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(pgd_t *pgd)
  28 {
  29         struct subpage_prot_table *spt = pgd_subpage_prot(pgd);
  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 static void hpte_flush_range(struct mm_struct *mm, unsigned long addr,
  55                              int npages)
  56 {
  57         pgd_t *pgd;
  58         pud_t *pud;
  59         pmd_t *pmd;
  60         pte_t *pte;
  61         spinlock_t *ptl;
  62
  63         pgd = pgd_offset(mm, addr);
  64         if (pgd_none(*pgd))
  65                 return;
  66         pud = pud_offset(pgd, addr);
  67         if (pud_none(*pud))
  68                 return;
  69         pmd = pmd_offset(pud, addr);
  70         if (pmd_none(*pmd))
  71                 return;
  72         pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
  73         arch_enter_lazy_mmu_mode();
  74         for (; npages > 0; --npages) {
  75                 pte_update(mm, addr, pte, 0, 0);
  76                 addr += PAGE_SIZE;
  77                 ++pte;
  78         }
  79         arch_leave_lazy_mmu_mode();
  80         pte_unmap_unlock(pte - 1, ptl);
  81 }
  82
  83 /*
  84  * Clear the subpage protection map for an address range, allowing
  85  * all accesses that are allowed by the pte permissions.
  86  */
  87 static void subpage_prot_clear(unsigned long addr, unsigned long len)
  88 {
  89         struct mm_struct *mm = current->mm;
  90         struct subpage_prot_table *spt = pgd_subpage_prot(mm->pgd);
  91         u32 **spm, *spp;
  92         int i, nw;
  93         unsigned long next, limit;
  94
  95         down_write(&mm->mmap_sem);
  96         limit = addr + len;
  97         if (limit > spt->maxaddr)
  98                 limit = spt->maxaddr;
  99         for (; addr < limit; addr = next) {
 100                 next = pmd_addr_end(addr, limit);
 101                 if (addr < 0x100000000) {
 102                         spm = spt->low_prot;
 103                 } else {
 104                         spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 105                         if (!spm)
 106                                 continue;
 107                 }
 108                 spp = spm[(addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1)];
 109                 if (!spp)
 110                         continue;
 111                 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 112
 113                 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 114                 nw = PTRS_PER_PTE - i;
 115                 if (addr + (nw << PAGE_SHIFT) > next)
 116                         nw = (next - addr) >> PAGE_SHIFT;
 117
 118                 memset(spp, 0, nw * sizeof(u32));
 119
 120                 /* now flush any existing HPTEs for the range */
 121                 hpte_flush_range(mm, addr, nw);
 122         }
 123         up_write(&mm->mmap_sem);
 124 }
 125
 126 /*
 127  * Copy in a subpage protection map for an address range.
 128  * The map has 2 bits per 4k subpage, so 32 bits per 64k page.
 129  * Each 2-bit field is 0 to allow any access, 1 to prevent writes,
 130  * 2 or 3 to prevent all accesses.
 131  * Note that the normal page protections also apply; the subpage
 132  * protection mechanism is an additional constraint, so putting 0
 133  * in a 2-bit field won't allow writes to a page that is otherwise
 134  * write-protected.
 135  */
 136 long sys_subpage_prot(unsigned long addr, unsigned long len, u32 __user *map)
 137 {
 138         struct mm_struct *mm = current->mm;
 139         struct subpage_prot_table *spt = pgd_subpage_prot(mm->pgd);
 140         u32 **spm, *spp;
 141         int i, nw;
 142         unsigned long next, limit;
 143         int err;
 144
 145         /* Check parameters */
 146         if ((addr & ~PAGE_MASK) || (len & ~PAGE_MASK) ||
 147             addr >= TASK_SIZE || len >= TASK_SIZE || addr + len > TASK_SIZE)
 148                 return -EINVAL;
 149
 150         if (is_hugepage_only_range(mm, addr, len))
 151                 return -EINVAL;
 152
 153         if (!map) {
 154                 /* Clear out the protection map for the address range */
 155                 subpage_prot_clear(addr, len);
 156                 return 0;
 157         }
 158
 159         if (!access_ok(VERIFY_READ, map, (len >> PAGE_SHIFT) * sizeof(u32)))
 160                 return -EFAULT;
 161
 162         down_write(&mm->mmap_sem);
 163         for (limit = addr + len; addr < limit; addr = next) {
 164                 next = pmd_addr_end(addr, limit);
 165                 err = -ENOMEM;
 166                 if (addr < 0x100000000) {
 167                         spm = spt->low_prot;
 168                 } else {
 169                         spm = spt->protptrs[addr >> SBP_L3_SHIFT];
 170                         if (!spm) {
 171                                 spm = (u32 **)get_zeroed_page(GFP_KERNEL);
 172                                 if (!spm)
 173                                         goto out;
 174                                 spt->protptrs[addr >> SBP_L3_SHIFT] = spm;
 175                         }
 176                 }
 177                 spm += (addr >> SBP_L2_SHIFT) & (SBP_L2_COUNT - 1);
 178                 spp = *spm;
 179                 if (!spp) {
 180                         spp = (u32 *)get_zeroed_page(GFP_KERNEL);
 181                         if (!spp)
 182                                 goto out;
 183                         *spm = spp;
 184                 }
 185                 spp += (addr >> PAGE_SHIFT) & (SBP_L1_COUNT - 1);
 186
 187                 local_irq_disable();
 188                 demote_segment_4k(mm, addr);
 189                 local_irq_enable();
 190
 191                 i = (addr >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
 192                 nw = PTRS_PER_PTE - i;
 193                 if (addr + (nw << PAGE_SHIFT) > next)
 194                         nw = (next - addr) >> PAGE_SHIFT;
 195
 196                 up_write(&mm->mmap_sem);
 197                 err = -EFAULT;
 198                 if (__copy_from_user(spp, map, nw * sizeof(u32)))
 199                         goto out2;
 200                 map += nw;
 201                 down_write(&mm->mmap_sem);
 202
 203                 /* now flush any existing HPTEs for the range */
 204                 hpte_flush_range(mm, addr, nw);
 205         }
 206         if (limit > spt->maxaddr)
 207                 spt->maxaddr = limit;
 208         err = 0;
 209  out:
 210         up_write(&mm->mmap_sem);
 211  out2:
 212         return err;
 213 }