my solution to lab5

lab/user/testptelibrary.c

@@ -0,0 +1,42 @@
+#include <inc/lib.h>
+
+#define VA ((char *) 0xA0000000)
+const char *msg = "hello, world\n";
+const char *msg2 = "goodbye, world\n";
+
+void childofspawn(void);
+
+void
+umain(int argc, char **argv)
+{
+	int r;
+
+	if (argc != 0)
+		childofspawn();
+
+	if ((r = sys_page_alloc(0, VA, PTE_P|PTE_W|PTE_U|PTE_SHARE)) < 0)
+		panic("sys_page_alloc: %e", r);
+
+	// check fork
+	if ((r = fork()) < 0)
+		panic("fork: %e", r);
+	if (r == 0) {
+		strcpy(VA, msg);
+		exit();
+	}
+	wait(r);
+	cprintf("fork handles PTE_SHARE %s\n", strcmp(VA, msg) == 0 ? "right" : "wrong");
+
+	// check spawn
+	if ((r = spawnl("/testptelibrary", "testptelibrary", "arg", 0)) < 0)
+		panic("spawn: %e", r);
+	wait(r);
+	cprintf("spawn handles PTE_SHARE %s\n", strcmp(VA, msg2) == 0 ? "right" : "wrong");
+}
+
+void
+childofspawn(void)
+{
+	strcpy(VA, msg2);
+	exit();
+}