/*
 * arch/arm64/mm/hugetlbpage.c
 *
 * Copyright (C) 2013 Linaro Ltd.
 *
 * Based on arch/x86/mm/hugetlbpage.c.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <asm/mman.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/pgalloc.h>

int pmd_huge(pmd_t pmd)
{
        return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT);
}

int pud_huge(pud_t pud)
{
#ifndef __PAGETABLE_PMD_FOLDED
        return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT);
#else
        return 0;
#endif
}

/*
 * Select all bits except the pfn
 */
static inline pgprot_t pte_pgprot(pte_t pte)
{
        unsigned long pfn = pte_pfn(pte);

        return __pgprot(pte_val(pfn_pte(pfn, __pgprot(0))) ^ pte_val(pte));
}

static int find_num_contig(struct mm_struct *mm, unsigned long addr,
                           pte_t *ptep, size_t *pgsize)
{
        pgd_t *pgdp = pgd_offset(mm, addr);
        pud_t *pudp;
        pmd_t *pmdp;

        *pgsize = PAGE_SIZE;
        pudp = pud_offset(pgdp, addr);
        pmdp = pmd_offset(pudp, addr);
        if ((pte_t *)pmdp == ptep) {
                *pgsize = PMD_SIZE;
                return CONT_PMDS;
        }
        return CONT_PTES;
}

static inline int num_contig_ptes(unsigned long size, size_t *pgsize)
{
        int contig_ptes = 0;

        *pgsize = size;

        switch (size) {
#ifdef CONFIG_ARM64_4K_PAGES
        case PUD_SIZE:
#endif
        case PMD_SIZE:
                contig_ptes = 1;
                break;
        case CONT_PMD_SIZE:
                *pgsize = PMD_SIZE;
                contig_ptes = CONT_PMDS;
                break;
        case CONT_PTE_SIZE:
                *pgsize = PAGE_SIZE;
                contig_ptes = CONT_PTES;
                break;
        }

        return contig_ptes;
}

/*
 * Changing some bits of contiguous entries requires us to follow a
 * Break-Before-Make approach, breaking the whole contiguous set
 * before we can change any entries. See ARM DDI 0487A.k_iss10775,
 * "Misprogramming of the Contiguous bit", page D4-1762.
 *
 * This helper performs the break step.
 */
static pte_t get_clear_flush(struct mm_struct *mm,
                             unsigned long addr,
                             pte_t *ptep,
                             unsigned long pgsize,
                             unsigned long ncontig)
{
        pte_t orig_pte = huge_ptep_get(ptep);
        bool valid = pte_valid(orig_pte);
        unsigned long i, saddr = addr;

        for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
                pte_t pte = ptep_get_and_clear(mm, addr, ptep);

                /*
                 * If HW_AFDBM is enabled, then the HW could turn on
                 * the dirty or accessed bit for any page in the set,
                 * so check them all.
                 */
                if (pte_dirty(pte))
                        orig_pte = pte_mkdirty(orig_pte);

                if (pte_young(pte))
                        orig_pte = pte_mkyoung(orig_pte);
        }

        if (valid) {
                struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
                flush_tlb_range(&vma, saddr, addr);
        }
        return orig_pte;
}

/*
 * Changing some bits of contiguous entries requires us to follow a
 * Break-Before-Make approach, breaking the whole contiguous set
 * before we can change any entries. See ARM DDI 0487A.k_iss10775,
 * "Misprogramming of the Contiguous bit", page D4-1762.
 *
 * This helper performs the break step for use cases where the
 * original pte is not needed.
 */
static void clear_flush(struct mm_struct *mm,
                             unsigned long addr,
                             pte_t *ptep,
                             unsigned long pgsize,
                             unsigned long ncontig)
{
        struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
        unsigned long i, saddr = addr;

        for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
                pte_clear(mm, addr, ptep);

        flush_tlb_range(&vma, saddr, addr);
}

void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
                            pte_t *ptep, pte_t pte)
{
        size_t pgsize;
        int i;
        int ncontig;
        unsigned long pfn, dpfn;
        pgprot_t hugeprot;

        /*
         * Code needs to be expanded to handle huge swap and migration
         * entries. Needed for HUGETLB and MEMORY_FAILURE.
         */
        WARN_ON(!pte_present(pte));

        if (!pte_cont(pte)) {
                set_pte_at(mm, addr, ptep, pte);
                return;
        }

        ncontig = find_num_contig(mm, addr, ptep, &pgsize);
        pfn = pte_pfn(pte);
        dpfn = pgsize >> PAGE_SHIFT;
        hugeprot = pte_pgprot(pte);

        clear_flush(mm, addr, ptep, pgsize, ncontig);

        for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
                set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
}

void set_huge_swap_pte_at(struct mm_struct *mm, unsigned long addr,
                          pte_t *ptep, pte_t pte, unsigned long sz)
{
        int i, ncontig;
        size_t pgsize;

        ncontig = num_contig_ptes(sz, &pgsize);

        for (i = 0; i < ncontig; i++, ptep++)
                set_pte(ptep, pte);
}

pte_t *huge_pte_alloc(struct mm_struct *mm,
                      unsigned long addr, unsigned long sz)
{
        pgd_t *pgdp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep = NULL;

        pgdp = pgd_offset(mm, addr);
        pudp = pud_alloc(mm, pgdp, addr);
        if (!pudp)
                return NULL;

        if (sz == PUD_SIZE) {
                ptep = (pte_t *)pudp;
        } else if (sz == (CONT_PTE_SIZE)) {
                pmdp = pmd_alloc(mm, pudp, addr);

                WARN_ON(addr & (sz - 1));
                /*
                 * Note that if this code were ever ported to the
                 * 32-bit arm platform then it will cause trouble in
                 * the case where CONFIG_HIGHPTE is set, since there
                 * will be no pte_unmap() to correspond with this
                 * pte_alloc_map().
                 */
                ptep = pte_alloc_map(mm, pmdp, addr);
        } else if (sz == PMD_SIZE) {
                if (IS_ENABLED(CONFIG_ARCH_WANT_HUGE_PMD_SHARE) &&
                    pud_none(READ_ONCE(*pudp)))
                        ptep = huge_pmd_share(mm, addr, pudp);
                else
                        ptep = (pte_t *)pmd_alloc(mm, pudp, addr);
        } else if (sz == (CONT_PMD_SIZE)) {
                pmdp = pmd_alloc(mm, pudp, addr);
                WARN_ON(addr & (sz - 1));
                return (pte_t *)pmdp;
        }

        return ptep;
}

pte_t *huge_pte_offset(struct mm_struct *mm,
                       unsigned long addr, unsigned long sz)
{
        pgd_t *pgdp;
        pud_t *pudp, pud;
        pmd_t *pmdp, pmd;

        pgdp = pgd_offset(mm, addr);
        if (!pgd_present(READ_ONCE(*pgdp)))
                return NULL;

        pudp = pud_offset(pgdp, addr);
        pud = READ_ONCE(*pudp);
        if (sz != PUD_SIZE && pud_none(pud))
                return NULL;
        /* hugepage or swap? */
        if (pud_huge(pud) || !pud_present(pud))
                return (pte_t *)pudp;
        /* table; check the next level */

        if (sz == CONT_PMD_SIZE)
                addr &= CONT_PMD_MASK;

        pmdp = pmd_offset(pudp, addr);
        pmd = READ_ONCE(*pmdp);
        if (!(sz == PMD_SIZE || sz == CONT_PMD_SIZE) &&
            pmd_none(pmd))
                return NULL;
        if (pmd_huge(pmd) || !pmd_present(pmd))
                return (pte_t *)pmdp;

        if (sz == CONT_PTE_SIZE)
                return pte_offset_kernel(pmdp, (addr & CONT_PTE_MASK));

        return NULL;
}

pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
                         struct page *page, int writable)
{
        size_t pagesize = huge_page_size(hstate_vma(vma));

        if (pagesize == CONT_PTE_SIZE) {
                entry = pte_mkcont(entry);
        } else if (pagesize == CONT_PMD_SIZE) {
                entry = pmd_pte(pmd_mkcont(pte_pmd(entry)));
        } else if (pagesize != PUD_SIZE && pagesize != PMD_SIZE) {
                pr_warn("%s: unrecognized huge page size 0x%lx\n",
                        __func__, pagesize);
        }
        return entry;
}

void huge_pte_clear(struct mm_struct *mm, unsigned long addr,
                    pte_t *ptep, unsigned long sz)
{
        int i, ncontig;
        size_t pgsize;

        ncontig = num_contig_ptes(sz, &pgsize);

        for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
                pte_clear(mm, addr, ptep);
}

pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
                              unsigned long addr, pte_t *ptep)
{
        int ncontig;
        size_t pgsize;
        pte_t orig_pte = huge_ptep_get(ptep);

        if (!pte_cont(orig_pte))
                return ptep_get_and_clear(mm, addr, ptep);

        ncontig = find_num_contig(mm, addr, ptep, &pgsize);

        return get_clear_flush(mm, addr, ptep, pgsize, ncontig);
}

/*
 * huge_ptep_set_access_flags will update access flags (dirty, accesssed)
 * and write permission.
 *
 * For a contiguous huge pte range we need to check whether or not write
 * permission has to change only on the first pte in the set. Then for
 * all the contiguous ptes we need to check whether or not there is a
 * discrepancy between dirty or young.
 */
static int __cont_access_flags_changed(pte_t *ptep, pte_t pte, int ncontig)
{
        int i;

        if (pte_write(pte) != pte_write(huge_ptep_get(ptep)))
                return 1;

        for (i = 0; i < ncontig; i++) {
                pte_t orig_pte = huge_ptep_get(ptep + i);

                if (pte_dirty(pte) != pte_dirty(orig_pte))
                        return 1;

                if (pte_young(pte) != pte_young(orig_pte))
                        return 1;
        }

        return 0;
}

int huge_ptep_set_access_flags(struct vm_area_struct *vma,
                               unsigned long addr, pte_t *ptep,
                               pte_t pte, int dirty)
{
        int ncontig, i;
        size_t pgsize = 0;
        unsigned long pfn = pte_pfn(pte), dpfn;
        pgprot_t hugeprot;
        pte_t orig_pte;

        if (!pte_cont(pte))
                return ptep_set_access_flags(vma, addr, ptep, pte, dirty);

        ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
        dpfn = pgsize >> PAGE_SHIFT;

        if (!__cont_access_flags_changed(ptep, pte, ncontig))
                return 0;

        orig_pte = get_clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);

        /* Make sure we don't lose the dirty or young state */
        if (pte_dirty(orig_pte))
                pte = pte_mkdirty(pte);

        if (pte_young(orig_pte))
                pte = pte_mkyoung(pte);

        hugeprot = pte_pgprot(pte);
        for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
                set_pte_at(vma->vm_mm, addr, ptep, pfn_pte(pfn, hugeprot));

        return 1;
}

void huge_ptep_set_wrprotect(struct mm_struct *mm,
                             unsigned long addr, pte_t *ptep)
{
        unsigned long pfn, dpfn;
        pgprot_t hugeprot;
        int ncontig, i;
        size_t pgsize;
        pte_t pte;

        if (!pte_cont(READ_ONCE(*ptep))) {
                ptep_set_wrprotect(mm, addr, ptep);
                return;
        }

        ncontig = find_num_contig(mm, addr, ptep, &pgsize);
        dpfn = pgsize >> PAGE_SHIFT;

        pte = get_clear_flush(mm, addr, ptep, pgsize, ncontig);
        pte = pte_wrprotect(pte);

        hugeprot = pte_pgprot(pte);
        pfn = pte_pfn(pte);

        for (i = 0; i < ncontig; i++, ptep++, addr += pgsize, pfn += dpfn)
                set_pte_at(mm, addr, ptep, pfn_pte(pfn, hugeprot));
}

void huge_ptep_clear_flush(struct vm_area_struct *vma,
                           unsigned long addr, pte_t *ptep)
{
        size_t pgsize;
        int ncontig;

        if (!pte_cont(READ_ONCE(*ptep))) {
                ptep_clear_flush(vma, addr, ptep);
                return;
        }

        ncontig = find_num_contig(vma->vm_mm, addr, ptep, &pgsize);
        clear_flush(vma->vm_mm, addr, ptep, pgsize, ncontig);
}

static int __init hugetlbpage_init(void)
{
#ifdef CONFIG_ARM64_4K_PAGES
        hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
#endif
        hugetlb_add_hstate((CONT_PMD_SHIFT + PMD_SHIFT) - PAGE_SHIFT);
        hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
        hugetlb_add_hstate((CONT_PTE_SHIFT + PAGE_SHIFT) - PAGE_SHIFT);

        return 0;
}
arch_initcall(hugetlbpage_init);

bool __init arch_hugetlb_valid_size(unsigned long size)
{
        switch (size) {
#ifdef CONFIG_ARM64_4K_PAGES
        case PUD_SIZE:
#endif
        case CONT_PMD_SIZE:
        case PMD_SIZE:
        case CONT_PTE_SIZE:
                return true;
        }

        return false;
}