/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
 */

#include "namespace.h"
#include <errno.h>
#include <link.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include "atexit.h"
#include "un-namespace.h"
#include "block_abi.h"

#include "libc_private.h"

/**
 * The _Block_copy() function is provided by the block runtime.
 */
__attribute__((weak)) void*
_Block_copy(void*);

#define ATEXIT_FN_EMPTY 0
#define ATEXIT_FN_STD   1
#define ATEXIT_FN_CXA   2

static pthread_mutex_t atexit_mutex = PTHREAD_MUTEX_INITIALIZER;
static void *current_finalize_dso = NULL;
static bool call_finalize_again = false;

#define _MUTEX_LOCK(x)          if (__isthreaded) _pthread_mutex_lock(x)
#define _MUTEX_UNLOCK(x)        if (__isthreaded) _pthread_mutex_unlock(x)
#define _MUTEX_DESTROY(x)       if (__isthreaded) _pthread_mutex_destroy(x)

struct atexit {
        struct atexit *next;                    /* next in list */
        int ind;                                /* next index in this table */
        struct atexit_fn {
                int fn_type;                    /* ATEXIT_? from above */
                union {
                        void (*std_func)(void);
                        void (*cxa_func)(void *);
                } fn_ptr;                       /* function pointer */
                void *fn_arg;                   /* argument for CXA callback */
                void *fn_dso;                   /* shared module handle */
        } fns[ATEXIT_SIZE];                     /* the table itself */
};

static struct atexit *__atexit;         /* points to head of LIFO stack */
typedef DECLARE_BLOCK(void, atexit_block, void);

int atexit_b(atexit_block);
int __cxa_atexit(void (*)(void *), void *, void *);

/*
 * Register the function described by 'fptr' to be called at application
 * exit or owning shared object unload time. This is a helper function
 * for atexit and __cxa_atexit.
 */
static int
atexit_register(struct atexit_fn *fptr)
{
        static struct atexit __atexit0; /* one guaranteed table */
        struct atexit *p;

        _MUTEX_LOCK(&atexit_mutex);
        if ((p = __atexit) == NULL)
                __atexit = p = &__atexit0;
        else while (p->ind >= ATEXIT_SIZE) {
                struct atexit *old__atexit;
                old__atexit = __atexit;
                _MUTEX_UNLOCK(&atexit_mutex);
                if ((p = (struct atexit *)malloc(sizeof(*p))) == NULL)
                        return (-1);
                _MUTEX_LOCK(&atexit_mutex);
                if (old__atexit != __atexit) {
                        /* Lost race, retry operation */
                        _MUTEX_UNLOCK(&atexit_mutex);
                        free(p);
                        _MUTEX_LOCK(&atexit_mutex);
                        p = __atexit;
                        continue;
                }
                p->ind = 0;
                p->next = __atexit;
                __atexit = p;
        }
        p->fns[p->ind++] = *fptr;
        if (current_finalize_dso != NULL &&
            current_finalize_dso == fptr->fn_dso)
                call_finalize_again = true;
        _MUTEX_UNLOCK(&atexit_mutex);
        return 0;
}

/*
 * Register a function to be performed at exit.
 */
int
atexit(void (*func)(void))
{
        struct atexit_fn fn;
        int error;

        fn.fn_type = ATEXIT_FN_STD;
        fn.fn_ptr.std_func = func;
        fn.fn_arg = NULL;
        fn.fn_dso = NULL;

        error = atexit_register(&fn);
        return (error);
}
__weak_reference(atexit, __libc_atexit);

/**
 * Register a block to be performed at exit.
 */
int
atexit_b(atexit_block func)
{
        struct atexit_fn fn;
        int error;
        if (_Block_copy == 0) {
                errno = ENOSYS;
                return -1;
        }
        func = _Block_copy(func);

        // Blocks are not C++ destructors, but they have the same signature (a
        // single void* parameter), so we can pretend that they are.
        fn.fn_type = ATEXIT_FN_CXA;
        fn.fn_ptr.cxa_func = (void(*)(void*))GET_BLOCK_FUNCTION(func);
        fn.fn_arg = func;
        fn.fn_dso = NULL;

        error = atexit_register(&fn);
        return (error);
}

/*
 * Register a function to be performed at exit or when an shared object
 * with given dso handle is unloaded dynamically.
 */
int
__cxa_atexit(void (*func)(void *), void *arg, void *dso)
{
        struct atexit_fn fn;
        int error;

        fn.fn_type = ATEXIT_FN_CXA;
        fn.fn_ptr.cxa_func = func;
        fn.fn_arg = arg;
        fn.fn_dso = dso;

        error = atexit_register(&fn);
        return (error);
}

#pragma weak __pthread_cxa_finalize
void __pthread_cxa_finalize(const struct dl_phdr_info *);

static int global_exit;

/*
 * Call all handlers registered with __cxa_atexit for the shared
 * object owning 'dso'.  Note: if 'dso' is NULL, then all remaining
 * handlers are called.
 */
void
__cxa_finalize(void *dso)
{
        struct dl_phdr_info phdr_info;
        struct atexit *p;
        struct atexit_fn fn;
        int n, has_phdr;

        if (dso != NULL) {
                has_phdr = _rtld_addr_phdr(dso, &phdr_info);
        } else {
                has_phdr = 0;
                global_exit = 1;
        }

        _MUTEX_LOCK(&atexit_mutex);
        current_finalize_dso = dso;
        do {
                call_finalize_again = false;
                for (p = __atexit; p; p = p->next) {
                        for (n = p->ind; --n >= 0;) {
                                if (p->fns[n].fn_type == ATEXIT_FN_EMPTY)
                                        continue; /* already been called */
                                fn = p->fns[n];
                                if (dso != NULL && dso != fn.fn_dso) {
                                        /* wrong DSO ? */
                                        if (!has_phdr || global_exit ||
                                            !__elf_phdr_match_addr(&phdr_info,
                                            fn.fn_ptr.cxa_func))
                                                continue;
                                }
                                /*
                                  Mark entry to indicate that this particular
                                  handler has already been called.
                                */
                                p->fns[n].fn_type = ATEXIT_FN_EMPTY;
                                _MUTEX_UNLOCK(&atexit_mutex);

                                /* Call the function of correct type. */
                                if (fn.fn_type == ATEXIT_FN_CXA)
                                        fn.fn_ptr.cxa_func(fn.fn_arg);
                                else if (fn.fn_type == ATEXIT_FN_STD)
                                        fn.fn_ptr.std_func();
                                _MUTEX_LOCK(&atexit_mutex);
                        }
                }
        } while (call_finalize_again);
        current_finalize_dso = NULL;
        _MUTEX_UNLOCK(&atexit_mutex);
        if (dso == NULL)
                _MUTEX_DESTROY(&atexit_mutex);

        if (has_phdr && !global_exit && &__pthread_cxa_finalize != NULL)
                __pthread_cxa_finalize(&phdr_info);
}