1/* Copyright (C) 1996-2022 Free Software Foundation, Inc.
2
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/* clone() is even more special than fork() as it mucks with stacks
20 and invokes a function in the right context after its all over. */
21
22#include <sysdep.h>
23#define _ERRNO_H 1
24#include <bits/errno.h>
25
26/* int clone(int (*fn)(void *arg), x0
27 void *child_stack, x1
28 int flags, x2
29 void *arg, x3
30 pid_t *ptid, x4
31 struct user_desc *tls, x5
32 pid_t *ctid); x6
33 */
34 .text
35ENTRY(__clone)
36 PTR_ARG (0)
37 PTR_ARG (1)
38 PTR_ARG (3)
39 PTR_ARG (4)
40 PTR_ARG (5)
41 PTR_ARG (6)
42 /* Save args for the child. */
43 mov x10, x0
44 mov x11, x2
45 mov x12, x3
46
47 /* Sanity check args. */
48 mov x0, #-EINVAL
49 cbz x10, .Lsyscall_error
50 /* Align sp. */
51 and x1, x1, -16
52 cbz x1, .Lsyscall_error
53
54 /* Do the system call. */
55 /* X0:flags, x1:newsp, x2:parenttidptr, x3:newtls, x4:childtid. */
56 mov x0, x2 /* flags */
57 /* New sp is already in x1. */
58 mov x2, x4 /* ptid */
59 mov x3, x5 /* tls */
60 mov x4, x6 /* ctid */
61 mov x8, #SYS_ify(clone)
62 svc 0x0
63
64 cmp x0, #0
65 beq thread_start
66 blt .Lsyscall_error
67 RET
68PSEUDO_END (__clone)
69
70 .align 4
71 .type thread_start, %function
72thread_start:
73 cfi_startproc
74 cfi_undefined (x30)
75 mov x29, 0
76
77 /* Pick the function arg and execute. */
78 mov x0, x12
79 blr x10
80
81 /* We are done, pass the return value through x0. */
82 mov x8, #SYS_ify(exit)
83 svc 0x0
84 cfi_endproc
85 .size thread_start, .-thread_start
86
87libc_hidden_def (__clone)
88weak_alias (__clone, clone)
89

source code of glibc/sysdeps/unix/sysv/linux/aarch64/clone.S