1 files changed, 71 insertions, 0 deletions
diff --git a/src/lib/malloc/map_anon.h b/src/lib/malloc/map_anon.h
new file mode 100644
index 0000000000..0354668d65
--- /dev/null
+++ b/src/lib/malloc/map_anon.h
@@ -0,0 +1,71 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file map_anon.h
+ * \brief Headers for map_anon.c
+ **/
+
+#ifndef TOR_MAP_ANON_H
+#define TOR_MAP_ANON_H
+
+#include "lib/malloc/malloc.h"
+#include <stddef.h>
+
+/**
+ * When this flag is specified, try to prevent the mapping from being
+ * swapped or dumped.
+ *
+ * In some operating systems, this flag is not implemented.
+ */
+#define ANONMAP_PRIVATE   (1u<<0)
+/**
+ * When this flag is specified, try to prevent the mapping from being
+ * inherited after a fork().  In some operating systems, trying to access it
+ * afterwards will cause its contents to be zero.  In others, trying to access
+ * it afterwards will cause a crash.
+ *
+ * In some operating systems, this flag is not implemented at all.
+ */
+#define ANONMAP_NOINHERIT (1u<<1)
+
+typedef enum {
+  /** Possible value for inherit_result_out: the memory will be kept
+   * by any child process. */
+  INHERIT_RES_KEEP=0,
+  /** Possible value for inherit_result_out: the memory will be dropped in the
+   * child process. Attempting to access it will likely cause a segfault. */
+  INHERIT_RES_DROP,
+  /** Possible value for inherit_result_out: the memory will be cleared in
+   * the child process. */
+  INHERIT_RES_ZERO
+} inherit_res_t;
+
+/* Here we define the NOINHERIT_CAN_FAIL macro if and only if
+ * it's possible that ANONMAP_NOINHERIT might yield inheritable memory.
+ */
+#ifdef _WIN32
+/* Windows can't fork, so NOINHERIT is never needed. */
+#elif defined(HAVE_MINHERIT)
+/* minherit() will always have a working MAP_INHERIT_NONE or MAP_INHERIT_ZERO.
+ * NOINHERIT should always work.
+ */
+#elif defined(HAVE_MADVISE)
+/* madvise() sometimes has neither MADV_DONTFORK and MADV_WIPEONFORK.
+ * We need to be ready for the possibility it failed.
+ *
+ * (Linux added DONTFORK in 2.6.16 and WIPEONFORK in 4.14. If we someday
+ * require 2.6.16 or later, we can assume that DONTFORK will work.)
+ */
+#define NOINHERIT_CAN_FAIL
+#else
+#define NOINHERIT_CAN_FAIL
+#endif /* defined(_WIN32) || ... */
+
+void *tor_mmap_anonymous(size_t sz, unsigned flags,
+                         inherit_res_t *inherit_result_out);
+void tor_munmap_anonymous(void *mapping, size_t sz);
+
+#endif /* !defined(TOR_MAP_ANON_H) */