arch/x86/include/asm/pgtable-3level.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_X86_PGTABLE_3LEVEL_H
 #define _ASM_X86_PGTABLE_3LEVEL_H

 #include <asm/atomic64_32.h>

 /*
  * Intel Physical Address Extension (PAE) Mode - three-level page
  * tables on PPro+ CPUs.
  *
  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
  */

 #define pte_ERROR(e)							\
 	pr_err("%s:%d: bad pte %p(%08lx%08lx)\n",			\
 	       __FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low)
 #define pmd_ERROR(e)							\
 	pr_err("%s:%d: bad pmd %p(%016Lx)\n",				\
 	       __FILE__, __LINE__, &(e), pmd_val(e))
 #define pgd_ERROR(e)							\
 	pr_err("%s:%d: bad pgd %p(%016Lx)\n",				\
 	       __FILE__, __LINE__, &(e), pgd_val(e))

 /* Rules for using set_pte: the pte being assigned *must* be
  * either not present or in a state where the hardware will
  * not attempt to update the pte.  In places where this is
  * not possible, use pte_get_and_clear to obtain the old pte
  * value and then use set_pte to update it.  -ben
  */
 static inline void native_set_pte(pte_t *ptep, pte_t pte)
 {
 	ptep->pte_high = pte.pte_high;
 	smp_wmb();
 	ptep->pte_low = pte.pte_low;
 }

 #define pmd_read_atomic pmd_read_atomic
 /*
  * pte_offset_map_lock() on 32-bit PAE kernels was reading the pmd_t with
  * a "*pmdp" dereference done by GCC. Problem is, in certain places
  * where pte_offset_map_lock() is called, concurrent page faults are
  * allowed, if the mmap_lock is hold for reading. An example is mincore
  * vs page faults vs MADV_DONTNEED. On the page fault side
  * pmd_populate() rightfully does a set_64bit(), but if we're reading the
  * pmd_t with a "*pmdp" on the mincore side, a SMP race can happen
  * because GCC will not read the 64-bit value of the pmd atomically.
  *
  * To fix this all places running pte_offset_map_lock() while holding the
  * mmap_lock in read mode, shall read the pmdp pointer using this
  * function to know if the pmd is null or not, and in turn to know if
  * they can run pte_offset_map_lock() or pmd_trans_huge() or other pmd
  * operations.
  *
  * Without THP if the mmap_lock is held for reading, the pmd can only
  * transition from null to not null while pmd_read_atomic() runs. So
  * we can always return atomic pmd values with this function.
  *
  * With THP if the mmap_lock is held for reading, the pmd can become
  * trans_huge or none or point to a pte (and in turn become "stable")
  * at any time under pmd_read_atomic(). We could read it truly
  * atomically here with an atomic64_read() for the THP enabled case (and
  * it would be a whole lot simpler), but to avoid using cmpxchg8b we
  * only return an atomic pmdval if the low part of the pmdval is later
  * found to be stable (i.e. pointing to a pte). We are also returning a
  * 'none' (zero) pmdval if the low part of the pmd is zero.
  *
  * In some cases the high and low part of the pmdval returned may not be
  * consistent if THP is enabled (the low part may point to previously
  * mapped hugepage, while the high part may point to a more recently
  * mapped hugepage), but pmd_none_or_trans_huge_or_clear_bad() only
  * needs the low part of the pmd to be read atomically to decide if the
  * pmd is unstable or not, with the only exception when the low part
  * of the pmd is zero, in which case we return a 'none' pmd.
  */
 static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
 {
 	pmdval_t ret;
 	u32 *tmp = (u32 *)pmdp;

 	ret = (pmdval_t) (*tmp);
 	if (ret) {
 		/*
 		 * If the low part is null, we must not read the high part
 		 * or we can end up with a partial pmd.
 		 */
 		smp_rmb();
 		ret |= ((pmdval_t)*(tmp + 1)) << 32;
 	}

 	return (pmd_t) { ret };
 }

 static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
 {
 	set_64bit((unsigned long long *)(ptep), native_pte_val(pte));
 }

 static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
 {
 	set_64bit((unsigned long long *)(pmdp), native_pmd_val(pmd));
 }

 static inline void native_set_pud(pud_t *pudp, pud_t pud)
 {
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	pud.p4d.pgd = pti_set_user_pgtbl(&pudp->p4d.pgd, pud.p4d.pgd);
 #endif
 	set_64bit((unsigned long long *)(pudp), native_pud_val(pud));
 }

 /*
  * For PTEs and PDEs, we must clear the P-bit first when clearing a page table
  * entry, so clear the bottom half first and enforce ordering with a compiler
  * barrier.
  */
 static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
 				    pte_t *ptep)
 {
 	ptep->pte_low = 0;
 	smp_wmb();
 	ptep->pte_high = 0;
 }

 static inline void native_pmd_clear(pmd_t *pmd)
 {
 	u32 *tmp = (u32 *)pmd;
 	*tmp = 0;
 	smp_wmb();
 	*(tmp + 1) = 0;
 }

 static inline void native_pud_clear(pud_t *pudp)
 {
 }

 static inline void pud_clear(pud_t *pudp)
 {
 	set_pud(pudp, __pud(0));

 	/*
 	 * According to Intel App note "TLBs, Paging-Structure Caches,
 	 * and Their Invalidation", April 2007, document 317080-001,
 	 * section 8.1: in PAE mode we explicitly have to flush the
 	 * TLB via cr3 if the top-level pgd is changed...
 	 *
 	 * Currently all places where pud_clear() is called either have
 	 * flush_tlb_mm() followed or don't need TLB flush (x86_64 code or
 	 * pud_clear_bad()), so we don't need TLB flush here.
 	 */
 }

 #ifdef CONFIG_SMP
 static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
 {
 	pte_t res;

 	res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0);

 	return res;
 }
 #else
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
 #endif

 union split_pmd {
 	struct {
 		u32 pmd_low;
 		u32 pmd_high;
 	};
 	pmd_t pmd;
 };

 #ifdef CONFIG_SMP
 static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 {
 	union split_pmd res, *orig = (union split_pmd *)pmdp;

 	/* xchg acts as a barrier before setting of the high bits */
 	res.pmd_low = xchg(&orig->pmd_low, 0);
 	res.pmd_high = orig->pmd_high;
 	orig->pmd_high = 0;

 	return res.pmd;
 }
 #else
 #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
 #endif

 #ifndef pmdp_establish
 #define pmdp_establish pmdp_establish
 static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
 		unsigned long address, pmd_t *pmdp, pmd_t pmd)
 {
 	pmd_t old;

 	/*
 	 * If pmd has present bit cleared we can get away without expensive
 	 * cmpxchg64: we can update pmdp half-by-half without racing with
 	 * anybody.
 	 */
 	if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
 		union split_pmd old, new, *ptr;

 		ptr = (union split_pmd *)pmdp;

 		new.pmd = pmd;

 		/* xchg acts as a barrier before setting of the high bits */
 		old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
 		old.pmd_high = ptr->pmd_high;
 		ptr->pmd_high = new.pmd_high;
 		return old.pmd;
 	}

 	do {
 		old = *pmdp;
 	} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);

 	return old;
 }
 #endif

 #ifdef CONFIG_SMP
 union split_pud {
 	struct {
 		u32 pud_low;
 		u32 pud_high;
 	};
 	pud_t pud;
 };

 static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
 {
 	union split_pud res, *orig = (union split_pud *)pudp;

 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 	pti_set_user_pgtbl(&pudp->p4d.pgd, __pgd(0));
 #endif

 	/* xchg acts as a barrier before setting of the high bits */
 	res.pud_low = xchg(&orig->pud_low, 0);
 	res.pud_high = orig->pud_high;
 	orig->pud_high = 0;

 	return res.pud;
 }
 #else
 #define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
 #endif

 /* Encode and de-code a swap entry */
 #define SWP_TYPE_BITS		5

 #define SWP_OFFSET_FIRST_BIT	(_PAGE_BIT_PROTNONE + 1)

 /* We always extract/encode the offset by shifting it all the way up, and then down again */
 #define SWP_OFFSET_SHIFT	(SWP_OFFSET_FIRST_BIT + SWP_TYPE_BITS)

 #define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5)
 #define __swp_type(x)			(((x).val) & 0x1f)
 #define __swp_offset(x)			((x).val >> 5)
 #define __swp_entry(type, offset)	((swp_entry_t){(type) | (offset) << 5})

 /*
  * Normally, __swp_entry() converts from arch-independent swp_entry_t to
  * arch-dependent swp_entry_t, and __swp_entry_to_pte() just stores the result
  * to pte. But here we have 32bit swp_entry_t and 64bit pte, and need to use the
  * whole 64 bits. Thus, we shift the "real" arch-dependent conversion to
  * __swp_entry_to_pte() through the following helper macro based on 64bit
  * __swp_entry().
  */
 #define __swp_pteval_entry(type, offset) ((pteval_t) { \
 	(~(pteval_t)(offset) << SWP_OFFSET_SHIFT >> SWP_TYPE_BITS) \
 	| ((pteval_t)(type) << (64 - SWP_TYPE_BITS)) })

 #define __swp_entry_to_pte(x)	((pte_t){ .pte = \
 		__swp_pteval_entry(__swp_type(x), __swp_offset(x)) })
 /*
  * Analogically, __pte_to_swp_entry() doesn't just extract the arch-dependent
  * swp_entry_t, but also has to convert it from 64bit to the 32bit
  * intermediate representation, using the following macros based on 64bit
  * __swp_type() and __swp_offset().
  */
 #define __pteval_swp_type(x) ((unsigned long)((x).pte >> (64 - SWP_TYPE_BITS)))
 #define __pteval_swp_offset(x) ((unsigned long)(~((x).pte) << SWP_TYPE_BITS >> SWP_OFFSET_SHIFT))

 #define __pte_to_swp_entry(pte)	(__swp_entry(__pteval_swp_type(pte), \
 					     __pteval_swp_offset(pte)))

 #include <asm/pgtable-invert.h>

 #endif /* _ASM_X86_PGTABLE_3LEVEL_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef _ASM_X86_PGTABLE_3LEVEL_H
	#define _ASM_X86_PGTABLE_3LEVEL_H

	#include <asm/atomic64_32.h>

	/*
	* Intel Physical Address Extension (PAE) Mode - three-level page
	* tables on PPro+ CPUs.
	*
	* Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
	*/

	#define pte_ERROR(e) \
	pr_err("%s:%d: bad pte %p(%08lx%08lx)\n", \
	__FILE__, __LINE__, &(e), (e).pte_high, (e).pte_low)
	#define pmd_ERROR(e) \
	pr_err("%s:%d: bad pmd %p(%016Lx)\n", \
	__FILE__, __LINE__, &(e), pmd_val(e))
	#define pgd_ERROR(e) \
	pr_err("%s:%d: bad pgd %p(%016Lx)\n", \
	__FILE__, __LINE__, &(e), pgd_val(e))

	/* Rules for using set_pte: the pte being assigned must be
	* either not present or in a state where the hardware will
	* not attempt to update the pte. In places where this is
	* not possible, use pte_get_and_clear to obtain the old pte
	* value and then use set_pte to update it. -ben
	*/
	static inline void native_set_pte(pte_t *ptep, pte_t pte)
	{
	ptep->pte_high = pte.pte_high;
	smp_wmb();
	ptep->pte_low = pte.pte_low;
	}

	#define pmd_read_atomic pmd_read_atomic
	/*
	* pte_offset_map_lock() on 32-bit PAE kernels was reading the pmd_t with
	* a "*pmdp" dereference done by GCC. Problem is, in certain places
	* where pte_offset_map_lock() is called, concurrent page faults are
	* allowed, if the mmap_lock is hold for reading. An example is mincore
	* vs page faults vs MADV_DONTNEED. On the page fault side
	* pmd_populate() rightfully does a set_64bit(), but if we're reading the
	* pmd_t with a "*pmdp" on the mincore side, a SMP race can happen
	* because GCC will not read the 64-bit value of the pmd atomically.
	*
	* To fix this all places running pte_offset_map_lock() while holding the
	* mmap_lock in read mode, shall read the pmdp pointer using this
	* function to know if the pmd is null or not, and in turn to know if
	* they can run pte_offset_map_lock() or pmd_trans_huge() or other pmd
	* operations.
	*
	* Without THP if the mmap_lock is held for reading, the pmd can only
	* transition from null to not null while pmd_read_atomic() runs. So
	* we can always return atomic pmd values with this function.
	*
	* With THP if the mmap_lock is held for reading, the pmd can become
	* trans_huge or none or point to a pte (and in turn become "stable")
	* at any time under pmd_read_atomic(). We could read it truly
	* atomically here with an atomic64_read() for the THP enabled case (and
	* it would be a whole lot simpler), but to avoid using cmpxchg8b we
	* only return an atomic pmdval if the low part of the pmdval is later
	* found to be stable (i.e. pointing to a pte). We are also returning a
	* 'none' (zero) pmdval if the low part of the pmd is zero.
	*
	* In some cases the high and low part of the pmdval returned may not be
	* consistent if THP is enabled (the low part may point to previously
	* mapped hugepage, while the high part may point to a more recently
	* mapped hugepage), but pmd_none_or_trans_huge_or_clear_bad() only
	* needs the low part of the pmd to be read atomically to decide if the
	* pmd is unstable or not, with the only exception when the low part
	* of the pmd is zero, in which case we return a 'none' pmd.
	*/
	static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
	{
	pmdval_t ret;
	u32 tmp = (u32 )pmdp;

	ret = (pmdval_t) (*tmp);
	if (ret) {
	/*
	* If the low part is null, we must not read the high part
	* or we can end up with a partial pmd.
	*/
	smp_rmb();
	ret \|= ((pmdval_t)*(tmp + 1)) << 32;
	}

	return (pmd_t) { ret };
	}

	static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
	{
	set_64bit((unsigned long long *)(ptep), native_pte_val(pte));
	}

	static inline void native_set_pmd(pmd_t *pmdp, pmd_t pmd)
	{
	set_64bit((unsigned long long *)(pmdp), native_pmd_val(pmd));
	}

	static inline void native_set_pud(pud_t *pudp, pud_t pud)
	{
	#ifdef CONFIG_PAGE_TABLE_ISOLATION
	pud.p4d.pgd = pti_set_user_pgtbl(&pudp->p4d.pgd, pud.p4d.pgd);
	#endif
	set_64bit((unsigned long long *)(pudp), native_pud_val(pud));
	}

	/*
	* For PTEs and PDEs, we must clear the P-bit first when clearing a page table
	* entry, so clear the bottom half first and enforce ordering with a compiler
	* barrier.
	*/
	static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
	pte_t *ptep)
	{
	ptep->pte_low = 0;
	smp_wmb();
	ptep->pte_high = 0;
	}

	static inline void native_pmd_clear(pmd_t *pmd)
	{
	u32 tmp = (u32 )pmd;
	*tmp = 0;
	smp_wmb();
	*(tmp + 1) = 0;
	}

	static inline void native_pud_clear(pud_t *pudp)
	{
	}

	static inline void pud_clear(pud_t *pudp)
	{
	set_pud(pudp, __pud(0));

	/*
	* According to Intel App note "TLBs, Paging-Structure Caches,
	* and Their Invalidation", April 2007, document 317080-001,
	* section 8.1: in PAE mode we explicitly have to flush the
	* TLB via cr3 if the top-level pgd is changed...
	*
	* Currently all places where pud_clear() is called either have
	* flush_tlb_mm() followed or don't need TLB flush (x86_64 code or
	* pud_clear_bad()), so we don't need TLB flush here.
	*/
	}

	#ifdef CONFIG_SMP
	static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
	{
	pte_t res;

	res.pte = (pteval_t)arch_atomic64_xchg((atomic64_t *)ptep, 0);

	return res;
	}
	#else
	#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
	#endif

	union split_pmd {
	struct {
	u32 pmd_low;
	u32 pmd_high;
	};
	pmd_t pmd;
	};

	#ifdef CONFIG_SMP
	static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
	{
	union split_pmd res, orig = (union split_pmd )pmdp;

	/* xchg acts as a barrier before setting of the high bits */
	res.pmd_low = xchg(&orig->pmd_low, 0);
	res.pmd_high = orig->pmd_high;
	orig->pmd_high = 0;

	return res.pmd;
	}
	#else
	#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
	#endif

	#ifndef pmdp_establish
	#define pmdp_establish pmdp_establish
	static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
	unsigned long address, pmd_t *pmdp, pmd_t pmd)
	{
	pmd_t old;

	/*
	* If pmd has present bit cleared we can get away without expensive
	* cmpxchg64: we can update pmdp half-by-half without racing with
	* anybody.
	*/
	if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
	union split_pmd old, new, *ptr;

	ptr = (union split_pmd *)pmdp;

	new.pmd = pmd;

	/* xchg acts as a barrier before setting of the high bits */
	old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
	old.pmd_high = ptr->pmd_high;
	ptr->pmd_high = new.pmd_high;
	return old.pmd;
	}

	do {
	old = *pmdp;
	} while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);

	return old;
	}
	#endif

	#ifdef CONFIG_SMP
	union split_pud {
	struct {
	u32 pud_low;
	u32 pud_high;
	};
	pud_t pud;
	};

	static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
	{
	union split_pud res, orig = (union split_pud )pudp;

	#ifdef CONFIG_PAGE_TABLE_ISOLATION
	pti_set_user_pgtbl(&pudp->p4d.pgd, __pgd(0));
	#endif

	/* xchg acts as a barrier before setting of the high bits */
	res.pud_low = xchg(&orig->pud_low, 0);
	res.pud_high = orig->pud_high;
	orig->pud_high = 0;

	return res.pud;
	}
	#else
	#define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
	#endif

	/* Encode and de-code a swap entry */
	#define SWP_TYPE_BITS 5

	#define SWP_OFFSET_FIRST_BIT (_PAGE_BIT_PROTNONE + 1)

	/* We always extract/encode the offset by shifting it all the way up, and then down again */
	#define SWP_OFFSET_SHIFT (SWP_OFFSET_FIRST_BIT + SWP_TYPE_BITS)

	#define MAX_SWAPFILES_CHECK() BUILD_BUG_ON(MAX_SWAPFILES_SHIFT > 5)
	#define __swp_type(x) (((x).val) & 0x1f)
	#define __swp_offset(x) ((x).val >> 5)
	#define __swp_entry(type, offset) ((swp_entry_t){(type) \| (offset) << 5})

	/*
	* Normally, __swp_entry() converts from arch-independent swp_entry_t to
	* arch-dependent swp_entry_t, and __swp_entry_to_pte() just stores the result
	* to pte. But here we have 32bit swp_entry_t and 64bit pte, and need to use the
	* whole 64 bits. Thus, we shift the "real" arch-dependent conversion to
	* __swp_entry_to_pte() through the following helper macro based on 64bit
	* __swp_entry().
	*/
	#define __swp_pteval_entry(type, offset) ((pteval_t) { \
	(~(pteval_t)(offset) << SWP_OFFSET_SHIFT >> SWP_TYPE_BITS) \
	\| ((pteval_t)(type) << (64 - SWP_TYPE_BITS)) })

	#define __swp_entry_to_pte(x) ((pte_t){ .pte = \
	__swp_pteval_entry(__swp_type(x), __swp_offset(x)) })
	/*
	* Analogically, __pte_to_swp_entry() doesn't just extract the arch-dependent
	* swp_entry_t, but also has to convert it from 64bit to the 32bit
	* intermediate representation, using the following macros based on 64bit
	* __swp_type() and __swp_offset().
	*/
	#define __pteval_swp_type(x) ((unsigned long)((x).pte >> (64 - SWP_TYPE_BITS)))
	#define __pteval_swp_offset(x) ((unsigned long)(~((x).pte) << SWP_TYPE_BITS >> SWP_OFFSET_SHIFT))

	#define __pte_to_swp_entry(pte) (__swp_entry(__pteval_swp_type(pte), \
	__pteval_swp_offset(pte)))

	#include <asm/pgtable-invert.h>

	#endif /* _ASM_X86_PGTABLE_3LEVEL_H */