From 7a73d4e3022cb0480f528d137d8c9612a77f35c4 Mon Sep 17 00:00:00 2001
From: Yifan Wu <shinbokuow@163.com>
Date: Wed, 31 May 2023 21:17:53 +0800
Subject: [PATCH] Fix issue #123

---
 os/src/mm/address.rs | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/os/src/mm/address.rs b/os/src/mm/address.rs
index cf147a080..df3e130fa 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -101,7 +101,11 @@ impl VirtAddr {
         VirtPageNum(self.0 / PAGE_SIZE)
     }
     pub fn ceil(&self) -> VirtPageNum {
-        VirtPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+        if self.0 == 0 {
+            VirtPageNum(0)
+        } else {
+            VirtPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+        }
     }
     pub fn page_offset(&self) -> usize {
         self.0 & (PAGE_SIZE - 1)
@@ -126,7 +130,11 @@ impl PhysAddr {
         PhysPageNum(self.0 / PAGE_SIZE)
     }
     pub fn ceil(&self) -> PhysPageNum {
-        PhysPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+        if self.0 == 0 {
+            PhysPageNum(0)
+        } else {
+            PhysPageNum((self.0 - 1 + PAGE_SIZE) / PAGE_SIZE)
+        }
     }
     pub fn page_offset(&self) -> usize {
         self.0 & (PAGE_SIZE - 1)