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diff --git a/libbacktrace/mmapio.c b/libbacktrace/mmapio.c
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+/* mmapio.c -- File views using mmap.
+ Copyright (C) 2012-2021 Free Software Foundation, Inc.
+ Written by Ian Lance Taylor, Google.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+ (1) Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+
+ (2) Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in
+ the documentation and/or other materials provided with the
+ distribution.
+
+ (3) The name of the author may not be used to
+ endorse or promote products derived from this software without
+ specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
+INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
+IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE. */
+
+#include "config.h"
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include "backtrace.h"
+#include "internal.h"
+
+#ifndef HAVE_DECL_GETPAGESIZE
+extern int getpagesize (void);
+#endif
+
+#ifndef MAP_FAILED
+#define MAP_FAILED ((void *)-1)
+#endif
+
+/* This file implements file views and memory allocation when mmap is
+ available. */
+
+/* Create a view of SIZE bytes from DESCRIPTOR at OFFSET. */
+
+int
+backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
+ int descriptor, off_t offset, uint64_t size,
+ backtrace_error_callback error_callback,
+ void *data, struct backtrace_view *view)
+{
+ size_t pagesize;
+ unsigned int inpage;
+ off_t pageoff;
+ void *map;
+
+ if ((uint64_t) (size_t) size != size)
+ {
+ error_callback (data, "file size too large", 0);
+ return 0;
+ }
+
+ pagesize = getpagesize ();
+ inpage = offset % pagesize;
+ pageoff = offset - inpage;
+
+ size += inpage;
+ size = (size + (pagesize - 1)) & ~ (pagesize - 1);
+
+ map = mmap (NULL, size, PROT_READ, MAP_PRIVATE, descriptor, pageoff);
+ if (map == MAP_FAILED)
+ {
+ error_callback (data, "mmap", errno);
+ return 0;
+ }
+
+ view->data = (char *) map + inpage;
+ view->base = map;
+ view->len = size;
+
+ return 1;
+}
+
+/* Release a view read by backtrace_get_view. */
+
+void
+backtrace_release_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
+ struct backtrace_view *view,
+ backtrace_error_callback error_callback,
+ void *data)
+{
+ union {
+ const void *cv;
+ void *v;
+ } const_cast;
+
+ const_cast.cv = view->base;
+ if (munmap (const_cast.v, view->len) < 0)
+ error_callback (data, "munmap", errno);
+}