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"
@@ -616,6 +617,9 @@ void dispatch(void)
         next_task->state = TASK_RUNNING;
     next_task->time_slice = get_priority_timeslice(next_task->prio_level);
 
+    /* Switch PMP configuration if tasks have different memory spaces */
+    pmp_switch_context(prev_task->mspace, next_task->mspace);
+
     /* Perform context switch based on scheduling mode */
     if (kcb->preemptive) {
         /* Same task - no context switch needed */
@@ -675,7 +679,15 @@ void yield(void)
     /* In cooperative mode, delays are only processed on an explicit yield. */
     list_foreach(kcb->tasks, delay_update, NULL);
 
+    /* Save current task before scheduler modifies task_current */
+    tcb_t *prev_task = (tcb_t *) kcb->task_current->data;
+
     sched_select_next_task(); /* Use O(1) priority scheduler */
+
+    /* Switch PMP configuration if tasks have different memory spaces */
+    tcb_t *next_task = (tcb_t *) kcb->task_current->data;
+    pmp_switch_context(prev_task->mspace, next_task->mspace);
+
     hal_context_restore(((tcb_t *) kcb->task_current->data)->context, 1);
 }