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[babeltrace.git] / src / common / mmap-align.h
1 #ifndef _BABELTRACE_MMAP_ALIGN_H
2 #define _BABELTRACE_MMAP_ALIGN_H
3
4 /*
5 * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE.
24 */
25
26 #include "common/align.h"
27 #include <stdlib.h>
28 #include <stdint.h>
29 #include "compat/mman.h"
30 #include "common/common.h"
31
32 /*
33 * This header implements a wrapper over mmap (mmap_align) that memory
34 * maps a file region that is not necessarily multiple of the page size.
35 * It returns a structure (instead of a pointer) that contains the mmap
36 * pointer (page-aligned) and a pointer to the offset requested within
37 * that page. Note: in the current implementation, the "addr" parameter
38 * cannot be forced, so we allocate at an address chosen by the OS.
39 */
40
41 struct mmap_align {
42 void *page_aligned_addr; /* mmap address, aligned to floor */
43 size_t page_aligned_length; /* mmap length, containing range */
44
45 void *addr; /* virtual mmap address */
46 size_t length; /* virtual mmap length */
47 };
48
49 #ifdef __WIN32__
50 #include <windows.h>
51
52 /*
53 * On windows the memory mapping offset must be aligned to the memory
54 * allocator allocation granularity and not the page size.
55 */
56 static inline
57 off_t get_page_aligned_offset(off_t offset, size_t page_size)
58 {
59 SYSTEM_INFO sysinfo;
60
61 GetNativeSystemInfo(&sysinfo);
62
63 return ALIGN_FLOOR(offset, sysinfo.dwAllocationGranularity);
64 }
65 #else
66 static inline
67 off_t get_page_aligned_offset(off_t offset, size_t page_size)
68 {
69 return ALIGN_FLOOR(offset, page_size);
70 }
71 #endif
72
73 static inline
74 struct mmap_align *mmap_align(size_t length, int prot,
75 int flags, int fd, off_t offset)
76 {
77 struct mmap_align *mma;
78 off_t page_aligned_offset; /* mmap offset, aligned to floor */
79 size_t page_size;
80
81 page_size = bt_common_get_page_size();
82
83 mma = malloc(sizeof(*mma));
84 if (!mma)
85 return MAP_FAILED;
86 mma->length = length;
87 page_aligned_offset = get_page_aligned_offset(offset, page_size);
88 /*
89 * Page aligned length needs to contain the requested range.
90 * E.g., for a small range that fits within a single page, we might
91 * require a 2 pages page_aligned_length if the range crosses a page
92 * boundary.
93 */
94 mma->page_aligned_length = ALIGN(length + offset - page_aligned_offset, page_size);
95 mma->page_aligned_addr = bt_mmap(NULL, mma->page_aligned_length,
96 prot, flags, fd, page_aligned_offset);
97 if (mma->page_aligned_addr == MAP_FAILED) {
98 free(mma);
99 return MAP_FAILED;
100 }
101 mma->addr = ((uint8_t *) mma->page_aligned_addr) + (offset - page_aligned_offset);
102 return mma;
103 }
104
105 static inline
106 int munmap_align(struct mmap_align *mma)
107 {
108 void *page_aligned_addr;
109 size_t page_aligned_length;
110
111 page_aligned_addr = mma->page_aligned_addr;
112 page_aligned_length = mma->page_aligned_length;
113 free(mma);
114 return bt_munmap(page_aligned_addr, page_aligned_length);
115 }
116
117 static inline
118 void *mmap_align_addr(struct mmap_align *mma)
119 {
120 return mma->addr;
121 }
122
123 /*
124 * Helper for special-cases, normally unused.
125 */
126 static inline
127 void mmap_align_set_addr(struct mmap_align *mma, void *addr)
128 {
129 mma->addr = addr;
130 }
131
132 #endif /* _BABELTRACE_MMAP_ALIGN_H */
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