/*      $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 <[email protected]>.
* 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);
}

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