summaryrefslogtreecommitdiff
path: root/libc/sysdeps/linux/xtensa/vfork.S
blob: 6aced0a504170890df843a425398bf2f37e09311 (plain)
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
/* Copyright (C) 2005-2013 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/>.  */

#include "sysdep.h"
#include <sys/syscall.h>
#define _SIGNAL_H
#include <bits/signum.h>
#define __ASSEMBLY__
#include <linux/sched.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.

*/

#ifndef SAVE_PID
#define SAVE_PID(a,b,c,d)
#endif
#ifndef RESTORE_PID
#define RESTORE_PID(a,b,c)
#endif
#ifndef RESTORE_PID12
#define RESTORE_PID12(a,b,c)
#endif

/*
   pid_t vfork(void);
   Implemented as __clone_syscall(CLONE_VFORK | CLONE_VM | SIGCHLD, 0)
 */


HIDDEN_ENTRY (__vfork)
        .literal .Ljumptable, 0, .L4, .L8, .L12

	mov	a3, a0			# move return address out of the way
	movi	a0, .Ljumptable
	extui	a2, a3, 30, 2		# call-size: call4/8/12 = 1/2/3
	addx4	a0, a2, a0		# find return address in jumptable
	slli	a2, a2, 30
	l32i	a0, a0, 0

	xor	a3, a3, a2		# remove call-size from return address
	or	a0, a0, a2		# create temporary return address
	retw

	/* a7: return address */

.L4:	mov	a12, a2
	mov	a13, a3

	SAVE_PID(a5,a15,a2,a3)

	/* use syscall 'clone' and 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(a5,a15,a2)

	movi	a5, -4096

	mov	a6, a2
	mov	a2, a12
	mov	a3, a13

	bgeu	a6, a5, 1f
	jx	a7

1:	call4	.Lerr

	/* a11: return address */

.L8:	mov	a12, a2
	mov	a13, a3
	mov	a14, a6

	SAVE_PID(a9,a15,a2,a3)

	movi	a2, SYS_ify(clone)
	movi	a3, 0
	movi	a6, CLONE_VM | CLONE_VFORK | SIGCHLD

	syscall

	RESTORE_PID(a9,a15,a2)

	movi	a9, -4096

	mov	a10, a2
	mov	a2, a12
	mov	a3, a13
	mov	a6, a14

	bgeu	a10, a9, 1f
	jx	a11

1:	call8	.Lerr


	/* a15: return address */

.L12:	mov	a12, a2
	mov	a13, a3
	mov	a14, a6

	SAVE_PID (a2,a3,a2,a6)

	movi	a2, SYS_ify(clone)
	movi	a3, 0
	movi	a6, CLONE_VM | CLONE_VFORK | SIGCHLD

	syscall

	RESTORE_PID12(a3,a6,a15)

	mov	a3, a13
	movi	a13, -4096

	mov	a6, a14
	mov	a14, a2

	mov	a2, a12

	bgeu	a14, a13, 1f
	jx	a15

1:	call12	.Lerr

	.align 4

.Lerr:	entry	a1, 16

	/* Restore return address */

	extui	a4, a0, 30, 2
	slli	a4, a4, 30
	or	a0, a3, a4

	PSEUDO_END (__vfork)
.Lpseudo_end:
	retw

weak_alias (__vfork, vfork)
libc_hidden_def(vfork)