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IABSD.fr/src/lib/libc/stdlib/atexit.c
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- lib/libc/stdlib/atexit.c
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/* $OpenBSD: atexit.c,v 1.27 2017/12/16 20:06:56 guenther Exp $ */ /* * Copyright (c) 2002 Daniel Hartmeier * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - 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 COPYRIGHT HOLDERS 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 * COPYRIGHT HOLDERS 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/types.h> #include <sys/mman.h> #include <stdlib.h> #include <string.h> #include <tib.h> #include <unistd.h> #include "atexit.h" #include "atfork.h" #include "thread_private.h" struct atexit *__atexit; static int restartloop; /* define and initialize the list */ struct atfork_listhead _atfork_list = TAILQ_HEAD_INITIALIZER(_atfork_list); /* * Function pointers are stored in a linked list of pages. The list * is initially empty, and pages are allocated on demand. The first * function pointer in the first allocated page (the last one in * the linked list) is reserved for the cleanup function. * * Outside the following functions, all pages are mprotect()'ed * to prevent unintentional/malicious corruption. */ /* * Register a function to be performed at exit or when a shared object * with the given dso handle is unloaded dynamically. Also used as * the backend for atexit(). For more info on this API, see: * * http://www.codesourcery.com/cxx-abi/abi.html#dso-dtor */ int __cxa_atexit(void (*func)(void *), void *arg, void *dso) { struct atexit *p = __atexit; struct atexit_fn *fnp; int pgsize = getpagesize(); int ret = -1; if (pgsize < sizeof(*p)) return (-1); _ATEXIT_LOCK(); p = __atexit; if (p != NULL) { if (p->ind + 1 >= p->max) p = NULL; else if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) goto unlock; } if (p == NULL) { p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); if (p == MAP_FAILED) goto unlock; if (__atexit == NULL) { memset(&p->fns[0], 0, sizeof(p->fns[0])); p->ind = 1; } else p->ind = 0; p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / sizeof(p->fns[0]); p->next = __atexit; __atexit = p; } fnp = &p->fns[p->ind++]; fnp->fn_ptr = func; fnp->fn_arg = arg; fnp->fn_dso = dso; if (mprotect(p, pgsize, PROT_READ)) goto unlock; restartloop = 1; ret = 0; unlock: _ATEXIT_UNLOCK(); return (ret); } DEF_STRONG(__cxa_atexit); /* * Copy of atexit() used by libc and anything staticly linked into the * executable. This passes NULL for the dso, so the callbacks are only * invoked by exit() and not dlclose() */ int atexit(void (*fn)(void)) { return (__cxa_atexit((void (*)(void *))fn, NULL, NULL)); } DEF_STRONG(atexit); void _thread_finalize(void) { struct tib *tib = TIB_GET(); while (tib->tib_atexit) { struct thread_atexit_fn *fnp = tib->tib_atexit; tib->tib_atexit = fnp->next; fnp->func(fnp->arg); free(fnp); } } /* * 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 atexit *p, *q; struct atexit_fn fn; int n, pgsize = getpagesize(); static int call_depth; if (dso == NULL) _thread_finalize(); _ATEXIT_LOCK(); call_depth++; restart: restartloop = 0; for (p = __atexit; p != NULL; p = p->next) { for (n = p->ind; --n >= 0;) { if (p->fns[n].fn_ptr == NULL) continue; /* already called */ if (dso != NULL && dso != p->fns[n].fn_dso) continue; /* wrong DSO */ /* * Mark handler as having been already called to avoid * dupes and loops, then call the appropriate function. */ fn = p->fns[n]; if (mprotect(p, pgsize, PROT_READ | PROT_WRITE) == 0) { p->fns[n].fn_ptr = NULL; mprotect(p, pgsize, PROT_READ); } _ATEXIT_UNLOCK(); (*fn.fn_ptr)(fn.fn_arg); _ATEXIT_LOCK(); if (restartloop) goto restart; } } call_depth--; /* * If called via exit(), unmap the pages since we have now run * all the handlers. We defer this until calldepth == 0 so that * we don't unmap things prematurely if called recursively. */ if (dso == NULL && call_depth == 0) { for (p = __atexit; p != NULL; ) { q = p; p = p->next; munmap(q, pgsize); } __atexit = NULL; } _ATEXIT_UNLOCK(); /* * If unloading a DSO, unregister any atfork handlers registered * by it. Skip the locking if the list is currently empty. */ if (dso != NULL && TAILQ_FIRST(&_atfork_list) != NULL) { struct atfork_fn *af, *afnext; _ATFORK_LOCK(); TAILQ_FOREACH_SAFE(af, &_atfork_list, fn_next, afnext) if (af->fn_dso == dso) { TAILQ_REMOVE(&_atfork_list, af, fn_next); free(af); } _ATFORK_UNLOCK(); } } DEF_STRONG(__cxa_finalize); /* * Register the cleanup function */ void __atexit_register_cleanup(void (*func)(void)) { struct atexit *p; int pgsize = getpagesize(); if (pgsize < sizeof(*p)) return; _ATEXIT_LOCK(); p = __atexit; while (p != NULL && p->next != NULL) p = p->next; if (p == NULL) { p = mmap(NULL, pgsize, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0); if (p == MAP_FAILED) goto unlock; p->ind = 1; p->max = (pgsize - ((char *)&p->fns[0] - (char *)p)) / sizeof(p->fns[0]); p->next = NULL; __atexit = p; } else { if (mprotect(p, pgsize, PROT_READ | PROT_WRITE)) goto unlock; } p->fns[0].fn_ptr = (void (*)(void *))func; p->fns[0].fn_arg = NULL; p->fns[0].fn_dso = NULL; mprotect(p, pgsize, PROT_READ); restartloop = 1; unlock: _ATEXIT_UNLOCK(); }