82 lines
3.2 KiB
C
82 lines
3.2 KiB
C
|
#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 usabale.
|
||
|
* 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 int raw_clone(unsigned long flags) {
|
||
|
assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
|
||
|
CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
|
||
|
#if defined(__s390__) || defined(__CRIS__)
|
||
|
/* On s390 and cris the order of the first and second arguments
|
||
|
* of the raw clone() system call is reversed. */
|
||
|
return (int) 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;
|
||
|
int 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" );
|
||
|
if (in_child)
|
||
|
return 0;
|
||
|
else
|
||
|
return child_pid;
|
||
|
}
|
||
|
#else
|
||
|
return (int) syscall(__NR_clone, flags, NULL);
|
||
|
#endif
|
||
|
}
|