/*      $OpenBSD: arc4random_linux.h,v 1.12 2019/07/11 10:37:28 inoguchi Exp $  */

/*
 * Copyright (c) 1996, David Mazieres <dm@uun.org>
 * Copyright (c) 2008, Damien Miller <djm@openbsd.org>
 * Copyright (c) 2013, Markus Friedl <markus@openbsd.org>
 * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Stub functions for portability.
 */

#include <sys/mman.h>

#include <pthread.h>
#include <signal.h>

static pthread_mutex_t arc4random_mtx = PTHREAD_MUTEX_INITIALIZER;
#define _ARC4_LOCK()   pthread_mutex_lock(&arc4random_mtx)
#define _ARC4_UNLOCK() pthread_mutex_unlock(&arc4random_mtx)

#if defined(__GLIBC__) && !(defined(__UCLIBC__) && !defined(__ARCH_USE_MMU__))
extern void *__dso_handle;
extern int __register_atfork(void (*)(void), void(*)(void), void (*)(void), void *);
#define _ARC4_ATFORK(f) __register_atfork(NULL, NULL, (f), __dso_handle)
#else
#define _ARC4_ATFORK(f) pthread_atfork(NULL, NULL, (f))
#endif

static inline void
_getentropy_fail(void)
{
        raise(SIGKILL);
}

static volatile sig_atomic_t _rs_forked;

static inline void
_rs_forkhandler(void)
{
        _rs_forked = 1;
}

static inline void
_rs_forkdetect(void)
{
        static pid_t _rs_pid = 0;
        pid_t pid = getpid();

        /* XXX unusual calls to clone() can bypass checks */
        if (_rs_pid == 0 || _rs_pid == 1 || _rs_pid != pid || _rs_forked) {
                _rs_pid = pid;
                _rs_forked = 0;
                if (rs)
                        memset(rs, 0, sizeof(*rs));
        }
}

static inline int
_rs_allocate(struct _rs **rsp, struct _rsx **rsxp)
{
        if ((*rsp = mmap(NULL, sizeof(**rsp), PROT_READ|PROT_WRITE,
            MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
                return (-1);

        if ((*rsxp = mmap(NULL, sizeof(**rsxp), PROT_READ|PROT_WRITE,
            MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) {
                munmap(*rsp, sizeof(**rsp));
                *rsp = NULL;
                return (-1);
        }

        _ARC4_ATFORK(_rs_forkhandler);
        return (0);
}