Initial Pintos

1 files changed, 52 insertions, 0 deletions

diff --git a/src/examples/buffer_with_hole.c b/src/examples/buffer_with_hole.c
new file mode 100644
index 0000000..8d81009
--- /dev/null
+++ b/src/examples/buffer_with_hole.c
@@ -0,0 +1,52 @@
+/* klaar@ida
+
+   Create a buffer that spans invalid pages. Used to check memory
+   verification.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <syscall.h>
+
+/* global variables are placed by the compiler in the process image,
+ * among the initialized variables
+ * the process image is loaded at the bottom of the virtual memory space
+ */
+char global = 0;
+
+int main (int argc, char *argv[])
+{
+   /* local variables are allocated on the proces stack during runtime
+    * the stack is at top of the virtual memory space
+    */
+   char local = 0;
+   int fd;
+   int count;
+   unsigned l, g;
+
+   /* both adresses will of course be valid */
+   printf("global: %p\n", &global);
+   printf("local : %p\n", &local);
+
+   /* and a pointer starting at the global variable adress, and ending
+    * at the local variable addres will have valid start and end
+    * but will all addresses (about 3 GB) inbetween be valid?
+    */
+   l = (unsigned)&local;
+   g = (unsigned)&global;
+   printf("size : %u MiB\n", (l - g)/1024/1024);
+
+   create("somefile", 1000);
+   fd = open("somefile");
+
+   /* this tries to use the buffer (it should fail verification) */
+   count = read(fd, &global, (l - g + 1));
+   printf("read %i out of %u bytes\n", count, (l - g + 1));
+   
+   /* this tries to use a buffer probably ending before the stack */
+   count = read(fd, &global, (l - g + 1) - 4096);
+   printf("read %i out of %u bytes\n", count, (l - g + 1) - 4096);
+   
+   close(fd);
+
+   return 0;
+}