arch/arm64/include/asm/pkeys.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Copyright (C) 2023 Arm Ltd.
   4  *
   5  * Based on arch/x86/include/asm/pkeys.h
   6  */
   7
   8 #ifndef _ASM_ARM64_PKEYS_H
   9 #define _ASM_ARM64_PKEYS_H
  10
  11 #define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2)
  12
  13 #define arch_max_pkey() 8
  14
  15 int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
  16                 unsigned long init_val);
  17
  18 static inline bool arch_pkeys_enabled(void)
  19 {
  20         return system_supports_poe();
  21 }
  22
  23 static inline int vma_pkey(struct vm_area_struct *vma)
  24 {
  25         return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
  26 }
  27
  28 static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
  29                 int prot, int pkey)
  30 {
  31         if (pkey != -1)
  32                 return pkey;
  33
  34         return vma_pkey(vma);
  35 }
  36
  37 static inline int execute_only_pkey(struct mm_struct *mm)
  38 {
  39         // Execute-only mappings are handled by EPAN/FEAT_PAN3.
  40         return -1;
  41 }
  42
  43 #define mm_pkey_allocation_map(mm)      (mm)->context.pkey_allocation_map
  44 #define mm_set_pkey_allocated(mm, pkey) do {            \
  45         mm_pkey_allocation_map(mm) |= (1U << pkey);     \
  46 } while (0)
  47 #define mm_set_pkey_free(mm, pkey) do {                 \
  48         mm_pkey_allocation_map(mm) &= ~(1U << pkey);    \
  49 } while (0)
  50
  51 static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
  52 {
  53         /*
  54          * "Allocated" pkeys are those that have been returned
  55          * from pkey_alloc() or pkey 0 which is allocated
  56          * implicitly when the mm is created.
  57          */
  58         if (pkey < 0 || pkey >= arch_max_pkey())
  59                 return false;
  60
  61         return mm_pkey_allocation_map(mm) & (1U << pkey);
  62 }
  63
  64 /*
  65  * Returns a positive, 3-bit key on success, or -1 on failure.
  66  */
  67 static inline int mm_pkey_alloc(struct mm_struct *mm)
  68 {
  69         /*
  70          * Note: this is the one and only place we make sure
  71          * that the pkey is valid as far as the hardware is
  72          * concerned.  The rest of the kernel trusts that
  73          * only good, valid pkeys come out of here.
  74          */
  75         u8 all_pkeys_mask = GENMASK(arch_max_pkey() - 1, 0);
  76         int ret;
  77
  78         if (!arch_pkeys_enabled())
  79                 return -1;
  80
  81         /*
  82          * Are we out of pkeys?  We must handle this specially
  83          * because ffz() behavior is undefined if there are no
  84          * zeros.
  85          */
  86         if (mm_pkey_allocation_map(mm) == all_pkeys_mask)
  87                 return -1;
  88
  89         ret = ffz(mm_pkey_allocation_map(mm));
  90
  91         mm_set_pkey_allocated(mm, ret);
  92
  93         return ret;
  94 }
  95
  96 static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
  97 {
  98         if (!mm_pkey_is_allocated(mm, pkey))
  99                 return -EINVAL;
 100
 101         mm_set_pkey_free(mm, pkey);
 102
 103         return 0;
 104 }
 105
 106 #endif /* _ASM_ARM64_PKEYS_H */