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/* fork - create a child process.
Copyright (C) 1991-2024 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <fork.h>
#include <libio/libioP.h>
#include <ldsodefs.h>
#include <malloc/malloc-internal.h>
#include <nss/nss_database.h>
#include <register-atfork.h>
#include <stdio-lock.h>
#include <sys/single_threaded.h>
#include <unwind-link.h>
static void
fresetlockfiles (void)
{
_IO_ITER i;
for (i = _IO_iter_begin(); i != _IO_iter_end(); i = _IO_iter_next(i))
if ((_IO_iter_file (i)->_flags & _IO_USER_LOCK) == 0)
_IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
}
pid_t
__libc_fork (void)
{
/* Determine if we are running multiple threads. We skip some fork
handlers in the single-thread case, to make fork safer to use in
signal handlers. Although POSIX has dropped async-signal-safe
requirement for fork (Austin Group tracker issue #62) this is
best effort to make is async-signal-safe at least for single-thread
case. */
bool multiple_threads = !SINGLE_THREAD_P;
uint64_t lastrun;
lastrun = __run_prefork_handlers (multiple_threads);
struct nss_database_data nss_database_data;
/* If we are not running multiple threads, we do not have to
preserve lock state. If fork runs from a signal handler, only
async-signal-safe functions can be used in the child. These data
structures are only used by unsafe functions, so their state does
not matter if fork was called from a signal handler. */
if (multiple_threads)
{
call_function_static_weak (__nss_database_fork_prepare_parent,
&nss_database_data);
_IO_list_lock ();
/* Acquire malloc locks. This needs to come last because fork
handlers may use malloc, and the libio list lock has an
indirect malloc dependency as well (via the getdelim
function). */
call_function_static_weak (__malloc_fork_lock_parent);
}
pid_t pid = _Fork ();
if (pid == 0)
{
fork_system_setup ();
/* Reset the lock state in the multi-threaded case. */
if (multiple_threads)
{
__libc_unwind_link_after_fork ();
fork_system_setup_after_fork ();
/* Release malloc locks. */
call_function_static_weak (__malloc_fork_unlock_child);
/* Reset the file list. These are recursive mutexes. */
fresetlockfiles ();
/* Reset locks in the I/O code. */
_IO_list_resetlock ();
call_function_static_weak (__nss_database_fork_subprocess,
&nss_database_data);
}
/* Reset the lock the dynamic loader uses to protect its data. */
__rtld_lock_initialize (GL(dl_load_lock));
/* Reset the lock protecting dynamic TLS related data. */
__rtld_lock_initialize (GL(dl_load_tls_lock));
reclaim_stacks ();
/* Run the handlers registered for the child. */
__run_postfork_handlers (atfork_run_child, multiple_threads, lastrun);
}
else
{
/* If _Fork failed, preserve its errno value. */
int save_errno = errno;
/* Release acquired locks in the multi-threaded case. */
if (multiple_threads)
{
/* Release malloc locks, parent process variant. */
call_function_static_weak (__malloc_fork_unlock_parent);
/* We execute this even if the 'fork' call failed. */
_IO_list_unlock ();
}
/* Run the handlers registered for the parent. */
__run_postfork_handlers (atfork_run_parent, multiple_threads, lastrun);
if (pid < 0)
__set_errno (save_errno);
}
return pid;
}
weak_alias (__libc_fork, __fork)
libc_hidden_def (__fork)
weak_alias (__libc_fork, fork)
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