arch/arm64/mm/mmap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Based on arch/arm/mm/mmap.c
   4  *
   5  * Copyright (C) 2012 ARM Ltd.
   6  */
   7
   8 #include <linux/elf.h>
   9 #include <linux/fs.h>
  10 #include <linux/memblock.h>
  11 #include <linux/mm.h>
  12 #include <linux/mman.h>
  13 #include <linux/export.h>
  14 #include <linux/shm.h>
  15 #include <linux/sched/signal.h>
  16 #include <linux/sched/mm.h>
  17 #include <linux/io.h>
  18 #include <linux/personality.h>
  19 #include <linux/random.h>
  20
  21 #include <asm/cputype.h>
  22
  23 /*
  24  * You really shouldn't be using read() or write() on /dev/mem.  This might go
  25  * away in the future.
  26  */
  27 int valid_phys_addr_range(phys_addr_t addr, size_t size)
  28 {
  29         /*
  30          * Check whether addr is covered by a memory region without the
  31          * MEMBLOCK_NOMAP attribute, and whether that region covers the
  32          * entire range. In theory, this could lead to false negatives
  33          * if the range is covered by distinct but adjacent memory regions
  34          * that only differ in other attributes. However, few of such
  35          * attributes have been defined, and it is debatable whether it
  36          * follows that /dev/mem read() calls should be able traverse
  37          * such boundaries.
  38          */
  39         return memblock_is_region_memory(addr, size) &&
  40                memblock_is_map_memory(addr);
  41 }
  42
  43 /*
  44  * Do not allow /dev/mem mappings beyond the supported physical range.
  45  */
  46 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  47 {
  48         return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
  49 }
  50
  51 #ifdef CONFIG_STRICT_DEVMEM
  52
  53 #include <linux/ioport.h>
  54
  55 /*
  56  * devmem_is_allowed() checks to see if /dev/mem access to a certain address
  57  * is valid. The argument is a physical page number.  We mimic x86 here by
  58  * disallowing access to system RAM as well as device-exclusive MMIO regions.
  59  * This effectively disable read()/write() on /dev/mem.
  60  */
  61 int devmem_is_allowed(unsigned long pfn)
  62 {
  63         if (iomem_is_exclusive(pfn << PAGE_SHIFT))
  64                 return 0;
  65         if (!page_is_ram(pfn))
  66                 return 1;
  67         return 0;
  68 }
  69
  70 #endif