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
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
|
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
* Copyright 2017 Joyent, Inc.
*/
#include <errno.h>
#include <unistd.h>
#include <sys/fork.h>
#include <sys/syscall.h>
#include <sys/debug.h>
#include <strings.h>
#include <sys/lx_debug.h>
#include <sys/lx_misc.h>
#include <sys/lx_syscall.h>
/*
* fork() and vfork()
*
* These cannot be pass thru system calls because we need libc to do its own
* initialization or else bad things will happen (i.e. ending up with a bad
* schedctl page). On Linux, there is no such thing as forkall(), so we use
* fork1() here.
*/
long
lx_fork(void)
{
int ret;
/*
* Inform the in-kernel ptrace(2) subsystem that we are about to
* emulate fork(2).
*/
lx_ptrace_clone_begin(LX_PTRACE_O_TRACEFORK, B_FALSE, 0);
/*
* Suspend signal delivery, run the stack management prefork handler
* and perform the fork operation.
*/
_sigoff();
lx_stack_prefork();
ret = fork1();
lx_stack_postfork();
switch (ret) {
case -1:
_sigon();
return (-errno);
case 0:
/*
* Returning in the new child. We must free the stacks and
* thread-specific data objects for the threads we did not
* duplicate; i.e. every other thread.
*/
lx_free_other_stacks();
lx_ptrace_stop_if_option(LX_PTRACE_O_TRACEFORK, B_TRUE, 0,
NULL);
/*
* Re-enable signal delivery in the child and return to the
* new process.
*/
_sigon();
return (0);
default:
lx_ptrace_stop_if_option(LX_PTRACE_O_TRACEFORK, B_FALSE,
(ulong_t)ret, NULL);
/*
* Re-enable signal delivery in the parent and return from
* the emulated system call.
*/
_sigon();
return (ret);
}
}
long
lx_vfork(void)
{
int ret;
lx_sighandlers_t saved;
ucontext_t vforkuc;
ucontext_t *ucp;
lx_tsd_t *lx_tsd = lx_get_tsd();
ucp = lx_syscall_regs();
/*
* Inform the in-kernel ptrace(2) subsystem that we are about to
* emulate vfork(2).
*/
lx_ptrace_clone_begin(LX_PTRACE_O_TRACEVFORK, B_FALSE, 0);
/*
* Suspend signal delivery, run the stack management prefork handler
* and perform the vfork operation. We use the same approach as in
* lx_clone for signal handling and child return across vfork. See
* the comments in lx_clone for more detail.
*/
lx_block_all_signals();
lx_stack_prefork();
lx_sighandlers_save(&saved);
lx_tsd->lxtsd_is_vforked++;
ret = vfork();
if (ret != 0) {
/* parent/error */
lx_tsd->lxtsd_is_vforked--;
lx_sighandlers_restore(&saved);
}
switch (ret) {
case -1:
lx_stack_postfork();
lx_unblock_all_signals();
return (-errno);
case 0:
/*
* child
* Unlike the regular fork case where the child also calls
* lx_stack_postfork(), we only do that in the parent once it
* resumes execution. This is required there to wake any other
* threads in that process that are blocked on the lock taken
* in lx_stack_prefork().
*/
bcopy(ucp, &vforkuc, sizeof (vforkuc));
vforkuc.uc_brand_data[1] = (caddr_t)vforkuc.uc_brand_data[1] -
LX_NATIVE_STACK_VFORK_GAP;
vforkuc.uc_link = NULL;
lx_debug("\tvfork native stack sp %p",
vforkuc.uc_brand_data[1]);
lx_unblock_all_signals();
/* Stop for ptrace if required. */
lx_ptrace_stop_if_option(LX_PTRACE_O_TRACEVFORK, B_TRUE, 0,
NULL);
/*
* Return to the child via the specially constructed vfork(2)
* context.
*/
LX_EMULATE_RETURN(&vforkuc, LX_SYS_vfork, 0, 0);
(void) syscall(SYS_brand, B_EMULATION_DONE, &vforkuc,
LX_SYS_vfork, 0, 0);
VERIFY(0);
return (0);
default:
/* parent - child should have exited or exec-ed by now */
lx_stack_postfork();
lx_unblock_all_signals();
lx_ptrace_stop_if_option(LX_PTRACE_O_TRACEVFORK, B_FALSE,
(ulong_t)ret, NULL);
return (ret);
}
}
|
