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 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                 void *p;
 202
 203                 for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 204                         md = p;
 205                         if (!is_available_memory(md))
 206                                 continue;
 207                         addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 208                         end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;
 209
 210                         if ((pagenr >= addr) && (pagenr < end))
 211                                 return 1;
 212                 }
 213                 return 0;
 214         }
 215
 216         for (i = 0; i < e820.nr_map; i++) {
 217
 218                 if (e820.map[i].type != E820_RAM)       /* not usable memory */
 219                         continue;
 220                 /*
 221                  *      !!!FIXME!!! Some BIOSen report areas as RAM that
 222                  *      are not. Notably the 640->1Mb area. We need a sanity
 223                  *      check here.
 224                  */
 225                 addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 226                 end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
 227                 if  ((pagenr >= addr) && (pagenr < end))
 228                         return 1;
 229         }
 230         return 0;
 231 }
 232
 233 #ifdef CONFIG_HIGHMEM
 234 pte_t *kmap_pte;
 235 pgprot_t kmap_prot;
 236
 237 #define kmap_get_fixmap_pte(vaddr)                                      \
 238         pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), vaddr), (vaddr)), (vaddr))
 239
 240 static void __init kmap_init(void)
 241 {
 242         unsigned long kmap_vstart;
 243
 244         /* cache the first kmap pte */
 245         kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
 246         kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
 247
 248         kmap_prot = PAGE_KERNEL;
 249 }
 250
 251 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 252 {
 253         pgd_t *pgd;
 254         pud_t *pud;
 255         pmd_t *pmd;
 256         pte_t *pte;
 257         unsigned long vaddr;
 258
 259         vaddr = PKMAP_BASE;
 260         page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);
 261
 262         pgd = swapper_pg_dir + pgd_index(vaddr);
 263         pud = pud_offset(pgd, vaddr);
 264         pmd = pmd_offset(pud, vaddr);
 265         pte = pte_offset_kernel(pmd, vaddr);
 266         pkmap_page_table = pte;
 267 }
 268
 269 void __init one_highpage_init(struct page *page, int pfn, int bad_ppro)
 270 {
 271         if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
 272                 ClearPageReserved(page);
 273                 set_page_count(page, 1);
 274                 __free_page(page);
 275                 totalhigh_pages++;
 276         } else
 277                 SetPageReserved(page);
 278 }
 279
 280 #ifdef CONFIG_NUMA
 281 extern void set_highmem_pages_init(int);
 282 #else
 283 static void __init set_highmem_pages_init(int bad_ppro)
 284 {
 285         int pfn;
 286         for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
 287                 one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
 288         totalram_pages += totalhigh_pages;
 289 }
 290 #endif /* CONFIG_FLATMEM */
 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 EXPORT_SYMBOL(__PAGE_KERNEL);
 300 unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;
 301
 302 #ifdef CONFIG_NUMA
 303 extern void __init remap_numa_kva(void);
 304 #else
 305 #define remap_numa_kva() do {} while (0)
 306 #endif
 307
 308 static void __init pagetable_init (void)
 309 {
 310         unsigned long vaddr;
 311         pgd_t *pgd_base = swapper_pg_dir;
 312
 313 #ifdef CONFIG_X86_PAE
 314         int i;
 315         /* Init entries of the first-level page table to the zero page */
 316         for (i = 0; i < PTRS_PER_PGD; i++)
 317                 set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
 318 #endif
 319
 320         /* Enable PSE if available */
 321         if (cpu_has_pse) {
 322                 set_in_cr4(X86_CR4_PSE);
 323         }
 324
 325         /* Enable PGE if available */
 326         if (cpu_has_pge) {
 327                 set_in_cr4(X86_CR4_PGE);
 328                 __PAGE_KERNEL |= _PAGE_GLOBAL;
 329                 __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
 330         }
 331
 332         kernel_physical_mapping_init(pgd_base);
 333         remap_numa_kva();
 334
 335         /*
 336          * Fixed mappings, only the page table structure has to be
 337          * created - mappings will be set by set_fixmap():
 338          */
 339         vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
 340         page_table_range_init(vaddr, 0, pgd_base);
 341
 342         permanent_kmaps_init(pgd_base);
 343
 344 #ifdef CONFIG_X86_PAE
 345         /*
 346          * Add low memory identity-mappings - SMP needs it when
 347          * starting up on an AP from real-mode. In the non-PAE
 348          * case we already have these mappings through head.S.
 349          * All user-space mappings are explicitly cleared after
 350          * SMP startup.
 351          */
 352         set_pgd(&pgd_base[0], pgd_base[USER_PTRS_PER_PGD]);
 353 #endif
 354 }
 355
 356 #ifdef CONFIG_SOFTWARE_SUSPEND
 357 /*
 358  * Swap suspend & friends need this for resume because things like the intel-agp
 359  * driver might have split up a kernel 4MB mapping.
 360  */
 361 char __nosavedata swsusp_pg_dir[PAGE_SIZE]
 362         __attribute__ ((aligned (PAGE_SIZE)));
 363
 364 static inline void save_pg_dir(void)
 365 {
 366         memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
 367 }
 368 #else
 369 static inline void save_pg_dir(void)
 370 {
 371 }
 372 #endif
 373
 374 void zap_low_mappings (void)
 375 {
 376         int i;
 377
 378         save_pg_dir();
 379
 380         /*
 381          * Zap initial low-memory mappings.
 382          *
 383          * Note that "pgd_clear()" doesn't do it for
 384          * us, because pgd_clear() is a no-op on i386.
 385          */
 386         for (i = 0; i < USER_PTRS_PER_PGD; i++)
 387 #ifdef CONFIG_X86_PAE
 388                 set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
 389 #else
 390                 set_pgd(swapper_pg_dir+i, __pgd(0));
 391 #endif
 392         flush_tlb_all();
 393 }
 394
 395 static int disable_nx __initdata = 0;
 396 u64 __supported_pte_mask __read_mostly = ~_PAGE_NX;
 397
 398 /*
 399  * noexec = on|off
 400  *
 401  * Control non executable mappings.
 402  *
 403  * on      Enable
 404  * off     Disable
 405  */
 406 void __init noexec_setup(const char *str)
 407 {
 408         if (!strncmp(str, "on",2) && cpu_has_nx) {
 409                 __supported_pte_mask |= _PAGE_NX;
 410                 disable_nx = 0;
 411         } else if (!strncmp(str,"off",3)) {
 412                 disable_nx = 1;
 413                 __supported_pte_mask &= ~_PAGE_NX;
 414         }
 415 }
 416
 417 int nx_enabled = 0;
 418 #ifdef CONFIG_X86_PAE
 419
 420 static void __init set_nx(void)
 421 {
 422         unsigned int v[4], l, h;
 423
 424         if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
 425                 cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
 426                 if ((v[3] & (1 << 20)) && !disable_nx) {
 427                         rdmsr(MSR_EFER, l, h);
 428                         l |= EFER_NX;
 429                         wrmsr(MSR_EFER, l, h);
 430                         nx_enabled = 1;
 431                         __supported_pte_mask |= _PAGE_NX;
 432                 }
 433         }
 434 }
 435
 436 /*
 437  * Enables/disables executability of a given kernel page and
 438  * returns the previous setting.
 439  */
 440 int __init set_kernel_exec(unsigned long vaddr, int enable)
 441 {
 442         pte_t *pte;
 443         int ret = 1;
 444
 445         if (!nx_enabled)
 446                 goto out;
 447
 448         pte = lookup_address(vaddr);
 449         BUG_ON(!pte);
 450
 451         if (!pte_exec_kernel(*pte))
 452                 ret = 0;
 453
 454         if (enable)
 455                 pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
 456         else
 457                 pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
 458         __flush_tlb_all();
 459 out:
 460         return ret;
 461 }
 462
 463 #endif
 464
 465 /*
 466  * paging_init() sets up the page tables - note that the first 8MB are
 467  * already mapped by head.S.
 468  *
 469  * This routines also unmaps the page at virtual kernel address 0, so
 470  * that we can trap those pesky NULL-reference errors in the kernel.
 471  */
 472 void __init paging_init(void)
 473 {
 474 #ifdef CONFIG_X86_PAE
 475         set_nx();
 476         if (nx_enabled)
 477                 printk("NX (Execute Disable) protection: active\n");
 478 #endif
 479
 480         pagetable_init();
 481
 482         load_cr3(swapper_pg_dir);
 483
 484 #ifdef CONFIG_X86_PAE
 485         /*
 486          * We will bail out later - printk doesn't work right now so
 487          * the user would just see a hanging kernel.
 488          */
 489         if (cpu_has_pae)
 490                 set_in_cr4(X86_CR4_PAE);
 491 #endif
 492         __flush_tlb_all();
 493
 494         kmap_init();
 495 }
 496
 497 /*
 498  * Test if the WP bit works in supervisor mode. It isn't supported on 386's
 499  * and also on some strange 486's (NexGen etc.). All 586+'s are OK. This
 500  * used to involve black magic jumps to work around some nasty CPU bugs,
 501  * but fortunately the switch to using exceptions got rid of all that.
 502  */
 503
 504 static void __init test_wp_bit(void)
 505 {
 506         printk("Checking if this processor honours the WP bit even in supervisor mode... ");
 507
 508         /* Any page-aligned address will do, the test is non-destructive */
 509         __set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_READONLY);
 510         boot_cpu_data.wp_works_ok = do_test_wp_bit();
 511         clear_fixmap(FIX_WP_TEST);
 512
 513         if (!boot_cpu_data.wp_works_ok) {
 514                 printk("No.\n");
 515 #ifdef CONFIG_X86_WP_WORKS_OK
 516                 panic("This kernel doesn't support CPU's with broken WP. Recompile it for a 386!");
 517 #endif
 518         } else {
 519                 printk("Ok.\n");
 520         }
 521 }
 522
 523 static void __init set_max_mapnr_init(void)
 524 {
 525 #ifdef CONFIG_HIGHMEM
 526         num_physpages = highend_pfn;
 527 #else
 528         num_physpages = max_low_pfn;
 529 #endif
 530 #ifdef CONFIG_FLATMEM
 531         max_mapnr = num_physpages;
 532 #endif
 533 }
 534
 535 static struct kcore_list kcore_mem, kcore_vmalloc;
 536
 537 void __init mem_init(void)
 538 {
 539         extern int ppro_with_ram_bug(void);
 540         int codesize, reservedpages, datasize, initsize;
 541         int tmp;
 542         int bad_ppro;
 543
 544 #ifdef CONFIG_FLATMEM
 545         if (!mem_map)
 546                 BUG();
 547 #endif
 548
 549         bad_ppro = ppro_with_ram_bug();
 550
 551 #ifdef CONFIG_HIGHMEM
 552         /* check that fixmap and pkmap do not overlap */
 553         if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
 554                 printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
 555                 printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
 556                                 PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
 557                 BUG();
 558         }
 559 #endif
 560
 561         set_max_mapnr_init();
 562
 563 #ifdef CONFIG_HIGHMEM
 564         high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
 565 #else
 566         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 567 #endif
 568
 569         /* this will put all low memory onto the freelists */
 570         totalram_pages += free_all_bootmem();
 571
 572         reservedpages = 0;
 573         for (tmp = 0; tmp < max_low_pfn; tmp++)
 574                 /*
 575                  * Only count reserved RAM pages
 576                  */
 577                 if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
 578                         reservedpages++;
 579
 580         set_highmem_pages_init(bad_ppro);
 581
 582         codesize =  (unsigned long) &_etext - (unsigned long) &_text;
 583         datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
 584         initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;
 585
 586         kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT);
 587         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 588                    VMALLOC_END-VMALLOC_START);
 589
 590         printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
 591                 (unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
 592                 num_physpages << (PAGE_SHIFT-10),
 593                 codesize >> 10,
 594                 reservedpages << (PAGE_SHIFT-10),
 595                 datasize >> 10,
 596                 initsize >> 10,
 597                 (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
 598                );
 599
 600 #ifdef CONFIG_X86_PAE
 601         if (!cpu_has_pae)
 602                 panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
 603 #endif
 604         if (boot_cpu_data.wp_works_ok < 0)
 605                 test_wp_bit();
 606
 607         /*
 608          * Subtle. SMP is doing it's boot stuff late (because it has to
 609          * fork idle threads) - but it also needs low mappings for the
 610          * protected-mode entry to work. We zap these entries only after
 611          * the WP-bit has been tested.
 612          */
 613 #ifndef CONFIG_SMP
 614         zap_low_mappings();
 615 #endif
 616 }
 617
 618 kmem_cache_t *pgd_cache;
 619 kmem_cache_t *pmd_cache;
 620
 621 void __init pgtable_cache_init(void)
 622 {
 623         if (PTRS_PER_PMD > 1) {
 624                 pmd_cache = kmem_cache_create("pmd",
 625                                         PTRS_PER_PMD*sizeof(pmd_t),
 626                                         PTRS_PER_PMD*sizeof(pmd_t),
 627                                         0,
 628                                         pmd_ctor,
 629                                         NULL);
 630                 if (!pmd_cache)
 631                         panic("pgtable_cache_init(): cannot create pmd cache");
 632         }
 633         pgd_cache = kmem_cache_create("pgd",
 634                                 PTRS_PER_PGD*sizeof(pgd_t),
 635                                 PTRS_PER_PGD*sizeof(pgd_t),
 636                                 0,
 637                                 pgd_ctor,
 638                                 PTRS_PER_PMD == 1 ? pgd_dtor : NULL);
 639         if (!pgd_cache)
 640                 panic("pgtable_cache_init(): Cannot create pgd cache");
 641 }
 642
 643 /*
 644  * This function cannot be __init, since exceptions don't work in that
 645  * section.  Put this after the callers, so that it cannot be inlined.
 646  */
 647 static int noinline do_test_wp_bit(void)
 648 {
 649         char tmp_reg;
 650         int flag;
 651
 652         __asm__ __volatile__(
 653                 "       movb %0,%1      \n"
 654                 "1:     movb %1,%0      \n"
 655                 "       xorl %2,%2      \n"
 656                 "2:                     \n"
 657                 ".section __ex_table,\"a\"\n"
 658                 "       .align 4        \n"
 659                 "       .long 1b,2b     \n"
 660                 ".previous              \n"
 661                 :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
 662                  "=q" (tmp_reg),
 663                  "=r" (flag)
 664                 :"2" (1)
 665                 :"memory");
 666
 667         return flag;
 668 }
 669
 670 void free_initmem(void)
 671 {
 672         unsigned long addr;
 673
 674         addr = (unsigned long)(&__init_begin);
 675         for (; addr < (unsigned long)(&__init_end); addr += PAGE_SIZE) {
 676                 ClearPageReserved(virt_to_page(addr));
 677                 set_page_count(virt_to_page(addr), 1);
 678                 memset((void *)addr, 0xcc, PAGE_SIZE);
 679                 free_page(addr);
 680                 totalram_pages++;
 681         }
 682         printk (KERN_INFO "Freeing unused kernel memory: %dk freed\n", (__init_end - __init_begin) >> 10);
 683 }
 684
 685 #ifdef CONFIG_BLK_DEV_INITRD
 686 void free_initrd_mem(unsigned long start, unsigned long end)
 687 {
 688         if (start < end)
 689                 printk (KERN_INFO "Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 690         for (; start < end; start += PAGE_SIZE) {
 691                 ClearPageReserved(virt_to_page(start));
 692                 set_page_count(virt_to_page(start), 1);
 693                 free_page(start);
 694                 totalram_pages++;
 695         }
 696 }
 697 #endif