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         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  */
  88 static 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
 131 err_out:
 132         mmap_write_unlock(mm);
 133 }
 134
 135 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 136 static 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
 144 static const struct mm_walk_ops subpage_walk_ops = {
 145         .pmd_entry      = subpage_walk_pmd_entry,
 146 };
 147
 148 static 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
 173 static 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  */
 190 SYSCALL_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_sem 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 }