending_idx;
 	PEND_RING_IDX dc, dp;
 	netif_t *netif;
+	int ret;
 
 	dc = dealloc_cons;
 	dp = dealloc_prod;
@@ -436,8 +444,9 @@ inline static void net_tx_action_dealloc(void)
 		gop->handle       = grant_tx_ref[pending_idx];
 		gop++;
 	}
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_unmap_grant_ref, tx_unmap_ops, gop - tx_unmap_ops));
+	ret = HYPERVISOR_grant_table_op(
+		GNTTABOP_unmap_grant_ref, tx_unmap_ops, gop - tx_unmap_ops);
+	BUG_ON(ret);
 
 	while (dealloc_cons != dp) {
 		pending_idx = dealloc_ring[MASK_PEND_IDX(dealloc_cons++)];
@@ -477,6 +486,7 @@ static void net_tx_action(unsigned long unused)
 	NETIF_RING_IDX i;
 	gnttab_map_grant_ref_t *mop;
 	unsigned int data_len;
+	int ret;
 
 	if (dealloc_cons != dealloc_prod)
 		net_tx_action_dealloc();
@@ -599,8 +609,9 @@ static void net_tx_action(unsigned long unused)
 	if (mop == tx_map_ops)
 		return;
 
-	BUG_ON(HYPERVISOR_grant_table_op(
-		GNTTABOP_map_grant_ref, tx_map_ops, mop - tx_map_ops));
+	ret = HYPERVISOR_grant_table_op(
+		GNTTABOP_map_grant_ref, tx_map_ops, mop - tx_map_ops);
+	BUG_ON(ret);
 
 	mop = tx_map_ops;
 	while ((skb = __skb_dequeue(&tx_queue)) != NULL) {

linux-2.6-xen-sparse/drivers/xen/tpmback/interface.c

@@ -78,6 +78,7 @@ tpmif_find(domid_t domid, long int instance)
 static int
 map_frontend_page(tpmif_t *tpmif, unsigned long shared_page)
 {
+	int ret;
 	struct gnttab_map_grant_ref op = {
 		.host_addr = (unsigned long)tpmif->tx_area->addr,
 		.flags = GNTMAP_host_map,
@@ -86,8 +87,9 @@ map_frontend_page(tpmif_t *tpmif, unsigned long shared_page)
 	};
 
 	lock_vm_area(tpmif->tx_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, &op, 1);
 	unlock_vm_area(tpmif->tx_area);
+	BUG_ON(ret);
 
 	if (op.handle < 0) {
 		DPRINTK(" Grant table operation failure !\n");
@@ -104,14 +106,16 @@ static void
 unmap_frontend_page(tpmif_t *tpmif)
 {
 	struct gnttab_unmap_grant_ref op;
+	int ret;
 
 	op.host_addr    = (unsigned long)tpmif->tx_area->addr;
 	op.handle       = tpmif->shmem_handle;
 	op.dev_bus_addr = 0;
 
 	lock_vm_area(tpmif->tx_area);
-	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1));
+	ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, &op, 1);
 	unlock_vm_area(tpmif->tx_area);
+	BUG_ON(ret);
 }
 
 int

linux-2.6-xen-sparse/drivers/xen/util.c

@@ -34,7 +34,9 @@ struct vm_struct *alloc_vm_area(unsigned long size)
 
 void free_vm_area(struct vm_struct *area)
 {
-	BUG_ON(remove_vm_area(area->addr) != area);
+	struct vm_struct *ret;
+	ret = remove_vm_area(area->addr);
+	BUG_ON(ret != area);
 	kfree(area);
 }
 

linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_probe.c

@@ -737,6 +737,7 @@ static int __init xenbus_probe_init(void)
 
 		unsigned long page;
 		evtchn_op_t op = { 0 };
+		int ret;
 
 
 		/* Allocate page. */
@@ -757,7 +758,8 @@ static int __init xenbus_probe_init(void)
 		op.u.alloc_unbound.dom        = DOMID_SELF;
 		op.u.alloc_unbound.remote_dom = 0; 
 
-		BUG_ON(HYPERVISOR_event_channel_op(&op)); 
+		ret = HYPERVISOR_event_channel_op(&op);
+		BUG_ON(ret); 
 		xen_start_info->store_evtchn = op.u.alloc_unbound.port;
 
 		/* And finally publish the above info in /proc/xen */