// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright 2007-2008 Paul Mackerras, IBM Corp.
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/types.h>
#include <linux/pagewalk.h>
#include <linux/hugetlb.h>
#include <linux/syscalls.h>

#include <linux/pgtable.h>
#include <linux/uaccess.h>

/*
 * Free all pages allocated for subpage protection maps and pointers.
 * Also makes sure that the subpage_prot_table structure is
 * reinitialized for the next user.
 */
void subpage_prot_free(struct mm_struct *mm)
{
        struct subpage_prot_table *spt = mm_ctx_subpage_prot(&mm->context);
        unsigned long i, j, addr;
        u32 **p;

        if (!spt)
                return;

        for (i = 0; i < 4; ++i) {
                if (spt->low_prot[i]) {
                        free_page((unsigned long)spt->low_prot[i]);
                        spt->low_prot[i] = NULL;
                }
        }
        addr = 0;
        for (i = 0; i < (TASK_SIZE_USER64 >> 43); ++i) {
                p = spt->protptrs[i];
                if (!p)
                        continue;
                spt->protptrs[i] = NULL;
                for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
                     ++j, addr += PAGE_SIZE)
                        if (p[j])
                                free_page((unsigned long)p[j]);
                free_page((unsigned long)p);
        }
        spt->maxaddr = 0;
        kfree(spt);
}

static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
                             int npages)
{
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        spinlock_t *ptl;

        pgd = pgd_offset(mm, addr);
        p4d = p4d_offset(pgd, addr);
        if (p4d_none(*p4d))
                return;
        pud = pud_offset(p4d, addr);
        if (pud_none(*pud))
                return;
        pmd = pmd_offset(pud, addr);
        if (pmd_none(*pmd))
                return;
        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
        if (!pte)
                return;
        lazy_mmu_mode_enable();
        for (; npages > 0; --npages) {
                pte_update(mm, addr, pte, 0, 0, 0);
                addr += PAGE_SIZE;
                ++pte;
        }
        lazy_mmu_mode_disable();
        pte_unmap_unlock(pte - 1, ptl);
}

/*
 * Clear the subpage protection map for an address range, allowing
 * all accesses that are allowed by the pte permissions.
 */
static void subpage_prot_clear(unsigned long addr, unsigned long len)
{
        struct mm_struct *mm = current->mm;
        struct subpage_prot_table *spt;
        u32 **spm, *spp;
        unsigned long i;
        size_t nw;
        unsigned long next, limit;

        mmap_write_lock(mm);

        spt = mm_ctx_subpage_prot(&mm->context);
        if (!spt)
                goto err_out;

        limit = addr + len;
        if (limit > spt->maxaddr)
                limit = spt->maxaddr;
        for (; addr < limit; addr = next) {
                next = pmd_addr_end(addr, limit);
                if (addr < 0x100000000UL) {
                        spm = spt->low_prot;
                } else {
                        spm = spt->protptrs[addr >> SBP_L3_SHIFT];
                        if (!spm)
                                continue;
                }
                spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
                if (!spp)
                        continue;
                spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);

                i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
                nw = PTRS_PER_PTE - i;
                if (addr + (nw << PAGE_SHIFT) > next)
                        nw = (next - addr) >> PAGE_SHIFT;

                memset(spp, 0, nw * sizeof(u32));

                /* now flush any existing HPTEs for the range */
                hpte_flush_range(mm, addr, nw);
        }

err_out:
        mmap_write_unlock(mm);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
                                  unsigned long end, struct mm_walk *walk)
{
        struct vm_area_struct *vma = walk->vma;
        split_huge_pmd(vma, pmd, addr);
        return 0;
}

static const struct mm_walk_ops subpage_walk_ops = {
        .pmd_entry      = subpage_walk_pmd_entry,
        .walk_lock      = PGWALK_WRLOCK_VERIFY,
};

static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
                                    unsigned long len)
{
        struct vm_area_struct *vma;
        VMA_ITERATOR(vmi, mm, addr);

        /*
         * We don't try too hard, we just mark all the vma in that range
         * VM_NOHUGEPAGE and split them.
         */
        for_each_vma_range(vmi, vma, addr + len) {
                vm_flags_set(vma, VM_NOHUGEPAGE);
                walk_page_vma(vma, &subpage_walk_ops, NULL);
        }
}
#else
static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
                                    unsigned long len)
{
        return;
}
#endif

/*
 * Copy in a subpage protection map for an address range.
 * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
 * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
 * 2 or 3 to prevent all accesses.
 * Note that the normal page protections also apply; the subpage
 * protection mechanism is an additional constraint, so putting 0
 * in a 2-bit field won't allow writes to a page that is otherwise
 * write-protected.
 */
SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,
                unsigned long, len, u32 __user *, map)
{
        struct mm_struct *mm = current->mm;
        struct subpage_prot_table *spt;
        u32 **spm, *spp;
        unsigned long i;
        size_t nw;
        unsigned long next, limit;
        int err;

        if (radix_enabled())
                return -ENOENT;

        /* Check parameters */
        if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
            addr >= mm->task_size || len >= mm->task_size ||
            addr + len > mm->task_size)
                return -EINVAL;

        if (is_hugepage_only_range(mm, addr, len))
                return -EINVAL;

        if (!map) {
                /* Clear out the protection map for the address range */
                subpage_prot_clear(addr, len);
                return 0;
        }

        if (!access_ok(map, (len >> PAGE_SHIFT) * sizeof(u32)))
                return -EFAULT;

        mmap_write_lock(mm);

        spt = mm_ctx_subpage_prot(&mm->context);
        if (!spt) {
                /*
                 * Allocate subpage prot table if not already done.
                 * Do this with mmap_lock held
                 */
                spt = kzalloc_obj(struct subpage_prot_table);
                if (!spt) {
                        err = -ENOMEM;
                        goto out;
                }
                mm->context.hash_context->spt = spt;
        }

        subpage_mark_vma_nohuge(mm, addr, len);
        for (limit = addr + len; addr < limit; addr = next) {
                next = pmd_addr_end(addr, limit);
                err = -ENOMEM;
                if (addr < 0x100000000UL) {
                        spm = spt->low_prot;
                } else {
                        spm = spt->protptrs[addr >> SBP_L3_SHIFT];
                        if (!spm) {
                                spm = (u32 **)get_zeroed_page(GFP_KERNEL);
                                if (!spm)
                                        goto out;
                                spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
                        }
                }
                spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
                spp = *spm;
                if (!spp) {
                        spp = (u32 *)get_zeroed_page(GFP_KERNEL);
                        if (!spp)
                                goto out;
                        *spm = spp;
                }
                spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);

                local_irq_disable();
                demote_segment_4k(mm, addr);
                local_irq_enable();

                i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
                nw = PTRS_PER_PTE - i;
                if (addr + (nw << PAGE_SHIFT) > next)
                        nw = (next - addr) >> PAGE_SHIFT;

                mmap_write_unlock(mm);
                if (__copy_from_user(spp, map, nw * sizeof(u32)))
                        return -EFAULT;
                map += nw;
                mmap_write_lock(mm);

                /* now flush any existing HPTEs for the range */
                hpte_flush_range(mm, addr, nw);
        }
        if (limit > spt->maxaddr)
                spt->maxaddr = limit;
        err = 0;
 out:
        mmap_write_unlock(mm);
        return err;
}