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 #include <linux/memory_hotplug.h>
  31
  32 #include <asm/processor.h>
  33 #include <asm/system.h>
  34 #include <asm/uaccess.h>
  35 #include <asm/pgtable.h>
  36 #include <asm/dma.h>
  37 #include <asm/fixmap.h>
  38 #include <asm/e820.h>
  39 #include <asm/apic.h>
  40 #include <asm/tlb.h>
  41 #include <asm/tlbflush.h>
  42 #include <asm/sections.h>
  43
  44 unsigned int __VMALLOC_RESERVE = 128 << 20;
  45
  46 DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);
  47 unsigned long highstart_pfn, highend_pfn;
  48
  49 static int noinline do_test_wp_bit(void);
  50
  51 /*
  52  * Creates a middle page table and puts a pointer to it in the
  53  * given global directory entry. This only returns the gd entry
  54  * in non-PAE compilation mode, since the middle layer is folded.
  55  */
  56 static pmd_t * __init one_md_table_init(pgd_t *pgd)
  57 {
  58         pud_t *pud;
  59         pmd_t *pmd_table;
  60
  61 #ifdef CONFIG_X86_PAE
  62         pmd_table = (pmd_t *) alloc_bootmem_low_pages(PAGE_SIZE);
  63         set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
  64         pud = pud_offset(pgd, 0);
  65         if (pmd_table != pmd_offset(pud, 0))
  66                 BUG();
  67 #else
  68         pud = pud_offset(pgd, 0);
  69         pmd_table = pmd_offset(pud, 0);
  70 #endif
  71
  72         return pmd_table;
  73 }
  74
  75 /*
  76  * Create a page table and place a pointer to it in a middle page
  77  * directory entry.
  78  */
  79 static pte_t * __init one_page_table_init(pmd_t *pmd)
  80 {
  81         if (pmd_none(*pmd)) {
  82                 pte_t *page_table = (pte_t *) alloc_bootmem_low_pages(PAGE_SIZE);
  83                 set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));
  84                 if (page_table != pte_offset_kernel(pmd, 0))
  85                         BUG();
  86
  87                 return page_table;
  88         }
  89
  90         return pte_offset_kernel(pmd, 0);
  91 }
  92
  93 /*
  94  * This function initializes a certain range of kernel virtual memory
  95  * with new bootmem page tables, everywhere page tables are missing in
  96  * the given range.
  97  */
  98
  99 /*
 100  * NOTE: The pagetables are allocated contiguous on the physical space
 101  * so we can cache the place of the first one and move around without
 102  * checking the pgd every time.
 103  */
 104 static void __init page_table_range_init (unsigned long start, unsigned long end, pgd_t *pgd_base)
 105 {
 106         pgd_t *pgd;
 107         pud_t *pud;
 108         pmd_t *pmd;
 109         int pgd_idx, pmd_idx;
 110         unsigned long vaddr;
 111
 112         vaddr = start;
 113         pgd_idx = pgd_index(vaddr);
 114         pmd_idx = pmd_index(vaddr);
 115         pgd = pgd_base + pgd_idx;
 116
 117         for ( ; (pgd_idx < PTRS_PER_PGD) && (vaddr != end); pgd++, pgd_idx++) {
 118                 if (pgd_none(*pgd))
 119                         one_md_table_init(pgd);
 120                 pud = pud_offset(pgd, vaddr);
 121                 pmd = pmd_offset(pud, vaddr);
 122                 for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); pmd++, pmd_idx++) {
 123                         if (pmd_none(*pmd))
 124                                 one_page_table_init(pmd);
 125
 126                         vaddr += PMD_SIZE;
 127                 }
 128                 pmd_idx = 0;
 129         }
 130 }
 131
 132 static inline int is_kernel_text(unsigned long addr)
 133 {
 134         if (addr >= PAGE_OFFSET && addr <= (unsigned long)__init_end)
 135                 return 1;
 136         return 0;
 137 }
 138
 139 /*
 140  * This maps the physical memory to kernel virtual address space, a total
 141  * of max_low_pfn pages, by creating page tables starting from address
 142  * PAGE_OFFSET.
 143  */
 144 static void __init kernel_physical_mapping_init(pgd_t *pgd_base)
 145 {
 146         unsigned long pfn;
 147         pgd_t *pgd;
 148         pmd_t *pmd;
 149         pte_t *pte;
 150         int pgd_idx, pmd_idx, pte_ofs;
 151
 152         pgd_idx = pgd_index(PAGE_OFFSET);
 153         pgd = pgd_base + pgd_idx;
 154         pfn = 0;
 155
 156         for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
 157                 pmd = one_md_table_init(pgd);
 158                 if (pfn >= max_low_pfn)
 159                         continue;
 160                 for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD && pfn < max_low_pfn; pmd++, pmd_idx++) {
 161                         unsigned int address = pfn * PAGE_SIZE + PAGE_OFFSET;
 162
 163                         /* Map with big pages if possible, otherwise create normal page tables. */
 164                         if (cpu_has_pse) {
 165                                 unsigned int address2 = (pfn + PTRS_PER_PTE - 1) * PAGE_SIZE + PAGE_OFFSET + PAGE_SIZE-1;
 166
 167                                 if (is_kernel_text(address) || is_kernel_text(address2))
 168                                         set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
 169                                 else
 170                                         set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE));
 171                                 pfn += PTRS_PER_PTE;
 172                         } else {
 173                                 pte = one_page_table_init(pmd);
 174
 175                                 for (pte_ofs = 0; pte_ofs < PTRS_PER_PTE && pfn < max_low_pfn; pte++, pfn++, pte_ofs++) {
 176                                                 if (is_kernel_text(address))
 177                                                         set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
 178                                                 else
 179                                                         set_pte(pte, pfn_pte(pfn, PAGE_KERNEL));
 180                                 }
 181                         }
 182                 }
 183         }
 184 }
 185
 186 static inline int page_kills_ppro(unsigned long pagenr)
 187 {
 188         if (pagenr >= 0x70000 && pagenr <= 0x7003F)
 189                 return 1;
 190         return 0;
 191 }
 192
 193 extern int is_available_memory(efi_memory_desc_t *);
 194
 195 int page_is_ram(unsigned long pagenr)
 196 {
 197         int i;
 198         unsigned long addr, end;
 199
 200         if (efi_enabled) {
 201                 efi_memory_desc_t *md;
 202                 void *p;
 203
 204                 for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
 205                         md = p;
 206                         if (!is_available_memory(md))
 207                                 continue;
 208                         addr = (md->phys_addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 209                         end = (md->phys_addr + (md->num_pages << EFI_PAGE_SHIFT)) >> PAGE_SHIFT;
 210
 211                         if ((pagenr >= addr) && (pagenr < end))
 212                                 return 1;
 213                 }
 214                 return 0;
 215         }
 216
 217         for (i = 0; i < e820.nr_map; i++) {
 218
 219                 if (e820.map[i].type != E820_RAM)       /* not usable memory */
 220                         continue;
 221                 /*
 222                  *      !!!FIXME!!! Some BIOSen report areas as RAM that
 223                  *      are not. Notably the 640->1Mb area. We need a sanity
 224                  *      check here.
 225                  */
 226                 addr = (e820.map[i].addr+PAGE_SIZE-1) >> PAGE_SHIFT;
 227                 end = (e820.map[i].addr+e820.map[i].size) >> PAGE_SHIFT;
 228                 if  ((pagenr >= addr) && (pagenr < end))
 229                         return 1;
 230         }
 231         return 0;
 232 }
 233
 234 #ifdef CONFIG_HIGHMEM
 235 pte_t *kmap_pte;
 236 pgprot_t kmap_prot;
 237
 238 #define kmap_get_fixmap_pte(vaddr)                                      \
 239         pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), vaddr), (vaddr)), (vaddr))
 240
 241 static void __init kmap_init(void)
 242 {
 243         unsigned long kmap_vstart;
 244
 245         /* cache the first kmap pte */
 246         kmap_vstart = __fix_to_virt(FIX_KMAP_BEGIN);
 247         kmap_pte = kmap_get_fixmap_pte(kmap_vstart);
 248
 249         kmap_prot = PAGE_KERNEL;
 250 }
 251
 252 static void __init permanent_kmaps_init(pgd_t *pgd_base)
 253 {
 254         pgd_t *pgd;
 255         pud_t *pud;
 256         pmd_t *pmd;
 257         pte_t *pte;
 258         unsigned long vaddr;
 259
 260         vaddr = PKMAP_BASE;
 261         page_table_range_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, pgd_base);
 262
 263         pgd = swapper_pg_dir + pgd_index(vaddr);
 264         pud = pud_offset(pgd, vaddr);
 265         pmd = pmd_offset(pud, vaddr);
 266         pte = pte_offset_kernel(pmd, vaddr);
 267         pkmap_page_table = pte;
 268 }
 269
 270 void __devinit free_new_highpage(struct page *page)
 271 {
 272         set_page_count(page, 1);
 273         __free_page(page);
 274         totalhigh_pages++;
 275 }
 276
 277 void __init add_one_highpage_init(struct page *page, int pfn, int bad_ppro)
 278 {
 279         if (page_is_ram(pfn) && !(bad_ppro && page_kills_ppro(pfn))) {
 280                 ClearPageReserved(page);
 281                 free_new_highpage(page);
 282         } else
 283                 SetPageReserved(page);
 284 }
 285
 286 static int add_one_highpage_hotplug(struct page *page, unsigned long pfn)
 287 {
 288         free_new_highpage(page);
 289         totalram_pages++;
 290 #ifdef CONFIG_FLATMEM
 291         max_mapnr = max(pfn, max_mapnr);
 292 #endif
 293         num_physpages++;
 294         return 0;
 295 }
 296
 297 /*
 298  * Not currently handling the NUMA case.
 299  * Assuming single node and all memory that
 300  * has been added dynamically that would be
 301  * onlined here is in HIGHMEM
 302  */
 303 void online_page(struct page *page)
 304 {
 305         ClearPageReserved(page);
 306         add_one_highpage_hotplug(page, page_to_pfn(page));
 307 }
 308
 309
 310 #ifdef CONFIG_NUMA
 311 extern void set_highmem_pages_init(int);
 312 #else
 313 static void __init set_highmem_pages_init(int bad_ppro)
 314 {
 315         int pfn;
 316         for (pfn = highstart_pfn; pfn < highend_pfn; pfn++)
 317                 add_one_highpage_init(pfn_to_page(pfn), pfn, bad_ppro);
 318         totalram_pages += totalhigh_pages;
 319 }
 320 #endif /* CONFIG_FLATMEM */
 321
 322 #else
 323 #define kmap_init() do { } while (0)
 324 #define permanent_kmaps_init(pgd_base) do { } while (0)
 325 #define set_highmem_pages_init(bad_ppro) do { } while (0)
 326 #endif /* CONFIG_HIGHMEM */
 327
 328 unsigned long long __PAGE_KERNEL = _PAGE_KERNEL;
 329 EXPORT_SYMBOL(__PAGE_KERNEL);
 330 unsigned long long __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;
 331
 332 #ifdef CONFIG_NUMA
 333 extern void __init remap_numa_kva(void);
 334 #else
 335 #define remap_numa_kva() do {} while (0)
 336 #endif
 337
 338 static void __init pagetable_init (void)
 339 {
 340         unsigned long vaddr;
 341         pgd_t *pgd_base = swapper_pg_dir;
 342
 343 #ifdef CONFIG_X86_PAE
 344         int i;
 345         /* Init entries of the first-level page table to the zero page */
 346         for (i = 0; i < PTRS_PER_PGD; i++)
 347                 set_pgd(pgd_base + i, __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
 348 #endif
 349
 350         /* Enable PSE if available */
 351         if (cpu_has_pse) {
 352                 set_in_cr4(X86_CR4_PSE);
 353         }
 354
 355         /* Enable PGE if available */
 356         if (cpu_has_pge) {
 357                 set_in_cr4(X86_CR4_PGE);
 358                 __PAGE_KERNEL |= _PAGE_GLOBAL;
 359                 __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
 360         }
 361
 362         kernel_physical_mapping_init(pgd_base);
 363         remap_numa_kva();
 364
 365         /*
 366          * Fixed mappings, only the page table structure has to be
 367          * created - mappings will be set by set_fixmap():
 368          */
 369         vaddr = __fix_to_virt(__end_of_fixed_addresses - 1) & PMD_MASK;
 370         page_table_range_init(vaddr, 0, pgd_base);
 371
 372         permanent_kmaps_init(pgd_base);
 373
 374 #ifdef CONFIG_X86_PAE
 375         /*
 376          * Add low memory identity-mappings - SMP needs it when
 377          * starting up on an AP from real-mode. In the non-PAE
 378          * case we already have these mappings through head.S.
 379          * All user-space mappings are explicitly cleared after
 380          * SMP startup.
 381          */
 382         set_pgd(&pgd_base[0], pgd_base[USER_PTRS_PER_PGD]);
 383 #endif
 384 }
 385
 386 #ifdef CONFIG_SOFTWARE_SUSPEND
 387 /*
 388  * Swap suspend & friends need this for resume because things like the intel-agp
 389  * driver might have split up a kernel 4MB mapping.
 390  */
 391 char __nosavedata swsusp_pg_dir[PAGE_SIZE]
 392         __attribute__ ((aligned (PAGE_SIZE)));
 393
 394 static inline void save_pg_dir(void)
 395 {
 396         memcpy(swsusp_pg_dir, swapper_pg_dir, PAGE_SIZE);
 397 }
 398 #else
 399 static inline void save_pg_dir(void)
 400 {
 401 }
 402 #endif
 403
 404 void zap_low_mappings (void)
 405 {
 406         int i;
 407
 408         save_pg_dir();
 409
 410         /*
 411          * Zap initial low-memory mappings.
 412          *
 413          * Note that "pgd_clear()" doesn't do it for
 414          * us, because pgd_clear() is a no-op on i386.
 415          */
 416         for (i = 0; i < USER_PTRS_PER_PGD; i++)
 417 #ifdef CONFIG_X86_PAE
 418                 set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
 419 #else
 420                 set_pgd(swapper_pg_dir+i, __pgd(0));
 421 #endif
 422         flush_tlb_all();
 423 }
 424
 425 static int disable_nx __initdata = 0;
 426 u64 __supported_pte_mask __read_mostly = ~_PAGE_NX;
 427
 428 /*
 429  * noexec = on|off
 430  *
 431  * Control non executable mappings.
 432  *
 433  * on      Enable
 434  * off     Disable
 435  */
 436 void __init noexec_setup(const char *str)
 437 {
 438         if (!strncmp(str, "on",2) && cpu_has_nx) {
 439                 __supported_pte_mask |= _PAGE_NX;
 440                 disable_nx = 0;
 441         } else if (!strncmp(str,"off",3)) {
 442                 disable_nx = 1;
 443                 __supported_pte_mask &= ~_PAGE_NX;
 444         }
 445 }
 446
 447 int nx_enabled = 0;
 448 #ifdef CONFIG_X86_PAE
 449
 450 static void __init set_nx(void)
 451 {
 452         unsigned int v[4], l, h;
 453
 454         if (cpu_has_pae && (cpuid_eax(0x80000000) > 0x80000001)) {
 455                 cpuid(0x80000001, &v[0], &v[1], &v[2], &v[3]);
 456                 if ((v[3] & (1 << 20)) && !disable_nx) {
 457                         rdmsr(MSR_EFER, l, h);
 458                         l |= EFER_NX;
 459                         wrmsr(MSR_EFER, l, h);
 460                         nx_enabled = 1;
 461                         __supported_pte_mask |= _PAGE_NX;
 462                 }
 463         }
 464 }
 465
 466 /*
 467  * Enables/disables executability of a given kernel page and
 468  * returns the previous setting.
 469  */
 470 int __init set_kernel_exec(unsigned long vaddr, int enable)
 471 {
 472         pte_t *pte;
 473         int ret = 1;
 474
 475         if (!nx_enabled)
 476                 goto out;
 477
 478         pte = lookup_address(vaddr);
 479         BUG_ON(!pte);
 480
 481         if (!pte_exec_kernel(*pte))
 482                 ret = 0;
 483
 484         if (enable)
 485                 pte->pte_high &= ~(1 << (_PAGE_BIT_NX - 32));
 486         else
 487                 pte->pte_high |= 1 << (_PAGE_BIT_NX - 32);
 488         __flush_tlb_all();
 489 out:
 490         return ret;
 491 }
 492
 493 #endif
 494
 495 /*
 496  * paging_init() sets up the page tables - note that the first 8MB are
 497  * already mapped by head.S.
 498  *
 499  * This routines also unmaps the page at virtual kernel address 0, so
 500  * that we can trap those pesky NULL-reference errors in the kernel.
 501  */
 502 void __init paging_init(void)
 503 {
 504 #ifdef CONFIG_X86_PAE
 505         set_nx();
 506         if (nx_enabled)
 507                 printk("NX (Execute Disable) protection: active\n");
 508 #endif
 509
 510         pagetable_init();
 511
 512         load_cr3(swapper_pg_dir);
 513
 514 #ifdef CONFIG_X86_PAE
 515         /*
 516          * We will bail out later - printk doesn't work right now so
 517          * the user would just see a hanging kernel.
 518          */
 519         if (cpu_has_pae)
 520                 set_in_cr4(X86_CR4_PAE);
 521 #endif
 522         __flush_tlb_all();
 523
 524         kmap_init();
 525 }
 526
 527 /*
 528  * Test if the WP bit works in supervisor mode. It isn't supported on 386's
 529  * and also on some strange 486's (NexGen etc.). All 586+'s are OK. This
 530  * used to involve black magic jumps to work around some nasty CPU bugs,
 531  * but fortunately the switch to using exceptions got rid of all that.
 532  */
 533
 534 static void __init test_wp_bit(void)
 535 {
 536         printk("Checking if this processor honours the WP bit even in supervisor mode... ");
 537
 538         /* Any page-aligned address will do, the test is non-destructive */
 539         __set_fixmap(FIX_WP_TEST, __pa(&swapper_pg_dir), PAGE_READONLY);
 540         boot_cpu_data.wp_works_ok = do_test_wp_bit();
 541         clear_fixmap(FIX_WP_TEST);
 542
 543         if (!boot_cpu_data.wp_works_ok) {
 544                 printk("No.\n");
 545 #ifdef CONFIG_X86_WP_WORKS_OK
 546                 panic("This kernel doesn't support CPU's with broken WP. Recompile it for a 386!");
 547 #endif
 548         } else {
 549                 printk("Ok.\n");
 550         }
 551 }
 552
 553 static void __init set_max_mapnr_init(void)
 554 {
 555 #ifdef CONFIG_HIGHMEM
 556         num_physpages = highend_pfn;
 557 #else
 558         num_physpages = max_low_pfn;
 559 #endif
 560 #ifdef CONFIG_FLATMEM
 561         max_mapnr = num_physpages;
 562 #endif
 563 }
 564
 565 static struct kcore_list kcore_mem, kcore_vmalloc;
 566
 567 void __init mem_init(void)
 568 {
 569         extern int ppro_with_ram_bug(void);
 570         int codesize, reservedpages, datasize, initsize;
 571         int tmp;
 572         int bad_ppro;
 573
 574 #ifdef CONFIG_FLATMEM
 575         if (!mem_map)
 576                 BUG();
 577 #endif
 578
 579         bad_ppro = ppro_with_ram_bug();
 580
 581 #ifdef CONFIG_HIGHMEM
 582         /* check that fixmap and pkmap do not overlap */
 583         if (PKMAP_BASE+LAST_PKMAP*PAGE_SIZE >= FIXADDR_START) {
 584                 printk(KERN_ERR "fixmap and kmap areas overlap - this will crash\n");
 585                 printk(KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n",
 586                                 PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE, FIXADDR_START);
 587                 BUG();
 588         }
 589 #endif
 590
 591         set_max_mapnr_init();
 592
 593 #ifdef CONFIG_HIGHMEM
 594         high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
 595 #else
 596         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 597 #endif
 598
 599         /* this will put all low memory onto the freelists */
 600         totalram_pages += free_all_bootmem();
 601
 602         reservedpages = 0;
 603         for (tmp = 0; tmp < max_low_pfn; tmp++)
 604                 /*
 605                  * Only count reserved RAM pages
 606                  */
 607                 if (page_is_ram(tmp) && PageReserved(pfn_to_page(tmp)))
 608                         reservedpages++;
 609
 610         set_highmem_pages_init(bad_ppro);
 611
 612         codesize =  (unsigned long) &_etext - (unsigned long) &_text;
 613         datasize =  (unsigned long) &_edata - (unsigned long) &_etext;
 614         initsize =  (unsigned long) &__init_end - (unsigned long) &__init_begin;
 615
 616         kclist_add(&kcore_mem, __va(0), max_low_pfn << PAGE_SHIFT);
 617         kclist_add(&kcore_vmalloc, (void *)VMALLOC_START,
 618                    VMALLOC_END-VMALLOC_START);
 619
 620         printk(KERN_INFO "Memory: %luk/%luk available (%dk kernel code, %dk reserved, %dk data, %dk init, %ldk highmem)\n",
 621                 (unsigned long) nr_free_pages() << (PAGE_SHIFT-10),
 622                 num_physpages << (PAGE_SHIFT-10),
 623                 codesize >> 10,
 624                 reservedpages << (PAGE_SHIFT-10),
 625                 datasize >> 10,
 626                 initsize >> 10,
 627                 (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
 628                );
 629
 630 #ifdef CONFIG_X86_PAE
 631         if (!cpu_has_pae)
 632                 panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
 633 #endif
 634         if (boot_cpu_data.wp_works_ok < 0)
 635                 test_wp_bit();
 636
 637         /*
 638          * Subtle. SMP is doing it's boot stuff late (because it has to
 639          * fork idle threads) - but it also needs low mappings for the
 640          * protected-mode entry to work. We zap these entries only after
 641          * the WP-bit has been tested.
 642          */
 643 #ifndef CONFIG_SMP
 644         zap_low_mappings();
 645 #endif
 646 }
 647
 648 /*
 649  * this is for the non-NUMA, single node SMP system case.
 650  * Specifically, in the case of x86, we will always add
 651  * memory to the highmem for now.
 652  */
 653 #ifndef CONFIG_NEED_MULTIPLE_NODES
 654 int add_memory(u64 start, u64 size)
 655 {
 656         struct pglist_data *pgdata = &contig_page_data;
 657         struct zone *zone = pgdata->node_zones + MAX_NR_ZONES-1;
 658         unsigned long start_pfn = start >> PAGE_SHIFT;
 659         unsigned long nr_pages = size >> PAGE_SHIFT;
 660
 661         return __add_pages(zone, start_pfn, nr_pages);
 662 }
 663
 664 int remove_memory(u64 start, u64 size)
 665 {
 666         return -EINVAL;
 667 }
 668 #endif
 669
 670 kmem_cache_t *pgd_cache;
 671 kmem_cache_t *pmd_cache;
 672
 673 void __init pgtable_cache_init(void)
 674 {
 675         if (PTRS_PER_PMD > 1) {
 676                 pmd_cache = kmem_cache_create("pmd",
 677                                         PTRS_PER_PMD*sizeof(pmd_t),
 678                                         PTRS_PER_PMD*sizeof(pmd_t),
 679                                         0,
 680                                         pmd_ctor,
 681                                         NULL);
 682                 if (!pmd_cache)
 683                         panic("pgtable_cache_init(): cannot create pmd cache");
 684         }
 685         pgd_cache = kmem_cache_create("pgd",
 686                                 PTRS_PER_PGD*sizeof(pgd_t),
 687                                 PTRS_PER_PGD*sizeof(pgd_t),
 688                                 0,
 689                                 pgd_ctor,
 690                                 PTRS_PER_PMD == 1 ? pgd_dtor : NULL);
 691         if (!pgd_cache)
 692                 panic("pgtable_cache_init(): Cannot create pgd cache");
 693 }
 694
 695 /*
 696  * This function cannot be __init, since exceptions don't work in that
 697  * section.  Put this after the callers, so that it cannot be inlined.
 698  */
 699 static int noinline do_test_wp_bit(void)
 700 {
 701         char tmp_reg;
 702         int flag;
 703
 704         __asm__ __volatile__(
 705                 "       movb %0,%1      \n"
 706                 "1:     movb %1,%0      \n"
 707                 "       xorl %2,%2      \n"
 708                 "2:                     \n"
 709                 ".section __ex_table,\"a\"\n"
 710                 "       .align 4        \n"
 711                 "       .long 1b,2b     \n"
 712                 ".previous              \n"
 713                 :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
 714                  "=q" (tmp_reg),
 715                  "=r" (flag)
 716                 :"2" (1)
 717                 :"memory");
 718
 719         return flag;
 720 }
 721
 722 void free_initmem(void)
 723 {
 724         unsigned long addr;
 725
 726         addr = (unsigned long)(&__init_begin);
 727         for (; addr < (unsigned long)(&__init_end); addr += PAGE_SIZE) {
 728                 ClearPageReserved(virt_to_page(addr));
 729                 set_page_count(virt_to_page(addr), 1);
 730                 memset((void *)addr, 0xcc, PAGE_SIZE);
 731                 free_page(addr);
 732                 totalram_pages++;
 733         }
 734         printk (KERN_INFO "Freeing unused kernel memory: %dk freed\n", (__init_end - __init_begin) >> 10);
 735 }
 736
 737 #ifdef CONFIG_BLK_DEV_INITRD
 738 void free_initrd_mem(unsigned long start, unsigned long end)
 739 {
 740         if (start < end)
 741                 printk (KERN_INFO "Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 742         for (; start < end; start += PAGE_SIZE) {
 743                 ClearPageReserved(virt_to_page(start));
 744                 set_page_count(virt_to_page(start), 1);
 745                 free_page(start);
 746                 totalram_pages++;
 747         }
 748 }
 749 #endif