1/* The internal wrapper of clone and clone3.
2 Copyright (C) 2021-2023 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#ifdef __ia64__
58 ret = __clone2 (func, stack, cl_args->stack_size,
59 flags, arg,
60 cast_to_pointer (cl_args->parent_tid),
61 cast_to_pointer (cl_args->tls),
62 cast_to_pointer (cl_args->child_tid));
63#else
64# if !_STACK_GROWS_DOWN && !_STACK_GROWS_UP
65# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
66# endif
67
68# if _STACK_GROWS_DOWN
69 stack += cl_args->stack_size;
70# endif
71 ret = __clone (func, stack, flags, arg,
72 cast_to_pointer (cl_args->parent_tid),
73 cast_to_pointer (cl_args->tls),
74 cast_to_pointer (cl_args->child_tid));
75#endif
76 return ret;
77}
78
79int
80__clone3_internal (struct clone_args *cl_args, int (*func) (void *args),
81 void *arg)
82{
83#ifdef HAVE_CLONE3_WRAPPER
84# if __ASSUME_CLONE3
85 return __clone3 (cl_args, sizeof (*cl_args), func, arg);
86# else
87 static int clone3_supported = 1;
88 if (atomic_load_relaxed (&clone3_supported) == 1)
89 {
90 int ret = __clone3 (cl_args, sizeof (*cl_args), func, arg);
91 if (ret != -1 || errno != ENOSYS)
92 return ret;
93
94 atomic_store_relaxed (&clone3_supported, 0);
95 }
96# endif
97#endif
98 __set_errno (ENOSYS);
99 return -1;
100}
101
102int
103__clone_internal (struct clone_args *cl_args,
104 int (*func) (void *arg), void *arg)
105{
106#ifdef HAVE_CLONE3_WRAPPER
107 int saved_errno = errno;
108 int ret = __clone3_internal (cl_args, func, arg);
109 if (ret != -1 || errno != ENOSYS)
110 return ret;
111
112 /* NB: Restore errno since errno may be checked against non-zero
113 return value. */
114 __set_errno (saved_errno);
115#endif
116
117 return __clone_internal_fallback (cl_args, func, arg);
118}
119
120libc_hidden_def (__clone_internal)
121