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/io.h>
   9 #include <linux/memblock.h>
  10 #include <linux/mm.h>
  11 #include <linux/types.h>
  12
  13 #include <asm/cpufeature.h>
  14 #include <asm/page.h>
  15
  16 static pgprot_t protection_map[16] __ro_after_init = {
  17         [VM_NONE]                                       = PAGE_NONE,
  18         [VM_READ]                                       = PAGE_READONLY,
  19         [VM_WRITE]                                      = PAGE_READONLY,
  20         [VM_WRITE | VM_READ]                            = PAGE_READONLY,
  21         /* PAGE_EXECONLY if Enhanced PAN */
  22         [VM_EXEC]                                       = PAGE_READONLY_EXEC,
  23         [VM_EXEC | VM_READ]                             = PAGE_READONLY_EXEC,
  24         [VM_EXEC | VM_WRITE]                            = PAGE_READONLY_EXEC,
  25         [VM_EXEC | VM_WRITE | VM_READ]                  = PAGE_READONLY_EXEC,
  26         [VM_SHARED]                                     = PAGE_NONE,
  27         [VM_SHARED | VM_READ]                           = PAGE_READONLY,
  28         [VM_SHARED | VM_WRITE]                          = PAGE_SHARED,
  29         [VM_SHARED | VM_WRITE | VM_READ]                = PAGE_SHARED,
  30         /* PAGE_EXECONLY if Enhanced PAN */
  31         [VM_SHARED | VM_EXEC]                           = PAGE_READONLY_EXEC,
  32         [VM_SHARED | VM_EXEC | VM_READ]                 = PAGE_READONLY_EXEC,
  33         [VM_SHARED | VM_EXEC | VM_WRITE]                = PAGE_SHARED_EXEC,
  34         [VM_SHARED | VM_EXEC | VM_WRITE | VM_READ]      = PAGE_SHARED_EXEC
  35 };
  36
  37 /*
  38  * You really shouldn't be using read() or write() on /dev/mem.  This might go
  39  * away in the future.
  40  */
  41 int valid_phys_addr_range(phys_addr_t addr, size_t size)
  42 {
  43         /*
  44          * Check whether addr is covered by a memory region without the
  45          * MEMBLOCK_NOMAP attribute, and whether that region covers the
  46          * entire range. In theory, this could lead to false negatives
  47          * if the range is covered by distinct but adjacent memory regions
  48          * that only differ in other attributes. However, few of such
  49          * attributes have been defined, and it is debatable whether it
  50          * follows that /dev/mem read() calls should be able traverse
  51          * such boundaries.
  52          */
  53         return memblock_is_region_memory(addr, size) &&
  54                memblock_is_map_memory(addr);
  55 }
  56
  57 /*
  58  * Do not allow /dev/mem mappings beyond the supported physical range.
  59  */
  60 int valid_mmap_phys_addr_range(unsigned long pfn, size_t size)
  61 {
  62         return !(((pfn << PAGE_SHIFT) + size) & ~PHYS_MASK);
  63 }
  64
  65 static int __init adjust_protection_map(void)
  66 {
  67         /*
  68          * With Enhanced PAN we can honour the execute-only permissions as
  69          * there is no PAN override with such mappings.
  70          */
  71         if (cpus_have_const_cap(ARM64_HAS_EPAN)) {
  72                 protection_map[VM_EXEC] = PAGE_EXECONLY;
  73                 protection_map[VM_EXEC | VM_SHARED] = PAGE_EXECONLY;
  74         }
  75
  76         return 0;
  77 }
  78 arch_initcall(adjust_protection_map);
  79
  80 pgprot_t vm_get_page_prot(unsigned long vm_flags)
  81 {
  82         pteval_t prot = pgprot_val(protection_map[vm_flags &
  83                                    (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]);
  84
  85         if (vm_flags & VM_ARM64_BTI)
  86                 prot |= PTE_GP;
  87
  88         /*
  89          * There are two conditions required for returning a Normal Tagged
  90          * memory type: (1) the user requested it via PROT_MTE passed to
  91          * mmap() or mprotect() and (2) the corresponding vma supports MTE. We
  92          * register (1) as VM_MTE in the vma->vm_flags and (2) as
  93          * VM_MTE_ALLOWED. Note that the latter can only be set during the
  94          * mmap() call since mprotect() does not accept MAP_* flags.
  95          * Checking for VM_MTE only is sufficient since arch_validate_flags()
  96          * does not permit (VM_MTE & !VM_MTE_ALLOWED).
  97          */
  98         if (vm_flags & VM_MTE)
  99                 prot |= PTE_ATTRINDX(MT_NORMAL_TAGGED);
 100
 101         return __pgprot(prot);
 102 }
 103 EXPORT_SYMBOL(vm_get_page_prot);