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
 15int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
 16		unsigned long init_val);
 17
 18static inline bool arch_pkeys_enabled(void)
 19{
 20	return system_supports_poe();
 21}
 22
 23static inline int vma_pkey(struct vm_area_struct *vma)
 24{
 25	return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
 26}
 27
 28static 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
 37static 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
 51static 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 */
 67static 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
 96static 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 */