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