1 #ifndef _BABELTRACE_MMAP_ALIGN_H
2 #define _BABELTRACE_MMAP_ALIGN_H
5 * BabelTrace mmap-align.h - mmap alignment header
7 * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
9 * Permission is hereby granted, free of charge, to any person obtaining a copy
10 * of this software and associated documentation files (the "Software"), to deal
11 * in the Software without restriction, including without limitation the rights
12 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
13 * copies of the Software, and to permit persons to whom the Software is
14 * furnished to do so, subject to the following conditions:
16 * The above copyright notice and this permission notice shall be included in
17 * all copies or substantial portions of the Software.
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
20 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
21 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
22 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
23 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
24 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
28 #include <babeltrace/align-internal.h>
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.
42 void *page_aligned_addr
; /* mmap address, aligned to floor */
43 size_t page_aligned_length
; /* mmap length, containing range */
45 void *addr
; /* virtual mmap address */
46 size_t length
; /* virtual mmap length */
50 struct mmap_align
*mmap_align(size_t length
, int prot
,
51 int flags
, int fd
, off_t offset
)
53 struct mmap_align
*mma
;
54 off_t page_aligned_offset
; /* mmap offset, aligned to floor */
56 mma
= malloc(sizeof(*mma
));
60 page_aligned_offset
= ALIGN_FLOOR(offset
, PAGE_SIZE
);
62 * Page aligned length needs to contain the requested range.
63 * E.g., for a small range that fits within a single page, we might
64 * require a 2 pages page_aligned_length if the range crosses a page
67 mma
->page_aligned_length
= ALIGN(length
+ offset
- page_aligned_offset
, PAGE_SIZE
);
68 mma
->page_aligned_addr
= mmap(NULL
, mma
->page_aligned_length
,
69 prot
, flags
, fd
, page_aligned_offset
);
70 if (mma
->page_aligned_addr
== (void *) -1UL) {
74 mma
->addr
= mma
->page_aligned_addr
+ (offset
- page_aligned_offset
);
79 int munmap_align(struct mmap_align
*mma
)
81 void *page_aligned_addr
;
82 size_t page_aligned_length
;
84 page_aligned_addr
= mma
->page_aligned_addr
;
85 page_aligned_length
= mma
->page_aligned_length
;
87 return munmap(page_aligned_addr
, page_aligned_length
);
91 void *mmap_align_addr(struct mmap_align
*mma
)
97 * Helper for special-cases, normally unused.
100 void mmap_align_set_addr(struct mmap_align
*mma
, void *addr
)
105 #endif /* _BABELTRACE_MMAP_ALIGN_H */