xref: /freebsd/lib/libc/sys/shm_open.c (revision 66fd12cf4896eb08ad8e7a2627537f84ead84dd3)
1 /*
2  * SPDX-License-Identifier: BSD-2-Clause
3  *
4  * Copyright (c) 2019 Kyle Evans <kevans@FreeBSD.org>
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice(s), this list of conditions and the following disclaimer as
11  *    the first lines of this file unmodified other than the possible
12  *    addition of one or more copyright notices.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice(s), this list of conditions and the following disclaimer in
15  *    the documentation and/or other materials provided with the
16  *    distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
19  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
22  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
25  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
26  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
27  * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
28  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30 
31 #include <sys/cdefs.h>
32 __FBSDID("$FreeBSD$");
33 
34 #include <sys/param.h>
35 #include <sys/filio.h>
36 #include <sys/mman.h>
37 
38 #include <errno.h>
39 #include <fcntl.h>
40 #include <limits.h>
41 #include <stdlib.h>
42 #include <stdio.h>
43 #include <string.h>
44 #include <unistd.h>
45 
46 #include "libc_private.h"
47 
48 __weak_reference(shm_open, _shm_open);
49 __weak_reference(shm_open, __sys_shm_open);
50 
51 #define	MEMFD_NAME_PREFIX	"memfd:"
52 
53 int
54 shm_open(const char *path, int flags, mode_t mode)
55 {
56 
57 	return (__sys_shm_open2(path, flags | O_CLOEXEC, mode, 0, NULL));
58 }
59 
60 int
61 shm_create_largepage(const char *path, int flags, int psind, int alloc_policy,
62     mode_t mode)
63 {
64 	struct shm_largepage_conf slc;
65 	int error, fd, saved_errno;
66 
67 	fd = __sys_shm_open2(path, flags | O_CREAT, mode, SHM_LARGEPAGE, NULL);
68 	if (fd == -1)
69 		return (-1);
70 
71 	memset(&slc, 0, sizeof(slc));
72 	slc.psind = psind;
73 	slc.alloc_policy = alloc_policy;
74 	error = ioctl(fd, FIOSSHMLPGCNF, &slc);
75 	if (error == -1) {
76 		saved_errno = errno;
77 		close(fd);
78 		errno = saved_errno;
79 		return (-1);
80 	}
81 	return (fd);
82 }
83 
84 /*
85  * The path argument is passed to the kernel, but the kernel doesn't currently
86  * do anything with it.  Linux exposes it in linprocfs for debugging purposes
87  * only, but our kernel currently will not do the same.
88  */
89 int
90 memfd_create(const char *name, unsigned int flags)
91 {
92 	char memfd_name[NAME_MAX + 1];
93 	size_t namelen, *pgs, pgsize;
94 	struct shm_largepage_conf slc;
95 	int error, fd, npgs, oflags, pgidx, saved_errno, shmflags;
96 
97 	if (name == NULL) {
98 		errno = EBADF;
99 		return (-1);
100 	}
101 	namelen = strlen(name);
102 	if (namelen + sizeof(MEMFD_NAME_PREFIX) - 1 > NAME_MAX) {
103 		errno = EINVAL;
104 		return (-1);
105 	}
106 	if ((flags & ~(MFD_CLOEXEC | MFD_ALLOW_SEALING | MFD_HUGETLB |
107 	    MFD_HUGE_MASK)) != 0) {
108 		errno = EINVAL;
109 		return (-1);
110 	}
111 	/* Size specified but no HUGETLB. */
112 	if ((flags & MFD_HUGE_MASK) != 0 && (flags & MFD_HUGETLB) == 0) {
113 		errno = EINVAL;
114 		return (-1);
115 	}
116 
117 	/* We've already validated that we're sufficiently sized. */
118 	snprintf(memfd_name, NAME_MAX + 1, "%s%s", MEMFD_NAME_PREFIX, name);
119 	oflags = O_RDWR;
120 	shmflags = 0;
121 	if ((flags & MFD_CLOEXEC) != 0)
122 		oflags |= O_CLOEXEC;
123 	if ((flags & MFD_ALLOW_SEALING) != 0)
124 		shmflags |= SHM_ALLOW_SEALING;
125 	if ((flags & MFD_HUGETLB) != 0)
126 		shmflags |= SHM_LARGEPAGE;
127 	else
128 		shmflags |= SHM_GROW_ON_WRITE;
129 	fd = __sys_shm_open2(SHM_ANON, oflags, 0, shmflags, memfd_name);
130 	if (fd == -1 || (flags & MFD_HUGETLB) == 0)
131 		return (fd);
132 
133 	pgs = NULL;
134 	npgs = getpagesizes(NULL, 0);
135 	if (npgs == -1)
136 		goto clean;
137 	pgs = calloc(npgs, sizeof(size_t));
138 	if (pgs == NULL)
139 		goto clean;
140 	error = getpagesizes(pgs, npgs);
141 	if (error == -1)
142 		goto clean;
143 	pgsize = (size_t)1 << ((flags & MFD_HUGE_MASK) >> MFD_HUGE_SHIFT);
144 	for (pgidx = 0; pgidx < npgs; pgidx++) {
145 		if (pgsize == pgs[pgidx])
146 			break;
147 	}
148 	if (pgidx == npgs) {
149 		errno = EOPNOTSUPP;
150 		goto clean;
151 	}
152 	free(pgs);
153 	pgs = NULL;
154 
155 	memset(&slc, 0, sizeof(slc));
156 	slc.psind = pgidx;
157 	slc.alloc_policy = SHM_LARGEPAGE_ALLOC_DEFAULT;
158 	error = ioctl(fd, FIOSSHMLPGCNF, &slc);
159 	if (error == -1)
160 		goto clean;
161 	return (fd);
162 
163 clean:
164 	saved_errno = errno;
165 	close(fd);
166 	free(pgs);
167 	errno = saved_errno;
168 	return (-1);
169 }
170