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 static inline
  50 off_t get_page_aligned_offset(off_t offset, int log_level)
  51 {
  52        return ALIGN_FLOOR(offset, bt_mmap_get_offset_align_size(log_level));
  53 }
  54
  55 static inline
  56 struct mmap_align *mmap_align(size_t length, int prot,
  57                 int flags, int fd, off_t offset, int log_level)
  58 {
  59         struct mmap_align *mma;
  60         off_t page_aligned_offset;      /* mmap offset, aligned to floor */
  61         size_t page_size;
  62
  63         page_size = bt_common_get_page_size(log_level);
  64
  65         mma = malloc(sizeof(*mma));
  66         if (!mma)
  67                 return MAP_FAILED;
  68         mma->length = length;
  69         page_aligned_offset = get_page_aligned_offset(offset, log_level);
  70         /*
  71          * Page aligned length needs to contain the requested range.
  72          * E.g., for a small range that fits within a single page, we might
  73          * require a 2 pages page_aligned_length if the range crosses a page
  74          * boundary.
  75          */
  76         mma->page_aligned_length = ALIGN(length + offset - page_aligned_offset, page_size);
  77         mma->page_aligned_addr = bt_mmap(NULL, mma->page_aligned_length,
  78                 prot, flags, fd, page_aligned_offset, log_level);
  79         if (mma->page_aligned_addr == MAP_FAILED) {
  80                 free(mma);
  81                 return MAP_FAILED;
  82         }
  83         mma->addr = ((uint8_t *) mma->page_aligned_addr) + (offset - page_aligned_offset);
  84         return mma;
  85 }
  86
  87 static inline
  88 int munmap_align(struct mmap_align *mma)
  89 {
  90         void *page_aligned_addr;
  91         size_t page_aligned_length;
  92
  93         page_aligned_addr = mma->page_aligned_addr;
  94         page_aligned_length = mma->page_aligned_length;
  95         free(mma);
  96         return bt_munmap(page_aligned_addr, page_aligned_length);
  97 }
  98
  99 static inline
 100 void *mmap_align_addr(struct mmap_align *mma)
 101 {
 102         return mma->addr;
 103 }
 104
 105 /*
 106  * Helper for special-cases, normally unused.
 107  */
 108 static inline
 109 void mmap_align_set_addr(struct mmap_align *mma, void *addr)
 110 {
 111         mma->addr = addr;
 112 }
 113
 114 #endif /* _BABELTRACE_MMAP_ALIGN_H */