// SPDX-License-Identifier: GPL-2.0-only
/*
 * arch/arm64/mm/hugetlbpage.c
 *
 * Copyright (C) 2013 Linaro Ltd.
 *
 * Based on arch/x86/mm/hugetlbpage.c.
 */

#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>

/*
 * HugeTLB Support Matrix
 *
 * ---------------------------------------------------
 * | Page Size | CONT PTE |  PMD  | CONT PMD |  PUD  |
 * ---------------------------------------------------
 * |     4K    |   64K    |   2M  |    32M   |   1G  |
 * |    16K    |    2M    |  32M  |     1G   |       |
 * |    64K    |    2M    | 512M  |    16G   |       |
 * ---------------------------------------------------
 */

/*
 * Reserve CMA areas for the largest supported gigantic
 * huge page when requested. Any other smaller gigantic
 * huge pages could still be served from those areas.
 */
#ifdef CONFIG_CMA
unsigned int arch_hugetlb_cma_order(void)
{
        if (pud_sect_supported())
                return PUD_SHIFT - PAGE_SHIFT;

        return CONT_PMD_SHIFT - PAGE_SHIFT;
}
#endif /* CONFIG_CMA */

static bool __hugetlb_valid_size(unsigned long size)
{
        switch (size) {
#ifndef __PAGETABLE_PMD_FOLDED
        case PUD_SIZE:
                return pud_sect_supported();
#endif
        case CONT_PMD_SIZE:
        case PMD_SIZE:
        case CONT_PTE_SIZE:
                return true;
        }

        return false;
}

#ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
bool arch_hugetlb_migration_supported(struct hstate *h)
{
        size_t pagesize = huge_page_size(h);

        if (!__hugetlb_valid_size(pagesize)) {
                pr_warn("%s: unrecognized huge page size 0x%lx\n",
                        __func__, pagesize);
                return false;
        }
        return true;
}
#endif

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);
        p4d_t *p4dp;
        pud_t *pudp;
        pmd_t *pmdp;

        *pgsize = PAGE_SIZE;
        p4dp = p4d_offset(pgdp, addr);
        pudp = pud_offset(p4dp, 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 = 1;

        *pgsize = size;

        switch (size) {
        case CONT_PMD_SIZE:
                *pgsize = PMD_SIZE;
                contig_ptes = CONT_PMDS;
                break;
        case CONT_PTE_SIZE:
                *pgsize = PAGE_SIZE;
                contig_ptes = CONT_PTES;
                break;
        default:
                WARN_ON(!__hugetlb_valid_size(size));
        }

        return contig_ptes;
}

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

        if (!pte_present(orig_pte) || !pte_cont(orig_pte))
                return orig_pte;

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

                if (pte_dirty(pte))
                        orig_pte = pte_mkdirty(orig_pte);

                if (pte_young(pte))
                        orig_pte = pte_mkyoung(orig_pte);
        }
        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.
 */
static pte_t get_clear_contig(struct mm_struct *mm,
                             unsigned long addr,
                             pte_t *ptep,
                             unsigned long pgsize,
                             unsigned long ncontig)
{
        pte_t pte, tmp_pte;
        bool present;

        pte = __ptep_get_and_clear_anysz(mm, addr, ptep, pgsize);
        present = pte_present(pte);
        while (--ncontig) {
                ptep++;
                addr += pgsize;
                tmp_pte = __ptep_get_and_clear_anysz(mm, addr, ptep, pgsize);
                if (present) {
                        if (pte_dirty(tmp_pte))
                                pte = pte_mkdirty(pte);
                        if (pte_young(tmp_pte))
                                pte = pte_mkyoung(pte);
                }
        }
        return pte;
}

static pte_t get_clear_contig_flush(struct mm_struct *mm,
                                    unsigned long addr,
                                    pte_t *ptep,
                                    unsigned long pgsize,
                                    unsigned long ncontig)
{
        pte_t orig_pte = get_clear_contig(mm, addr, ptep, pgsize, ncontig);
        struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
        unsigned long end = addr + (pgsize * ncontig);

        __flush_hugetlb_tlb_range(&vma, addr, end, pgsize, true);
        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++)
                __ptep_get_and_clear_anysz(mm, addr, ptep, pgsize);

        if (mm == &init_mm)
                flush_tlb_kernel_range(saddr, addr);
        else
                __flush_hugetlb_tlb_range(&vma, saddr, addr, pgsize, true);
}

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

        ncontig = num_contig_ptes(sz, &pgsize);

        if (!pte_present(pte)) {
                for (i = 0; i < ncontig; i++, ptep++, addr += pgsize)
                        __set_ptes_anysz(mm, addr, ptep, pte, 1, pgsize);
                return;
        }

        /* Only need to "break" if transitioning valid -> valid. */
        if (pte_cont(pte) && pte_valid(__ptep_get(ptep)))
                clear_flush(mm, addr, ptep, pgsize, ncontig);

        __set_ptes_anysz(mm, addr, ptep, pte, ncontig, pgsize);
}

pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
                      unsigned long addr, unsigned long sz)
{
        pgd_t *pgdp;
        p4d_t *p4dp;
        pud_t *pudp;
        pmd_t *pmdp;
        pte_t *ptep = NULL;

        pgdp = pgd_offset(mm, addr);
        p4dp = p4d_alloc(mm, pgdp, addr);
        if (!p4dp)
                return NULL;

        pudp = pud_alloc(mm, p4dp, 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);
                if (!pmdp)
                        return NULL;

                WARN_ON(addr & (sz - 1));
                ptep = pte_alloc_huge(mm, pmdp, addr);
        } else if (sz == PMD_SIZE) {
                if (want_pmd_share(vma, addr) && pud_none(READ_ONCE(*pudp)))
                        ptep = huge_pmd_share(mm, vma, 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;
        p4d_t *p4dp;
        pud_t *pudp, pud;
        pmd_t *pmdp, pmd;

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

        p4dp = p4d_offset(pgdp, addr);
        if (!p4d_present(READ_ONCE(*p4dp)))
                return NULL;

        pudp = pud_offset(p4dp, addr);
        pud = READ_ONCE(*pudp);
        if (sz != PUD_SIZE && pud_none(pud))
                return NULL;
        /* hugepage or swap? */
        if (pud_leaf(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_leaf(pmd) || !pmd_present(pmd))
                return (pte_t *)pmdp;

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

        return NULL;
}

unsigned long hugetlb_mask_last_page(struct hstate *h)
{
        unsigned long hp_size = huge_page_size(h);

        switch (hp_size) {
#ifndef __PAGETABLE_PMD_FOLDED
        case PUD_SIZE:
                if (pud_sect_supported())
                        return PGDIR_SIZE - PUD_SIZE;
                break;
#endif
        case CONT_PMD_SIZE:
                return PUD_SIZE - CONT_PMD_SIZE;
        case PMD_SIZE:
                return PUD_SIZE - PMD_SIZE;
        case CONT_PTE_SIZE:
                return PMD_SIZE - CONT_PTE_SIZE;
        default:
                break;
        }

        return 0UL;
}

pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
{
        size_t pagesize = 1UL << shift;

        switch (pagesize) {
#ifndef __PAGETABLE_PMD_FOLDED
        case PUD_SIZE:
                if (pud_sect_supported())
                        return pud_pte(pud_mkhuge(pte_pud(entry)));
                break;
#endif
        case CONT_PMD_SIZE:
                return pmd_pte(pmd_mkhuge(pmd_mkcont(pte_pmd(entry))));
        case PMD_SIZE:
                return pmd_pte(pmd_mkhuge(pte_pmd(entry)));
        case CONT_PTE_SIZE:
                return pte_mkcont(entry);
        default:
                break;
        }
        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, unsigned long sz)
{
        int ncontig;
        size_t pgsize;

        ncontig = num_contig_ptes(sz, &pgsize);
        return get_clear_contig(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(__ptep_get(ptep)))
                return 1;

        for (i = 0; i < ncontig; i++) {
                pte_t orig_pte = __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;
        size_t pgsize = 0;
        struct mm_struct *mm = vma->vm_mm;
        pte_t orig_pte;

        VM_WARN_ON(!pte_present(pte));

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

        ncontig = num_contig_ptes(huge_page_size(hstate_vma(vma)), &pgsize);

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

        orig_pte = get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig);
        VM_WARN_ON(!pte_present(orig_pte));

        /* 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);

        __set_ptes_anysz(mm, addr, ptep, pte, ncontig, pgsize);
        return 1;
}

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

        pte = __ptep_get(ptep);
        VM_WARN_ON(!pte_present(pte));

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

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

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

        __set_ptes_anysz(mm, addr, ptep, pte, ncontig, pgsize);
}

pte_t huge_ptep_clear_flush(struct vm_area_struct *vma,
                            unsigned long addr, pte_t *ptep)
{
        struct mm_struct *mm = vma->vm_mm;
        size_t pgsize;
        int ncontig;

        ncontig = num_contig_ptes(huge_page_size(hstate_vma(vma)), &pgsize);
        return get_clear_contig_flush(mm, addr, ptep, pgsize, ncontig);
}

static int __init hugetlbpage_init(void)
{
        /*
         * HugeTLB pages are supported on maximum four page table
         * levels (PUD, CONT PMD, PMD, CONT PTE) for a given base
         * page size, corresponding to hugetlb_add_hstate() calls
         * here.
         *
         * HUGE_MAX_HSTATE should at least match maximum supported
         * HugeTLB page sizes on the platform. Any new addition to
         * supported HugeTLB page sizes will also require changing
         * HUGE_MAX_HSTATE as well.
         */
        BUILD_BUG_ON(HUGE_MAX_HSTATE < 4);
        if (pud_sect_supported())
                hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);

        hugetlb_add_hstate(CONT_PMD_SHIFT - PAGE_SHIFT);
        hugetlb_add_hstate(PMD_SHIFT - PAGE_SHIFT);
        hugetlb_add_hstate(CONT_PTE_SHIFT - PAGE_SHIFT);

        return 0;
}
arch_initcall(hugetlbpage_init);

bool __init arch_hugetlb_valid_size(unsigned long size)
{
        return __hugetlb_valid_size(size);
}

pte_t huge_ptep_modify_prot_start(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep)
{
        unsigned long psize = huge_page_size(hstate_vma(vma));

        if (alternative_has_cap_unlikely(ARM64_WORKAROUND_2645198)) {
                /*
                 * Break-before-make (BBM) is required for all user space mappings
                 * when the permission changes from executable to non-executable
                 * in cases where cpu is affected with errata #2645198.
                 */
                if (pte_user_exec(__ptep_get(ptep)))
                        return huge_ptep_clear_flush(vma, addr, ptep);
        }
        return huge_ptep_get_and_clear(vma->vm_mm, addr, ptep, psize);
}

void huge_ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr, pte_t *ptep,
                                  pte_t old_pte, pte_t pte)
{
        unsigned long psize = huge_page_size(hstate_vma(vma));

        set_huge_pte_at(vma->vm_mm, addr, ptep, pte, psize);
}