1/* Copyright (C) 1996-2022 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library; if not, see
16   <https://www.gnu.org/licenses/>.  */
17
18/* clone() is even more special than fork() as it mucks with stacks
19   and invokes a function in the right context after its all over.  */
20
21#include <sysdep.h>
22#define _ERRNO_H	1
23#include <bits/errno.h>
24#include <asm-syntax.h>
25
26/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,
27	     pid_t *ptid, struct user_desc *tls, pid_t *ctid); */
28
29#define PARMS	4		/* no space for saved regs */
30#define FUNC	PARMS
31#define STACK	FUNC+4
32#define FLAGS	STACK+4
33#define ARG	FLAGS+4
34#define PTID	ARG+4
35#define TLS	PTID+4
36#define CTID	TLS+4
37
38#define __NR_clone 120
39#define SYS_clone 120
40
41        .text
42ENTRY (__clone)
43	/* Sanity check arguments.  */
44	movl	$-EINVAL,%eax
45	movl	FUNC(%esp),%ecx		/* no NULL function pointers */
46	testl	%ecx,%ecx
47	jz	SYSCALL_ERROR_LABEL
48	movl	STACK(%esp),%ecx	/* no NULL stack pointers */
49	testl	%ecx,%ecx
50	jz	SYSCALL_ERROR_LABEL
51
52	/* Insert the argument onto the new stack.  Make sure the new
53	   thread is started with an alignment of (mod 16).  */
54	andl	$0xfffffff0, %ecx
55	subl	$28,%ecx
56	movl	ARG(%esp),%eax		/* no negative argument counts */
57	movl	%eax,12(%ecx)
58
59	/* Save the function pointer as the zeroth argument.
60	   It will be popped off in the child in the ebx frobbing below.  */
61	movl	FUNC(%esp),%eax
62	movl	%eax,8(%ecx)
63	/* Don't leak any information.  */
64	movl	$0,4(%ecx)
65
66	/* Do the system call */
67	pushl	%ebx
68	cfi_adjust_cfa_offset (4)
69	pushl	%esi
70	cfi_adjust_cfa_offset (4)
71	pushl	%edi
72	cfi_adjust_cfa_offset (4)
73
74	movl	TLS+12(%esp),%esi
75	cfi_rel_offset (esi, 4)
76	movl	PTID+12(%esp),%edx
77	movl	FLAGS+12(%esp),%ebx
78	cfi_rel_offset (ebx, 8)
79	movl	CTID+12(%esp),%edi
80	cfi_rel_offset (edi, 0)
81	movl	$SYS_ify(clone),%eax
82
83	/* Remember the flag value.  */
84	movl	%ebx, (%ecx)
85
86	/* End FDE now, because in the child the unwind info will be
87	   wrong.  */
88	cfi_endproc
89
90	int	$0x80
91	popl	%edi
92	popl	%esi
93	popl	%ebx
94
95	test	%eax,%eax
96	jl	SYSCALL_ERROR_LABEL
97	jz	L(thread_start)
98
99	ret
100
101L(thread_start):
102	cfi_startproc;
103	/* Clearing frame pointer is insufficient, use CFI.  */
104	cfi_undefined (eip);
105	/* Note: %esi is zero.  */
106	movl	%esi,%ebp	/* terminate the stack frame */
107	call	*%ebx
108	movl	%eax, %ebx
109	movl	$SYS_ify(exit), %eax
110	ENTER_KERNEL
111
112PSEUDO_END (__clone)
113
114libc_hidden_def (__clone)
115weak_alias (__clone, clone)
116