staging: rtl8712: reduce stack usage, again

commit fbd6b250 upstream.

An earlier patch I sent reduced the stack usage enough to get
below the warning limit, and I could show this was safe, but with
GCC_PLUGIN_STRUCTLEAK_BYREF_ALL, it gets worse again because large stack
variables in the same function no longer overlap:

drivers/staging/rtl8712/rtl871x_ioctl_linux.c: In function 'translate_scan.isra.2':
drivers/staging/rtl8712/rtl871x_ioctl_linux.c:322:1: error: the frame size of 1200 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Split out the largest two blocks in the affected function into two
separate functions and mark those noinline_for_stack.

Fixes: 8c5af16f ("staging: rtl8712: reduce stack usage")
Fixes: 81a56f6d ("gcc-plugins: structleak: Generalize to all variable types")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8712/rtl871x_ioctl_linux.c

@@ -124,10 +124,91 @@ static inline void handle_group_key(struct ieee_param *param,
 	}
 }
 
-static noinline_for_stack char *translate_scan(struct _adapter *padapter,
-				   struct iw_request_info *info,
-				   struct wlan_network *pnetwork,
-				   char *start, char *stop)
+static noinline_for_stack char *translate_scan_wpa(struct iw_request_info *info,
+						   struct wlan_network *pnetwork,
+						   struct iw_event *iwe,
+						   char *start, char *stop)
+{
+	/* parsing WPA/WPA2 IE */
+	u8 buf[MAX_WPA_IE_LEN];
+	u8 wpa_ie[255], rsn_ie[255];
+	u16 wpa_len = 0, rsn_len = 0;
+	int n, i;
+
+	r8712_get_sec_ie(pnetwork->network.IEs,
+			 pnetwork->network.IELength, rsn_ie, &rsn_len,
+			 wpa_ie, &wpa_len);
+	if (wpa_len > 0) {
+		memset(buf, 0, MAX_WPA_IE_LEN);
+		n = sprintf(buf, "wpa_ie=");
+		for (i = 0; i < wpa_len; i++) {
+			n += snprintf(buf + n, MAX_WPA_IE_LEN - n,
+						"%02x", wpa_ie[i]);
+			if (n >= MAX_WPA_IE_LEN)
+				break;
+		}
+		memset(iwe, 0, sizeof(*iwe));
+		iwe->cmd = IWEVCUSTOM;
+		iwe->u.data.length = (u16)strlen(buf);
+		start = iwe_stream_add_point(info, start, stop,
+			iwe, buf);
+		memset(iwe, 0, sizeof(*iwe));
+		iwe->cmd = IWEVGENIE;
+		iwe->u.data.length = (u16)wpa_len;
+		start = iwe_stream_add_point(info, start, stop,
+			iwe, wpa_ie);
+	}
+	if (rsn_len > 0) {
+		memset(buf, 0, MAX_WPA_IE_LEN);
+		n = sprintf(buf, "rsn_ie=");
+		for (i = 0; i < rsn_len; i++) {
+			n += snprintf(buf + n, MAX_WPA_IE_LEN - n,
+						"%02x", rsn_ie[i]);
+			if (n >= MAX_WPA_IE_LEN)
+				break;
+		}
+		memset(iwe, 0, sizeof(*iwe));
+		iwe->cmd = IWEVCUSTOM;
+		iwe->u.data.length = strlen(buf);
+		start = iwe_stream_add_point(info, start, stop,
+			iwe, buf);
+		memset(iwe, 0, sizeof(*iwe));
+		iwe->cmd = IWEVGENIE;
+		iwe->u.data.length = rsn_len;
+		start = iwe_stream_add_point(info, start, stop, iwe,
+			rsn_ie);
+	}
+
+	return start;
+}
+
+static noinline_for_stack char *translate_scan_wps(struct iw_request_info *info,
+						   struct wlan_network *pnetwork,
+						   struct iw_event *iwe,
+						   char *start, char *stop)
+{
+	/* parsing WPS IE */
+	u8 wps_ie[512];
+	uint wps_ielen;
+
+	if (r8712_get_wps_ie(pnetwork->network.IEs,
+	    pnetwork->network.IELength,
+	    wps_ie, &wps_ielen)) {
+		if (wps_ielen > 2) {
+			iwe->cmd = IWEVGENIE;
+			iwe->u.data.length = (u16)wps_ielen;
+			start = iwe_stream_add_point(info, start, stop,
+				iwe, wps_ie);
+		}
+	}
+
+	return start;
+}
+
+static char *translate_scan(struct _adapter *padapter,
+			    struct iw_request_info *info,
+			    struct wlan_network *pnetwork,
+			    char *start, char *stop)
 {
 	struct iw_event iwe;
 	struct ieee80211_ht_cap *pht_capie;
@@ -240,73 +321,11 @@ static noinline_for_stack char *translate_scan(struct _adapter *padapter,
 	/* Check if we added any event */
 	if ((current_val - start) > iwe_stream_lcp_len(info))
 		start = current_val;
-	/* parsing WPA/WPA2 IE */
-	{
-		u8 buf[MAX_WPA_IE_LEN];
-		u8 wpa_ie[255], rsn_ie[255];
-		u16 wpa_len = 0, rsn_len = 0;
-		int n;
-
-		r8712_get_sec_ie(pnetwork->network.IEs,
-				 pnetwork->network.IELength, rsn_ie, &rsn_len,
-				 wpa_ie, &wpa_len);
-		if (wpa_len > 0) {
-			memset(buf, 0, MAX_WPA_IE_LEN);
-			n = sprintf(buf, "wpa_ie=");
-			for (i = 0; i < wpa_len; i++) {
-				n += snprintf(buf + n, MAX_WPA_IE_LEN - n,
-							"%02x", wpa_ie[i]);
-				if (n >= MAX_WPA_IE_LEN)
-					break;
-			}
-			memset(&iwe, 0, sizeof(iwe));
-			iwe.cmd = IWEVCUSTOM;
-			iwe.u.data.length = (u16)strlen(buf);
-			start = iwe_stream_add_point(info, start, stop,
-				&iwe, buf);
-			memset(&iwe, 0, sizeof(iwe));
-			iwe.cmd = IWEVGENIE;
-			iwe.u.data.length = (u16)wpa_len;
-			start = iwe_stream_add_point(info, start, stop,
-				&iwe, wpa_ie);
-		}
-		if (rsn_len > 0) {
-			memset(buf, 0, MAX_WPA_IE_LEN);
-			n = sprintf(buf, "rsn_ie=");
-			for (i = 0; i < rsn_len; i++) {
-				n += snprintf(buf + n, MAX_WPA_IE_LEN - n,
-							"%02x", rsn_ie[i]);
-				if (n >= MAX_WPA_IE_LEN)
-					break;
-			}
-			memset(&iwe, 0, sizeof(iwe));
-			iwe.cmd = IWEVCUSTOM;
-			iwe.u.data.length = strlen(buf);
-			start = iwe_stream_add_point(info, start, stop,
-				&iwe, buf);
-			memset(&iwe, 0, sizeof(iwe));
-			iwe.cmd = IWEVGENIE;
-			iwe.u.data.length = rsn_len;
-			start = iwe_stream_add_point(info, start, stop, &iwe,
-				rsn_ie);
-		}
-	}
 
-	{ /* parsing WPS IE */
-		u8 wps_ie[512];
-		uint wps_ielen;
+	start = translate_scan_wpa(info, pnetwork, &iwe, start, stop);
+
+	start = translate_scan_wps(info, pnetwork, &iwe, start, stop);
 
-		if (r8712_get_wps_ie(pnetwork->network.IEs,
-		    pnetwork->network.IELength,
-		    wps_ie, &wps_ielen)) {
-			if (wps_ielen > 2) {
-				iwe.cmd = IWEVGENIE;
-				iwe.u.data.length = (u16)wps_ielen;
-				start = iwe_stream_add_point(info, start, stop,
-					&iwe, wps_ie);
-			}
-		}
-	}
 	/* Add quality statistics */
 	iwe.cmd = IWEVQUAL;
 	rssi = r8712_signal_scale_mapping(pnetwork->network.Rssi);