map_anon.h (2346B)
1 /* Copyright (c) 2003-2004, Roger Dingledine 2 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. 3 * Copyright (c) 2007-2021, The Tor Project, Inc. */ 4 /* See LICENSE for licensing information */ 5 6 /** 7 * \file map_anon.h 8 * \brief Headers for map_anon.c 9 **/ 10 11 #ifndef TOR_MAP_ANON_H 12 #define TOR_MAP_ANON_H 13 14 #include "lib/malloc/malloc.h" 15 #include <stddef.h> 16 17 /** 18 * When this flag is specified, try to prevent the mapping from being 19 * swapped or dumped. 20 * 21 * In some operating systems, this flag is not implemented. 22 */ 23 #define ANONMAP_PRIVATE (1u<<0) 24 /** 25 * When this flag is specified, try to prevent the mapping from being 26 * inherited after a fork(). In some operating systems, trying to access it 27 * afterwards will cause its contents to be zero. In others, trying to access 28 * it afterwards will cause a crash. 29 * 30 * In some operating systems, this flag is not implemented at all. 31 */ 32 #define ANONMAP_NOINHERIT (1u<<1) 33 34 typedef enum { 35 /** Possible value for inherit_result_out: the memory will be kept 36 * by any child process. */ 37 INHERIT_RES_KEEP=0, 38 /** Possible value for inherit_result_out: the memory will be dropped in the 39 * child process. Attempting to access it will likely cause a segfault. */ 40 INHERIT_RES_DROP, 41 /** Possible value for inherit_result_out: the memory will be cleared in 42 * the child process. */ 43 INHERIT_RES_ZERO 44 } inherit_res_t; 45 46 /* Here we define the NOINHERIT_CAN_FAIL macro if and only if 47 * it's possible that ANONMAP_NOINHERIT might yield inheritable memory. 48 */ 49 #ifdef _WIN32 50 /* Windows can't fork, so NOINHERIT is never needed. */ 51 #elif defined(HAVE_MINHERIT) 52 /* minherit() will always have a working MAP_INHERIT_NONE or MAP_INHERIT_ZERO. 53 * NOINHERIT should always work. 54 */ 55 #elif defined(HAVE_MADVISE) 56 /* madvise() sometimes has neither MADV_DONTFORK and MADV_WIPEONFORK. 57 * We need to be ready for the possibility it failed. 58 * 59 * (Linux added DONTFORK in 2.6.16 and WIPEONFORK in 4.14. If we someday 60 * require 2.6.16 or later, we can assume that DONTFORK will work.) 61 */ 62 #define NOINHERIT_CAN_FAIL 63 #else 64 #define NOINHERIT_CAN_FAIL 65 #endif /* defined(_WIN32) || ... */ 66 67 void *tor_mmap_anonymous(size_t sz, unsigned flags, 68 inherit_res_t *inherit_result_out); 69 void tor_munmap_anonymous(void *mapping, size_t sz); 70 71 #endif /* !defined(TOR_MAP_ANON_H) */