Integrate PMP context switching into dispatcher

Switch memory protection configuration during task context switches for
both preemptive and cooperative scheduling. The old task's memory space
is captured before the scheduler updates its internal state, allowing
both old and new memory spaces to be passed to the PMP switching logic.

Author: HeatCrab

kernel/task.c

@@ -8,6 +8,7 @@
 #include <hal.h>
 #include <lib/libc.h>
 #include <lib/queue.h>
+#include <pmp.h>
 #include <sys/task.h>
 
 #include "private/error.h"
@@ -492,12 +493,19 @@ void dispatch(void)
     uint32_t ready_count = 0;
     list_foreach(kcb->tasks, delay_update_batch, &ready_count);
 
+    /* Save old task before scheduler modifies task_current */
+    memspace_t *old_mspace = ((tcb_t *) kcb->task_current->data)->mspace;
+
     /* Hook for real-time scheduler - if it selects a task, use it */
     if (kcb->rt_sched() < 0)
         sched_select_next_task(); /* Use O(1) priority scheduler */
 
     hal_interrupt_tick();
 
+    /* Switch PMP configuration if tasks have different memory spaces */
+    memspace_t *new_mspace = ((tcb_t *) kcb->task_current->data)->mspace;
+    pmp_switch_context(old_mspace, new_mspace);
+
     /* Restore next task context */
     hal_context_restore(((tcb_t *) kcb->task_current->data)->context, 1);
 }
@@ -523,7 +531,15 @@ void yield(void)
     if (!kcb->preemptive)
         list_foreach(kcb->tasks, delay_update, NULL);
 
+    /* Save old task before scheduler modifies task_current */
+    memspace_t *old_mspace = ((tcb_t *) kcb->task_current->data)->mspace;
+
     sched_select_next_task(); /* Use O(1) priority scheduler */
+
+    /* Switch PMP configuration if tasks have different memory spaces */
+    memspace_t *new_mspace = ((tcb_t *) kcb->task_current->data)->mspace;
+    pmp_switch_context(old_mspace, new_mspace);
+
     hal_context_restore(((tcb_t *) kcb->task_current->data)->context, 1);
 }