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