map_anon.h

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/* Copyright (c) 2003-2004, Roger Dingledine
 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2019, The Tor Project, Inc. */
/* See LICENSE for licensing information */

#ifndef TOR_MAP_ANON_H
#define TOR_MAP_ANON_H

#include "lib/malloc/malloc.h"
#include <stddef.h>

#define ANONMAP_PRIVATE   (1u<<0)

#define ANONMAP_NOINHERIT (1u<<1)

typedef enum {
  INHERIT_RES_KEEP=0,
  INHERIT_RES_DROP,
  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) */