src/wrapper/page_alloc.c

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  * wrapper/page_alloc.c
   3  *
   4  * wrapper around get_pfnblock_flags_mask and Ubuntu
   5  * get_pageblock_flags_mask. Using KALLSYMS to get their address when
   6  * available, else we need to have a kernel that exports this function
   7  * to GPL modules.
   8  *
   9  * Copyright (C) 2015 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  10  */
  11
  12 #ifdef CONFIG_KALLSYMS
  13
  14 #include <linux/kallsyms.h>
  15 #include <linux/mm_types.h>
  16 #include <linux/module.h>
  17 #include <wrapper/kallsyms.h>
  18 #include <wrapper/page_alloc.h>
  19
  20 static
  21 unsigned long (*get_pfnblock_flags_mask_sym)(struct page *page,
  22                 unsigned long pfn,
  23                 unsigned long end_bitidx,
  24                 unsigned long mask);
  25
  26 unsigned long wrapper_get_pfnblock_flags_mask(struct page *page,
  27                 unsigned long pfn,
  28                 unsigned long end_bitidx,
  29                 unsigned long mask)
  30 {
  31         WARN_ON_ONCE(!get_pfnblock_flags_mask_sym);
  32         if (get_pfnblock_flags_mask_sym) {
  33                 return get_pfnblock_flags_mask_sym(page, pfn, end_bitidx, mask);
  34         } else {
  35                 return -ENOSYS;
  36         }
  37 }
  38 EXPORT_SYMBOL_GPL(wrapper_get_pfnblock_flags_mask);
  39
  40 int wrapper_get_pfnblock_flags_mask_init(void)
  41 {
  42         get_pfnblock_flags_mask_sym =
  43                 (void *) kallsyms_lookup_funcptr("get_pfnblock_flags_mask");
  44         if (!get_pfnblock_flags_mask_sym)
  45                 return -1;
  46         return 0;
  47 }
  48 EXPORT_SYMBOL_GPL(wrapper_get_pfnblock_flags_mask_init);
  49
  50 /*
  51  * Canary function to check for 'get_pfnblock_flags_mask()' at compile time.
  52  *
  53  * From 'include/linux/pageblock-flags.h':
  54  *
  55  *   unsigned long get_pfnblock_flags_mask(struct page *page,
  56  *                                         unsigned long pfn,
  57  *                                         unsigned long end_bitidx,
  58  *                                         unsigned long mask);
  59  */
  60 __attribute__((unused)) static
  61 unsigned long __canary__get_pfnblock_flags_mask(struct page *page,
  62                                                 unsigned long pfn,
  63                                                 unsigned long end_bitidx,
  64                                                 unsigned long mask)
  65 {
  66         return get_pfnblock_flags_mask(page, pfn, end_bitidx, mask);
  67 }
  68
  69 #else
  70
  71 #include <linux/pageblock-flags.h>
  72
  73 #endif