tests: Run all tests through a randomized readdir()

Having undefined ordering (but in practice rarely changing)
ordering for `readdir()` ended up screwing us over with respect
to bootloader config file read ordering.

Let's make things significantly more likely to fail more quickly in
the future if similar bugs are introduced.  We accomplish this by
introducing a little `LD_PRELOAD` library that randomizes the results
of `readdir()`.

1 files changed, 124 insertions, 0 deletions

diff --git a/tests/readdir-rand.c b/tests/readdir-rand.c
new file mode 100644
index 00000000..70a001fe
--- /dev/null
+++ b/tests/readdir-rand.c
@@ -0,0 +1,124 @@
+#define _GNU_SOURCE
+#include <dirent.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <glib.h>
+
+struct linux_dirent {
+  long           d_ino;
+  off_t          d_off;
+  unsigned short d_reclen;
+  char           d_name[];
+};
+
+#define BUF_SIZE 1024
+
+static GHashTable *direntcache;
+static GMutex direntcache_lock;
+static gsize initialized;
+
+typedef struct {
+  GPtrArray *entries;
+  guint offset;
+} DirEntries;
+
+static void
+dir_entries_free (gpointer data)
+{
+  DirEntries *d = data;
+  g_ptr_array_unref (d->entries);
+  g_free (d);
+}
+
+static DirEntries *
+dir_entries_new (void)
+{
+  DirEntries *d = g_new0 (DirEntries, 1);
+  d->entries = g_ptr_array_new_with_free_func (g_free);
+  return d;
+}
+
+static void
+ensure_initialized (void)
+{
+  if (g_once_init_enter (&initialized))
+    {
+      direntcache = g_hash_table_new_full (NULL, NULL, NULL, dir_entries_free);
+      g_mutex_init (&direntcache_lock);
+      g_once_init_leave (&initialized, 1);
+    }
+}
+
+struct dirent *
+readdir (DIR *dirp)
+{
+  struct dirent *(*real_readdir)(DIR *dirp) = dlsym (RTLD_NEXT, "readdir");
+  struct dirent *ret;
+  gboolean doloop = TRUE;
+  
+  ensure_initialized ();
+
+  while (doloop)
+    {
+      DirEntries *de;
+      GSList *l;
+
+      errno = 0;
+      ret = real_readdir (dirp);
+      if (ret == NULL && errno != 0)
+	goto out;
+
+      g_mutex_lock (&direntcache_lock);
+      de = g_hash_table_lookup (direntcache, dirp);
+      if (ret)
+	{
+	  if (g_random_boolean ())
+	    {
+	      if (!de)
+		{
+		  de = dir_entries_new ();
+		  g_hash_table_insert (direntcache, dirp, de);
+		}
+	      struct dirent *copy;
+	      copy = g_memdup (ret, sizeof (struct dirent));
+	      g_ptr_array_add (de->entries, copy);
+	    }
+	  else
+	    {
+	      doloop = FALSE;
+	    }
+	}
+      else
+	{
+	  if (de && de->offset < de->entries->len)
+	    {
+	      ret = de->entries->pdata[de->offset];
+	      de->offset++;
+	    }
+	  doloop = FALSE;
+	}
+      g_mutex_unlock (&direntcache_lock);
+    }
+  
+ out:
+  return ret;
+}
+
+int
+closedir (DIR *dirp)
+{
+  int (*real_closedir)(DIR *dirp) = dlsym (RTLD_NEXT, "closedir");
+
+  ensure_initialized ();
+  
+  g_mutex_lock (&direntcache_lock);
+  g_hash_table_remove (direntcache, dirp);
+  g_mutex_unlock (&direntcache_lock);
+
+  return real_closedir (dirp);
+}