/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_PGTABLE_3LEVEL_H
#define _ASM_X86_PGTABLE_3LEVEL_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)
{
        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;

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

        /* 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 */