From e3512e581807f0b7d0eeda44fcf002062ddd558a Mon Sep 17 00:00:00 2001
From: Sanjit Bhat <sanjit.bhat@gmail.com>
Date: Wed, 13 Sep 2023 01:54:57 -0400
Subject: release lab cow

---
 user/cowtest.c | 197 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 197 insertions(+)
 create mode 100644 user/cowtest.c

(limited to 'user')

diff --git a/user/cowtest.c b/user/cowtest.c
new file mode 100644
index 0000000..29b918f
--- /dev/null
+++ b/user/cowtest.c
@@ -0,0 +1,197 @@
+//
+// tests for copy-on-write fork() assignment.
+//
+
+#include "kernel/types.h"
+#include "kernel/memlayout.h"
+#include "user/user.h"
+
+// allocate more than half of physical memory,
+// then fork. this will fail in the default
+// kernel, which does not support copy-on-write.
+void
+simpletest()
+{
+  uint64 phys_size = PHYSTOP - KERNBASE;
+  int sz = (phys_size / 3) * 2;
+
+  printf("simple: ");
+  
+  char *p = sbrk(sz);
+  if(p == (char*)0xffffffffffffffffL){
+    printf("sbrk(%d) failed\n", sz);
+    exit(-1);
+  }
+
+  for(char *q = p; q < p + sz; q += 4096){
+    *(int*)q = getpid();
+  }
+
+  int pid = fork();
+  if(pid < 0){
+    printf("fork() failed\n");
+    exit(-1);
+  }
+
+  if(pid == 0)
+    exit(0);
+
+  wait(0);
+
+  if(sbrk(-sz) == (char*)0xffffffffffffffffL){
+    printf("sbrk(-%d) failed\n", sz);
+    exit(-1);
+  }
+
+  printf("ok\n");
+}
+
+// three processes all write COW memory.
+// this causes more than half of physical memory
+// to be allocated, so it also checks whether
+// copied pages are freed.
+void
+threetest()
+{
+  uint64 phys_size = PHYSTOP - KERNBASE;
+  int sz = phys_size / 4;
+  int pid1, pid2;
+
+  printf("three: ");
+  
+  char *p = sbrk(sz);
+  if(p == (char*)0xffffffffffffffffL){
+    printf("sbrk(%d) failed\n", sz);
+    exit(-1);
+  }
+
+  pid1 = fork();
+  if(pid1 < 0){
+    printf("fork failed\n");
+    exit(-1);
+  }
+  if(pid1 == 0){
+    pid2 = fork();
+    if(pid2 < 0){
+      printf("fork failed");
+      exit(-1);
+    }
+    if(pid2 == 0){
+      for(char *q = p; q < p + (sz/5)*4; q += 4096){
+        *(int*)q = getpid();
+      }
+      for(char *q = p; q < p + (sz/5)*4; q += 4096){
+        if(*(int*)q != getpid()){
+          printf("wrong content\n");
+          exit(-1);
+        }
+      }
+      exit(-1);
+    }
+    for(char *q = p; q < p + (sz/2); q += 4096){
+      *(int*)q = 9999;
+    }
+    exit(0);
+  }
+
+  for(char *q = p; q < p + sz; q += 4096){
+    *(int*)q = getpid();
+  }
+
+  wait(0);
+
+  sleep(1);
+
+  for(char *q = p; q < p + sz; q += 4096){
+    if(*(int*)q != getpid()){
+      printf("wrong content\n");
+      exit(-1);
+    }
+  }
+
+  if(sbrk(-sz) == (char*)0xffffffffffffffffL){
+    printf("sbrk(-%d) failed\n", sz);
+    exit(-1);
+  }
+
+  printf("ok\n");
+}
+
+char junk1[4096];
+int fds[2];
+char junk2[4096];
+char buf[4096];
+char junk3[4096];
+
+// test whether copyout() simulates COW faults.
+void
+filetest()
+{
+  printf("file: ");
+  
+  buf[0] = 99;
+
+  for(int i = 0; i < 4; i++){
+    if(pipe(fds) != 0){
+      printf("pipe() failed\n");
+      exit(-1);
+    }
+    int pid = fork();
+    if(pid < 0){
+      printf("fork failed\n");
+      exit(-1);
+    }
+    if(pid == 0){
+      sleep(1);
+      if(read(fds[0], buf, sizeof(i)) != sizeof(i)){
+        printf("error: read failed\n");
+        exit(1);
+      }
+      sleep(1);
+      int j = *(int*)buf;
+      if(j != i){
+        printf("error: read the wrong value\n");
+        exit(1);
+      }
+      exit(0);
+    }
+    if(write(fds[1], &i, sizeof(i)) != sizeof(i)){
+      printf("error: write failed\n");
+      exit(-1);
+    }
+  }
+
+  int xstatus = 0;
+  for(int i = 0; i < 4; i++) {
+    wait(&xstatus);
+    if(xstatus != 0) {
+      exit(1);
+    }
+  }
+
+  if(buf[0] != 99){
+    printf("error: child overwrote parent\n");
+    exit(1);
+  }
+
+  printf("ok\n");
+}
+
+int
+main(int argc, char *argv[])
+{
+  simpletest();
+
+  // check that the first simpletest() freed the physical memory.
+  simpletest();
+
+  threetest();
+  threetest();
+  threetest();
+
+  filetest();
+
+  printf("ALL COW TESTS PASSED\n");
+
+  exit(0);
+}
-- 
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