init commit of lab2_challenge1

LICENSE.txt

@@ -4,8 +4,9 @@ Copyright License
 The PKE software is:
 
 Copyright (c) 2021, Zhiyuan Shao (zyshao@hust.edu.cn), 
-                    Yi Gui (gy163email@163.com), 
+                    Yixin Song (474309045@qq.com),
-                    Yan Jiao (773709579@qq.com),
+                    Ziming Yuan (1223962053@qq.com),
+                    Boyang Li (liboyang_hust@163.com),
                    Huazhong University of Science and Technology
 
 Permission is hereby granted, free of charge, to any person obtaining

user/app_sum_sequence.c

@@ -1,5 +1,6 @@
 /*
- * The application of lab2_3.
+ * The application of lab2_challenge1_pagefault.
+ * Based on application of lab2_3.
  */
 
 #include "user_lib.h"
@@ -12,17 +13,24 @@
 // may consume more memory (from stack) than a physical 4KB page, leading to a page fault.
 // PKE kernel needs to improved to handle such page fault by expanding the stack.
 //
-uint64 sum_sequence(uint64 n) {
+uint64 sum_sequence(uint64 n, int *p) {
   if (n == 0)
     return 0;
   else
-    return sum_sequence( n-1 ) + n;
+    return *p=sum_sequence( n-1, p+1 ) + n;
 }
 
 int main(void) {
-  // we need a large enough "n" to trigger pagefaults in the user stack
+  // FIRST, we need a large enough "n" to trigger pagefaults in the user stack
-  uint64 n = 1000;
+  uint64 n = 1024;
+
+  // alloc a page size array(int) to store the result of every step
+  // the max limit of the number is 4kB/4 = 1024
+
+  // SECOND, we use array out of bound to trigger pagefaults in an invalid address
+  int *ans = (int *)naive_malloc();
+
+  printu("Summation of an arithmetic sequence from 0 to %ld is: %ld \n", n, sum_sequence(n+1, ans) );
 
-  printu("Summation of an arithmetic sequence from 0 to %ld is: %ld \n", n, sum_sequence(1000) );
   exit(0);
 }