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Diffstat (limited to 'src/lib/malloc/map_anon.c')
| -rw-r--r-- | src/lib/malloc/map_anon.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/src/lib/malloc/map_anon.c b/src/lib/malloc/map_anon.c new file mode 100644 index 0000000000..2430f7ad11 --- /dev/null +++ b/src/lib/malloc/map_anon.c @@ -0,0 +1,217 @@ +/* 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 */ + +/** + * \file map_anon.c + * \brief Manage anonymous mappings. + **/ + +#include "orconfig.h" +#include "lib/malloc/map_anon.h" +#include "lib/malloc/malloc.h" +#include "lib/err/torerr.h" + +#ifdef HAVE_SYS_MMAN_H +#include <sys/mman.h> +#endif +#ifdef HAVE_SYS_TYPES_H +#include <sys/types.h> +#endif +#ifdef HAVE_MACH_VM_INHERIT_H +#include <mach/vm_inherit.h> +#endif + +#ifdef _WIN32 +#include <windows.h> +#endif + +/** + * Macro to get the high bytes of a size_t, if there are high bytes. + * Windows needs this; other operating systems define a size_t that does + * what it should. + */ +#if SIZEOF_SIZE_T > 4 +#define HIGH_SIZE_T_BYTES(sz) ((sz) >> 32) +#else +#define HIGH_SIZE_T_BYTES(sz) (0) +#endif + +/* Here we define a MINHERIT macro that is minherit() or madvise(), depending + * on what we actually want. + * + * If there's a flag that sets pages to zero after fork, we define FLAG_ZERO + * to be that flag. If there's a flag unmaps pages after fork, we define + * FLAG_NOINHERIT to be that flag. + */ +#if defined(HAVE_MINHERIT) +#define MINHERIT minherit + +#ifdef INHERIT_ZERO +#define FLAG_ZERO INHERIT_ZERO +#elif defined(MAP_INHERIT_ZERO) +#define FLAG_ZERO MAP_INHERIT_ZERO +#endif +#ifdef INHERIT_NONE +#define FLAG_NOINHERIT INHERIT_NONE +#elif defined(VM_INHERIT_NONE) +#define FLAG_NOINHERIT VM_INHERIT_NONE +#elif defined(MAP_INHERIT_NONE) +#define FLAG_NOINHERIT MAP_INHERIT_NONE +#endif + +#elif defined(HAVE_MADVISE) + +#define MINHERIT madvise + +#ifdef MADV_WIPEONFORK +#define FLAG_ZERO MADV_WIPEONFORK +#endif +#ifdef MADV_DONTFORK +#define FLAG_NOINHERIT MADV_DONTFORK +#endif + +#endif + +/** + * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from being swapped + * to disk. Return 0 on success or if the facility is not available on this + * OS; return -1 on failure. + */ +static int +lock_mem(void *mem, size_t sz) +{ +#ifdef _WIN32 + return VirtualLock(mem, sz) ? 0 : -1; +#elif defined(HAVE_MLOCK) + return mlock(mem, sz); +#else + (void) mem; + (void) sz; + + return 0; +#endif +} + +/** + * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from appearing in + * a core dump. Return 0 on success or if the facility is not available on + * this OS; return -1 on failure. + */ +static int +nodump_mem(void *mem, size_t sz) +{ +#if defined(MADV_DONTDUMP) + return madvise(mem, sz, MADV_DONTDUMP); +#else + (void) mem; + (void) sz; + return 0; +#endif +} + +/** + * Helper: try to prevent the <b>sz</b> bytes at <b>mem</b> from being + * accessible in child processes -- ideally by having them set to 0 after a + * fork, and if that doesn't work, by having them unmapped after a fork. + * Return 0 on success or if the facility is not available on this OS; return + * -1 on failure. + */ +static int +noinherit_mem(void *mem, size_t sz) +{ +#ifdef FLAG_ZERO + int r = MINHERIT(mem, sz, FLAG_ZERO); + if (r == 0) + return 0; +#endif +#ifdef FLAG_NOINHERIT + return MINHERIT(mem, sz, FLAG_NOINHERIT); +#else + (void)mem; + (void)sz; + return 0; +#endif +} + +/** + * Return a new anonymous memory mapping that holds <b>sz</b> bytes. + * + * Memory mappings are unlike the results from malloc() in that they are + * handled separately by the operating system, and as such can have different + * kernel-level flags set on them. + * + * The "flags" argument may be zero or more of ANONMAP_PRIVATE and + * ANONMAP_NOINHERIT. + * + * Memory returned from this function must be released with + * tor_munmap_anonymous(). + * + * [Note: OS people use the word "anonymous" here to mean that the memory + * isn't associated with any file. This has *nothing* to do with the kind of + * anonymity that Tor is trying to provide.] + */ +void * +tor_mmap_anonymous(size_t sz, unsigned flags) +{ + void *ptr; +#if defined(_WIN32) + HANDLE mapping = CreateFileMapping(INVALID_HANDLE_VALUE, + NULL, /*attributes*/ + PAGE_READWRITE, + HIGH_SIZE_T_BYTES(sz), + sz & 0xffffffff, + NULL /* name */); + raw_assert(mapping != NULL); + ptr = MapViewOfFile(mapping, FILE_MAP_WRITE, + 0, 0, /* Offset */ + 0 /* Extend to end of mapping */); + raw_assert(ptr); + CloseHandle(mapping); /* mapped view holds a reference */ +#elif defined(HAVE_SYS_MMAN_H) + ptr = mmap(NULL, sz, + PROT_READ|PROT_WRITE, + MAP_ANON|MAP_PRIVATE, + -1, 0); + raw_assert(ptr != MAP_FAILED); + raw_assert(ptr != NULL); +#else + ptr = tor_malloc_zero(sz); +#endif + + if (flags & ANONMAP_PRIVATE) { + int lock_result = lock_mem(ptr, sz); + raw_assert(lock_result == 0); + int nodump_result = nodump_mem(ptr, sz); + raw_assert(nodump_result == 0); + } + + if (flags & ANONMAP_NOINHERIT) { + int noinherit_result = noinherit_mem(ptr, sz); + raw_assert(noinherit_result == 0); + } + + return ptr; +} + +/** + * Release <b>sz</b> bytes of memory that were previously mapped at + * <b>mapping</b> by tor_mmap_anonymous(). + **/ +void +tor_munmap_anonymous(void *mapping, size_t sz) +{ + if (!mapping) + return; + +#if defined(_WIN32) + (void)sz; + UnmapViewOfFile(mapping); +#elif defined(HAVE_SYS_MMAN_H) + munmap(mapping, sz); +#else + (void)sz; + tor_free(mapping); +#endif +} |