LXR linux/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 */
  27int 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 */
  46int 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 */
  61int 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
  71