1 /* mmapio.c -- File views using mmap. 2 Copyright (C) 2012-2018 Free Software Foundation, Inc. 3 Written by Ian Lance Taylor, Google. 4 5 Redistribution and use in source and binary forms, with or without 6 modification, are permitted provided that the following conditions are 7 met: 8 9 (1) Redistributions of source code must retain the above copyright 10 notice, this list of conditions and the following disclaimer. 11 12 (2) Redistributions in binary form must reproduce the above copyright 13 notice, this list of conditions and the following disclaimer in 14 the documentation and/or other materials provided with the 15 distribution. 16 17 (3) The name of the author may not be used to 18 endorse or promote products derived from this software without 19 specific prior written permission. 20 21 THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22 IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 23 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 24 DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, 25 INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 26 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 27 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 29 STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 30 IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 31 POSSIBILITY OF SUCH DAMAGE. */ 32 33 #include "config.h" 34 35 #include <errno.h> 36 #include <sys/types.h> 37 #include <sys/mman.h> 38 #include <unistd.h> 39 40 #include "backtrace.h" 41 #include "internal.h" 42 43 #ifndef MAP_FAILED 44 #define MAP_FAILED ((void *)-1) 45 #endif 46 47 /* This file implements file views and memory allocation when mmap is 48 available. */ 49 50 /* Create a view of SIZE bytes from DESCRIPTOR at OFFSET. */ 51 52 int backtrace_get_view(struct backtrace_state * state ATTRIBUTE_UNUSED,int descriptor,off_t offset,size_t size,backtrace_error_callback error_callback,void * data,struct backtrace_view * view)53 backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED, 54 int descriptor, off_t offset, size_t size, 55 backtrace_error_callback error_callback, 56 void *data, struct backtrace_view *view) 57 { 58 size_t pagesize; 59 unsigned int inpage; 60 off_t pageoff; 61 void *map; 62 63 pagesize = getpagesize (); 64 inpage = offset % pagesize; 65 pageoff = offset - inpage; 66 67 size += inpage; 68 size = (size + (pagesize - 1)) & ~ (pagesize - 1); 69 70 map = mmap (NULL, size, PROT_READ, MAP_PRIVATE, descriptor, pageoff); 71 if (map == MAP_FAILED) 72 { 73 error_callback (data, "mmap", errno); 74 return 0; 75 } 76 77 view->data = (char *) map + inpage; 78 view->base = map; 79 view->len = size; 80 81 return 1; 82 } 83 84 /* Release a view read by backtrace_get_view. */ 85 86 void backtrace_release_view(struct backtrace_state * state ATTRIBUTE_UNUSED,struct backtrace_view * view,backtrace_error_callback error_callback,void * data)87 backtrace_release_view (struct backtrace_state *state ATTRIBUTE_UNUSED, 88 struct backtrace_view *view, 89 backtrace_error_callback error_callback, 90 void *data) 91 { 92 union { 93 const void *cv; 94 void *v; 95 } const_cast; 96 97 const_cast.cv = view->base; 98 if (munmap (const_cast.v, view->len) < 0) 99 error_callback (data, "munmap", errno); 100 } 101