/* $NetBSD: atexit.c,v 1.35 2025/10/18 20:03:33 riastradh Exp $ */ /*- * Copyright (c) 2003 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. */ #include <sys/cdefs.h> #if defined(LIBC_SCCS) && !defined(lint) __RCSID("$NetBSD: atexit.c,v 1.35 2025/10/18 20:03:33 riastradh Exp $"); #endif /* LIBC_SCCS and not lint */ #include "reentrant.h" #include <assert.h> #include <stdlib.h> #include "atexit.h" struct atexit_handler { struct atexit_handler *ah_next; union { void (*fun_atexit)(void); void (*fun_cxa_atexit)(void *); } ah_fun; #define ah_atexit ah_fun.fun_atexit #define ah_cxa_atexit ah_fun.fun_cxa_atexit void *ah_arg; /* argument for cxa_atexit handlers */ void *ah_dso; /* home DSO for cxa_atexit handlers */ }; /* * There must be at least 32 to guarantee ANSI conformance, plus * 3 additional ones for the benefit of the startup code, which * may use them to register the dynamic loader's cleanup routine, * the profiling cleanup routine, and the global destructor routine. */ #define NSTATIC_HANDLERS (32 + 3) static struct atexit_handler atexit_handler0[NSTATIC_HANDLERS]; #define STATIC_HANDLER_P(ah) \ (ah >= &atexit_handler0[0] && ah < &atexit_handler0[NSTATIC_HANDLERS]) /* * Stack of atexit handlers. Handlers must be called in the opposite * order they were registered. */ static struct atexit_handler *atexit_handler_stack; #ifdef _REENTRANT /* ..and a mutex to protect it all. */ mutex_t __atexit_mutex; #endif /* _REENTRANT */ void __libc_atexit_init(void) __attribute__ ((visibility("hidden"))); /* * Allocate an atexit handler descriptor. If "dso" is NULL, it indicates * a normal atexit handler, which must be allocated from the static pool, * if possible. cxa_atexit handlers are never allocated from the static * pool. * * __atexit_mutex must be held. */ static struct atexit_handler * atexit_handler_alloc(void *dso) { struct atexit_handler *ah; int i; if (dso == NULL) { for (i = 0; i < NSTATIC_HANDLERS; i++) { ah = &atexit_handler0[i]; if (ah->ah_atexit == NULL && ah->ah_next == NULL) { /* Slot is free. */ return (ah); } } } /* * Either no static slot was free, or this is a cxa_atexit * handler. Allocate a new one. We keep the __atexit_mutex * held to prevent handlers from being run while we (potentially) * block in malloc(). */ ah = malloc(sizeof(*ah)); return (ah); } /* * Initialize __atexit_mutex with the PTHREAD_MUTEX_RECURSIVE attribute. * Note that __cxa_finalize may generate calls to __cxa_atexit. */ void __section(".text.startup") __libc_atexit_init(void) { #ifdef _REENTRANT mutexattr_t atexit_mutex_attr; mutexattr_init(&atexit_mutex_attr); mutexattr_settype(&atexit_mutex_attr, PTHREAD_MUTEX_RECURSIVE); mutex_init(&__atexit_mutex, &atexit_mutex_attr); #endif } /* * Register an atexit routine. This is suitable either for a cxa_atexit * or normal atexit type handler. The __cxa_atexit() name and arguments * are specified by the C++ ABI. See: * * https://web.archive.org/web/20030222125703/http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor */ #if defined(__ARM_EABI__) && !defined(lint) int __aeabi_atexit(void *arg, void (*func)(void *), void *dso); int __aeabi_atexit(void *arg, void (*func)(void *), void *dso) { return (__cxa_atexit(func, arg, dso)); } #endif static int __cxa_atexit_internal(void (*func)(void *), void *arg, void *dso) { struct atexit_handler *ah; _DIAGASSERT(func != NULL); mutex_lock(&__atexit_mutex); ah = atexit_handler_alloc(dso); if (ah == NULL) { mutex_unlock(&__atexit_mutex); return (-1); } ah->ah_cxa_atexit = func; ah->ah_arg = arg; ah->ah_dso = dso; ah->ah_next = atexit_handler_stack; atexit_handler_stack = ah; mutex_unlock(&__atexit_mutex); return (0); } int __cxa_atexit(void (*func)(void *), void *arg, void *dso) { /* * If this assertion fires, it is because the caller is not * properly passing &__dso_handle, which is never null, so the * caller cannot work safely in a shared object. This is a bug * in the caller; the caller must be fixed to pass * &__dso_handle. * * If you want to register an atexit handler that is not tied * to the current shared object, then you must use atexit(3) * itself, not __cxa_atexit. * * DO NOT REMOVE THIS ASSERTION. */ _DIAGASSERT(dso != NULL); return (__cxa_atexit_internal(func, arg, dso)); } /* * Run the list of atexit handlers. If dso is NULL, run all of them, * otherwise run only those matching the specified dso. * * Note that we can be recursively invoked; rtld cleanup is via an * atexit handler, and rtld cleanup invokes _fini() for DSOs, which * in turn invokes __cxa_finalize() for the DSO. */ void __cxa_finalize(void *dso) { static u_int call_depth; struct atexit_handler *ah, *dead_handlers = NULL, **prevp; void (*cxa_func)(void *); void (*atexit_func)(void); mutex_lock(&__atexit_mutex); call_depth++; /* * If we are at call depth 1 (which is usually the "do everything" * call from exit(3)), we go ahead and remove elements from the * list as we call them. This will prevent any nested calls from * having to traverse elements we've already processed. If we are * at call depth > 1, we simply mark elements we process as unused. * When the depth 1 caller sees those, it will simply unlink them * for us. */ again: for (prevp = &atexit_handler_stack; (ah = (*prevp)) != NULL;) { if (dso == NULL || dso == ah->ah_dso || ah->ah_atexit == NULL) { if (ah->ah_atexit != NULL) { void *p = atexit_handler_stack; if (ah->ah_dso != NULL) { cxa_func = ah->ah_cxa_atexit; ah->ah_cxa_atexit = NULL; (*cxa_func)(ah->ah_arg); } else { atexit_func = ah->ah_atexit; ah->ah_atexit = NULL; (*atexit_func)(); } /* Restart if new atexit handler was added. */ if (p != atexit_handler_stack) goto again; } if (call_depth == 1) { *prevp = ah->ah_next; if (STATIC_HANDLER_P(ah)) ah->ah_next = NULL; else { ah->ah_next = dead_handlers; dead_handlers = ah; } } else prevp = &ah->ah_next; } else prevp = &ah->ah_next; } call_depth--; mutex_unlock(&__atexit_mutex); if (call_depth > 0) return; /* * Now free any dead handlers. Do this even if we're about to * exit, in case a leak-detecting malloc is being used. */ while ((ah = dead_handlers) != NULL) { dead_handlers = ah->ah_next; free(ah); } } /* * Register a function to be performed at exit. */ int atexit(void (*func)(void)) { return (__cxa_atexit_internal((void (*)(void *))func, NULL, NULL)); }
