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
|
/*
* memfd.c
*
* Copyright (c) 2015 Red Hat, Inc.
*
* QEMU library functions on POSIX which are shared between QEMU and
* the QEMU tools.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/memfd.h"
#include "qemu/host-utils.h"
#if defined CONFIG_LINUX && !defined CONFIG_MEMFD
#include <sys/syscall.h>
#include <asm/unistd.h>
static int memfd_create(const char *name, unsigned int flags)
{
#ifdef __NR_memfd_create
return syscall(__NR_memfd_create, name, flags);
#else
errno = ENOSYS;
return -1;
#endif
}
#endif
int qemu_memfd_create(const char *name, size_t size, bool hugetlb,
uint64_t hugetlbsize, unsigned int seals, Error **errp)
{
int htsize = hugetlbsize ? ctz64(hugetlbsize) : 0;
if (htsize && 1ULL << htsize != hugetlbsize) {
error_setg(errp, "Hugepage size must be a power of 2");
return -1;
}
htsize = htsize << MFD_HUGE_SHIFT;
#ifdef CONFIG_LINUX
int mfd = -1;
unsigned int flags = MFD_CLOEXEC;
if (seals) {
flags |= MFD_ALLOW_SEALING;
}
if (hugetlb) {
flags |= MFD_HUGETLB;
flags |= htsize;
}
mfd = memfd_create(name, flags);
if (mfd < 0) {
error_setg_errno(errp, errno,
"failed to create memfd with flags 0x%x", flags);
goto err;
}
if (ftruncate(mfd, size) == -1) {
error_setg_errno(errp, errno, "failed to resize memfd to %zu", size);
goto err;
}
if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
error_setg_errno(errp, errno, "failed to add seals 0x%x", seals);
goto err;
}
return mfd;
err:
if (mfd >= 0) {
close(mfd);
}
#else
error_setg_errno(errp, ENOSYS, "failed to create memfd");
#endif
return -1;
}
/*
* This is a best-effort helper for shared memory allocation, with
* optional sealing. The helper will do his best to allocate using
* memfd with sealing, but may fallback on other methods without
* sealing.
*/
void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
int *fd, Error **errp)
{
void *ptr;
int mfd = qemu_memfd_create(name, size, false, 0, seals, NULL);
/* some systems have memfd without sealing */
if (mfd == -1) {
mfd = qemu_memfd_create(name, size, false, 0, 0, NULL);
}
if (mfd == -1) {
const char *tmpdir = g_get_tmp_dir();
gchar *fname;
fname = g_strdup_printf("%s/memfd-XXXXXX", tmpdir);
mfd = mkstemp(fname);
unlink(fname);
g_free(fname);
if (mfd == -1 ||
ftruncate(mfd, size) == -1) {
goto err;
}
}
ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
if (ptr == MAP_FAILED) {
goto err;
}
*fd = mfd;
return ptr;
err:
error_setg_errno(errp, errno, "failed to allocate shared memory");
if (mfd >= 0) {
close(mfd);
}
return NULL;
}
void qemu_memfd_free(void *ptr, size_t size, int fd)
{
if (ptr) {
munmap(ptr, size);
}
if (fd != -1) {
close(fd);
}
}
enum {
MEMFD_KO,
MEMFD_OK,
MEMFD_TODO
};
/**
* qemu_memfd_alloc_check():
*
* Check if qemu_memfd_alloc() can allocate, including using a
* fallback implementation when host doesn't support memfd.
*/
bool qemu_memfd_alloc_check(void)
{
static int memfd_check = MEMFD_TODO;
if (memfd_check == MEMFD_TODO) {
int fd;
void *ptr;
fd = -1;
ptr = qemu_memfd_alloc("test", 4096, 0, &fd, NULL);
memfd_check = ptr ? MEMFD_OK : MEMFD_KO;
qemu_memfd_free(ptr, 4096, fd);
}
return memfd_check == MEMFD_OK;
}
/**
* qemu_memfd_check():
*
* Check if host supports memfd.
*/
bool qemu_memfd_check(unsigned int flags)
{
#ifdef CONFIG_LINUX
int mfd = memfd_create("test", flags | MFD_CLOEXEC);
if (mfd >= 0) {
close(mfd);
return true;
}
#endif
return false;
}
|
