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/* 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) */
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