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      1 /*
      2  * Copyright (C) 2015 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 <assert.h>
     30 #include <errno.h>
     31 #include <stddef.h>
     32 #include <stdlib.h>
     33 #include <string.h>
     34 #include <sys/auxv.h>
     35 #include <sys/cdefs.h>
     36 
     37 #include <async_safe/log.h>
     38 
     39 #include "private/bionic_arc4random.h"
     40 #include "private/bionic_globals.h"
     41 #include "private/KernelArgumentBlock.h"
     42 
     43 void __libc_init_setjmp_cookie(libc_globals* globals, KernelArgumentBlock& args) {
     44   long value;
     45   __libc_safe_arc4random_buf(&value, sizeof(value), args);
     46 
     47   // Mask off the last bit to store the signal flag.
     48   globals->setjmp_cookie = value & ~1;
     49 }
     50 
     51 extern "C" __LIBC_HIDDEN__ long __bionic_setjmp_cookie_get(long sigflag) {
     52   if (sigflag & ~1) {
     53     async_safe_fatal("unexpected sigflag value: %ld", sigflag);
     54   }
     55 
     56   return __libc_globals->setjmp_cookie | sigflag;
     57 }
     58 
     59 // Aborts if cookie doesn't match, returns the signal flag otherwise.
     60 extern "C" __LIBC_HIDDEN__ long __bionic_setjmp_cookie_check(long cookie) {
     61   if (__libc_globals->setjmp_cookie != (cookie & ~1)) {
     62     async_safe_fatal("setjmp cookie mismatch");
     63   }
     64 
     65   return cookie & 1;
     66 }
     67 
     68 extern "C" __LIBC_HIDDEN__ long __bionic_setjmp_checksum_mismatch() {
     69   async_safe_fatal("setjmp checksum mismatch");
     70 }
     71