[Bugfix rtems-lwip 4/4] Fix crash due to link_detect_thread

[Bernd Moessner]

Within xemac_add, the link_detect_thread is set up before the ethernet
interface is configured and all data structures have been set up correctly.
The steps within xemac_add are basically:
1) Set up link_detect_thread
2) Initialize the interface
3) Set up the link speed / start autonegotiation
4) When autonegotiate has completed, set up the data structures

The issue is here that, for example if no cable is connected, the
autonegotiate sequence will suspend the calling task. As soon as
this happens, the link_detect_thread gets into running state and
dereferences the data structures that havent been set up. Unfortunatelly,
it isnt as easy as checking the pointer to the relevant data structure
for being NULL within the link_detect_thread. Not going into details,
the pointer (netif->state) isnt NULL in this moment of time, but it
has to point to something completely different.

It seems to me that the easiest solution to this problem is to reorder
the sequence within xemac_add. Initialize the interface and set up the
data structures, then create the link_detect_thread which requires all of
this. After applying this patch, the sequence becomes:

1) Initialize the interface
2) Set up the link speed / start autonegotiation
3) When autonegotiate has completed, set up the data structures
4) Set up link_detect_thread
---
 .../src/contrib/ports/xilinx/netif/xadapter.c | 32 ++++++++++++++-----
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/embeddedsw/ThirdParty/sw_services/lwip211/src/contrib/ports/xilinx/netif/xadapter.c b/embeddedsw/ThirdParty/sw_services/lwip211/src/contrib/ports/xilinx/netif/xadapter.c
index 93ff148..79a10c1 100644
--- a/embeddedsw/ThirdParty/sw_services/lwip211/src/contrib/ports/xilinx/netif/xadapter.c
+++ b/embeddedsw/ThirdParty/sw_services/lwip211/src/contrib/ports/xilinx/netif/xadapter.c
@@ -126,8 +126,9 @@ xemac_add(struct netif *netif,
 	UINTPTR mac_baseaddr)
 {
 	int i;
+	struct netif * ret = NULL;
 
-#if !NO_SYS
+#if !NO_SYS && !defined(__rtems__)
 	/* Start thread to detect link periodically for Hot Plug autodetect */
 	sys_thread_new("link_detect_thread", link_detect_thread, netif,
 			THREAD_STACKSIZE, tskIDLE_PRIORITY);
@@ -142,7 +143,7 @@ xemac_add(struct netif *netif,
 		switch (find_mac_type(mac_baseaddr)) {
 			case xemac_type_xps_emaclite:
 #ifdef XLWIP_CONFIG_INCLUDE_EMACLITE
-				return netif_add(netif, ipaddr, netmask, gw,
+				ret = netif_add(netif, ipaddr, netmask, gw,
 					(void*)mac_baseaddr,
 					xemacliteif_init,
 #if NO_SYS
@@ -151,12 +152,14 @@ xemac_add(struct netif *netif,
 					tcpip_input
 #endif
 					);
+				break;
 #else
-				return NULL;
+				ret = NULL;
+				break;
 #endif
 			case xemac_type_axi_ethernet:
 #ifdef XLWIP_CONFIG_INCLUDE_AXI_ETHERNET
-				return netif_add(netif, ipaddr, netmask, gw,
+				ret = netif_add(netif, ipaddr, netmask, gw,
 					(void*)mac_baseaddr,
 					xaxiemacif_init,
 #if NO_SYS
@@ -165,16 +168,18 @@ xemac_add(struct netif *netif,
 					tcpip_input
 #endif
 					);
+				break;
 #else
-				return NULL;
+				ret = NULL;
+				break;
 #endif
 #if defined (__arm__) || defined (__aarch64__)
 			case xemac_type_emacps:
 #ifdef XLWIP_CONFIG_INCLUDE_GEM
 #ifndef __rtems__
-				return netif_add(netif, ipaddr, netmask, gw,
+				ret = netif_add(netif, ipaddr, netmask, gw,
 #else /* __rtems__ */
-				return netif_add( netif,
+				ret = netif_add( netif,
 						(const ip4_addr_t *) ipaddr,
 						(const ip4_addr_t *) netmask,
 						(const ip4_addr_t *) gw,
@@ -188,7 +193,10 @@ xemac_add(struct netif *netif,
 #endif
 
 						);
+				break;
 #endif
+				ret = NULL;
+				break;
 #endif
 			default:
 #ifndef __rtems__
@@ -199,8 +207,16 @@ xemac_add(struct netif *netif,
 						mac_baseaddr);
 				xil_printf("\r\n");
 #endif
-				return NULL;
+				ret = NULL;
 	}
+
+#if defined(__rtems__)
+	/* Start thread to detect link periodically for Hot Plug autodetect */
+	sys_thread_new("link_detect_thread", link_detect_thread, netif,
+			THREAD_STACKSIZE, tskIDLE_PRIORITY);
+#endif
+
+	return ret;
 }
 
 #if !NO_SYS
-- 
2.34.1