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
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
|
/* Copyright (C) 2000 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <fcntl.h>
#include <mntent.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/statfs.h>
#include <bits/libc-lock.h>
#include "linux_fsinfo.h"
/* Mount point of the shared memory filesystem. */
static struct
{
char *dir;
size_t dirlen;
} mountpoint;
/* This is the default directory. */
const char defaultdir[] = "/dev/shm/";
/* Protect the `mountpoint' variable above. */
__libc_once_define (static, once);
/* Determine where the shmfs is mounted (if at all). */
static void
where_is_shmfs (void)
{
char buf[512];
struct statfs f;
struct mntent resmem;
struct mntent *mp;
FILE *fp;
/* The canonical place is /var/shm. This is at least what the
documentation tells everybody to do. */
if (__statfs (defaultdir, &f) == 0 && f.f_type == SHMFS_SUPER_MAGIC)
{
/* It is in the normal place. */
mountpoint.dir = (char *) defaultdir;
mountpoint.dirlen = sizeof (defaultdir) - 1;
return;
}
/* OK, do it the hard way. Look through the /proc/mounts file and if
this does not exist through /etc/fstab to find the mount point. */
fp = __setmntent ("/proc/mounts", "r");
if (__builtin_expect (fp == NULL, 0))
{
fp = __setmntent (_PATH_MNTTAB, "r");
if (__builtin_expect (fp == NULL, 0))
/* There is nothing we can do. Blind guesses are not helpful. */
return;
}
/* Now read the entries. */
while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL)
if (strcmp (mp->mnt_type, "shm") == 0)
{
/* Found it. There might be more than one place where the
filesystem is mounted but one is enough for us. */
size_t namelen = strlen (mp->mnt_dir);
if (namelen == 0)
/* Hum, maybe some crippled entry. Keep on searching. */
continue;
mountpoint.dir = (char *) malloc (namelen + 2);
if (mountpoint.dir != NULL)
{
char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen);
if (cp[-1] != '/')
*cp++ = '/';
*cp = '\0';
mountpoint.dirlen = cp - mountpoint.dir;
}
break;
}
/* Close the stream. */
__endmntent (fp);
}
/* Open shared memory object. This implementation assumes the shmfs
implementation introduced in the late 2.3.x kernel series to be
available. Normally the filesystem will be mounted at /var/shm but
we fall back on searching for the actual mount point should opening
such a file fail. */
int
shm_open (const char *name, int oflag, mode_t mode)
{
size_t namelen;
char *fname;
int fd;
/* Determine where the shmfs is mounted. */
__libc_once (once, where_is_shmfs);
/* If we don't know the mount points there is nothing we can do. Ever. */
if (mountpoint.dir == NULL)
{
__set_errno (ENOSYS);
return -1;
}
/* Construct the filename. */
while (name[0] == '/')
++name;
if (name[0] == '\0')
{
/* The name "/" is not supported. */
__set_errno (EINVAL);
return -1;
}
namelen = strlen (name);
fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
name, namelen + 1);
/* And get the file descriptor.
XXX Maybe we should test each descriptor whether it really is for a
file on the shmfs. If this is what should be done the whole function
should be revamped since we can determine whether shmfs is available
while trying to open the file, all in one turn. */
fd = open (fname, oflag, mode);
if (fd != -1)
{
/* We got a descriptor. Now set the FD_CLOEXEC bit. */
int flags = fcntl (fd, F_GETFD, 0);
if (__builtin_expect (flags, 0) >= 0)
{
flags |= FD_CLOEXEC;
flags = fcntl (fd, F_SETFD, flags);
}
if (flags == -1)
{
/* Something went wrong. We cannot return the descriptor. */
int save_errno = errno;
close (fd);
fd = -1;
__set_errno (save_errno);
}
}
return fd;
}
/* Unlink a shared memory object. */
int
shm_unlink (const char *name)
{
size_t namelen;
char *fname;
/* Determine where the shmfs is mounted. */
__libc_once (once, where_is_shmfs);
if (mountpoint.dir == NULL)
{
/* We cannot find the shmfs. If `name' is really a shared
memory object it must have been created by another process
and we have no idea where that process found the mountpoint. */
__set_errno (ENOENT);
return -1;
}
/* Construct the filename. */
while (name[0] == '/')
++name;
if (name[0] == '\0')
{
/* The name "/" is not supported. */
__set_errno (ENOENT);
return -1;
}
namelen = strlen (name);
fname = (char *) alloca (mountpoint.dirlen + namelen + 1);
__mempcpy (__mempcpy (fname, mountpoint.dir, mountpoint.dirlen),
name, namelen + 1);
/* And get the file descriptor.
XXX Maybe we should test each descriptor whether it really is for a
file on the shmfs. If this is what should be done the whole function
should be revamped since we can determine whether shmfs is available
while trying to open the file, all in one turn. */
return unlink (fname);
}
void
freeit (void)
{
if (mountpoint.dir != NULL && mountpoint.dir != defaultdir)
free (mountpoint.dir);
}
/* Make sure the table is freed if we want to free everything before
exiting. */
text_set_element (__libc_subfreeres, freeit);
|
