xref: /linux/arch/powerpc/include/asm/pkeys.h (revision d0034a7a4ac7fae708146ac0059b9c47a1543f0d)

/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * PowerPC Memory Protection Keys management
 *
 * Copyright 2017, Ram Pai, IBM Corporation.
 */

#ifndef _ASM_POWERPC_KEYS_H
#define _ASM_POWERPC_KEYS_H

#include <linux/jump_label.h>
#include <asm/firmware.h>

extern int num_pkey;
extern u32 reserved_allocation_mask; /* bits set for reserved keys */

#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \
			    VM_PKEY_BIT3 | VM_PKEY_BIT4)

/* Override any generic PKEY permission defines */
#define PKEY_DISABLE_EXECUTE   0x4
#define PKEY_ACCESS_MASK       (PKEY_DISABLE_ACCESS | \
				PKEY_DISABLE_WRITE  | \
				PKEY_DISABLE_EXECUTE)

#ifdef CONFIG_PPC_BOOK3S_64
#include <asm/book3s/64/pkeys.h>
#else
#error "Not supported"
#endif


static inline u64 pkey_to_vmflag_bits(u16 pkey)
{
	return (((u64)pkey << VM_PKEY_SHIFT) & ARCH_VM_PKEY_FLAGS);
}

static inline int vma_pkey(struct vm_area_struct *vma)
{
	if (!mmu_has_feature(MMU_FTR_PKEY))
		return 0;
	return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT;
}

static inline int arch_max_pkey(void)
{
	return num_pkey;
}

#define pkey_alloc_mask(pkey) (0x1 << pkey)

#define mm_pkey_allocation_map(mm) (mm->context.pkey_allocation_map)

#define __mm_pkey_allocated(mm, pkey) {	\
	mm_pkey_allocation_map(mm) |= pkey_alloc_mask(pkey); \
}

#define __mm_pkey_free(mm, pkey) {	\
	mm_pkey_allocation_map(mm) &= ~pkey_alloc_mask(pkey);	\
}

#define __mm_pkey_is_allocated(mm, pkey)	\
	(mm_pkey_allocation_map(mm) & pkey_alloc_mask(pkey))

#define __mm_pkey_is_reserved(pkey) (reserved_allocation_mask & \
				       pkey_alloc_mask(pkey))

static inline bool mm_pkey_is_allocated(struct mm_struct *mm, int pkey)
{
	if (pkey < 0 || pkey >= arch_max_pkey())
		return false;

	/* Reserved keys are never allocated. */
	if (__mm_pkey_is_reserved(pkey))
		return false;

	return __mm_pkey_is_allocated(mm, pkey);
}

/*
 * Returns a positive, 5-bit key on success, or -1 on failure.
 * Relies on the mmap_lock to protect against concurrency in mm_pkey_alloc() and
 * mm_pkey_free().
 */
static inline int mm_pkey_alloc(struct mm_struct *mm)
{
	/*
	 * Note: this is the one and only place we make sure that the pkey is
	 * valid as far as the hardware is concerned. The rest of the kernel
	 * trusts that only good, valid pkeys come out of here.
	 */
	u32 all_pkeys_mask = (u32)(~(0x0));
	int ret;

	if (!mmu_has_feature(MMU_FTR_PKEY))
		return -1;
	/*
	 * Are we out of pkeys? We must handle this specially because ffz()
	 * behavior is undefined if there are no zeros.
	 */
	if (mm_pkey_allocation_map(mm) == all_pkeys_mask)
		return -1;

	ret = ffz((u32)mm_pkey_allocation_map(mm));
	__mm_pkey_allocated(mm, ret);

	return ret;
}

static inline int mm_pkey_free(struct mm_struct *mm, int pkey)
{
	if (!mmu_has_feature(MMU_FTR_PKEY))
		return -1;

	if (!mm_pkey_is_allocated(mm, pkey))
		return -EINVAL;

	__mm_pkey_free(mm, pkey);

	return 0;
}

/*
 * Try to dedicate one of the protection keys to be used as an
 * execute-only protection key.
 */
extern int execute_only_pkey(struct mm_struct *mm);
extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma,
					 int prot, int pkey);
static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma,
					      int prot, int pkey)
{
	if (!mmu_has_feature(MMU_FTR_PKEY))
		return 0;

	/*
	 * Is this an mprotect_pkey() call? If so, never override the value that
	 * came from the user.
	 */
	if (pkey != -1)
		return pkey;

	return __arch_override_mprotect_pkey(vma, prot, pkey);
}

extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
				       unsigned long init_val);
static inline int arch_set_user_pkey_access(struct task_struct *tsk, int pkey,
					    unsigned long init_val)
{
	if (!mmu_has_feature(MMU_FTR_PKEY))
		return -EINVAL;

	/*
	 * userspace should not change pkey-0 permissions.
	 * pkey-0 is associated with every page in the kernel.
	 * If userspace denies any permission on pkey-0, the
	 * kernel cannot operate.
	 */
	if (pkey == 0)
		return init_val ? -EINVAL : 0;

	return __arch_set_user_pkey_access(tsk, pkey, init_val);
}

static inline bool arch_pkeys_enabled(void)
{
	return mmu_has_feature(MMU_FTR_PKEY);
}

extern void pkey_mm_init(struct mm_struct *mm);
#endif /*_ASM_POWERPC_KEYS_H */