From c462545bfb182689c12f42468904e400f350a59e 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 97d29bb..f0ee691 100644
--- a/os/src/mm/address.rs
+++ b/os/src/mm/address.rs
@@ -107,7 +107,11 @@ impl VirtAddr {
     }
     ///`VirtAddr`->`VirtPageNum`
     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)
+        }
     }
     ///Get page offset
     pub fn page_offset(&self) -> usize {
@@ -136,7 +140,11 @@ impl PhysAddr {
     }
     ///`PhysAddr`->`PhysPageNum`
     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)
+        }
     }
     ///Get page offset
     pub fn page_offset(&self) -> usize {