platform_bionic/libc/bionic/fork.cpp
Elliott Hughes e104a2edf3 Generalize the clone function slightly.
* Allow clone where both the child function and stack are null. It's
obviously wrong to ask to call a function without a stack, but it's not
necessarily wrong to supply no stack if you're also not supplying a
function.

* Reimplement fork in terms of the clone function, rather than using the
clone system call directly.

This is intended as a step towards enabling use of pid namespaces.

Change-Id: I03c89bd1dc540d8b4ed1c8fdf6644290744b9e91
2016-05-06 16:37:00 -07:00

57 lines
2.1 KiB
C++

/*
* Copyright (C) 2008 The Android Open Source Project
* 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 OWNER 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 <unistd.h>
#include <sys/syscall.h>
#include "pthread_internal.h"
int fork() {
__bionic_atfork_run_prepare();
pthread_internal_t* self = __get_thread();
// Remember the parent pid and invalidate the cached value while we fork.
pid_t parent_pid = self->invalidate_cached_pid();
int result = clone(nullptr,
nullptr,
(CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD),
nullptr,
nullptr,
nullptr,
&(self->tid));
if (result == 0) {
self->set_cached_pid(gettid());
__bionic_atfork_run_child();
} else {
self->set_cached_pid(parent_pid);
__bionic_atfork_run_parent();
}
return result;
}