caif: reduce stack size with KASAN

When CONFIG_KASAN is set, we can use relatively large amounts of kernel
stack space:

net/caif/cfctrl.c:555:1: warning: the frame size of 1600 bytes is larger than 1280 bytes [-Wframe-larger-than=]

This adds convenience wrappers around cfpkt_extr_head(), which is responsible
for most of the stack growth. With those wrapper functions, gcc apparently
starts reusing the stack slots for each instance, thus avoiding the
problem.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/caif/cfpkt.h

@@ -32,6 +32,33 @@ void cfpkt_destroy(struct cfpkt *pkt);
  */
 int cfpkt_extr_head(struct cfpkt *pkt, void *data, u16 len);
 
+static inline u8 cfpkt_extr_head_u8(struct cfpkt *pkt)
+{
+	u8 tmp;
+
+	cfpkt_extr_head(pkt, &tmp, 1);
+
+	return tmp;
+}
+
+static inline u16 cfpkt_extr_head_u16(struct cfpkt *pkt)
+{
+	__le16 tmp;
+
+	cfpkt_extr_head(pkt, &tmp, 2);
+
+	return le16_to_cpu(tmp);
+}
+
+static inline u32 cfpkt_extr_head_u32(struct cfpkt *pkt)
+{
+	__le32 tmp;
+
+	cfpkt_extr_head(pkt, &tmp, 4);
+
+	return le32_to_cpu(tmp);
+}
+
 /*
  * Peek header from packet.
  * Reads data from packet without changing packet.

net/caif/cfctrl.c

@@ -352,15 +352,14 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 	u8 cmdrsp;
 	u8 cmd;
 	int ret = -1;
-	u16 tmp16;
 	u8 len;
 	u8 param[255];
-	u8 linkid;
+	u8 linkid = 0;
 	struct cfctrl *cfctrl = container_obj(layer);
 	struct cfctrl_request_info rsp, *req;
 
 
-	cfpkt_extr_head(pkt, &cmdrsp, 1);
+	cmdrsp = cfpkt_extr_head_u8(pkt);
 	cmd = cmdrsp & CFCTRL_CMD_MASK;
 	if (cmd != CFCTRL_CMD_LINK_ERR
 	    && CFCTRL_RSP_BIT != (CFCTRL_RSP_BIT & cmdrsp)
@@ -378,13 +377,12 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 			u8 physlinkid;
 			u8 prio;
 			u8 tmp;
-			u32 tmp32;
 			u8 *cp;
 			int i;
 			struct cfctrl_link_param linkparam;
 			memset(&linkparam, 0, sizeof(linkparam));
 
-			cfpkt_extr_head(pkt, &tmp, 1);
+			tmp = cfpkt_extr_head_u8(pkt);
 
 			serv = tmp & CFCTRL_SRV_MASK;
 			linkparam.linktype = serv;
@@ -392,13 +390,13 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 			servtype = tmp >> 4;
 			linkparam.chtype = servtype;
 
-			cfpkt_extr_head(pkt, &tmp, 1);
+			tmp = cfpkt_extr_head_u8(pkt);
 			physlinkid = tmp & 0x07;
 			prio = tmp >> 3;
 
 			linkparam.priority = prio;
 			linkparam.phyid = physlinkid;
-			cfpkt_extr_head(pkt, &endpoint, 1);
+			endpoint = cfpkt_extr_head_u8(pkt);
 			linkparam.endpoint = endpoint & 0x03;
 
 			switch (serv) {
@@ -407,45 +405,43 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 				if (CFCTRL_ERR_BIT & cmdrsp)
 					break;
 				/* Link ID */
-				cfpkt_extr_head(pkt, &linkid, 1);
+				linkid = cfpkt_extr_head_u8(pkt);
 				break;
 			case CFCTRL_SRV_VIDEO:
-				cfpkt_extr_head(pkt, &tmp, 1);
+				tmp = cfpkt_extr_head_u8(pkt);
 				linkparam.u.video.connid = tmp;
 				if (CFCTRL_ERR_BIT & cmdrsp)
 					break;
 				/* Link ID */
-				cfpkt_extr_head(pkt, &linkid, 1);
+				linkid = cfpkt_extr_head_u8(pkt);
 				break;
 
 			case CFCTRL_SRV_DATAGRAM:
-				cfpkt_extr_head(pkt, &tmp32, 4);
 				linkparam.u.datagram.connid =
-				    le32_to_cpu(tmp32);
+				    cfpkt_extr_head_u32(pkt);
 				if (CFCTRL_ERR_BIT & cmdrsp)
 					break;
 				/* Link ID */
-				cfpkt_extr_head(pkt, &linkid, 1);
+				linkid = cfpkt_extr_head_u8(pkt);
 				break;
 			case CFCTRL_SRV_RFM:
 				/* Construct a frame, convert
 				 * DatagramConnectionID
 				 * to network format long and copy it out...
 				 */
-				cfpkt_extr_head(pkt, &tmp32, 4);
 				linkparam.u.rfm.connid =
-				  le32_to_cpu(tmp32);
+				    cfpkt_extr_head_u32(pkt);
 				cp = (u8 *) linkparam.u.rfm.volume;
-				for (cfpkt_extr_head(pkt, &tmp, 1);
+				for (tmp = cfpkt_extr_head_u8(pkt);
 				     cfpkt_more(pkt) && tmp != '\0';
-				     cfpkt_extr_head(pkt, &tmp, 1))
+				     tmp = cfpkt_extr_head_u8(pkt))
 					*cp++ = tmp;
 				*cp = '\0';
 
 				if (CFCTRL_ERR_BIT & cmdrsp)
 					break;
 				/* Link ID */
-				cfpkt_extr_head(pkt, &linkid, 1);
+				linkid = cfpkt_extr_head_u8(pkt);
 
 				break;
 			case CFCTRL_SRV_UTIL:
@@ -454,13 +450,11 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 				 * to network format long and copy it out...
 				 */
 				/* Fifosize KB */
-				cfpkt_extr_head(pkt, &tmp16, 2);
 				linkparam.u.utility.fifosize_kb =
-				    le16_to_cpu(tmp16);
+				    cfpkt_extr_head_u16(pkt);
 				/* Fifosize bufs */
-				cfpkt_extr_head(pkt, &tmp16, 2);
 				linkparam.u.utility.fifosize_bufs =
-				    le16_to_cpu(tmp16);
+				    cfpkt_extr_head_u16(pkt);
 				/* name */
 				cp = (u8 *) linkparam.u.utility.name;
 				caif_assert(sizeof(linkparam.u.utility.name)
@@ -468,24 +462,24 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 				for (i = 0;
 				     i < UTILITY_NAME_LENGTH
 				     && cfpkt_more(pkt); i++) {
-					cfpkt_extr_head(pkt, &tmp, 1);
+					tmp = cfpkt_extr_head_u8(pkt);
 					*cp++ = tmp;
 				}
 				/* Length */
-				cfpkt_extr_head(pkt, &len, 1);
+				len = cfpkt_extr_head_u8(pkt);
 				linkparam.u.utility.paramlen = len;
 				/* Param Data */
 				cp = linkparam.u.utility.params;
 				while (cfpkt_more(pkt) && len--) {
-					cfpkt_extr_head(pkt, &tmp, 1);
+					tmp = cfpkt_extr_head_u8(pkt);
 					*cp++ = tmp;
 				}
 				if (CFCTRL_ERR_BIT & cmdrsp)
 					break;
 				/* Link ID */
-				cfpkt_extr_head(pkt, &linkid, 1);
+				linkid = cfpkt_extr_head_u8(pkt);
 				/* Length */
-				cfpkt_extr_head(pkt, &len, 1);
+				len = cfpkt_extr_head_u8(pkt);
 				/* Param Data */
 				cfpkt_extr_head(pkt, &param, len);
 				break;
@@ -522,7 +516,7 @@ static int cfctrl_recv(struct cflayer *layer, struct cfpkt *pkt)
 		}
 		break;
 	case CFCTRL_CMD_LINK_DESTROY:
-		cfpkt_extr_head(pkt, &linkid, 1);
+		linkid = cfpkt_extr_head_u8(pkt);
 		cfctrl->res.linkdestroy_rsp(cfctrl->serv.layer.up, linkid);
 		break;
 	case CFCTRL_CMD_LINK_ERR: