1/* The internal wrapper of clone and clone3.
2 Copyright (C) 2021-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <sysdep.h>
20#include <stddef.h>
21#include <errno.h>
22#include <sched.h>
23#include <clone_internal.h>
24#include <libc-pointer-arith.h> /* For cast_to_pointer. */
25#include <stackinfo.h> /* For _STACK_GROWS_{UP,DOWN}. */
26
27#define CLONE_ARGS_SIZE_VER0 64 /* sizeof first published struct */
28#define CLONE_ARGS_SIZE_VER1 80 /* sizeof second published struct */
29#define CLONE_ARGS_SIZE_VER2 88 /* sizeof third published struct */
30
31#define sizeof_field(TYPE, MEMBER) sizeof ((((TYPE *)0)->MEMBER))
32#define offsetofend(TYPE, MEMBER) \
33 (offsetof (TYPE, MEMBER) + sizeof_field (TYPE, MEMBER))
34
35_Static_assert (__alignof (struct clone_args) == 8,
36 "__alignof (struct clone_args) != 8");
37_Static_assert (offsetofend (struct clone_args, tls) == CLONE_ARGS_SIZE_VER0,
38 "offsetofend (struct clone_args, tls) != CLONE_ARGS_SIZE_VER0");
39_Static_assert (offsetofend (struct clone_args, set_tid_size) == CLONE_ARGS_SIZE_VER1,
40 "offsetofend (struct clone_args, set_tid_size) != CLONE_ARGS_SIZE_VER1");
41_Static_assert (offsetofend (struct clone_args, cgroup) == CLONE_ARGS_SIZE_VER2,
42 "offsetofend (struct clone_args, cgroup) != CLONE_ARGS_SIZE_VER2");
43_Static_assert (sizeof (struct clone_args) == CLONE_ARGS_SIZE_VER2,
44 "sizeof (struct clone_args) != CLONE_ARGS_SIZE_VER2");
45
46int
47__clone_internal_fallback (struct clone_args *cl_args,
48 int (*func) (void *arg), void *arg)
49{
50 /* Map clone3 arguments to clone arguments. NB: No need to check
51 invalid clone3 specific bits in flags nor exit_signal since this
52 is an internal function. */
53 int flags = cl_args->flags | cl_args->exit_signal;
54 void *stack = cast_to_pointer (cl_args->stack);
55 int ret;
56
57#if !_STACK_GROWS_DOWN && !_STACK_GROWS_UP
58# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
59#endif
60
61#if _STACK_GROWS_DOWN
62 stack += cl_args->stack_size;
63#endif
64 ret = __clone (func, stack, flags, arg,
65 cast_to_pointer (cl_args->parent_tid),
66 cast_to_pointer (cl_args->tls),
67 cast_to_pointer (cl_args->child_tid));
68 return ret;
69}
70
71int
72__clone3_internal (struct clone_args *cl_args, int (*func) (void *args),
73 void *arg)
74{
75#ifdef HAVE_CLONE3_WRAPPER
76# if __ASSUME_CLONE3
77 return __clone3 (cl_args, sizeof (*cl_args), func, arg);
78# else
79 static int clone3_supported = 1;
80 if (atomic_load_relaxed (&clone3_supported) == 1)
81 {
82 int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
83 if (ret != -1 || errno != ENOSYS)
84 return ret;
85
86 atomic_store_relaxed (&clone3_supported, 0);
87 }
88# endif
89#endif
90 __set_errno (ENOSYS);
91 return -1;
92}
93
94int
95__clone_internal (struct clone_args *cl_args,
96 int (*func) (void *arg), void *arg)
97{
98#ifdef HAVE_CLONE3_WRAPPER
99 int saved_errno = errno;
100 int ret = __clone3_internal (cl_args, func, arg);
101 if (ret != -1 || errno != ENOSYS)
102 return ret;
103
104 /* NB: Restore errno since errno may be checked against non-zero
105 return value. */
106 __set_errno (saved_errno);
107#endif
108
109 return __clone_internal_fallback (cl_args, func, arg);
110}
111
112libc_hidden_def (__clone_internal)
113

source code of glibc/sysdeps/unix/sysv/linux/clone-internal.c