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/slab.h>
  14 #include <linux/types.h>
  15 #include <linux/mm.h>
  16 #include <linux/hugetlb.h>
  17
  18 #include <asm/pgtable.h>
  19 #include <asm/uaccess.h>
  20 #include <asm/tlbflush.h>
  21
  22 /*
  23  * Free all pages allocated for subpage protection maps and pointers.
  24  * Also makes sure that the subpage_prot_table structure is
  25  * reinitialized for the next user.
  26  */
  27 void subpage_prot_free(struct mm_struct *mm)
  28 {
  29         struct subpage_prot_table *spt = &mm->context.spt;
  30         unsigned long i, j, addr;
  31         u32 **p;
  32
  33         for (i = 0; i < 4; ++i) {
  34                 if (spt->low_prot[i]) {
  35                         free_page((unsigned long)spt->low_prot[i]);
  36                         spt->low_prot[i] = NULL;
  37                 }
  38         }
  39         addr = 0;
  40         for (i = 0; i < 2; ++i) {
  41                 p = spt->protptrs[i];
  42                 if (!p)
  43                         continue;
  44                 spt->protptrs[i] = NULL;
  45                 for (j = 0; j < SBP_L2_COUNT && addr < spt->maxaddr;
  46                      ++j, addr += PAGE_SIZE)
  47                         if (p[j])
  48                                 free_page((unsigned long)p[j]);
  49                 free_page((unsigned long)p);
  50         }
  51         spt->maxaddr = 0;
  52 }
  53
  54 void subpage_prot_init_new_context(struct mm_struct *mm)
  55 {
  56         struct subpage_prot_table *spt = &mm->context.spt;
  57
  58         memset(spt, 0, sizeof(*spt));
  59 }
  60
  61 static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
  62                              int npages)
  63 {
  64         pgd_t *pgd;
  65         pud_t *pud;
  66         pmd_t *pmd;
  67         pte_t *pte;
  68         spinlock_t *ptl;
  69
  70         pgd = pgd_offset(mm, addr);
  71         if (pgd_none(*pgd))
  72                 return;
  73         pud = pud_offset(pgd, addr);
  74         if (pud_none(*pud))
  75                 return;
  76         pmd = pmd_offset(pud, addr);
  77         if (pmd_none(*pmd))
  78                 return;
  79         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
  80         arch_enter_lazy_mmu_mode();
  81         for (; npages > 0; --npages) {
  82                 pte_update(mm, addr, pte, 0, 0);
  83                 addr += PAGE_SIZE;
  84                 ++pte;
  85         }
  86         arch_leave_lazy_mmu_mode();
  87         pte_unmap_unlock(pte - 1, ptl);
  88 }
  89
  90 /*
  91  * Clear the subpage protection map for an address range, allowing
  92  * all accesses that are allowed by the pte permissions.
  93  */
  94 static void subpage_prot_clear(unsigned long addr, unsigned long len)
  95 {
  96         struct mm_struct *mm = current->mm;
  97         struct subpage_prot_table *spt = &mm->context.spt;
  98         u32 **spm, *spp;
  99         int i, nw;
 100         unsigned long next, limit;
 101
 102         down_write(&mm->mmap_sem);
 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 < 0x100000000) {
 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         up_write(&mm->mmap_sem);
 131 }
 132
 133 /*
 134  * Copy in a subpage protection map for an address range.
 135  * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
 136  * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
 137  * 2 or 3 to prevent all accesses.
 138  * Note that the normal page protections also apply; the subpage
 139  * protection mechanism is an additional constraint, so putting 0
 140  * in a 2-bit field won't allow writes to a page that is otherwise
 141  * write-protected.
 142  */
 143 long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
 144 {
 145         struct mm_struct *mm = current->mm;
 146         struct subpage_prot_table *spt = &mm->context.spt;
 147         u32 **spm, *spp;
 148         int i, nw;
 149         unsigned long next, limit;
 150         int err;
 151
 152         /* Check parameters */
 153         if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
 154             addr >= TASK_SIZE || len >= TASK_SIZE || addr + len > TASK_SIZE)
 155                 return -EINVAL;
 156
 157         if (is_hugepage_only_range(mm, addr, len))
 158                 return -EINVAL;
 159
 160         if (!map) {
 161                 /* Clear out the protection map for the address range */
 162                 subpage_prot_clear(addr, len);
 163                 return 0;
 164         }
 165
 166         if (!access_ok(VERIFY_READ, map, (len >> PAGE_SHIFT) * sizeof(u32)))
 167                 return -EFAULT;
 168
 169         down_write(&mm->mmap_sem);
 170         for (limit = addr + len; addr < limit; addr = next) {
 171                 next = pmd_addr_end(addr, limit);
 172                 err = -ENOMEM;
 173                 if (addr < 0x100000000) {
 174                         spm = spt->low_prot;
 175                 } else {
 176                         spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 177                         if (!spm) {
 178                                 spm = (u32 **)get_zeroed_page(GFP_KERNEL);
 179                                 if (!spm)
 180                                         goto out;
 181                                 spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
 182                         }
 183                 }
 184                 spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
 185                 spp = *spm;
 186                 if (!spp) {
 187                         spp = (u32 *)get_zeroed_page(GFP_KERNEL);
 188                         if (!spp)
 189                                 goto out;
 190                         *spm = spp;
 191                 }
 192                 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 193
 194                 local_irq_disable();
 195                 demote_segment_4k(mm, addr);
 196                 local_irq_enable();
 197
 198                 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 199                 nw = PTRS_PER_PTE - i;
 200                 if (addr + (nw << PAGE_SHIFT) > next)
 201                         nw = (next - addr) >> PAGE_SHIFT;
 202
 203                 up_write(&mm->mmap_sem);
 204                 err = -EFAULT;
 205                 if (__copy_from_user(spp, map, nw * sizeof(u32)))
 206                         goto out2;
 207                 map += nw;
 208                 down_write(&mm->mmap_sem);
 209
 210                 /* now flush any existing HPTEs for the range */
 211                 hpte_flush_range(mm, addr, nw);
 212         }
 213         if (limit > spt->maxaddr)
 214                 spt->maxaddr = limit;
 215         err = 0;
 216  out:
 217         up_write(&mm->mmap_sem);
 218  out2:
 219         return err;
 220 }