arch/powerpc/mm/mem.c

   1 /*
   2  *  PowerPC version
   3  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
   4  *
   5  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
   6  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
   7  *    Copyright (C) 1996 Paul Mackerras
   8  *  PPC44x/36-bit changes by Matt Porter (mporter@mvista.com)
   9  *
  10  *  Derived from "arch/i386/mm/init.c"
  11  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  12  *
  13  *  This program is free software; you can redistribute it and/or
  14  *  modify it under the terms of the GNU General Public License
  15  *  as published by the Free Software Foundation; either version
  16  *  2 of the License, or (at your option) any later version.
  17  *
  18  */
  19
  20 #include <linux/export.h>
  21 #include <linux/sched.h>
  22 #include <linux/kernel.h>
  23 #include <linux/errno.h>
  24 #include <linux/string.h>
  25 #include <linux/gfp.h>
  26 #include <linux/types.h>
  27 #include <linux/mm.h>
  28 #include <linux/stddef.h>
  29 #include <linux/init.h>
  30 #include <linux/bootmem.h>
  31 #include <linux/highmem.h>
  32 #include <linux/initrd.h>
  33 #include <linux/pagemap.h>
  34 #include <linux/suspend.h>
  35 #include <linux/memblock.h>
  36 #include <linux/hugetlb.h>
  37 #include <linux/slab.h>
  38
  39 #include <asm/pgalloc.h>
  40 #include <asm/prom.h>
  41 #include <asm/io.h>
  42 #include <asm/mmu_context.h>
  43 #include <asm/pgtable.h>
  44 #include <asm/mmu.h>
  45 #include <asm/smp.h>
  46 #include <asm/machdep.h>
  47 #include <asm/btext.h>
  48 #include <asm/tlb.h>
  49 #include <asm/sections.h>
  50 #include <asm/sparsemem.h>
  51 #include <asm/vdso.h>
  52 #include <asm/fixmap.h>
  53 #include <asm/swiotlb.h>
  54 #include <asm/rtas.h>
  55
  56 #include "mmu_decl.h"
  57
  58 #ifndef CPU_FTR_COHERENT_ICACHE
  59 #define CPU_FTR_COHERENT_ICACHE 0       /* XXX for now */
  60 #define CPU_FTR_NOEXECUTE       0
  61 #endif
  62
  63 int init_bootmem_done;
  64 int mem_init_done;
  65 unsigned long long memory_limit;
  66
  67 #ifdef CONFIG_HIGHMEM
  68 pte_t *kmap_pte;
  69 pgprot_t kmap_prot;
  70
  71 EXPORT_SYMBOL(kmap_prot);
  72 EXPORT_SYMBOL(kmap_pte);
  73
  74 static inline pte_t *virt_to_kpte(unsigned long vaddr)
  75 {
  76         return pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr),
  77                         vaddr), vaddr), vaddr);
  78 }
  79 #endif
  80
  81 int page_is_ram(unsigned long pfn)
  82 {
  83 #ifndef CONFIG_PPC64    /* XXX for now */
  84         return pfn < max_pfn;
  85 #else
  86         unsigned long paddr = (pfn << PAGE_SHIFT);
  87         struct memblock_region *reg;
  88
  89         for_each_memblock(memory, reg)
  90                 if (paddr >= reg->base && paddr < (reg->base + reg->size))
  91                         return 1;
  92         return 0;
  93 #endif
  94 }
  95
  96 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
  97                               unsigned long size, pgprot_t vma_prot)
  98 {
  99         if (ppc_md.phys_mem_access_prot)
 100                 return ppc_md.phys_mem_access_prot(file, pfn, size, vma_prot);
 101
 102         if (!page_is_ram(pfn))
 103                 vma_prot = pgprot_noncached(vma_prot);
 104
 105         return vma_prot;
 106 }
 107 EXPORT_SYMBOL(phys_mem_access_prot);
 108
 109 #ifdef CONFIG_MEMORY_HOTPLUG
 110
 111 #ifdef CONFIG_NUMA
 112 int memory_add_physaddr_to_nid(u64 start)
 113 {
 114         return hot_add_scn_to_nid(start);
 115 }
 116 #endif
 117
 118 int arch_add_memory(int nid, u64 start, u64 size)
 119 {
 120         struct pglist_data *pgdata;
 121         struct zone *zone;
 122         unsigned long start_pfn = start >> PAGE_SHIFT;
 123         unsigned long nr_pages = size >> PAGE_SHIFT;
 124
 125         pgdata = NODE_DATA(nid);
 126
 127         start = (unsigned long)__va(start);
 128         if (create_section_mapping(start, start + size))
 129                 return -EINVAL;
 130
 131         /* this should work for most non-highmem platforms */
 132         zone = pgdata->node_zones;
 133
 134         return __add_pages(nid, zone, start_pfn, nr_pages);
 135 }
 136
 137 #ifdef CONFIG_MEMORY_HOTREMOVE
 138 int arch_remove_memory(u64 start, u64 size)
 139 {
 140         unsigned long start_pfn = start >> PAGE_SHIFT;
 141         unsigned long nr_pages = size >> PAGE_SHIFT;
 142         struct zone *zone;
 143
 144         zone = page_zone(pfn_to_page(start_pfn));
 145         return __remove_pages(zone, start_pfn, nr_pages);
 146 }
 147 #endif
 148 #endif /* CONFIG_MEMORY_HOTPLUG */
 149
 150 /*
 151  * walk_memory_resource() needs to make sure there is no holes in a given
 152  * memory range.  PPC64 does not maintain the memory layout in /proc/iomem.
 153  * Instead it maintains it in memblock.memory structures.  Walk through the
 154  * memory regions, find holes and callback for contiguous regions.
 155  */
 156 int
 157 walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
 158                 void *arg, int (*func)(unsigned long, unsigned long, void *))
 159 {
 160         struct memblock_region *reg;
 161         unsigned long end_pfn = start_pfn + nr_pages;
 162         unsigned long tstart, tend;
 163         int ret = -1;
 164
 165         for_each_memblock(memory, reg) {
 166                 tstart = max(start_pfn, memblock_region_memory_base_pfn(reg));
 167                 tend = min(end_pfn, memblock_region_memory_end_pfn(reg));
 168                 if (tstart >= tend)
 169                         continue;
 170                 ret = (*func)(tstart, tend - tstart, arg);
 171                 if (ret)
 172                         break;
 173         }
 174         return ret;
 175 }
 176 EXPORT_SYMBOL_GPL(walk_system_ram_range);
 177
 178 /*
 179  * Initialize the bootmem system and give it all the memory we
 180  * have available.  If we are using highmem, we only put the
 181  * lowmem into the bootmem system.
 182  */
 183 #ifndef CONFIG_NEED_MULTIPLE_NODES
 184 void __init do_init_bootmem(void)
 185 {
 186         unsigned long start, bootmap_pages;
 187         unsigned long total_pages;
 188         struct memblock_region *reg;
 189         int boot_mapsize;
 190
 191         max_low_pfn = max_pfn = memblock_end_of_DRAM() >> PAGE_SHIFT;
 192         total_pages = (memblock_end_of_DRAM() - memstart_addr) >> PAGE_SHIFT;
 193 #ifdef CONFIG_HIGHMEM
 194         total_pages = total_lowmem >> PAGE_SHIFT;
 195         max_low_pfn = lowmem_end_addr >> PAGE_SHIFT;
 196 #endif
 197
 198         /*
 199          * Find an area to use for the bootmem bitmap.  Calculate the size of
 200          * bitmap required as (Total Memory) / PAGE_SIZE / BITS_PER_BYTE.
 201          * Add 1 additional page in case the address isn't page-aligned.
 202          */
 203         bootmap_pages = bootmem_bootmap_pages(total_pages);
 204
 205         start = memblock_alloc(bootmap_pages << PAGE_SHIFT, PAGE_SIZE);
 206
 207         min_low_pfn = MEMORY_START >> PAGE_SHIFT;
 208         boot_mapsize = init_bootmem_node(NODE_DATA(0), start >> PAGE_SHIFT, min_low_pfn, max_low_pfn);
 209
 210         /* Place all memblock_regions in the same node and merge contiguous
 211          * memblock_regions
 212          */
 213         memblock_set_node(0, (phys_addr_t)ULLONG_MAX, 0);
 214
 215         /* Add all physical memory to the bootmem map, mark each area
 216          * present.
 217          */
 218 #ifdef CONFIG_HIGHMEM
 219         free_bootmem_with_active_regions(0, lowmem_end_addr >> PAGE_SHIFT);
 220
 221         /* reserve the sections we're already using */
 222         for_each_memblock(reserved, reg) {
 223                 unsigned long top = reg->base + reg->size - 1;
 224                 if (top < lowmem_end_addr)
 225                         reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 226                 else if (reg->base < lowmem_end_addr) {
 227                         unsigned long trunc_size = lowmem_end_addr - reg->base;
 228                         reserve_bootmem(reg->base, trunc_size, BOOTMEM_DEFAULT);
 229                 }
 230         }
 231 #else
 232         free_bootmem_with_active_regions(0, max_pfn);
 233
 234         /* reserve the sections we're already using */
 235         for_each_memblock(reserved, reg)
 236                 reserve_bootmem(reg->base, reg->size, BOOTMEM_DEFAULT);
 237 #endif
 238         /* XXX need to clip this if using highmem? */
 239         sparse_memory_present_with_active_regions(0);
 240
 241         init_bootmem_done = 1;
 242 }
 243
 244 /* mark pages that don't exist as nosave */
 245 static int __init mark_nonram_nosave(void)
 246 {
 247         struct memblock_region *reg, *prev = NULL;
 248
 249         for_each_memblock(memory, reg) {
 250                 if (prev &&
 251                     memblock_region_memory_end_pfn(prev) < memblock_region_memory_base_pfn(reg))
 252                         register_nosave_region(memblock_region_memory_end_pfn(prev),
 253                                                memblock_region_memory_base_pfn(reg));
 254                 prev = reg;
 255         }
 256         return 0;
 257 }
 258
 259 /*
 260  * paging_init() sets up the page tables - in fact we've already done this.
 261  */
 262 void __init paging_init(void)
 263 {
 264         unsigned long long total_ram = memblock_phys_mem_size();
 265         phys_addr_t top_of_ram = memblock_end_of_DRAM();
 266         unsigned long max_zone_pfns[MAX_NR_ZONES];
 267
 268 #ifdef CONFIG_PPC32
 269         unsigned long v = __fix_to_virt(__end_of_fixed_addresses - 1);
 270         unsigned long end = __fix_to_virt(FIX_HOLE);
 271
 272         for (; v < end; v += PAGE_SIZE)
 273                 map_page(v, 0, 0); /* XXX gross */
 274 #endif
 275
 276 #ifdef CONFIG_HIGHMEM
 277         map_page(PKMAP_BASE, 0, 0);     /* XXX gross */
 278         pkmap_page_table = virt_to_kpte(PKMAP_BASE);
 279
 280         kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
 281         kmap_prot = PAGE_KERNEL;
 282 #endif /* CONFIG_HIGHMEM */
 283
 284         printk(KERN_DEBUG "Top of RAM: 0x%llx, Total RAM: 0x%llx\n",
 285                (unsigned long long)top_of_ram, total_ram);
 286         printk(KERN_DEBUG "Memory hole size: %ldMB\n",
 287                (long int)((top_of_ram - total_ram) >> 20));
 288         memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
 289 #ifdef CONFIG_HIGHMEM
 290         max_zone_pfns[ZONE_DMA] = lowmem_end_addr >> PAGE_SHIFT;
 291         max_zone_pfns[ZONE_HIGHMEM] = top_of_ram >> PAGE_SHIFT;
 292 #else
 293         max_zone_pfns[ZONE_DMA] = top_of_ram >> PAGE_SHIFT;
 294 #endif
 295         free_area_init_nodes(max_zone_pfns);
 296
 297         mark_nonram_nosave();
 298 }
 299 #endif /* ! CONFIG_NEED_MULTIPLE_NODES */
 300
 301 void __init mem_init(void)
 302 {
 303 #ifdef CONFIG_NEED_MULTIPLE_NODES
 304         int nid;
 305 #endif
 306         pg_data_t *pgdat;
 307         unsigned long i;
 308         struct page *page;
 309         unsigned long reservedpages = 0, codesize, initsize, datasize, bsssize;
 310
 311 #ifdef CONFIG_SWIOTLB
 312         swiotlb_init(0);
 313 #endif
 314
 315         num_physpages = memblock_phys_mem_size() >> PAGE_SHIFT;
 316         high_memory = (void *) __va(max_low_pfn * PAGE_SIZE);
 317
 318 #ifdef CONFIG_NEED_MULTIPLE_NODES
 319         for_each_online_node(nid) {
 320                 if (NODE_DATA(nid)->node_spanned_pages != 0) {
 321                         printk("freeing bootmem node %d\n", nid);
 322                         totalram_pages +=
 323                                 free_all_bootmem_node(NODE_DATA(nid));
 324                 }
 325         }
 326 #else
 327         max_mapnr = max_pfn;
 328         totalram_pages += free_all_bootmem();
 329 #endif
 330         for_each_online_pgdat(pgdat) {
 331                 for (i = 0; i < pgdat->node_spanned_pages; i++) {
 332                         if (!pfn_valid(pgdat->node_start_pfn + i))
 333                                 continue;
 334                         page = pgdat_page_nr(pgdat, i);
 335                         if (PageReserved(page))
 336                                 reservedpages++;
 337                 }
 338         }
 339
 340         codesize = (unsigned long)&_sdata - (unsigned long)&_stext;
 341         datasize = (unsigned long)&_edata - (unsigned long)&_sdata;
 342         initsize = (unsigned long)&__init_end - (unsigned long)&__init_begin;
 343         bsssize = (unsigned long)&__bss_stop - (unsigned long)&__bss_start;
 344
 345 #ifdef CONFIG_HIGHMEM
 346         {
 347                 unsigned long pfn, highmem_mapnr;
 348
 349                 highmem_mapnr = lowmem_end_addr >> PAGE_SHIFT;
 350                 for (pfn = highmem_mapnr; pfn < max_mapnr; ++pfn) {
 351                         phys_addr_t paddr = (phys_addr_t)pfn << PAGE_SHIFT;
 352                         struct page *page = pfn_to_page(pfn);
 353                         if (memblock_is_reserved(paddr))
 354                                 continue;
 355                         ClearPageReserved(page);
 356                         init_page_count(page);
 357                         __free_page(page);
 358                         totalhigh_pages++;
 359                         reservedpages--;
 360                 }
 361                 totalram_pages += totalhigh_pages;
 362                 printk(KERN_DEBUG "High memory: %luk\n",
 363                        totalhigh_pages << (PAGE_SHIFT-10));
 364         }
 365 #endif /* CONFIG_HIGHMEM */
 366
 367 #if defined(CONFIG_PPC_FSL_BOOK3E) && !defined(CONFIG_SMP)
 368         /*
 369          * If smp is enabled, next_tlbcam_idx is initialized in the cpu up
 370          * functions.... do it here for the non-smp case.
 371          */
 372         per_cpu(next_tlbcam_idx, smp_processor_id()) =
 373                 (mfspr(SPRN_TLB1CFG) & TLBnCFG_N_ENTRY) - 1;
 374 #endif
 375
 376         printk(KERN_INFO "Memory: %luk/%luk available (%luk kernel code, "
 377                "%luk reserved, %luk data, %luk bss, %luk init)\n",
 378                 nr_free_pages() << (PAGE_SHIFT-10),
 379                 num_physpages << (PAGE_SHIFT-10),
 380                 codesize >> 10,
 381                 reservedpages << (PAGE_SHIFT-10),
 382                 datasize >> 10,
 383                 bsssize >> 10,
 384                 initsize >> 10);
 385
 386 #ifdef CONFIG_PPC32
 387         pr_info("Kernel virtual memory layout:\n");
 388         pr_info("  * 0x%08lx..0x%08lx  : fixmap\n", FIXADDR_START, FIXADDR_TOP);
 389 #ifdef CONFIG_HIGHMEM
 390         pr_info("  * 0x%08lx..0x%08lx  : highmem PTEs\n",
 391                 PKMAP_BASE, PKMAP_ADDR(LAST_PKMAP));
 392 #endif /* CONFIG_HIGHMEM */
 393 #ifdef CONFIG_NOT_COHERENT_CACHE
 394         pr_info("  * 0x%08lx..0x%08lx  : consistent mem\n",
 395                 IOREMAP_TOP, IOREMAP_TOP + CONFIG_CONSISTENT_SIZE);
 396 #endif /* CONFIG_NOT_COHERENT_CACHE */
 397         pr_info("  * 0x%08lx..0x%08lx  : early ioremap\n",
 398                 ioremap_bot, IOREMAP_TOP);
 399         pr_info("  * 0x%08lx..0x%08lx  : vmalloc & ioremap\n",
 400                 VMALLOC_START, VMALLOC_END);
 401 #endif /* CONFIG_PPC32 */
 402
 403         mem_init_done = 1;
 404 }
 405
 406 void free_initmem(void)
 407 {
 408         unsigned long addr;
 409
 410         ppc_md.progress = ppc_printk_progress;
 411
 412         addr = (unsigned long)__init_begin;
 413         for (; addr < (unsigned long)__init_end; addr += PAGE_SIZE) {
 414                 memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
 415                 ClearPageReserved(virt_to_page(addr));
 416                 init_page_count(virt_to_page(addr));
 417                 free_page(addr);
 418                 totalram_pages++;
 419         }
 420         pr_info("Freeing unused kernel memory: %luk freed\n",
 421                 ((unsigned long)__init_end -
 422                 (unsigned long)__init_begin) >> 10);
 423 }
 424
 425 #ifdef CONFIG_BLK_DEV_INITRD
 426 void __init free_initrd_mem(unsigned long start, unsigned long end)
 427 {
 428         if (start >= end)
 429                 return;
 430
 431         start = _ALIGN_DOWN(start, PAGE_SIZE);
 432         end = _ALIGN_UP(end, PAGE_SIZE);
 433         pr_info("Freeing initrd memory: %ldk freed\n", (end - start) >> 10);
 434
 435         for (; start < end; start += PAGE_SIZE) {
 436                 ClearPageReserved(virt_to_page(start));
 437                 init_page_count(virt_to_page(start));
 438                 free_page(start);
 439                 totalram_pages++;
 440         }
 441 }
 442 #endif
 443
 444 /*
 445  * This is called when a page has been modified by the kernel.
 446  * It just marks the page as not i-cache clean.  We do the i-cache
 447  * flush later when the page is given to a user process, if necessary.
 448  */
 449 void flush_dcache_page(struct page *page)
 450 {
 451         if (cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 452                 return;
 453         /* avoid an atomic op if possible */
 454         if (test_bit(PG_arch_1, &page->flags))
 455                 clear_bit(PG_arch_1, &page->flags);
 456 }
 457 EXPORT_SYMBOL(flush_dcache_page);
 458
 459 void flush_dcache_icache_page(struct page *page)
 460 {
 461 #ifdef CONFIG_HUGETLB_PAGE
 462         if (PageCompound(page)) {
 463                 flush_dcache_icache_hugepage(page);
 464                 return;
 465         }
 466 #endif
 467 #ifdef CONFIG_BOOKE
 468         {
 469                 void *start = kmap_atomic(page);
 470                 __flush_dcache_icache(start);
 471                 kunmap_atomic(start);
 472         }
 473 #elif defined(CONFIG_8xx) || defined(CONFIG_PPC64)
 474         /* On 8xx there is no need to kmap since highmem is not supported */
 475         __flush_dcache_icache(page_address(page));
 476 #else
 477         __flush_dcache_icache_phys(page_to_pfn(page) << PAGE_SHIFT);
 478 #endif
 479 }
 480 EXPORT_SYMBOL(flush_dcache_icache_page);
 481
 482 void clear_user_page(void *page, unsigned long vaddr, struct page *pg)
 483 {
 484         clear_page(page);
 485
 486         /*
 487          * We shouldn't have to do this, but some versions of glibc
 488          * require it (ld.so assumes zero filled pages are icache clean)
 489          * - Anton
 490          */
 491         flush_dcache_page(pg);
 492 }
 493 EXPORT_SYMBOL(clear_user_page);
 494
 495 void copy_user_page(void *vto, void *vfrom, unsigned long vaddr,
 496                     struct page *pg)
 497 {
 498         copy_page(vto, vfrom);
 499
 500         /*
 501          * We should be able to use the following optimisation, however
 502          * there are two problems.
 503          * Firstly a bug in some versions of binutils meant PLT sections
 504          * were not marked executable.
 505          * Secondly the first word in the GOT section is blrl, used
 506          * to establish the GOT address. Until recently the GOT was
 507          * not marked executable.
 508          * - Anton
 509          */
 510 #if 0
 511         if (!vma->vm_file && ((vma->vm_flags & VM_EXEC) == 0))
 512                 return;
 513 #endif
 514
 515         flush_dcache_page(pg);
 516 }
 517
 518 void flush_icache_user_range(struct vm_area_struct *vma, struct page *page,
 519                              unsigned long addr, int len)
 520 {
 521         unsigned long maddr;
 522
 523         maddr = (unsigned long) kmap(page) + (addr & ~PAGE_MASK);
 524         flush_icache_range(maddr, maddr + len);
 525         kunmap(page);
 526 }
 527 EXPORT_SYMBOL(flush_icache_user_range);
 528
 529 /*
 530  * This is called at the end of handling a user page fault, when the
 531  * fault has been handled by updating a PTE in the linux page tables.
 532  * We use it to preload an HPTE into the hash table corresponding to
 533  * the updated linux PTE.
 534  *
 535  * This must always be called with the pte lock held.
 536  */
 537 void update_mmu_cache(struct vm_area_struct *vma, unsigned long address,
 538                       pte_t *ptep)
 539 {
 540 #ifdef CONFIG_PPC_STD_MMU
 541         unsigned long access = 0, trap;
 542
 543         /* We only want HPTEs for linux PTEs that have _PAGE_ACCESSED set */
 544         if (!pte_young(*ptep) || address >= TASK_SIZE)
 545                 return;
 546
 547         /* We try to figure out if we are coming from an instruction
 548          * access fault and pass that down to __hash_page so we avoid
 549          * double-faulting on execution of fresh text. We have to test
 550          * for regs NULL since init will get here first thing at boot
 551          *
 552          * We also avoid filling the hash if not coming from a fault
 553          */
 554         if (current->thread.regs == NULL)
 555                 return;
 556         trap = TRAP(current->thread.regs);
 557         if (trap == 0x400)
 558                 access |= _PAGE_EXEC;
 559         else if (trap != 0x300)
 560                 return;
 561         hash_preload(vma->vm_mm, address, access, trap);
 562 #endif /* CONFIG_PPC_STD_MMU */
 563 #if (defined(CONFIG_PPC_BOOK3E_64) || defined(CONFIG_PPC_FSL_BOOK3E)) \
 564         && defined(CONFIG_HUGETLB_PAGE)
 565         if (is_vm_hugetlb_page(vma))
 566                 book3e_hugetlb_preload(vma, address, *ptep);
 567 #endif
 568 }
 569
 570 /*
 571  * System memory should not be in /proc/iomem but various tools expect it
 572  * (eg kdump).
 573  */
 574 static int add_system_ram_resources(void)
 575 {
 576         struct memblock_region *reg;
 577
 578         for_each_memblock(memory, reg) {
 579                 struct resource *res;
 580                 unsigned long base = reg->base;
 581                 unsigned long size = reg->size;
 582
 583                 res = kzalloc(sizeof(struct resource), GFP_KERNEL);
 584                 WARN_ON(!res);
 585
 586                 if (res) {
 587                         res->name = "System RAM";
 588                         res->start = base;
 589                         res->end = base + size - 1;
 590                         res->flags = IORESOURCE_MEM;
 591                         WARN_ON(request_resource(&iomem_resource, res) < 0);
 592                 }
 593         }
 594
 595         return 0;
 596 }
 597 subsys_initcall(add_system_ram_resources);
 598
 599 #ifdef CONFIG_STRICT_DEVMEM
 600 /*
 601  * devmem_is_allowed(): check to see if /dev/mem access to a certain address
 602  * is valid. The argument is a physical page number.
 603  *
 604  * Access has to be given to non-kernel-ram areas as well, these contain the
 605  * PCI mmio resources as well as potential bios/acpi data regions.
 606  */
 607 int devmem_is_allowed(unsigned long pfn)
 608 {
 609         if (iomem_is_exclusive(pfn << PAGE_SHIFT))
 610                 return 0;
 611         if (!page_is_ram(pfn))
 612                 return 1;
 613         if (page_is_rtas_user_buf(pfn))
 614                 return 1;
 615         return 0;
 616 }
 617 #endif /* CONFIG_STRICT_DEVMEM */