arch/x86/mm/pgtable.c

   1 #include <linux/mm.h>
   2 #include <asm/pgalloc.h>
   3 #include <asm/pgtable.h>
   4 #include <asm/tlb.h>
   5 #include <asm/fixmap.h>
   6
   7 #define PGALLOC_GFP GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO
   8
   9 pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
  10 {
  11         return (pte_t *)__get_free_page(PGALLOC_GFP);
  12 }
  13
  14 pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
  15 {
  16         struct page *pte;
  17
  18 #ifdef CONFIG_HIGHPTE
  19         pte = alloc_pages(PGALLOC_GFP | __GFP_HIGHMEM, 0);
  20 #else
  21         pte = alloc_pages(PGALLOC_GFP, 0);
  22 #endif
  23         if (pte)
  24                 pgtable_page_ctor(pte);
  25         return pte;
  26 }
  27
  28 void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
  29 {
  30         pgtable_page_dtor(pte);
  31         paravirt_release_pte(page_to_pfn(pte));
  32         tlb_remove_page(tlb, pte);
  33 }
  34
  35 #if PAGETABLE_LEVELS > 2
  36 void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
  37 {
  38         paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
  39         tlb_remove_page(tlb, virt_to_page(pmd));
  40 }
  41
  42 #if PAGETABLE_LEVELS > 3
  43 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
  44 {
  45         paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
  46         tlb_remove_page(tlb, virt_to_page(pud));
  47 }
  48 #endif  /* PAGETABLE_LEVELS > 3 */
  49 #endif  /* PAGETABLE_LEVELS > 2 */
  50
  51 static inline void pgd_list_add(pgd_t *pgd)
  52 {
  53         struct page *page = virt_to_page(pgd);
  54
  55         list_add(&page->lru, &pgd_list);
  56 }
  57
  58 static inline void pgd_list_del(pgd_t *pgd)
  59 {
  60         struct page *page = virt_to_page(pgd);
  61
  62         list_del(&page->lru);
  63 }
  64
  65 #define UNSHARED_PTRS_PER_PGD                           \
  66         (SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD)
  67
  68 static void pgd_ctor(pgd_t *pgd)
  69 {
  70         /* If the pgd points to a shared pagetable level (either the
  71            ptes in non-PAE, or shared PMD in PAE), then just copy the
  72            references from swapper_pg_dir. */
  73         if (PAGETABLE_LEVELS == 2 ||
  74             (PAGETABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
  75             PAGETABLE_LEVELS == 4) {
  76                 clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
  77                                 swapper_pg_dir + KERNEL_PGD_BOUNDARY,
  78                                 KERNEL_PGD_PTRS);
  79                 paravirt_alloc_pmd_clone(__pa(pgd) >> PAGE_SHIFT,
  80                                          __pa(swapper_pg_dir) >> PAGE_SHIFT,
  81                                          KERNEL_PGD_BOUNDARY,
  82                                          KERNEL_PGD_PTRS);
  83         }
  84
  85         /* list required to sync kernel mapping updates */
  86         if (!SHARED_KERNEL_PMD)
  87                 pgd_list_add(pgd);
  88 }
  89
  90 static void pgd_dtor(pgd_t *pgd)
  91 {
  92         unsigned long flags; /* can be called from interrupt context */
  93
  94         if (SHARED_KERNEL_PMD)
  95                 return;
  96
  97         spin_lock_irqsave(&pgd_lock, flags);
  98         pgd_list_del(pgd);
  99         spin_unlock_irqrestore(&pgd_lock, flags);
 100 }
 101
 102 /*
 103  * List of all pgd's needed for non-PAE so it can invalidate entries
 104  * in both cached and uncached pgd's; not needed for PAE since the
 105  * kernel pmd is shared. If PAE were not to share the pmd a similar
 106  * tactic would be needed. This is essentially codepath-based locking
 107  * against pageattr.c; it is the unique case in which a valid change
 108  * of kernel pagetables can't be lazily synchronized by vmalloc faults.
 109  * vmalloc faults work because attached pagetables are never freed.
 110  * -- wli
 111  */
 112
 113 #ifdef CONFIG_X86_PAE
 114 /*
 115  * In PAE mode, we need to do a cr3 reload (=tlb flush) when
 116  * updating the top-level pagetable entries to guarantee the
 117  * processor notices the update.  Since this is expensive, and
 118  * all 4 top-level entries are used almost immediately in a
 119  * new process's life, we just pre-populate them here.
 120  *
 121  * Also, if we're in a paravirt environment where the kernel pmd is
 122  * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate
 123  * and initialize the kernel pmds here.
 124  */
 125 #define PREALLOCATED_PMDS       UNSHARED_PTRS_PER_PGD
 126
 127 void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
 128 {
 129         paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
 130
 131         /* Note: almost everything apart from _PAGE_PRESENT is
 132            reserved at the pmd (PDPT) level. */
 133         set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));
 134
 135         /*
 136          * According to Intel App note "TLBs, Paging-Structure Caches,
 137          * and Their Invalidation", April 2007, document 317080-001,
 138          * section 8.1: in PAE mode we explicitly have to flush the
 139          * TLB via cr3 if the top-level pgd is changed...
 140          */
 141         if (mm == current->active_mm)
 142                 write_cr3(read_cr3());
 143 }
 144 #else  /* !CONFIG_X86_PAE */
 145
 146 /* No need to prepopulate any pagetable entries in non-PAE modes. */
 147 #define PREALLOCATED_PMDS       0
 148
 149 #endif  /* CONFIG_X86_PAE */
 150
 151 static void free_pmds(pmd_t *pmds[])
 152 {
 153         int i;
 154
 155         for(i = 0; i < PREALLOCATED_PMDS; i++)
 156                 if (pmds[i])
 157                         free_page((unsigned long)pmds[i]);
 158 }
 159
 160 static int preallocate_pmds(pmd_t *pmds[])
 161 {
 162         int i;
 163         bool failed = false;
 164
 165         for(i = 0; i < PREALLOCATED_PMDS; i++) {
 166                 pmd_t *pmd = (pmd_t *)__get_free_page(PGALLOC_GFP);
 167                 if (pmd == NULL)
 168                         failed = true;
 169                 pmds[i] = pmd;
 170         }
 171
 172         if (failed) {
 173                 free_pmds(pmds);
 174                 return -ENOMEM;
 175         }
 176
 177         return 0;
 178 }
 179
 180 /*
 181  * Mop up any pmd pages which may still be attached to the pgd.
 182  * Normally they will be freed by munmap/exit_mmap, but any pmd we
 183  * preallocate which never got a corresponding vma will need to be
 184  * freed manually.
 185  */
 186 static void pgd_mop_up_pmds(struct mm_struct *mm, pgd_t *pgdp)
 187 {
 188         int i;
 189
 190         for(i = 0; i < PREALLOCATED_PMDS; i++) {
 191                 pgd_t pgd = pgdp[i];
 192
 193                 if (pgd_val(pgd) != 0) {
 194                         pmd_t *pmd = (pmd_t *)pgd_page_vaddr(pgd);
 195
 196                         pgdp[i] = native_make_pgd(0);
 197
 198                         paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT);
 199                         pmd_free(mm, pmd);
 200                 }
 201         }
 202 }
 203
 204 static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
 205 {
 206         pud_t *pud;
 207         unsigned long addr;
 208         int i;
 209
 210         if (PREALLOCATED_PMDS == 0) /* Work around gcc-3.4.x bug */
 211                 return;
 212
 213         pud = pud_offset(pgd, 0);
 214
 215         for (addr = i = 0; i < PREALLOCATED_PMDS;
 216              i++, pud++, addr += PUD_SIZE) {
 217                 pmd_t *pmd = pmds[i];
 218
 219                 if (i >= KERNEL_PGD_BOUNDARY)
 220                         memcpy(pmd, (pmd_t *)pgd_page_vaddr(swapper_pg_dir[i]),
 221                                sizeof(pmd_t) * PTRS_PER_PMD);
 222
 223                 pud_populate(mm, pud, pmd);
 224         }
 225 }
 226
 227 pgd_t *pgd_alloc(struct mm_struct *mm)
 228 {
 229         pgd_t *pgd;
 230         pmd_t *pmds[PREALLOCATED_PMDS];
 231         unsigned long flags;
 232
 233         pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
 234
 235         if (pgd == NULL)
 236                 goto out;
 237
 238         mm->pgd = pgd;
 239
 240         if (preallocate_pmds(pmds) != 0)
 241                 goto out_free_pgd;
 242
 243         if (paravirt_pgd_alloc(mm) != 0)
 244                 goto out_free_pmds;
 245
 246         /*
 247          * Make sure that pre-populating the pmds is atomic with
 248          * respect to anything walking the pgd_list, so that they
 249          * never see a partially populated pgd.
 250          */
 251         spin_lock_irqsave(&pgd_lock, flags);
 252
 253         pgd_ctor(pgd);
 254         pgd_prepopulate_pmd(mm, pgd, pmds);
 255
 256         spin_unlock_irqrestore(&pgd_lock, flags);
 257
 258         return pgd;
 259
 260 out_free_pmds:
 261         free_pmds(pmds);
 262 out_free_pgd:
 263         free_page((unsigned long)pgd);
 264 out:
 265         return NULL;
 266 }
 267
 268 void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 269 {
 270         pgd_mop_up_pmds(mm, pgd);
 271         pgd_dtor(pgd);
 272         paravirt_pgd_free(mm, pgd);
 273         free_page((unsigned long)pgd);
 274 }
 275
 276 int ptep_set_access_flags(struct vm_area_struct *vma,
 277                           unsigned long address, pte_t *ptep,
 278                           pte_t entry, int dirty)
 279 {
 280         int changed = !pte_same(*ptep, entry);
 281
 282         if (changed && dirty) {
 283                 *ptep = entry;
 284                 pte_update_defer(vma->vm_mm, address, ptep);
 285                 flush_tlb_page(vma, address);
 286         }
 287
 288         return changed;
 289 }
 290
 291 int ptep_test_and_clear_young(struct vm_area_struct *vma,
 292                               unsigned long addr, pte_t *ptep)
 293 {
 294         int ret = 0;
 295
 296         if (pte_young(*ptep))
 297                 ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
 298                                          (unsigned long *) &ptep->pte);
 299
 300         if (ret)
 301                 pte_update(vma->vm_mm, addr, ptep);
 302
 303         return ret;
 304 }
 305
 306 int ptep_clear_flush_young(struct vm_area_struct *vma,
 307                            unsigned long address, pte_t *ptep)
 308 {
 309         int young;
 310
 311         young = ptep_test_and_clear_young(vma, address, ptep);
 312         if (young)
 313                 flush_tlb_page(vma, address);
 314
 315         return young;
 316 }
 317
 318 /**
 319  * reserve_top_address - reserves a hole in the top of kernel address space
 320  * @reserve - size of hole to reserve
 321  *
 322  * Can be used to relocate the fixmap area and poke a hole in the top
 323  * of kernel address space to make room for a hypervisor.
 324  */
 325 void __init reserve_top_address(unsigned long reserve)
 326 {
 327 #ifdef CONFIG_X86_32
 328         BUG_ON(fixmaps_set > 0);
 329         printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
 330                (int)-reserve);
 331         __FIXADDR_TOP = -reserve - PAGE_SIZE;
 332 #endif
 333 }
 334
 335 int fixmaps_set;
 336
 337 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
 338 {
 339         unsigned long address = __fix_to_virt(idx);
 340
 341         if (idx >= __end_of_fixed_addresses) {
 342                 BUG();
 343                 return;
 344         }
 345         set_pte_vaddr(address, pte);
 346         fixmaps_set++;
 347 }
 348
 349 void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
 350                        pgprot_t flags)
 351 {
 352         __native_set_fixmap(idx, pfn_pte(phys >> PAGE_SHIFT, flags));
 353 }