arch/powerpc/mm/subpage-prot.c

   1 /*
   2  * Copyright 2007-2008 Paul Mackerras, IBM Corp.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  */
   9
  10 #include <linux/errno.h>
  11 #include <linux/kernel.h>
  12 #include <linux/gfp.h>
  13 #include <linux/types.h>
  14 #include <linux/mm.h>
  15 #include <linux/hugetlb.h>
  16
  17 #include <asm/pgtable.h>
  18 #include <asm/uaccess.h>
  19 #include <asm/tlbflush.h>
  20
  21 /*
  22  * Free all pages allocated for subpage protection maps and pointers.
  23  * Also makes sure that the subpage_prot_table structure is
  24  * reinitialized for the next user.
  25  */
  26 void subpage_prot_free(struct mm_struct *mm)
  27 {
  28         struct subpage_prot_table *spt = &mm->context.spt;
  29         unsigned long i, j, addr;
  30         u32 **p;
  31
  32         for (i = 0; i < 4; ++i) {
  33                 if (spt->low_prot[i]) {
  34                         free_page((unsigned long)spt->low_prot[i]);
  35                         spt->low_prot[i] = NULL;
  36                 }
  37         }
  38         addr = 0;
  39         for (i = 0; i < 2; ++i) {
  40                 p = spt->protptrs[i];
  41                 if (!p)
  42                         continue;
  43                 spt->protptrs[i] = NULL;
  44                 for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
  45                      ++j, addr += PAGE_SIZE)
  46                         if (p[j])
  47                                 free_page((unsigned long)p[j]);
  48                 free_page((unsigned long)p);
  49         }
  50         spt->maxaddr = 0;
  51 }
  52
  53 void subpage_prot_init_new_context(struct mm_struct *mm)
  54 {
  55         struct subpage_prot_table *spt = &mm->context.spt;
  56
  57         memset(spt, 0, sizeof(*spt));
  58 }
  59
  60 static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
  61                              int npages)
  62 {
  63         pgd_t *pgd;
  64         pud_t *pud;
  65         pmd_t *pmd;
  66         pte_t *pte;
  67         spinlock_t *ptl;
  68
  69         pgd = pgd_offset(mm, addr);
  70         if (pgd_none(*pgd))
  71                 return;
  72         pud = pud_offset(pgd, addr);
  73         if (pud_none(*pud))
  74                 return;
  75         pmd = pmd_offset(pud, addr);
  76         if (pmd_none(*pmd))
  77                 return;
  78         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
  79         arch_enter_lazy_mmu_mode();
  80         for (; npages > 0; --npages) {
  81                 pte_update(mm, addr, pte, 0, 0);
  82                 addr += PAGE_SIZE;
  83                 ++pte;
  84         }
  85         arch_leave_lazy_mmu_mode();
  86         pte_unmap_unlock(pte - 1, ptl);
  87 }
  88
  89 /*
  90  * Clear the subpage protection map for an address range, allowing
  91  * all accesses that are allowed by the pte permissions.
  92  */
  93 static void subpage_prot_clear(unsigned long addr, unsigned long len)
  94 {
  95         struct mm_struct *mm = current->mm;
  96         struct subpage_prot_table *spt = &mm->context.spt;
  97         u32 **spm, *spp;
  98         int i, nw;
  99         unsigned long next, limit;
 100
 101         down_write(&mm->mmap_sem);
 102         limit = addr + len;
 103         if (limit > spt->maxaddr)
 104                 limit = spt->maxaddr;
 105         for (; addr < limit; addr = next) {
 106                 next = pmd_addr_end(addr, limit);
 107                 if (addr < 0x100000000) {
 108                         spm = spt->low_prot;
 109                 } else {
 110                         spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 111                         if (!spm)
 112                                 continue;
 113                 }
 114                 spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
 115                 if (!spp)
 116                         continue;
 117                 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 118
 119                 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 120                 nw = PTRS_PER_PTE - i;
 121                 if (addr + (nw << PAGE_SHIFT) > next)
 122                         nw = (next - addr) >> PAGE_SHIFT;
 123
 124                 memset(spp, 0, nw * sizeof(u32));
 125
 126                 /* now flush any existing HPTEs for the range */
 127                 hpte_flush_range(mm, addr, nw);
 128         }
 129         up_write(&mm->mmap_sem);
 130 }
 131
 132 /*
 133  * Copy in a subpage protection map for an address range.
 134  * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
 135  * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
 136  * 2 or 3 to prevent all accesses.
 137  * Note that the normal page protections also apply; the subpage
 138  * protection mechanism is an additional constraint, so putting 0
 139  * in a 2-bit field won't allow writes to a page that is otherwise
 140  * write-protected.
 141  */
 142 long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
 143 {
 144         struct mm_struct *mm = current->mm;
 145         struct subpage_prot_table *spt = &mm->context.spt;
 146         u32 **spm, *spp;
 147         int i, nw;
 148         unsigned long next, limit;
 149         int err;
 150
 151         /* Check parameters */
 152         if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
 153             addr >= TASK_SIZE || len >= TASK_SIZE || addr + len > TASK_SIZE)
 154                 return -EINVAL;
 155
 156         if (is_hugepage_only_range(mm, addr, len))
 157                 return -EINVAL;
 158
 159         if (!map) {
 160                 /* Clear out the protection map for the address range */
 161                 subpage_prot_clear(addr, len);
 162                 return 0;
 163         }
 164
 165         if (!access_ok(VERIFY_READ, map, (len >> PAGE_SHIFT) * sizeof(u32)))
 166                 return -EFAULT;
 167
 168         down_write(&mm->mmap_sem);
 169         for (limit = addr + len; addr < limit; addr = next) {
 170                 next = pmd_addr_end(addr, limit);
 171                 err = -ENOMEM;
 172                 if (addr < 0x100000000) {
 173                         spm = spt->low_prot;
 174                 } else {
 175                         spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 176                         if (!spm) {
 177                                 spm = (u32 **)get_zeroed_page(GFP_KERNEL);
 178                                 if (!spm)
 179                                         goto out;
 180                                 spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
 181                         }
 182                 }
 183                 spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
 184                 spp = *spm;
 185                 if (!spp) {
 186                         spp = (u32 *)get_zeroed_page(GFP_KERNEL);
 187                         if (!spp)
 188                                 goto out;
 189                         *spm = spp;
 190                 }
 191                 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 192
 193                 local_irq_disable();
 194                 demote_segment_4k(mm, addr);
 195                 local_irq_enable();
 196
 197                 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 198                 nw = PTRS_PER_PTE - i;
 199                 if (addr + (nw << PAGE_SHIFT) > next)
 200                         nw = (next - addr) >> PAGE_SHIFT;
 201
 202                 up_write(&mm->mmap_sem);
 203                 err = -EFAULT;
 204                 if (__copy_from_user(spp, map, nw * sizeof(u32)))
 205                         goto out2;
 206                 map += nw;
 207                 down_write(&mm->mmap_sem);
 208
 209                 /* now flush any existing HPTEs for the range */
 210                 hpte_flush_range(mm, addr, nw);
 211         }
 212         if (limit > spt->maxaddr)
 213                 spt->maxaddr = limit;
 214         err = 0;
 215  out:
 216         up_write(&mm->mmap_sem);
 217  out2:
 218         return err;
 219 }