From 1be2b1fcdf51a22386163955d3eb4fb7c737bee3 Mon Sep 17 00:00:00 2001
From: KAAAsS <admin@kaaass.net>
Date: Sun, 23 May 2021 20:25:50 +0800
Subject: [PATCH] =?UTF-8?q?=E5=86=8D=E6=AC=A1=E4=BF=AE=E6=AD=A3=E9=A1=B5?=
 =?UTF-8?q?=E8=A1=A8=20bug?=
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---
 lab5/kernel/mm/page_table.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/lab5/kernel/mm/page_table.c b/lab5/kernel/mm/page_table.c
index b3376c9..a2d258d 100644
--- a/lab5/kernel/mm/page_table.c
+++ b/lab5/kernel/mm/page_table.c
@@ -217,9 +217,9 @@ int map_range_in_pgtbl(vaddr_t * pgtbl, vaddr_t va, paddr_t pa,
         va_end++;  // 有不完整的一页
     }
     for (va_cur = va_start; va_cur < va_end; va_cur += PAGE_SIZE) {
-        // 创建一页
+        // 搜寻前 N 页
         cur_ptp = (ptp_t *) pgtbl;
-        for (cur_level = 0; cur_level < 4; cur_level++) {
+        for (cur_level = 0; cur_level < 3; cur_level++) {
             page_type = get_next_ptp(cur_ptp, cur_level, va_cur, &next_ptp, &entry, true);
             if (page_type < 0) {
                 // 无法映射
@@ -232,9 +232,19 @@ int map_range_in_pgtbl(vaddr_t * pgtbl, vaddr_t va, paddr_t pa,
                 cur_ptp = next_ptp;
             }
         }
-        // 配置页
-        set_pte_flags(entry, flags, USER_PTE);
-        entry->l3_page.pfn = cur_pfn++;
+        // 三级页检查占用
+        page_type = get_next_ptp(cur_ptp, 3, va_cur, &next_ptp, &entry, false);
+        if (page_type == -ENOMAPPING) {
+            // 配置页
+            entry = &(cur_ptp->ent[GET_L3_INDEX(va_cur)]);
+            entry->pte = 0;
+            entry->l3_page.is_valid = 1;
+            entry->l3_page.is_page = 1;
+            entry->l3_page.pfn = cur_pfn++;
+            set_pte_flags(entry, flags, USER_PTE);
+        } else {
+            BUG("Page already mapped");
+        }
     }
     flush_tlb();
 	// </lab2>
@@ -272,7 +282,7 @@ int unmap_range_in_pgtbl(vaddr_t * pgtbl, vaddr_t va, size_t len)
         // 创建一页
         cur_ptp = (ptp_t *) pgtbl;
         for (cur_level = 0; cur_level < 4; cur_level++) {
-            page_type = get_next_ptp(cur_ptp, cur_level, va, &next_ptp, &entry, false);
+            page_type = get_next_ptp(cur_ptp, cur_level, va_cur, &next_ptp, &entry, false);
             if (page_type < 0) {
                 // 无法映射
                 break;