LXR linux/arch/powerpc/mm/book3s64/subpage

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright 2007-2008 Paul Mackerras, IBM Corp.
   4 */
   5
   6#include <linux/errno.h>
   7#include <linux/kernel.h>
   8#include <linux/gfp.h>
   9#include <linux/types.h>
  10#include <linux/pagewalk.h>
  11#include <linux/hugetlb.h>
  12#include <linux/syscalls.h>
  13
  14#include <linux/pgtable.h>
  15#include <linux/uaccess.h>
  16
  17/*
  18 * Free all pages allocated for subpage protection maps and pointers.
  19 * Also makes sure that the subpage_prot_table structure is
  20 * reinitialized for the next user.
  21 */
  22void subpage_prot_free(struct mm_struct *mm)
  23{
  24        struct subpage_prot_table *spt = mm_ctx_subpage_prot(&mm->context);
  25        unsigned long i, j, addr;
  26        u32 **p;
  27
  28        if (!spt)
  29                return;
  30
  31        for (i = 0; i < 4; ++i) {
  32                if (spt->low_prot[i]) {
  33                        free_page((unsigned long)spt->low_prot[i]);
  34                        spt->low_prot[i] = NULL;
  35                }
  36        }
  37        addr = 0;
  38        for (i = 0; i < (TASK_SIZE_USER64 >> 43); ++i) {
  39                p = spt->protptrs[i];
  40                if (!p)
  41                        continue;
  42                spt->protptrs[i] = NULL;
  43                for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
  44                     ++j, addr += PAGE_SIZE)
  45                        if (p[j])
  46                                free_page((unsigned long)p[j]);
  47                free_page((unsigned long)p);
  48        }
  49        spt->maxaddr = 0;
  50        kfree(spt);
  51}
  52
  53static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
  54                             int npages)
  55{
  56        pgd_t *pgd;
  57        p4d_t *p4d;
  58        pud_t *pud;
  59        pmd_t *pmd;
  60        pte_t *pte;
  61        spinlock_t *ptl;
  62
  63        pgd = pgd_offset(mm, addr);
  64        p4d = p4d_offset(pgd, addr);
  65        if (p4d_none(*p4d))
  66                return;
  67        pud = pud_offset(p4d, addr);
  68        if (pud_none(*pud))
  69                return;
  70        pmd = pmd_offset(pud, addr);
  71        if (pmd_none(*pmd))
  72                return;
  73        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
  74        arch_enter_lazy_mmu_mode();
  75        for (; npages > 0; --npages) {
  76                pte_update(mm, addr, pte, 0, 0, 0);
  77                addr += PAGE_SIZE;
  78                ++pte;
  79        }
  80        arch_leave_lazy_mmu_mode();
  81        pte_unmap_unlock(pte - 1, ptl);
  82}
  83
  84/*
  85 * Clear the subpage protection map for an address range, allowing
  86 * all accesses that are allowed by the pte permissions.
  87 */
  88static void subpage_prot_clear(unsigned long addr, unsigned long len)
  89{
  90        struct mm_struct *mm = current->mm;
  91        struct subpage_prot_table *spt;
  92        u32 **spm, *spp;
  93        unsigned long i;
  94        size_t nw;
  95        unsigned long next, limit;
  96
  97        mmap_write_lock(mm);
  98
  99        spt = mm_ctx_subpage_prot(&mm->context);
 100        if (!spt)
 101                goto err_out;
 102
 103        limit = addr + len;
 104        if (limit > spt->maxaddr)
 105                limit = spt->maxaddr;
 106        for (; addr < limit; addr = next) {
 107                next = pmd_addr_end(addr, limit);
 108                if (addr < 0x100000000UL) {
 109                        spm = spt->low_prot;
 110                } else {
 111                        spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 112                        if (!spm)
 113                                continue;
 114                }
 115                spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
 116                if (!spp)
 117                        continue;
 118                spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 119
 120                i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 121                nw = PTRS_PER_PTE - i;
 122                if (addr + (nw << PAGE_SHIFT) > next)
 123                        nw = (next - addr) >> PAGE_SHIFT;
 124
 125                memset(spp, 0, nw * sizeof(u32));
 126
 127                /* now flush any existing HPTEs for the range */
 128                hpte_flush_range(mm, addr, nw);
 129        }
 130
 131err_out:
 132        mmap_write_unlock(mm);
 133}
 134
 135#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 136static int subpage_walk_pmd_entry(pmd_t *pmd, unsigned long addr,
 137                                  unsigned long end, struct mm_walk *walk)
 138{
 139        struct vm_area_struct *vma = walk->vma;
 140        split_huge_pmd(vma, pmd, addr);
 141        return 0;
 142}
 143
 144static const struct mm_walk_ops subpage_walk_ops = {
 145        .pmd_entry      = subpage_walk_pmd_entry,
 146};
 147
 148static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
 149                                    unsigned long len)
 150{
 151        struct vm_area_struct *vma;
 152
 153        /*
 154         * We don't try too hard, we just mark all the vma in that range
 155         * VM_NOHUGEPAGE and split them.
 156         */
 157        vma = find_vma(mm, addr);
 158        /*
 159         * If the range is in unmapped range, just return
 160         */
 161        if (vma && ((addr + len) <= vma->vm_start))
 162                return;
 163
 164        while (vma) {
 165                if (vma->vm_start >= (addr + len))
 166                        break;
 167                vma->vm_flags |= VM_NOHUGEPAGE;
 168                walk_page_vma(vma, &subpage_walk_ops, NULL);
 169                vma = vma->vm_next;
 170        }
 171}
 172#else
 173static void subpage_mark_vma_nohuge(struct mm_struct *mm, unsigned long addr,
 174                                    unsigned long len)
 175{
 176        return;
 177}
 178#endif
 179
 180/*
 181 * Copy in a subpage protection map for an address range.
 182 * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
 183 * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
 184 * 2 or 3 to prevent all accesses.
 185 * Note that the normal page protections also apply; the subpage
 186 * protection mechanism is an additional constraint, so putting 0
 187 * in a 2-bit field won't allow writes to a page that is otherwise
 188 * write-protected.
 189 */
 190SYSCALL_DEFINE3(subpage_prot, unsigned long, addr,
 191                unsigned long, len, u32 __user *, map)
 192{
 193        struct mm_struct *mm = current->mm;
 194        struct subpage_prot_table *spt;
 195        u32 **spm, *spp;
 196        unsigned long i;
 197        size_t nw;
 198        unsigned long next, limit;
 199        int err;
 200
 201        if (radix_enabled())
 202                return -ENOENT;
 203
 204        /* Check parameters */
 205        if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
 206            addr >= mm->task_size || len >= mm->task_size ||
 207            addr + len > mm->task_size)
 208                return -EINVAL;
 209
 210        if (is_hugepage_only_range(mm, addr, len))
 211                return -EINVAL;
 212
 213        if (!map) {
 214                /* Clear out the protection map for the address range */
 215                subpage_prot_clear(addr, len);
 216                return 0;
 217        }
 218
 219        if (!access_ok(map, (len >> PAGE_SHIFT) * sizeof(u32)))
 220                return -EFAULT;
 221
 222        mmap_write_lock(mm);
 223
 224        spt = mm_ctx_subpage_prot(&mm->context);
 225        if (!spt) {
 226                /*
 227                 * Allocate subpage prot table if not already done.
 228                 * Do this with mmap_lock held
 229                 */
 230                spt = kzalloc(sizeof(struct subpage_prot_table), GFP_KERNEL);
 231                if (!spt) {
 232                        err = -ENOMEM;
 233                        goto out;
 234                }
 235                mm->context.hash_context->spt = spt;
 236        }
 237
 238        subpage_mark_vma_nohuge(mm, addr, len);
 239        for (limit = addr + len; addr < limit; addr = next) {
 240                next = pmd_addr_end(addr, limit);
 241                err = -ENOMEM;
 242                if (addr < 0x100000000UL) {
 243                        spm = spt->low_prot;
 244                } else {
 245                        spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 246                        if (!spm) {
 247                                spm = (u32 **)get_zeroed_page(GFP_KERNEL);
 248                                if (!spm)
 249                                        goto out;
 250                                spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
 251                        }
 252                }
 253                spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
 254                spp = *spm;
 255                if (!spp) {
 256                        spp = (u32 *)get_zeroed_page(GFP_KERNEL);
 257                        if (!spp)
 258                                goto out;
 259                        *spm = spp;
 260                }
 261                spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 262
 263                local_irq_disable();
 264                demote_segment_4k(mm, addr);
 265                local_irq_enable();
 266
 267                i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 268                nw = PTRS_PER_PTE - i;
 269                if (addr + (nw << PAGE_SHIFT) > next)
 270                        nw = (next - addr) >> PAGE_SHIFT;
 271
 272                mmap_write_unlock(mm);
 273                if (__copy_from_user(spp, map, nw * sizeof(u32)))
 274                        return -EFAULT;
 275                map += nw;
 276                mmap_write_lock(mm);
 277
 278                /* now flush any existing HPTEs for the range */
 279                hpte_flush_range(mm, addr, nw);
 280        }
 281        if (limit > spt->maxaddr)
 282                spt->maxaddr = limit;
 283        err = 0;
 284 out:
 285        mmap_write_unlock(mm);
 286        return err;
 287}
 288