Initialize per-task memory spaces at creation

Allocate a dedicated memory space for each task and register the
task stack as a flexpage. This establishes the memory protection
metadata that will be loaded into hardware regions during context
switches.

Author: HeatCrab

arch/riscv/pmp.h

@@ -9,6 +9,8 @@
 #include <sys/memprot.h>
 #include <types.h>
 
+#include "csr.h"
+
 /* PMP Region Priority Levels (lower value = higher priority)
  *
  * Used for eviction decisions when hardware PMP regions are exhausted.

kernel/task.c

@@ -606,6 +606,30 @@ int32_t mo_task_spawn(void *task_entry, uint16_t stack_size_req)
         panic(ERR_STACK_ALLOC);
     }
 
+    /* Create memory space for task */
+    tcb->mspace = mo_memspace_create(kcb->next_tid, 0);
+    if (!tcb->mspace) {
+        free(tcb->stack);
+        free(tcb);
+        panic(ERR_TCB_ALLOC);
+    }
+
+    /* Register stack as flexpage */
+    fpage_t *stack_fpage =
+        mo_fpage_create((uint32_t) tcb->stack, new_stack_size,
+                        PMPCFG_R | PMPCFG_W, PMP_PRIORITY_STACK);
+    if (!stack_fpage) {
+        mo_memspace_destroy(tcb->mspace);
+        free(tcb->stack);
+        free(tcb);
+        panic(ERR_TCB_ALLOC);
+    }
+
+    /* Add stack to memory space */
+    stack_fpage->as_next = tcb->mspace->first;
+    tcb->mspace->first = stack_fpage;
+    tcb->mspace->pmp_stack = stack_fpage;
+
     /* Minimize critical section duration */
     CRITICAL_ENTER();