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1 | #pragma once |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2010 Lennart Poettering | |
7 | Copyright 2016 Michael Karcher | |
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include <sched.h> | |
23 | #include <sys/syscall.h> | |
24 | ||
25 | #include "log.h" | |
26 | #include "macro.h" | |
27 | ||
28 | /** | |
29 | * raw_clone() - uses clone to create a new process with clone flags | |
30 | * @flags: Flags to pass to the clone system call | |
31 | * | |
32 | * Uses the clone system call to create a new process with the cloning | |
33 | * flags and termination signal passed in the flags parameter. Opposed | |
34 | * to glibc's clone funtion, using this function does not set up a | |
35 | * separate stack for the child, but relies on copy-on-write semantics | |
36 | * on the one stack at a common virtual address, just as fork does. | |
37 | * | |
38 | * To obtain copy-on-write semantics, flags must not contain CLONE_VM, | |
39 | * and thus CLONE_THREAD and CLONE_SIGHAND (which require CLONE_VM) are | |
40 | * not usabale. | |
41 | * Additionally, as this function does not pass the ptid, newtls and ctid | |
42 | * parameters to the kernel, flags must not contain CLONE_PARENT_SETTID, | |
43 | * CLONE_CHILD_SETTID, CLONE_CHILD_CLEARTID or CLONE_SETTLS. | |
44 | * | |
45 | * Returns: 0 in the child process and the child process id in the parent. | |
46 | */ | |
47 | static inline int raw_clone(unsigned long flags) { | |
48 | assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID| | |
49 | CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0); | |
ae9d60ce LP |
50 | #if defined(__s390x__) || defined(__s390__) || defined(__CRIS__) |
51 | /* On s390/s390x and cris the order of the first and second arguments | |
8869a0b4 MK |
52 | * of the raw clone() system call is reversed. */ |
53 | return (int) syscall(__NR_clone, NULL, flags); | |
54 | #elif defined(__sparc__) && defined(__arch64__) | |
55 | { | |
56 | /** | |
57 | * sparc64 always returns the other process id in %o0, and | |
58 | * a boolean flag whether this is the child or the parent in | |
59 | * %o1. Inline assembly is needed to get the flag returned | |
60 | * in %o1. | |
61 | */ | |
62 | int in_child; | |
63 | int child_pid; | |
64 | asm volatile("mov %2, %%g1\n\t" | |
65 | "mov %3, %%o0\n\t" | |
66 | "mov 0 , %%o1\n\t" | |
67 | "t 0x6d\n\t" | |
68 | "mov %%o1, %0\n\t" | |
69 | "mov %%o0, %1" : | |
70 | "=r"(in_child), "=r"(child_pid) : | |
71 | "i"(__NR_clone), "r"(flags) : | |
72 | "%o1", "%o0", "%g1" ); | |
73 | if (in_child) | |
74 | return 0; | |
75 | else | |
76 | return child_pid; | |
77 | } | |
78 | #else | |
79 | return (int) syscall(__NR_clone, flags, NULL); | |
80 | #endif | |
81 | } |