linux/arch/powerpc/mm/subpage-prot.c
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   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 */
  26void 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
  53void 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
  60static 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 */
  93static 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 */
 142long 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}
 220