arch/powerpc/mm/book3s64/subpage_prot.c

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