1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
|
/* Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/* clone() is even more special than fork() as it mucks with stacks
and invokes a function in the right context after its all over. */
#include <features.h>
#define _ERRNO_H 1
#include <bits/errno.h>
#include <sys/syscall.h>
#define CLONE_VM 0x00000100
#define CLONE_THREAD 0x00010000
/* The userland implementation is:
int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg),
the kernel entry is:
int clone (long flags, void *child_stack).
The parameters are passed in register and on the stack from userland:
rdi: fn
rsi: child_stack
rdx: flags
rcx: arg
r8d: TID field in parent
r9d: thread pointer
%esp+8: TID field in child
The kernel expects:
rax: system call number
rdi: flags
rsi: child_stack
rdx: TID field in parent
r10: TID field in child
r8: thread pointer */
.text
.global clone
.type clone,%function
clone:
/* Sanity check arguments. */
movq $-EINVAL,%rax
testq %rdi,%rdi /* no NULL function pointers */
jz __syscall_error
testq %rsi,%rsi /* no NULL stack pointers */
jz __syscall_error
/* Insert the argument onto the new stack. */
subq $16,%rsi
movq %rcx,8(%rsi)
/* Save the function pointer. It will be popped off in the
child in the ebx frobbing below. */
movq %rdi,0(%rsi)
/* Do the system call. */
movq %rdx, %rdi
movq %r8, %rdx
movq %r9, %r8
movq 8(%rsp), %r10
movl $__NR_clone,%eax
syscall
testq %rax,%rax
jl __syscall_error
jz .Lthread_start
.Lpseudo_end:
ret
.Lthread_start:
/* Clear the frame pointer. The ABI suggests this be done, to mark
the outermost frame obviously. */
xorl %ebp, %ebp
#ifdef RESET_PID
testq $CLONE_THREAD, %rdi
jne 1f
testq $CLONE_VM, %rdi
movl $-1, %eax
jne 2f
movl $__NR_getpid, %eax
syscall
2: movl %eax, %fs:PID
movl %eax, %fs:TID
1:
#endif
/* Set up arguments for the function call. */
popq %rax /* Function to call. */
popq %rdi /* Argument. */
call *%rax
/* Call exit with return value from function call. */
movq %rax, %rdi
movl $__NR_exit, %eax
syscall
.size clone,.-clone
weak_alias(clone, __clone)
|
