arch/i386/mm/init.c

   1 /*
   2  *  linux/arch/i386/mm/init.c
   3  *
   4  *  Copyright (C) 1995  Linus Torvalds
   5  *
   6  *  Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
   7  */
   8
   9 #include <linux/config.h>
  10 #include <linux/module.h>
  11 #include <linux/signal.h>
  12 #include <linux/sched.h>
  13 #include <linux/kernel.h>
  14 #include <linux/errno.h>
  15 #include <linux/string.h>
  16 #include <linux/types.h>
  17 #include <linux/ptrace.h>
  18 #include <linux/mman.h>
  19 #include <linux/mm.h>
  20 #include <linux/hugetlb.h>
  21 #include <linux/swap.h>
  22 #include <linux/smp.h>
  23 #include <linux/init.h>
  24 #include <linux/highmem.h>
  25 #include <linux/pagemap.h>
  26 #include <linux/bootmem.h>
  27 #include <linux/slab.h>
  28 #include <linux/proc_fs.h>
  29 #include <linux/efi.h>
  30
  31 #include <asm/processor.h>
  32 #include <asm/system.h>
  33 #include <asm/uaccess.h>
  34 #include <asm/pgtable.h>
  35 #include <asm/dma.h>
  36 #include <asm/fixmap.h>
  37 #include <asm/e820.h>
  38 #include <asm/apic.h>
  39 #include <asm/tlb.h>
  40 #include <asm/tlbflush.h>
  41 #include <asm/sections.h>
  42
  43 unsigned int __VMALLOC_RESERVE = 128 << 20;
  44
  45 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
  46 unsigned long highstart_pfn, highend_pfn;
  47
  48 static int noinline do_test_wp_bit(void);
  49
  50 /*
  51  * Creates a middle page table and puts a pointer to it in the
  52  * given global directory entry. This only returns the gd entry
  53  * in non-PAE compilation mode, since the middle layer is folded.
  54  */
  55 static pmd_t * __init one_md_table_init(pgd_t *pgd)
  56 {
  57         pud_t *pud;
  58         pmd_t *pmd_table;
  59
  60 #ifdef CONFIG_X86_PAE
  61         pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
  62         set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
  63         pud = pud_offset(pgd, 0);
  64         if (pmd_table != pmd_offset(pud, 0))
  65                 BUG();
  66 #else
  67         pud = pud_offset(pgd, 0);
  68         pmd_table = pmd_offset(pud, 0);
  69 #endif
  70
  71         return pmd_table;
  72 }
  73
  74 /*
  75  * Create a page table and place a pointer to it in a middle page
  76  * directory entry.
  77  */
  78 static pte_t * __init one_page_table_init(pmd_t *pmd)
  79 {
  80         if (pmd_none(*pmd)) {
  81                 pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
  82                 set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
  83                 if (page_table != pte_offset_kernel(pmd, 0))
  84                         BUG();
  85
  86                 return page_table;
  87         }
  88
  89         return pte_offset_kernel(pmd, 0);
  90 }
  91
  92 /*
  93  * This function initializes a certain range of kernel virtual memory
  94  * with new bootmem page tables, everywhere page tables are missing in
  95  * the given range.
  96  */
  97
  98 /*
  99  * NOTE: The pagetables are allocated contiguous on the physical space
 100  * so we can cache the place of the first one and move around without
 101  * checking the pgd every time.
 102  */
 103 static void __init page_table_range_init (unsigned long start, unsigned long end, pgd_t *pgd_base)
 104 {
 105         pgd_t *pgd;
 106         pud_t *pud;
 107         pmd_t *pmd;
 108         int pgd_idx, pmd_idx;
 109         unsigned long vaddr;
 110
 111         vaddr = start;
 112         pgd_idx = pgd_index(vaddr);
 113         pmd_idx = pmd_index(vaddr);
 114         pgd = pgd_base + pgd_idx;
 115
 116         for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd++, pgd_idx++) {
 117                 if (pgd_none(*pgd))
 118                         one_md_table_init(pgd);
 119                 pud = pud_offset(pgd, vaddr);
 120                 pmd = pmd_offset(pud, vaddr);
 121                 for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) {
 122                         if (pmd_none(*pmd))
 123                                 one_page_table_init(pmd);
 124
 125                         vaddr += PMD_SIZE;
 126                 }
 127                 pmd_idx = 0;
 128         }
 129 }
 130
 131 static inline int is_kernel_text(unsigned long addr)
 132 {
 133         if (addr >= PAGE_OFFSET && addr <= (unsigned long)__init_end)
 134                 return 1;
 135         return 0;
 136 }
 137
 138 /*
 139  * This maps the physical memory to kernel virtual address space, a total
 140  * of max_low_pfn pages, by creating page tables starting from address
 141  * PAGE_OFFSET.
 142  */
 143 static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
 144 {
 145         unsigned long pfn;
 146         pgd_t *pgd;
 147         pmd_t *pmd;
 148         pte_t *pte;
 149         int pgd_idx, pmd_idx, pte_ofs;
 150
 151         pgd_idx = pgd_index(PAGE_OFFSET);
 152         pgd = pgd_base + pgd_idx;
 153         pfn = 0;
 154
 155         for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
 156                 pmd = one_md_table_init(pgd);
 157                 if (pfn >= max_low_pfn)
 158                         continue;
 159                 for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
 160                         unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;
 161
 162                         /* Map with big pages if possible, otherwise create normal page tables. */
 163                         if (cpu_has_pse) {
 164                                 unsigned int address2 = (pfn + PTRS_PER_PTE - 1) * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;
 165
 166                                 if (is_kernel_text(address) || is_kernel_text(address2))
 167                                         set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
 168                                 else
 169                                         set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));
 170                                 pfn += PTRS_PER_PTE;
 171                         } else {
 172                                 pte = one_page_table_init(pmd);
 173
 174                                 for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn; pte++, pfn++, pte_ofs++) {
 175                                                 if (is_kernel_text(address))
 176                                                         set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 177                                                 else
 178                                                         set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));
 179                                 }
 180                         }
 181                 }
 182         }
 183 }
 184
 185 static inline int page_kills_ppro(unsigned long pagenr)
 186 {
 187         if (pagenr >= 0x70000 && pagenr <= 0x7003F)
 188                 return 1;
 189         return 0;
 190 }
 191
 192 extern int is_available_memory(efi_memory_desc_t *);
 193
 194 static inline int page_is_ram(unsigned long pagenr)
 195 {
 196         int i;
 197         unsigned long addr, end;
 198
 199         if (efi_enabled) {
 200                 efi_memory_desc_t *md;
 201
 202                 for (i = 0; i < memmap.nr_map; i++) {
 203                         md = &memmap.map[i];
 204                         if (!is_available_memory(md))
 205                                 continue;
 206                         addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 207                         end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;
 208
 209                         if ((pagenr >= addr) && (pagenr < end))
 210                                 return 1;
 211                 }
 212                 return 0;
 213         }
 214
 215         for (i = 0; i < e820.nr_map; i++) {
 216
 217                 if (e820.map[i].type != E820_RAM)       /* not usable memory */
 218                         continue;
 219                 /*
 220                  *      !!!FIXME!!! Some BIOSen report areas as RAM that
 221                  *      are not. Notably the 640->1Mb area. We need a sanity
 222                  *      check here.
 223                  */
 224                 addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 225                 end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
 226                 if  ((pagenr >= addr) && (pagenr < end))
 227                         return 1;
 228         }
 229         return 0;
 230 }
 231
 232 #ifdef CONFIG_HIGHMEM
 233 pte_t *kmap_pte;
 234 pgprot_t kmap_prot;
 235
 236 #define kmap_get_fixmap_pte(vaddr)                                      \
 237         pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), vaddr), (vaddr)), (vaddr))
 238
 239 static void __init kmap_init(void)
 240 {
 241         unsigned long kmap_vstart;
 242
 243         /* cache the first kmap pte */
 244         kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
 245         kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
 246
 247         kmap_prot = PAGE_KERNEL;
 248 }
 249
 250 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 251 {
 252         pgd_t *pgd;
 253         pud_t *pud;
 254         pmd_t *pmd;
 255         pte_t *pte;
 256         unsigned long vaddr;
 257
 258         vaddr = PKMAP_BASE;
 259         page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);
 260
 261         pgd = swapper_pg_dir + pgd_index(vaddr);
 262         pud = pud_offset(pgd, vaddr);
 263         pmd = pmd_offset(pud, vaddr);
 264         pte = pte_offset_kernel(pmd, vaddr);
 265         pkmap_page_table = pte;
 266 }
 267
 268 void __init one_highpage_init(struct page *page, int pfn, int bad_ppro)
 269 {
 270         if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
 271                 ClearPageReserved(page);
 272                 set_bit(PG_highmem, &page->flags);
 273                 set_page_count(page, 1);
 274                 __free_page(page);
 275                 totalhigh_pages++;
 276         } else
 277                 SetPageReserved(page);
 278 }
 279
 280 #ifndef CONFIG_DISCONTIGMEM
 281 static void __init set_highmem_pages_init(int bad_ppro)
 282 {
 283         int pfn;
 284         for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
 285                 one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
 286         totalram_pages += totalhigh_pages;
 287 }
 288 #else
 289 extern void set_highmem_pages_init(int);
 290 #endif /* !CONFIG_DISCONTIGMEM */
 291
 292 #else
 293 #define kmap_init() do { } while (0)
 294 #define permanent_kmaps_init(pgd_base) do { } while (0)
 295 #define set_highmem_pages_init(bad_ppro) do { } while (0)
 296 #endif /* CONFIG_HIGHMEM */
 297
 298 unsigned long long __PAGE_KERNEL = _PAGE_KERNEL;
 299 unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;
 300
 301 #ifndef CONFIG_DISCONTIGMEM
 302 #define remap_numa_kva() do {} while (0)
 303 #else
 304 extern void __init remap_numa_kva(void);
 305 #endif
 306
 307 static void __init pagetable_init (void)
 308 {
 309         unsigned long vaddr;
 310         pgd_t *pgd_base = swapper_pg_dir;
 311
 312 #ifdef CONFIG_X86_PAE
 313         int i;
 314         /* Init entries of the first-level page table to the zero page */
 315         for (i = 0; i < PTRS_PER_PGD; i++)
 316                 set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
 317 #endif
 318
 319         /* Enable PSE if available */
 320         if (cpu_has_pse) {
 321                 set_in_cr4(X86_CR4_PSE);
 322         }
 323
 324         /* Enable PGE if available */
 325         if (cpu_has_pge) {
 326                 set_in_cr4(X86_CR4_PGE);
 327                 __PAGE_KERNEL |= _PAGE_GLOBAL;
 328                 __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
 329         }
 330
 331         kernel_physical_mapping_init(pgd_base);
 332         remap_numa_kva();
 333
 334         /*
 335          * Fixed mappings, only the page table structure has to be
 336          * created - mappings will be set by set_fixmap():
 337          */
 338         vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
 339         page_table_range_init(vaddr, 0, pgd_base);
 340
 341         permanent_kmaps_init(pgd_base);
 342
 343 #ifdef CONFIG_X86_PAE
 344         /*
 345          * Add low memory identity-mappings - SMP needs it when
 346          * starting up on an AP from real-mode. In the non-PAE
 347          * case we already have these mappings through head.S.
 348          * All user-space mappings are explicitly cleared after
 349          * SMP startup.
 350          */
 351         pgd_base[0] = pgd_base[USER_PTRS_PER_PGD];
 352 #endif
 353 }
 354
 355 #if defined(CONFIG_PM_DISK) || defined(CONFIG_SOFTWARE_SUSPEND)
 356 /*
 357  * Swap suspend & friends need this for resume because things like the intel-agp
 358  * driver might have split up a kernel 4MB mapping.
 359  */
 360 char __nosavedata swsusp_pg_dir[PAGE_SIZE]
 361         __attribute__ ((aligned (PAGE_SIZE)));
 362
 363 static inline void save_pg_dir(void)
 364 {
 365         memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
 366 }
 367 #else
 368 static inline void save_pg_dir(void)
 369 {
 370 }
 371 #endif
 372
 373 void zap_low_mappings (void)
 374 {
 375         int i;
 376
 377         save_pg_dir();
 378
 379         /*
 380          * Zap initial low-memory mappings.
 381          *
 382          * Note that "pgd_clear()" doesn't do it for
 383          * us, because pgd_clear() is a no-op on i386.
 384          */
 385         for (i = 0; i < USER_PTRS_PER_PGD; i++)
 386 #ifdef CONFIG_X86_PAE
 387                 set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
 388 #else
 389                 set_pgd(swapper_pg_dir+i, __pgd(0));
 390 #endif
 391         flush_tlb_all();
 392 }
 393
 394 static int disable_nx __initdata = 0;
 395 u64 __supported_pte_mask = ~_PAGE_NX;
 396
 397 /*
 398  * noexec = on|off
 399  *
 400  * Control non executable mappings.
 401  *
 402  * on      Enable
 403  * off     Disable
 404  */
 405 void __init noexec_setup(const char *str)
 406 {
 407         if (!strncmp(str, "on",2) && cpu_has_nx) {
 408                 __supported_pte_mask |= _PAGE_NX;
 409                 disable_nx = 0;
 410         } else if (!strncmp(str,"off",3)) {
 411                 disable_nx = 1;
 412                 __supported_pte_mask &= ~_PAGE_NX;
 413         }
 414 }
 415
 416 int nx_enabled = 0;
 417 #ifdef CONFIG_X86_PAE
 418
 419 static void __init set_nx(void)
 420 {
 421         unsigned int v[4], l, h;
 422
 423         if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
 424                 cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
 425                 if ((v[3] & (1 << 20)) && !disable_nx) {
 426                         rdmsr(MSR_EFER, l, h);
 427                         l |= EFER_NX;
 428                         wrmsr(MSR_EFER, l, h);
 429                         nx_enabled = 1;
 430                         __supported_pte_mask |= _PAGE_NX;
 431                 }
 432         }
 433 }
 434
 435 /*
 436  * Enables/disables executability of a given kernel page and
 437  * returns the previous setting.
 438  */
 439 int __init set_kernel_exec(unsigned long vaddr, int enable)
 440 {
 441         pte_t *pte;
 442         int ret = 1;
 443
 444         if (!nx_enabled)
 445                 goto out;
 446
 447         pte = lookup_address(vaddr);
 448         BUG_ON(!pte);
 449
 450         if (!pte_exec_kernel(*pte))
 451                 ret = 0;
 452
 453         if (enable)
 454                 pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
 455         else
 456                 pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
 457         __flush_tlb_all();
 458 out:
 459         return ret;
 460 }
 461
 462 #endif
 463
 464 /*
 465  * paging_init() sets up the page tables - note that the first 8MB are
 466  * already mapped by head.S.
 467  *
 468  * This routines also unmaps the page at virtual kernel address 0, so
 469  * that we can trap those pesky NULL-reference errors in the kernel.
 470  */
 471 void __init paging_init(void)
 472 {
 473 #ifdef CONFIG_X86_PAE
 474         set_nx();
 475         if (nx_enabled)
 476                 printk("NX (Execute Disable) protection: active\n");
 477 #endif
 478
 479         pagetable_init();
 480
 481         load_cr3(swapper_pg_dir);
 482
 483 #ifdef CONFIG_X86_PAE
 484         /*
 485          * We will bail out later - printk doesn't work right now so
 486          * the user would just see a hanging kernel.
 487          */
 488         if (cpu_has_pae)
 489                 set_in_cr4(X86_CR4_PAE);
 490 #endif
 491         __flush_tlb_all();
 492
 493         kmap_init();
 494 }
 495
 496 /*
 497  * Test if the WP bit works in supervisor mode. It isn't supported on 386's
 498  * and also on some strange 486's (NexGen etc.). All 586+'s are OK. This
 499  * used to involve black magic jumps to work around some nasty CPU bugs,
 500  * but fortunately the switch to using exceptions got rid of all that.
 501  */
 502
 503 static void __init test_wp_bit(void)
 504 {
 505         printk("Checking if this processor honours the WP bit even in supervisor mode... ");
 506
 507         /* Any page-aligned address will do, the test is non-destructive */
 508         __set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_READONLY);
 509         boot_cpu_data.wp_works_ok = do_test_wp_bit();
 510         clear_fixmap(FIX_WP_TEST);
 511
 512         if (!boot_cpu_data.wp_works_ok) {
 513                 printk("No.\n");
 514 #ifdef CONFIG_X86_WP_WORKS_OK
 515                 panic("This kernel doesn't support CPU's with broken WP. Recompile it for a 386!");
 516 #endif
 517         } else {
 518                 printk("Ok.\n");
 519         }
 520 }
 521
 522 static void __init set_max_mapnr_init(void)
 523 {
 524 #ifdef CONFIG_HIGHMEM
 525         num_physpages = highend_pfn;
 526 #else
 527         num_physpages = max_low_pfn;
 528 #endif
 529 #ifndef CONFIG_DISCONTIGMEM
 530         max_mapnr = num_physpages;
 531 #endif
 532 }
 533
 534 static struct kcore_list kcore_mem, kcore_vmalloc;
 535
 536 void __init mem_init(void)
 537 {
 538         extern int ppro_with_ram_bug(void);
 539         int codesize, reservedpages, datasize, initsize;
 540         int tmp;
 541         int bad_ppro;
 542
 543 #ifndef CONFIG_DISCONTIGMEM
 544         if (!mem_map)
 545                 BUG();
 546 #endif
 547
 548         bad_ppro = ppro_with_ram_bug();
 549
 550 #ifdef CONFIG_HIGHMEM
 551         /* check that fixmap and pkmap do not overlap */
 552         if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
 553                 printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
 554                 printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
 555                                 PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
 556                 BUG();
 557         }
 558 #endif
 559
 560         set_max_mapnr_init();
 561
 562 #ifdef CONFIG_HIGHMEM
 563         high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
 564 #else
 565         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 566 #endif
 567
 568         /* this will put all low memory onto the freelists */
 569         totalram_pages += free_all_bootmem();
 570
 571         reservedpages = 0;
 572         for (tmp = 0; tmp < max_low_pfn; tmp++)
 573                 /*
 574                  * Only count reserved RAM pages
 575                  */
 576                 if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
 577                         reservedpages++;
 578
 579         set_highmem_pages_init(bad_ppro);
 580
 581         codesize =  (unsigned long) &_etext - (unsigned long) &_text;
 582         datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
 583         initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;
 584
 585         kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT);
 586         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 587                    VMALLOC_END-VMALLOC_START);
 588
 589         printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
 590                 (unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
 591                 num_physpages << (PAGE_SHIFT-10),
 592                 codesize >> 10,
 593                 reservedpages << (PAGE_SHIFT-10),
 594                 datasize >> 10,
 595                 initsize >> 10,
 596                 (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
 597                );
 598
 599 #ifdef CONFIG_X86_PAE
 600         if (!cpu_has_pae)
 601                 panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
 602 #endif
 603         if (boot_cpu_data.wp_works_ok < 0)
 604                 test_wp_bit();
 605
 606         /*
 607          * Subtle. SMP is doing it's boot stuff late (because it has to
 608          * fork idle threads) - but it also needs low mappings for the
 609          * protected-mode entry to work. We zap these entries only after
 610          * the WP-bit has been tested.
 611          */
 612 #ifndef CONFIG_SMP
 613         zap_low_mappings();
 614 #endif
 615 }
 616
 617 kmem_cache_t *pgd_cache;
 618 kmem_cache_t *pmd_cache;
 619
 620 void __init pgtable_cache_init(void)
 621 {
 622         if (PTRS_PER_PMD > 1) {
 623                 pmd_cache = kmem_cache_create("pmd",
 624                                         PTRS_PER_PMD*sizeof(pmd_t),
 625                                         PTRS_PER_PMD*sizeof(pmd_t),
 626                                         0,
 627                                         pmd_ctor,
 628                                         NULL);
 629                 if (!pmd_cache)
 630                         panic("pgtable_cache_init(): cannot create pmd cache");
 631         }
 632         pgd_cache = kmem_cache_create("pgd",
 633                                 PTRS_PER_PGD*sizeof(pgd_t),
 634                                 PTRS_PER_PGD*sizeof(pgd_t),
 635                                 0,
 636                                 pgd_ctor,
 637                                 PTRS_PER_PMD == 1 ? pgd_dtor : NULL);
 638         if (!pgd_cache)
 639                 panic("pgtable_cache_init(): Cannot create pgd cache");
 640 }
 641
 642 /*
 643  * This function cannot be __init, since exceptions don't work in that
 644  * section.  Put this after the callers, so that it cannot be inlined.
 645  */
 646 static int noinline do_test_wp_bit(void)
 647 {
 648         char tmp_reg;
 649         int flag;
 650
 651         __asm__ __volatile__(
 652                 "       movb %0,%1      \n"
 653                 "1:     movb %1,%0      \n"
 654                 "       xorl %2,%2      \n"
 655                 "2:                     \n"
 656                 ".section __ex_table,\"a\"\n"
 657                 "       .align 4        \n"
 658                 "       .long 1b,2b     \n"
 659                 ".previous              \n"
 660                 :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
 661                  "=q" (tmp_reg),
 662                  "=r" (flag)
 663                 :"2" (1)
 664                 :"memory");
 665
 666         return flag;
 667 }
 668
 669 void free_initmem(void)
 670 {
 671         unsigned long addr;
 672
 673         addr = (unsigned long)(&__init_begin);
 674         for (; addr < (unsigned long)(&__init_end); addr += PAGE_SIZE) {
 675                 ClearPageReserved(virt_to_page(addr));
 676                 set_page_count(virt_to_page(addr), 1);
 677                 memset((void *)addr, 0xcc, PAGE_SIZE);
 678                 free_page(addr);
 679                 totalram_pages++;
 680         }
 681         printk (KERN_INFO "Freeing unused kernel memory: %dk freed\n", (__init_end - __init_begin) >> 10);
 682 }
 683
 684 #ifdef CONFIG_BLK_DEV_INITRD
 685 void free_initrd_mem(unsigned long start, unsigned long end)
 686 {
 687         if (start < end)
 688                 printk (KERN_INFO "Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 689         for (; start < end; start += PAGE_SIZE) {
 690                 ClearPageReserved(virt_to_page(start));
 691                 set_page_count(virt_to_page(start), 1);
 692                 free_page(start);
 693                 totalram_pages++;
 694         }
 695 }
 696 #endif