1 /* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <errno.h> 30 #include <stdint.h> 31 #include <sys/mman.h> 32 #include <unistd.h> 33 34 #include "private/bionic_macros.h" 35 #include "private/ErrnoRestorer.h" 36 37 // mmap2(2) is like mmap(2), but the offset is in 4096-byte blocks, not bytes. 38 extern "C" void* __mmap2(void*, size_t, int, int, int, size_t); 39 40 #define MMAP2_SHIFT 12 // 2**12 == 4096 41 42 static bool kernel_has_MADV_MERGEABLE = true; 43 44 void* mmap64(void* addr, size_t size, int prot, int flags, int fd, off64_t offset) { 45 if (offset < 0 || (offset & ((1UL << MMAP2_SHIFT)-1)) != 0) { 46 errno = EINVAL; 47 return MAP_FAILED; 48 } 49 50 // prevent allocations large enough for `end - start` to overflow 51 size_t rounded = __BIONIC_ALIGN(size, PAGE_SIZE); 52 if (rounded < size || rounded > PTRDIFF_MAX) { 53 errno = ENOMEM; 54 return MAP_FAILED; 55 } 56 57 bool is_private_anonymous = 58 (flags & (MAP_PRIVATE | MAP_ANONYMOUS)) == (MAP_PRIVATE | MAP_ANONYMOUS); 59 bool is_stack_or_grows_down = (flags & (MAP_STACK | MAP_GROWSDOWN)) != 0; 60 61 void* result = __mmap2(addr, size, prot, flags, fd, offset >> MMAP2_SHIFT); 62 63 if (result != MAP_FAILED && kernel_has_MADV_MERGEABLE && 64 is_private_anonymous && !is_stack_or_grows_down) { 65 ErrnoRestorer errno_restorer; 66 int rc = madvise(result, size, MADV_MERGEABLE); 67 if (rc == -1 && errno == EINVAL) { 68 kernel_has_MADV_MERGEABLE = false; 69 } 70 } 71 72 return result; 73 } 74 75 void* mmap(void* addr, size_t size, int prot, int flags, int fd, off_t offset) { 76 return mmap64(addr, size, prot, flags, fd, static_cast<off64_t>(offset)); 77 } 78
