hw7: initial HW7 commit

07_DebuggingTracing/preloader.c

@@ -0,0 +1,16 @@
+#define _GNU_SOURCE
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+static int (*real_unlinkat)(int dirfd, const char* pathname, int flags) = NULL;
+
+int unlinkat(int dirfd, const char* pathname, int flags) {
+    printf("unlinkat: %s\n", pathname);
+    real_unlinkat = dlsym(RTLD_NEXT, "unlinkat");
+    if (strstr(pathname, "FIX") != NULL)
+        return EPERM;
+    return real_unlinkat(dirfd, pathname, flags);
+}