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.
20 #include <babeltrace/align.h>
25 * This header implements a wrapper over mmap (mmap_align) that memory
26 * maps a file region that is not necessarily multiple of the page size.
27 * It returns a structure (instead of a pointer) that contains the mmap
28 * pointer (page-aligned) and a pointer to the offset requested within
29 * that page. Note: in the current implementation, the "addr" parameter
30 * cannot be forced, so we allocate at an address chosen by the OS.
34 void *page_aligned_addr
; /* mmap address, aligned to floor */
35 size_t page_aligned_length
; /* mmap length, containing range */
37 void *addr
; /* virtual mmap address */
38 size_t length
; /* virtual mmap length */
42 struct mmap_align
*mmap_align(size_t length
, int prot
,
43 int flags
, int fd
, off_t offset
)
45 struct mmap_align
*mma
;
46 off_t page_aligned_offset
; /* mmap offset, aligned to floor */
48 mma
= malloc(sizeof(*mma
));
52 page_aligned_offset
= ALIGN_FLOOR(offset
, PAGE_SIZE
);
54 * Page aligned length needs to contain the requested range.
55 * E.g., for a small range that fits within a single page, we might
56 * require a 2 pages page_aligned_length if the range crosses a page
59 mma
->page_aligned_length
= ALIGN(length
+ offset
- page_aligned_offset
, PAGE_SIZE
);
60 mma
->page_aligned_addr
= mmap(NULL
, mma
->page_aligned_length
,
61 prot
, flags
, fd
, page_aligned_offset
);
62 if (mma
->page_aligned_addr
== (void *) -1UL) {
66 mma
->addr
= mma
->page_aligned_addr
+ (offset
- page_aligned_offset
);
71 int munmap_align(struct mmap_align
*mma
)
73 void *page_aligned_addr
;
74 size_t page_aligned_length
;
76 page_aligned_addr
= mma
->page_aligned_addr
;
77 page_aligned_length
= mma
->page_aligned_length
;
79 return munmap(page_aligned_addr
, page_aligned_length
);
83 void *mmap_align_addr(struct mmap_align
*mma
)
89 * Helper for special-cases, normally unused.
92 void mmap_align_set_addr(struct mmap_align
*mma
, void *addr
)
97 #endif /* _BABELTRACE_MMAP_ALIGN_H */