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      1 /*	$OpenBSD: arc4random_linux.h,v 1.7 2014/07/20 20:51:13 bcook Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1996, David Mazieres <dm (at) uun.org>
      5  * Copyright (c) 2008, Damien Miller <djm (at) openbsd.org>
      6  * Copyright (c) 2013, Markus Friedl <markus (at) openbsd.org>
      7  *
      8  * Permission to use, copy, modify, and distribute this software for any
      9  * purpose with or without fee is hereby granted, provided that the above
     10  * copyright notice and this permission notice appear in all copies.
     11  *
     12  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
     13  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     14  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
     15  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     16  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     17  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
     18  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     19  */
     20 
     21 /*
     22  * Stub functions for portability.
     23  */
     24 
     25 #include <sys/mman.h>
     26 
     27 #include <pthread.h>
     28 #include <signal.h>
     29 
     30 #include "private/bionic_prctl.h"
     31 #include "private/libc_logging.h"
     32 
     33 // Android gets these from "thread_private.h".
     34 #include "thread_private.h"
     35 //static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
     36 //#define _ARC4_LOCK()   pthread_mutex_lock(&arc4random_mtx)
     37 //#define _ARC4_UNLOCK() pthread_mutex_unlock(&arc4random_mtx)
     38 
     39 #ifdef __GLIBC__
     40 extern void *__dso_handle;
     41 extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
     42 #define _ARC4_ATFORK(f) __register_atfork(NULL, NULL, (f), __dso_handle)
     43 #else
     44 #define _ARC4_ATFORK(f) pthread_atfork(NULL, NULL, (f))
     45 #endif
     46 
     47 static inline void
     48 _getentropy_fail(void)
     49 {
     50 	__libc_fatal("getentropy failed");
     51 }
     52 
     53 volatile sig_atomic_t _rs_forked;
     54 
     55 static inline void
     56 _rs_forkdetect(void)
     57 {
     58 	static pid_t _rs_pid = 0;
     59 	pid_t pid = getpid();
     60 
     61 	if (_rs_pid == 0 || _rs_pid != pid || _rs_forked) {
     62 		_rs_pid = pid;
     63 		_rs_forked = 0;
     64 		if (rs)
     65 			memset(rs, 0, sizeof(*rs));
     66 	}
     67 }
     68 
     69 static inline int
     70 _rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
     71 {
     72 	// OpenBSD's arc4random_linux.h allocates two separate mappings, but for
     73 	// themselves they just allocate both structs into one mapping like this.
     74 	struct {
     75 		struct _rs rs;
     76 		struct _rsx rsx;
     77 	} *p;
     78 
     79 	if ((p = mmap(NULL, sizeof(*p), PROT_READ|PROT_WRITE,
     80 	    MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
     81 		return (-1);
     82 
     83 	prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, p, sizeof(*p), "arc4random data");
     84 
     85 	*rsp = &p->rs;
     86 	*rsxp = &p->rsx;
     87 
     88 	return (0);
     89 }
     90