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/* SPDX-License-Identifier: LGPL-2.1+ */
#pragma once
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
Copyright 2016 Michael Karcher
systemd 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.
systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <sched.h>
#include <sys/syscall.h>
#include "log.h"
#include "macro.h"
/**
* raw_clone() - uses clone to create a new process with clone flags
* @flags: Flags to pass to the clone system call
*
* Uses the clone system call to create a new process with the cloning flags and termination signal passed in the flags
* parameter. Opposed to glibc's clone funtion, using this function does not set up a separate stack for the child, but
* relies on copy-on-write semantics on the one stack at a common virtual address, just as fork does.
*
* To obtain copy-on-write semantics, flags must not contain CLONE_VM, and thus CLONE_THREAD and CLONE_SIGHAND (which
* require CLONE_VM) are not usable.
*
* Additionally, as this function does not pass the ptid, newtls and ctid parameters to the kernel, flags must not
* contain CLONE_PARENT_SETTID, CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID or CLONE_SETTLS.
*
* Returns: 0 in the child process and the child process id in the parent.
*/
static inline pid_t raw_clone(unsigned long flags) {
pid_t ret;
assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
#if defined(__s390x__) || defined(__s390__) || defined(__CRIS__)
/* On s390/s390x and cris the order of the first and second arguments
* of the raw clone() system call is reversed. */
ret = (pid_t) syscall(__NR_clone, NULL, flags);
#elif defined(__sparc__) && defined(__arch64__)
{
/**
* sparc64 always returns the other process id in %o0, and
* a boolean flag whether this is the child or the parent in
* %o1. Inline assembly is needed to get the flag returned
* in %o1.
*/
int in_child, child_pid;
asm volatile("mov %2, %%g1\n\t"
"mov %3, %%o0\n\t"
"mov 0 , %%o1\n\t"
"t 0x6d\n\t"
"mov %%o1, %0\n\t"
"mov %%o0, %1" :
"=r"(in_child), "=r"(child_pid) :
"i"(__NR_clone), "r"(flags) :
"%o1", "%o0", "%g1" );
ret = in_child ? 0 : child_pid;
}
#else
ret = (pid_t) syscall(__NR_clone, flags, NULL);
#endif
if (ret == 0)
reset_cached_pid();
return ret;
}
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