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
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
/* Copyright (C) 2005, 2007 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, write to the Free
Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
Boston, MA 02110-1301, USA. */
#include "sysdep.h"
#include <sys/syscall.h>
#define _SIGNAL_H
#include <bits/signum.h>
/* Clone the calling process, but without copying the whole address space.
The calling process is suspended until the new process exits or is
replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
and the process ID of the new process to the old process.
Note that it is important that we don't create a new stack frame for the
caller. */
/* The following are defined in linux/sched.h, which unfortunately
is not safe for inclusion in an assembly file. */
#define CLONE_VM 0x00000100 /* set if VM shared between processes */
#define CLONE_VFORK 0x00004000 /* set if the parent wants the child to
wake it up on mm_release */
#ifndef SAVE_PID
#define SAVE_PID
#endif
#ifndef RESTORE_PID
#define RESTORE_PID
#endif
/* pid_t vfork(void);
Implemented as __clone_syscall(CLONE_VFORK | CLONE_VM | SIGCHLD, 0) */
HIDDEN_ENTRY (__vfork)
movi a6, .Ljumptable
extui a2, a0, 30, 2 /* call-size: call4/8/12 = 1/2/3 */
addx4 a4, a2, a6 /* find return address in jumptable */
l32i a4, a4, 0
add a4, a4, a6
slli a2, a2, 30
xor a3, a0, a2 /* remove call-size from return addr */
extui a5, a4, 30, 2 /* get high bits of jump target */
slli a5, a5, 30
or a3, a3, a5 /* stuff them into the return address */
xor a4, a4, a5 /* clear high bits of jump target */
or a0, a4, a2 /* create temporary return address */
retw /* "return" to .L4, .L8, or .L12 */
.align 4
.Ljumptable:
.word 0
.word .L4 - .Ljumptable
.word .L8 - .Ljumptable
.word .L12 - .Ljumptable
/* a7: return address */
.L4: mov a12, a2
mov a13, a3
SAVE_PID
/* Use syscall 'clone'. Set new stack pointer to the same address. */
movi a2, SYS_ify (clone)
movi a3, 0
movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
syscall
RESTORE_PID
movi a5, -4096
mov a6, a2
mov a2, a12
mov a3, a13
bgeu a6, a5, 1f
jx a7
1: call4 .Lerr /* returns to original caller */
/* a11: return address */
.L8: mov a12, a2
mov a13, a3
mov a14, a6
SAVE_PID
movi a2, SYS_ify (clone)
movi a3, 0
movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
syscall
RESTORE_PID
movi a9, -4096
mov a10, a2
mov a2, a12
mov a3, a13
mov a6, a14
bgeu a10, a9, 1f
jx a11
1: call8 .Lerr /* returns to original caller */
/* a15: return address */
.L12: mov a12, a2
mov a13, a3
mov a14, a6
SAVE_PID
movi a2, SYS_ify (clone)
movi a3, 0
movi a6, CLONE_VM | CLONE_VFORK | SIGCHLD
syscall
RESTORE_PID
mov a3, a13
movi a13, -4096
mov a6, a14
mov a14, a2
mov a2, a12
bgeu a14, a13, 1f
jx a15
1: call12 .Lerr /* returns to original caller */
.align 4
.Lerr: entry a1, 16
/* Restore the return address. */
extui a4, a0, 30, 2 /* get the call-size bits */
slli a4, a4, 30
slli a3, a3, 2 /* clear high bits of target address */
srli a3, a3, 2
or a0, a3, a4 /* combine them */
PSEUDO_END (__vfork)
.Lpseudo_end:
retw
weak_alias (__vfork, vfork)
libc_hidden_def(vfork)
|
