From 9da813b1511fc61de192b6255d7a3abc030d3b54 Mon Sep 17 00:00:00 2001
From: ligr <liguorui1213@163.com>
Date: Thu, 13 Mar 2025 12:29:55 +0800
Subject: [PATCH] [libcpu][risc-v]add code for handling exception scenarios in
 _unmap_area.

---
 libcpu/risc-v/common64/mmu.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/libcpu/risc-v/common64/mmu.c b/libcpu/risc-v/common64/mmu.c
index db5a79b5a3..badb7bebe6 100644
--- a/libcpu/risc-v/common64/mmu.c
+++ b/libcpu/risc-v/common64/mmu.c
@@ -263,10 +263,23 @@ static size_t _unmap_area(struct rt_aspace *aspace, void *v_addr)
     lvl_entry[i] = ((rt_ubase_t *)aspace->page_table + lvl_off[i]);
     pentry = lvl_entry[i];
 
+    /* check if lvl_entry[0] is valid. if no, return 0 directly. */
+    if (!PTE_USED(*pentry))
+    {
+        return 0;
+    }
+
     /* find leaf page table entry */
     while (PTE_USED(*pentry) && !PAGE_IS_LEAF(*pentry))
     {
         i += 1;
+
+        if (i >= 3)
+        {
+            unmapped = 0;
+            break;
+        }
+
         lvl_entry[i] = ((rt_ubase_t *)PPN_TO_VPN(GET_PADDR(*pentry), PV_OFFSET) +
                         lvl_off[i]);
         pentry = lvl_entry[i];
@@ -278,6 +291,10 @@ static size_t _unmap_area(struct rt_aspace *aspace, void *v_addr)
     {
         _unmap_pte(pentry, lvl_entry, i);
     }
+    else
+    {
+        unmapped = 0; /* invalid pte, return 0. */
+    }
 
     return unmapped;
 }