include/babeltrace/mmap-align-internal.h

   1 #ifndef _BABELTRACE_MMAP_ALIGN_H
   2 #define _BABELTRACE_MMAP_ALIGN_H
   3
   4 /*
   5  * BabelTrace mmap-align.h - mmap alignment header
   6  *
   7  * Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   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:
  15  *
  16  * The above copyright notice and this permission notice shall be included in
  17  * all copies or substantial portions of the Software.
  18  *
  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
  25  * SOFTWARE.
  26  */
  27
  28 #include <babeltrace/align-internal.h>
  29 #include <stdlib.h>
  30 #include <stdint.h>
  31 #include <sys/mman.h>
  32 #include <babeltrace/common-internal.h>
  33
  34 /*
  35  * This header implements a wrapper over mmap (mmap_align) that memory
  36  * maps a file region that is not necessarily multiple of the page size.
  37  * It returns a structure (instead of a pointer) that contains the mmap
  38  * pointer (page-aligned) and a pointer to the offset requested within
  39  * that page. Note: in the current implementation, the "addr" parameter
  40  * cannot be forced, so we allocate at an address chosen by the OS.
  41  */
  42
  43 struct mmap_align {
  44         void *page_aligned_addr;        /* mmap address, aligned to floor */
  45         size_t page_aligned_length;     /* mmap length, containing range */
  46
  47         void *addr;                     /* virtual mmap address */
  48         size_t length;                  /* virtual mmap length */
  49 };
  50
  51 static inline
  52 struct mmap_align *mmap_align(size_t length, int prot,
  53                 int flags, int fd, off_t offset)
  54 {
  55         struct mmap_align *mma;
  56         off_t page_aligned_offset;      /* mmap offset, aligned to floor */
  57         size_t page_size;
  58
  59         page_size = bt_common_get_page_size();
  60
  61         mma = malloc(sizeof(*mma));
  62         if (!mma)
  63                 return MAP_FAILED;
  64         mma->length = length;
  65         page_aligned_offset = ALIGN_FLOOR(offset, page_size);
  66         /*
  67          * Page aligned length needs to contain the requested range.
  68          * E.g., for a small range that fits within a single page, we might
  69          * require a 2 pages page_aligned_length if the range crosses a page
  70          * boundary.
  71          */
  72         mma->page_aligned_length = ALIGN(length + offset - page_aligned_offset, page_size);
  73         mma->page_aligned_addr = mmap(NULL, mma->page_aligned_length,
  74                 prot, flags, fd, page_aligned_offset);
  75         if (mma->page_aligned_addr == (void *) -1UL) {
  76                 free(mma);
  77                 return MAP_FAILED;
  78         }
  79         mma->addr = ((uint8_t *) mma->page_aligned_addr) + (offset - page_aligned_offset);
  80         return mma;
  81 }
  82
  83 static inline
  84 int munmap_align(struct mmap_align *mma)
  85 {
  86         void *page_aligned_addr;
  87         size_t page_aligned_length;
  88
  89         page_aligned_addr = mma->page_aligned_addr;
  90         page_aligned_length = mma->page_aligned_length;
  91         free(mma);
  92         return munmap(page_aligned_addr, page_aligned_length);
  93 }
  94
  95 static inline
  96 void *mmap_align_addr(struct mmap_align *mma)
  97 {
  98         return mma->addr;
  99 }
 100
 101 /*
 102  * Helper for special-cases, normally unused.
 103  */
 104 static inline
 105 void mmap_align_set_addr(struct mmap_align *mma, void *addr)
 106 {
 107         mma->addr = addr;
 108 }
 109
 110 #endif /* _BABELTRACE_MMAP_ALIGN_H */