nbd: Don't use *_to_cpup() functions
[qemu.git] / util / mmap-alloc.c
1 /*
2 * Support for RAM backed by mmaped host memory.
3 *
4 * Copyright (c) 2015 Red Hat, Inc.
5 *
6 * Authors:
7 * Michael S. Tsirkin <mst@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2 or
10 * later. See the COPYING file in the top-level directory.
11 */
12 #include "qemu/osdep.h"
13 #include <qemu/mmap-alloc.h>
14
15 #define HUGETLBFS_MAGIC 0x958458f6
16
17 #ifdef CONFIG_LINUX
18 #include <sys/vfs.h>
19 #endif
20
21 size_t qemu_fd_getpagesize(int fd)
22 {
23 #ifdef CONFIG_LINUX
24 struct statfs fs;
25 int ret;
26
27 if (fd != -1) {
28 do {
29 ret = fstatfs(fd, &fs);
30 } while (ret != 0 && errno == EINTR);
31
32 if (ret == 0 && fs.f_type == HUGETLBFS_MAGIC) {
33 return fs.f_bsize;
34 }
35 }
36 #endif
37
38 return getpagesize();
39 }
40
41 void *qemu_ram_mmap(int fd, size_t size, size_t align, bool shared)
42 {
43 /*
44 * Note: this always allocates at least one extra page of virtual address
45 * space, even if size is already aligned.
46 */
47 size_t total = size + align;
48 #if defined(__powerpc64__) && defined(__linux__)
49 /* On ppc64 mappings in the same segment (aka slice) must share the same
50 * page size. Since we will be re-allocating part of this segment
51 * from the supplied fd, we should make sure to use the same page size, to
52 * this end we mmap the supplied fd. In this case, set MAP_NORESERVE to
53 * avoid allocating backing store memory.
54 * We do this unless we are using the system page size, in which case
55 * anonymous memory is OK.
56 */
57 int anonfd = fd == -1 || qemu_fd_getpagesize(fd) == getpagesize() ? -1 : fd;
58 int flags = anonfd == -1 ? MAP_ANONYMOUS : MAP_NORESERVE;
59 void *ptr = mmap(0, total, PROT_NONE, flags | MAP_PRIVATE, anonfd, 0);
60 #else
61 void *ptr = mmap(0, total, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
62 #endif
63 size_t offset = QEMU_ALIGN_UP((uintptr_t)ptr, align) - (uintptr_t)ptr;
64 void *ptr1;
65
66 if (ptr == MAP_FAILED) {
67 return MAP_FAILED;
68 }
69
70 /* Make sure align is a power of 2 */
71 assert(!(align & (align - 1)));
72 /* Always align to host page size */
73 assert(align >= getpagesize());
74
75 ptr1 = mmap(ptr + offset, size, PROT_READ | PROT_WRITE,
76 MAP_FIXED |
77 (fd == -1 ? MAP_ANONYMOUS : 0) |
78 (shared ? MAP_SHARED : MAP_PRIVATE),
79 fd, 0);
80 if (ptr1 == MAP_FAILED) {
81 munmap(ptr, total);
82 return MAP_FAILED;
83 }
84
85 ptr += offset;
86 total -= offset;
87
88 if (offset > 0) {
89 munmap(ptr - offset, offset);
90 }
91
92 /*
93 * Leave a single PROT_NONE page allocated after the RAM block, to serve as
94 * a guard page guarding against potential buffer overflows.
95 */
96 if (total > size + getpagesize()) {
97 munmap(ptr + size + getpagesize(), total - size - getpagesize());
98 }
99
100 return ptr;
101 }
102
103 void qemu_ram_munmap(void *ptr, size_t size)
104 {
105 if (ptr) {
106 /* Unmap both the RAM block and the guard page */
107 munmap(ptr, size + getpagesize());
108 }
109 }