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108 lines
4.4 KiB
C
108 lines
4.4 KiB
C
/* Copyright (C) 1999-2024 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <stdlib.h>
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#include "exit.h"
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#include <register-atfork.h>
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#include <pointer_guard.h>
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#include <stdint.h>
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/* If D is non-NULL, call all functions registered with `__cxa_atexit'
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with the same dso handle. Otherwise, if D is NULL, call all of the
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registered handlers. */
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void
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__cxa_finalize (void *d)
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{
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struct exit_function_list *funcs;
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__libc_lock_lock (__exit_funcs_lock);
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restart:
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for (funcs = __exit_funcs; funcs; funcs = funcs->next)
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{
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struct exit_function *f;
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for (f = &funcs->fns[funcs->idx - 1]; f >= &funcs->fns[0]; --f)
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if ((d == NULL || d == f->func.cxa.dso_handle) && f->flavor == ef_cxa)
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{
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const uint64_t check = __new_exitfn_called;
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void (*cxafn) (void *arg, int status) = f->func.cxa.fn;
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void *cxaarg = f->func.cxa.arg;
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/* We don't want to run this cleanup more than once. The Itanium
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C++ ABI requires that multiple calls to __cxa_finalize not
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result in calling termination functions more than once. One
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potential scenario where that could happen is with a concurrent
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dlclose and exit, where the running dlclose must at some point
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release the list lock, an exiting thread may acquire it, and
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without setting flavor to ef_free, might re-run this destructor
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which could result in undefined behaviour. Therefore we must
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set flavor to ef_free to avoid calling this destructor again.
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Note that the concurrent exit must also take the dynamic loader
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lock (for library finalizer processing) and therefore will
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block while dlclose completes the processing of any in-progress
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exit functions. Lastly, once we release the list lock for the
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entry marked ef_free, we must not read from that entry again
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since it may have been reused by the time we take the list lock
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again. Lastly the detection of new registered exit functions is
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based on a monotonically incrementing counter, and there is an
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ABA if between the unlock to run the exit function and the
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re-lock after completion the user registers 2^64 exit functions,
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the implementation will not detect this and continue without
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executing any more functions.
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One minor issue remains: A registered exit function that is in
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progress by a call to dlclose() may not completely finish before
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the next registered exit function is run. This may, according to
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some readings of POSIX violate the requirement that functions
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run in effective LIFO order. This should probably be fixed in a
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future implementation to ensure the functions do not run in
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parallel. */
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f->flavor = ef_free;
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PTR_DEMANGLE (cxafn);
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/* Unlock the list while we call a foreign function. */
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__libc_lock_unlock (__exit_funcs_lock);
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cxafn (cxaarg, 0);
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__libc_lock_lock (__exit_funcs_lock);
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/* It is possible that that last exit function registered
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more exit functions. Start the loop over. */
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if (__glibc_unlikely (check != __new_exitfn_called))
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goto restart;
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}
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}
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/* Also remove the quick_exit handlers, but do not call them. */
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for (funcs = __quick_exit_funcs; funcs; funcs = funcs->next)
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{
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struct exit_function *f;
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for (f = &funcs->fns[funcs->idx - 1]; f >= &funcs->fns[0]; --f)
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if (d == NULL || d == f->func.cxa.dso_handle)
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f->flavor = ef_free;
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}
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/* Remove the registered fork handlers. We do not have to
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unregister anything if the program is going to terminate anyway. */
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if (d != NULL)
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UNREGISTER_ATFORK (d);
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__libc_lock_unlock (__exit_funcs_lock);
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}
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