arch/x86/mm/pgtable.c

   1 #include <linux/mm.h>
   2 #include <linux/gfp.h>
   3 #include <asm/pgalloc.h>
   4 #include <asm/pgtable.h>
   5 #include <asm/tlb.h>
   6 #include <asm/fixmap.h>
   7
   8 #define PGALLOC_GFP GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO
   9
  10 #ifdef CONFIG_HIGHPTE
  11 #define PGALLOC_USER_GFP __GFP_HIGHMEM
  12 #else
  13 #define PGALLOC_USER_GFP 0
  14 #endif
  15
  16 gfp_t __userpte_alloc_gfp = PGALLOC_GFP | PGALLOC_USER_GFP;
  17
  18 pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
  19 {
  20         return (pte_t *)__get_free_page(PGALLOC_GFP);
  21 }
  22
  23 pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
  24 {
  25         struct page *pte;
  26
  27         pte = alloc_pages(__userpte_alloc_gfp, 0);
  28         if (pte)
  29                 pgtable_page_ctor(pte);
  30         return pte;
  31 }
  32
  33 static int __init setup_userpte(char *arg)
  34 {
  35         if (!arg)
  36                 return -EINVAL;
  37
  38         /*
  39          * "userpte=nohigh" disables allocation of user pagetables in
  40          * high memory.
  41          */
  42         if (strcmp(arg, "nohigh") == 0)
  43                 __userpte_alloc_gfp &= ~__GFP_HIGHMEM;
  44         else
  45                 return -EINVAL;
  46         return 0;
  47 }
  48 early_param("userpte", setup_userpte);
  49
  50 void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
  51 {
  52         pgtable_page_dtor(pte);
  53         paravirt_release_pte(page_to_pfn(pte));
  54         tlb_remove_page(tlb, pte);
  55 }
  56
  57 #if PAGETABLE_LEVELS > 2
  58 void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
  59 {
  60         paravirt_release_pmd(__pa(pmd) >> PAGE_SHIFT);
  61         tlb_remove_page(tlb, virt_to_page(pmd));
  62 }
  63
  64 #if PAGETABLE_LEVELS > 3
  65 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
  66 {
  67         paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
  68         tlb_remove_page(tlb, virt_to_page(pud));
  69 }
  70 #endif  /* PAGETABLE_LEVELS > 3 */
  71 #endif  /* PAGETABLE_LEVELS > 2 */
  72
  73 static inline void pgd_list_add(pgd_t *pgd)
  74 {
  75         struct page *page = virt_to_page(pgd);
  76
  77         list_add(&page->lru, &pgd_list);
  78 }
  79
  80 static inline void pgd_list_del(pgd_t *pgd)
  81 {
  82         struct page *page = virt_to_page(pgd);
  83
  84         list_del(&page->lru);
  85 }
  86
  87 #define UNSHARED_PTRS_PER_PGD                           \
  88         (SHARED_KERNEL_PMD ? KERNEL_PGD_BOUNDARY : PTRS_PER_PGD)
  89
  90
  91 static void pgd_set_mm(pgd_t *pgd, struct mm_struct *mm)
  92 {
  93         BUILD_BUG_ON(sizeof(virt_to_page(pgd)->index) < sizeof(mm));
  94         virt_to_page(pgd)->index = (pgoff_t)mm;
  95 }
  96
  97 struct mm_struct *pgd_page_get_mm(struct page *page)
  98 {
  99         return (struct mm_struct *)page->index;
 100 }
 101
 102 static void pgd_ctor(struct mm_struct *mm, pgd_t *pgd)
 103 {
 104         /* If the pgd points to a shared pagetable level (either the
 105            ptes in non-PAE, or shared PMD in PAE), then just copy the
 106            references from swapper_pg_dir. */
 107         if (PAGETABLE_LEVELS == 2 ||
 108             (PAGETABLE_LEVELS == 3 && SHARED_KERNEL_PMD) ||
 109             PAGETABLE_LEVELS == 4) {
 110                 clone_pgd_range(pgd + KERNEL_PGD_BOUNDARY,
 111                                 swapper_pg_dir + KERNEL_PGD_BOUNDARY,
 112                                 KERNEL_PGD_PTRS);
 113         }
 114
 115         /* list required to sync kernel mapping updates */
 116         if (!SHARED_KERNEL_PMD) {
 117                 pgd_set_mm(pgd, mm);
 118                 pgd_list_add(pgd);
 119         }
 120 }
 121
 122 static void pgd_dtor(pgd_t *pgd)
 123 {
 124         unsigned long flags; /* can be called from interrupt context */
 125
 126         if (SHARED_KERNEL_PMD)
 127                 return;
 128
 129         spin_lock_irqsave(&pgd_lock, flags);
 130         pgd_list_del(pgd);
 131         spin_unlock_irqrestore(&pgd_lock, flags);
 132 }
 133
 134 /*
 135  * List of all pgd's needed for non-PAE so it can invalidate entries
 136  * in both cached and uncached pgd's; not needed for PAE since the
 137  * kernel pmd is shared. If PAE were not to share the pmd a similar
 138  * tactic would be needed. This is essentially codepath-based locking
 139  * against pageattr.c; it is the unique case in which a valid change
 140  * of kernel pagetables can't be lazily synchronized by vmalloc faults.
 141  * vmalloc faults work because attached pagetables are never freed.
 142  * -- wli
 143  */
 144
 145 #ifdef CONFIG_X86_PAE
 146 /*
 147  * In PAE mode, we need to do a cr3 reload (=tlb flush) when
 148  * updating the top-level pagetable entries to guarantee the
 149  * processor notices the update.  Since this is expensive, and
 150  * all 4 top-level entries are used almost immediately in a
 151  * new process's life, we just pre-populate them here.
 152  *
 153  * Also, if we're in a paravirt environment where the kernel pmd is
 154  * not shared between pagetables (!SHARED_KERNEL_PMDS), we allocate
 155  * and initialize the kernel pmds here.
 156  */
 157 #define PREALLOCATED_PMDS       UNSHARED_PTRS_PER_PGD
 158
 159 void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd)
 160 {
 161         paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
 162
 163         /* Note: almost everything apart from _PAGE_PRESENT is
 164            reserved at the pmd (PDPT) level. */
 165         set_pud(pudp, __pud(__pa(pmd) | _PAGE_PRESENT));
 166
 167         /*
 168          * According to Intel App note "TLBs, Paging-Structure Caches,
 169          * and Their Invalidation", April 2007, document 317080-001,
 170          * section 8.1: in PAE mode we explicitly have to flush the
 171          * TLB via cr3 if the top-level pgd is changed...
 172          */
 173         if (mm == current->active_mm)
 174                 write_cr3(read_cr3());
 175 }
 176 #else  /* !CONFIG_X86_PAE */
 177
 178 /* No need to prepopulate any pagetable entries in non-PAE modes. */
 179 #define PREALLOCATED_PMDS       0
 180
 181 #endif  /* CONFIG_X86_PAE */
 182
 183 static void free_pmds(pmd_t *pmds[])
 184 {
 185         int i;
 186
 187         for(i = 0; i < PREALLOCATED_PMDS; i++)
 188                 if (pmds[i])
 189                         free_page((unsigned long)pmds[i]);
 190 }
 191
 192 static int preallocate_pmds(pmd_t *pmds[])
 193 {
 194         int i;
 195         bool failed = false;
 196
 197         for(i = 0; i < PREALLOCATED_PMDS; i++) {
 198                 pmd_t *pmd = (pmd_t *)__get_free_page(PGALLOC_GFP);
 199                 if (pmd == NULL)
 200                         failed = true;
 201                 pmds[i] = pmd;
 202         }
 203
 204         if (failed) {
 205                 free_pmds(pmds);
 206                 return -ENOMEM;
 207         }
 208
 209         return 0;
 210 }
 211
 212 /*
 213  * Mop up any pmd pages which may still be attached to the pgd.
 214  * Normally they will be freed by munmap/exit_mmap, but any pmd we
 215  * preallocate which never got a corresponding vma will need to be
 216  * freed manually.
 217  */
 218 static void pgd_mop_up_pmds(struct mm_struct *mm, pgd_t *pgdp)
 219 {
 220         int i;
 221
 222         for(i = 0; i < PREALLOCATED_PMDS; i++) {
 223                 pgd_t pgd = pgdp[i];
 224
 225                 if (pgd_val(pgd) != 0) {
 226                         pmd_t *pmd = (pmd_t *)pgd_page_vaddr(pgd);
 227
 228                         pgdp[i] = native_make_pgd(0);
 229
 230                         paravirt_release_pmd(pgd_val(pgd) >> PAGE_SHIFT);
 231                         pmd_free(mm, pmd);
 232                 }
 233         }
 234 }
 235
 236 static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
 237 {
 238         pud_t *pud;
 239         unsigned long addr;
 240         int i;
 241
 242         if (PREALLOCATED_PMDS == 0) /* Work around gcc-3.4.x bug */
 243                 return;
 244
 245         pud = pud_offset(pgd, 0);
 246
 247         for (addr = i = 0; i < PREALLOCATED_PMDS;
 248              i++, pud++, addr += PUD_SIZE) {
 249                 pmd_t *pmd = pmds[i];
 250
 251                 if (i >= KERNEL_PGD_BOUNDARY)
 252                         memcpy(pmd, (pmd_t *)pgd_page_vaddr(swapper_pg_dir[i]),
 253                                sizeof(pmd_t) * PTRS_PER_PMD);
 254
 255                 pud_populate(mm, pud, pmd);
 256         }
 257 }
 258
 259 pgd_t *pgd_alloc(struct mm_struct *mm)
 260 {
 261         pgd_t *pgd;
 262         pmd_t *pmds[PREALLOCATED_PMDS];
 263         unsigned long flags;
 264
 265         pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
 266
 267         if (pgd == NULL)
 268                 goto out;
 269
 270         mm->pgd = pgd;
 271
 272         if (preallocate_pmds(pmds) != 0)
 273                 goto out_free_pgd;
 274
 275         if (paravirt_pgd_alloc(mm) != 0)
 276                 goto out_free_pmds;
 277
 278         /*
 279          * Make sure that pre-populating the pmds is atomic with
 280          * respect to anything walking the pgd_list, so that they
 281          * never see a partially populated pgd.
 282          */
 283         spin_lock_irqsave(&pgd_lock, flags);
 284
 285         pgd_ctor(mm, pgd);
 286         pgd_prepopulate_pmd(mm, pgd, pmds);
 287
 288         spin_unlock_irqrestore(&pgd_lock, flags);
 289
 290         return pgd;
 291
 292 out_free_pmds:
 293         free_pmds(pmds);
 294 out_free_pgd:
 295         free_page((unsigned long)pgd);
 296 out:
 297         return NULL;
 298 }
 299
 300 void pgd_free(struct mm_struct *mm, pgd_t *pgd)
 301 {
 302         pgd_mop_up_pmds(mm, pgd);
 303         pgd_dtor(pgd);
 304         paravirt_pgd_free(mm, pgd);
 305         free_page((unsigned long)pgd);
 306 }
 307
 308 int ptep_set_access_flags(struct vm_area_struct *vma,
 309                           unsigned long address, pte_t *ptep,
 310                           pte_t entry, int dirty)
 311 {
 312         int changed = !pte_same(*ptep, entry);
 313
 314         if (changed && dirty) {
 315                 *ptep = entry;
 316                 pte_update_defer(vma->vm_mm, address, ptep);
 317                 flush_tlb_page(vma, address);
 318         }
 319
 320         return changed;
 321 }
 322
 323 int ptep_test_and_clear_young(struct vm_area_struct *vma,
 324                               unsigned long addr, pte_t *ptep)
 325 {
 326         int ret = 0;
 327
 328         if (pte_young(*ptep))
 329                 ret = test_and_clear_bit(_PAGE_BIT_ACCESSED,
 330                                          (unsigned long *) &ptep->pte);
 331
 332         if (ret)
 333                 pte_update(vma->vm_mm, addr, ptep);
 334
 335         return ret;
 336 }
 337
 338 int ptep_clear_flush_young(struct vm_area_struct *vma,
 339                            unsigned long address, pte_t *ptep)
 340 {
 341         int young;
 342
 343         young = ptep_test_and_clear_young(vma, address, ptep);
 344         if (young)
 345                 flush_tlb_page(vma, address);
 346
 347         return young;
 348 }
 349
 350 /**
 351  * reserve_top_address - reserves a hole in the top of kernel address space
 352  * @reserve - size of hole to reserve
 353  *
 354  * Can be used to relocate the fixmap area and poke a hole in the top
 355  * of kernel address space to make room for a hypervisor.
 356  */
 357 void __init reserve_top_address(unsigned long reserve)
 358 {
 359 #ifdef CONFIG_X86_32
 360         BUG_ON(fixmaps_set > 0);
 361         printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
 362                (int)-reserve);
 363         __FIXADDR_TOP = -reserve - PAGE_SIZE;
 364 #endif
 365 }
 366
 367 int fixmaps_set;
 368
 369 void __native_set_fixmap(enum fixed_addresses idx, pte_t pte)
 370 {
 371         unsigned long address = __fix_to_virt(idx);
 372
 373         if (idx >= __end_of_fixed_addresses) {
 374                 BUG();
 375                 return;
 376         }
 377         set_pte_vaddr(address, pte);
 378         fixmaps_set++;
 379 }
 380
 381 void native_set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
 382                        pgprot_t flags)
 383 {
 384         __native_set_fixmap(idx, pfn_pte(phys >> PAGE_SHIFT, flags));
 385 }