/*      $NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $ */

/*-
 * Copyright (c) 2003, 2019 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Jason R. Thorpe.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 FOUNDATION OR CONTRIBUTORS
 * 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.
 */

/*
 * Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
 * All rights reserved.
 * 
 * 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(s), this list of conditions and the following disclaimer as
 *    the first lines of this file unmodified other than the possible
 *    addition of one or more copyright notices.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice(s), this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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 <sys/cdefs.h>
__RCSID("$NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $");

#ifndef __LIBPTHREAD_SOURCE__
/*
 * There is no longer any difference between the libpthread and the librt
 * versions of sem.c; both are fully kernel-assisted via the _ksem_*()
 * system calls.  The only difference is the need to lock some internal
 * data structures in the pthread version, which could be achieved by
 * different means.  However, in order to maintain binary compatibility
 * with applications that use POSIX semaphores and linked against only
 * libpthread, we continue to maintain a copy of the implementation here
 * that does not depend on any additional libraries (other than libc).
 */
#define sem_init        _librt_sem_init
#define sem_destroy     _librt_sem_destroy
#define sem_open        _librt_sem_open
#define sem_close       _librt_sem_close
#define sem_unlink      _librt_sem_unlink
#define sem_wait        _librt_sem_wait
#define sem_timedwait   _librt_sem_timedwait
#define sem_trywait     _librt_sem_trywait
#define sem_post        _librt_sem_post
#define sem_getvalue    _librt_sem_getvalue
#endif /* ! __LIBPTHREAD_SOURCE__ */

#undef _LIBC
#define _LIBC

#include <sys/types.h>
#include <sys/ksem.h>
#include <sys/queue.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <semaphore.h>
#include <stdarg.h>

#ifdef __LIBPTHREAD_SOURCE__
#include "pthread.h"
#endif /* __LIBPTHREAD_SOURCE__ */

#define SEM_NAMED               0x4e414d44U     /* 'NAMD' */
#define SEM_MAGIC               0x90af0421U
#define SEM_MAGIC_NAMED         (SEM_MAGIC ^ SEM_NAMED)

#define SEMID_IS_KSEMID(id)     (((uint32_t)(id) & KSEM_MARKER_MASK)    \
                                                == KSEM_PSHARED_MARKER)
#define SEM_IS_KSEMID(k)        SEMID_IS_KSEMID((intptr_t)(k))  
                        

#define SEM_IS_UNNAMED(k)       (SEM_IS_KSEMID(k) ||                    \
                                 (k)->ksem_magic == SEM_MAGIC)

#define SEM_IS_NAMED(k)         (!SEM_IS_UNNAMED(k))

#define SEM_MAGIC_OK(k)         (SEM_IS_KSEMID(k) ||                    \
                                 (k)->ksem_magic == SEM_MAGIC ||        \
                                 (k)->ksem_magic == SEM_MAGIC_NAMED)

struct _sem_st {
        unsigned int    ksem_magic;
        intptr_t        ksem_semid;

        /* Used only to de-dup named semaphores. */
        LIST_ENTRY(_sem_st) ksem_list;
        sem_t           *ksem_identity;
};

static LIST_HEAD(, _sem_st) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
#ifdef __LIBPTHREAD_SOURCE__
static pthread_mutex_t named_sems_mtx = PTHREAD_MUTEX_INITIALIZER;

#define LOCK_NAMED_SEMS()       pthread_mutex_lock(&named_sems_mtx)
#define UNLOCK_NAMED_SEMS()     pthread_mutex_unlock(&named_sems_mtx)
#else /* ! __LIBPTHREAD_SOURCE__ */
#define LOCK_NAMED_SEMS()       __nothing
#define UNLOCK_NAMED_SEMS()     __nothing
#endif /* __LIBPTHREAD_SOURCE__ */

#ifndef __LIBPTHREAD_SOURCE__
#ifdef __weak_alias
__weak_alias(sem_init,_librt_sem_init)
__weak_alias(sem_destroy,_librt_sem_destroy)
__weak_alias(sem_open,_librt_sem_open)
__weak_alias(sem_close,_librt_sem_close)
__weak_alias(sem_unlink,_librt_sem_unlink)
__weak_alias(sem_wait,_librt_sem_wait)
__weak_alias(sem_timedwait,_librt_sem_timedwait)
__weak_alias(sem_trywait,_librt_sem_trywait)
__weak_alias(sem_post,_librt_sem_post)
__weak_alias(sem_getvalue,_librt_sem_getvalue)
#else
#error Weak aliases required to build POSIX semaphore support.
#endif /* __weak_alias */
#endif /* __LIBPTHREAD_SOURCE__ */

static inline intptr_t
sem_to_semid(sem_t *sem)
{

        if (SEM_IS_KSEMID(*sem))
                return (intptr_t)*sem;
        
        return (*sem)->ksem_semid;
}

static void
sem_free(sem_t sem)
{

        sem->ksem_magic = 0;
        free(sem);
}

static int
sem_alloc(unsigned int value, intptr_t semid, unsigned int magic, sem_t *semp)
{
        sem_t sem;

        if (value > SEM_VALUE_MAX)
                return EINVAL;

        if ((sem = malloc(sizeof(struct _sem_st))) == NULL)
                return ENOSPC;

        sem->ksem_magic = magic;
        sem->ksem_semid = semid;
 
        *semp = sem;
        return 0;
}

/* ARGSUSED */
int
sem_init(sem_t *sem, int pshared, unsigned int value)
{
        intptr_t        semid = pshared ? KSEM_PSHARED : 0;
        int error;

        if (_ksem_init(value, &semid) == -1)
                return -1;

        /*
         * pshared anonymous semaphores are treated a little differently.
         * We don't allocate a sem structure and return a pointer to it.
         * That pointer might live in the shared memory segment that's
         * shared between processes, but the _sem_st that contains the
         * important bits certainly would not be.
         *
         * So, instead, we return the ksem ID given to us by the kernel.
         * The kernel has arranged for the least-significant bit of the
         * ksem ID to always be 1 so as to ensure we can always tell
         * these IDs apart from the pointers that we vend out for other
         * non-pshared semaphores.
         */
        if (pshared) {
                if (!SEMID_IS_KSEMID(semid)) {
                        _ksem_destroy(semid);
                        errno = ENOTSUP;
                        return -1;
                }
                *sem = (sem_t)semid;
                return 0;
        }

        if ((error = sem_alloc(value, semid, SEM_MAGIC, sem)) != 0) {
                _ksem_destroy(semid);
                errno = error;
                return -1;
        }

        return 0;
}

int
sem_destroy(sem_t *sem)
{
        int error, save_errno;

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        if (SEM_IS_KSEMID(*sem)) {
                error = _ksem_destroy((intptr_t)*sem);
        } else {
                if (SEM_IS_NAMED(*sem)) {
                        errno = EINVAL;
                        return -1;
                }

                error = _ksem_destroy((*sem)->ksem_semid);
                save_errno = errno;
                sem_free(*sem);
                if (error == -1)
                        errno = save_errno;
        }

        return error;
}

sem_t *
sem_open(const char *name, int oflag, ...)
{
        sem_t *sem, s;
        intptr_t semid;
        mode_t mode;
        unsigned int value;
        int error;
        va_list ap;

        mode = 0;
        value = 0;

        if (oflag & O_CREAT) {
                va_start(ap, oflag);
                mode = va_arg(ap, int);
                value = va_arg(ap, unsigned int);
                va_end(ap);
        }

        /*
         * We can be lazy and let the kernel handle the oflag,
         * we'll just merge duplicate IDs into our list.
         */
        if (_ksem_open(name, oflag, mode, value, &semid) == -1)
                return SEM_FAILED;

        /*
         * Search for a duplicate ID, we must return the same sem_t *
         * if we locate one.
         */
        LOCK_NAMED_SEMS();
        LIST_FOREACH(s, &named_sems, ksem_list) {
                if (s->ksem_semid == semid) {
                        UNLOCK_NAMED_SEMS();
                        return s->ksem_identity;
                }
        }

        if ((sem = malloc(sizeof(*sem))) == NULL) {
                error = ENOSPC;
                goto bad;
        }
        if ((error = sem_alloc(value, semid, SEM_MAGIC_NAMED, sem)) != 0)
                goto bad;

        LIST_INSERT_HEAD(&named_sems, *sem, ksem_list);
        UNLOCK_NAMED_SEMS();
        (*sem)->ksem_identity = sem;

        return sem;

 bad:
        UNLOCK_NAMED_SEMS();
        _ksem_close(semid);
        if (sem != NULL) {
                if (*sem != NULL)
                        sem_free(*sem);
                free(sem);
        }
        errno = error;
        return SEM_FAILED;
}

int
sem_close(sem_t *sem)
{
        int error, save_errno;

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        if (!SEM_IS_NAMED(*sem)) {
                errno = EINVAL;
                return -1;
        }

        LOCK_NAMED_SEMS();
        error = _ksem_close((*sem)->ksem_semid);
        LIST_REMOVE((*sem), ksem_list);
        save_errno = errno;
        UNLOCK_NAMED_SEMS();
        sem_free(*sem);
        free(sem);
        if (error == -1)
                errno = save_errno;
        return error;
}

int
sem_unlink(const char *name)
{

        return _ksem_unlink(name);
}

int
sem_wait(sem_t *sem)
{

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        return _ksem_wait(sem_to_semid(sem));
}

int
sem_timedwait(sem_t *sem, const struct timespec * __restrict abstime)
{

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        return _ksem_timedwait(sem_to_semid(sem), abstime);
}

int
sem_trywait(sem_t *sem)
{

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        return _ksem_trywait(sem_to_semid(sem));
}

int
sem_post(sem_t *sem)
{

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        return _ksem_post(sem_to_semid(sem));
}

int
sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
{

#ifdef ERRORCHECK
        if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
                errno = EINVAL;
                return -1;
        }
#endif

        return _ksem_getvalue(sem_to_semid(sem), sval);
}