[lwip-users] LWIP_MPU_COMPATIBLE set to 1, but still get memory management fault in lwip_select.

[David Lockyer]

Hi,

I have a project that uses an STM32F MCU running FreeRTOS (cortex mpu port) & lwip, with the MPU enabled.

I'm upgrading to lwip 2.0.2 from lwip 1.4.1, that I had to customize to be compatible with the MPU, in particular in lwip_select().

The motivation was to use the LWIP_MPU_COMPATIBLE define, so a direct modification of the stack source was not required.  However for me it still appears to try to access another threads memory, triggering an exception.

The changes I had to make were:

Index: lib/lwip-2.0.2/src/api/sockets.c
===================================================================
--- lib/lwip-2.0.2/src/api/sockets.c    (revision xxxxx)
+++ lib/lwip-2.0.2/src/api/sockets.c    (working copy)
@@ -1428,7 +1428,9 @@
     /* Put this select_cb on top of list */
     select_cb.next = select_cb_list;
     if (select_cb_list != NULL) {
+      RAISE_PRIVILEGE();
       select_cb_list->prev = &select_cb;
+      RESET_PRIVILEGE();
     }
     select_cb_list = &select_cb;
     /* Increasing this counter tells event_callback that the list has changed. */
@@ -1508,7 +1510,9 @@
     /* Take us off the list */
     SYS_ARCH_PROTECT(lev);
     if (select_cb.next != NULL) {
+      RAISE_PRIVILEGE();
       select_cb.next->prev = select_cb.prev;
+      RESET_PRIVILEGE();
     }
     if (select_cb_list == &select_cb) {
       LWIP_ASSERT("select_cb.prev == NULL", select_cb.prev == NULL);
@@ -1515,7 +1519,9 @@
       select_cb_list = select_cb.next;
     } else {
       LWIP_ASSERT("select_cb.prev != NULL", select_cb.prev != NULL);
+      RAISE_PRIVILEGE();
       select_cb.prev->next = select_cb.next;
+      RESET_PRIVILEGE();
     }
     /* Increasing this counter tells event_callback that the list has changed. */
     select_cb_ctr++;

Is there something else I missed here that would remove the need for this modification?

Kind regards,

David Lockyer

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