arch/i386/mm/pageattr.c

   1 /*
   2  * Copyright 2002 Andi Kleen, SuSE Labs.
   3  * Thanks to Ben LaHaise for precious feedback.
   4  */
   5
   6 #include <linux/mm.h>
   7 #include <linux/sched.h>
   8 #include <linux/highmem.h>
   9 #include <linux/module.h>
  10 #include <linux/slab.h>
  11 #include <asm/uaccess.h>
  12 #include <asm/processor.h>
  13 #include <asm/tlbflush.h>
  14 #include <asm/pgalloc.h>
  15 #include <asm/sections.h>
  16
  17 static DEFINE_SPINLOCK(cpa_lock);
  18 static struct list_head df_list = LIST_HEAD_INIT(df_list);
  19
  20
  21 pte_t *lookup_address(unsigned long address)
  22 {
  23         pgd_t *pgd = pgd_offset_k(address);
  24         pud_t *pud;
  25         pmd_t *pmd;
  26         if (pgd_none(*pgd))
  27                 return NULL;
  28         pud = pud_offset(pgd, address);
  29         if (pud_none(*pud))
  30                 return NULL;
  31         pmd = pmd_offset(pud, address);
  32         if (pmd_none(*pmd))
  33                 return NULL;
  34         if (pmd_large(*pmd))
  35                 return (pte_t *)pmd;
  36         return pte_offset_kernel(pmd, address);
  37 }
  38
  39 static struct page *split_large_page(unsigned long address, pgprot_t prot,
  40                                         pgprot_t ref_prot)
  41 {
  42         int i;
  43         unsigned long addr;
  44         struct page *base;
  45         pte_t *pbase;
  46
  47         spin_unlock_irq(&cpa_lock);
  48         base = alloc_pages(GFP_KERNEL, 0);
  49         spin_lock_irq(&cpa_lock);
  50         if (!base)
  51                 return NULL;
  52
  53         /*
  54          * page_private is used to track the number of entries in
  55          * the page table page that have non standard attributes.
  56          */
  57         SetPagePrivate(base);
  58         page_private(base) = 0;
  59
  60         address = __pa(address);
  61         addr = address & LARGE_PAGE_MASK;
  62         pbase = (pte_t *)page_address(base);
  63         for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
  64                set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
  65                                           addr == address ? prot : ref_prot));
  66         }
  67         return base;
  68 }
  69
  70 static void flush_kernel_map(void *arg)
  71 {
  72         unsigned long adr = (unsigned long)arg;
  73
  74         if (adr && cpu_has_clflush) {
  75                 int i;
  76                 for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
  77                         asm volatile("clflush (%0)" :: "r" (adr + i));
  78         } else if (boot_cpu_data.x86_model >= 4)
  79                 wbinvd();
  80
  81         /* Flush all to work around Errata in early athlons regarding
  82          * large page flushing.
  83          */
  84         __flush_tlb_all();
  85 }
  86
  87 static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
  88 {
  89         struct page *page;
  90         unsigned long flags;
  91
  92         set_pte_atomic(kpte, pte);      /* change init_mm */
  93         if (PTRS_PER_PMD > 1)
  94                 return;
  95
  96         spin_lock_irqsave(&pgd_lock, flags);
  97         for (page = pgd_list; page; page = (struct page *)page->index) {
  98                 pgd_t *pgd;
  99                 pud_t *pud;
 100                 pmd_t *pmd;
 101                 pgd = (pgd_t *)page_address(page) + pgd_index(address);
 102                 pud = pud_offset(pgd, address);
 103                 pmd = pmd_offset(pud, address);
 104                 set_pte_atomic((pte_t *)pmd, pte);
 105         }
 106         spin_unlock_irqrestore(&pgd_lock, flags);
 107 }
 108
 109 /*
 110  * No more special protections in this 2/4MB area - revert to a
 111  * large page again.
 112  */
 113 static inline void revert_page(struct page *kpte_page, unsigned long address)
 114 {
 115         pgprot_t ref_prot;
 116         pte_t *linear;
 117
 118         ref_prot =
 119         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 120                 ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;
 121
 122         linear = (pte_t *)
 123                 pmd_offset(pud_offset(pgd_offset_k(address), address), address);
 124         set_pmd_pte(linear,  address,
 125                     pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
 126                             ref_prot));
 127 }
 128
 129 static int
 130 __change_page_attr(struct page *page, pgprot_t prot)
 131 {
 132         pte_t *kpte;
 133         unsigned long address;
 134         struct page *kpte_page;
 135
 136         BUG_ON(PageHighMem(page));
 137         address = (unsigned long)page_address(page);
 138
 139         kpte = lookup_address(address);
 140         if (!kpte)
 141                 return -EINVAL;
 142         kpte_page = virt_to_page(kpte);
 143         if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) {
 144                 if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 145                         set_pte_atomic(kpte, mk_pte(page, prot));
 146                 } else {
 147                         pgprot_t ref_prot;
 148                         struct page *split;
 149
 150                         ref_prot =
 151                         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 152                                 ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
 153                         split = split_large_page(address, prot, ref_prot);
 154                         if (!split)
 155                                 return -ENOMEM;
 156                         set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
 157                         kpte_page = split;
 158                 }
 159                 page_private(kpte_page)++;
 160         } else if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 161                 set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
 162                 BUG_ON(page_private(kpte_page) == 0);
 163                 page_private(kpte_page)--;
 164         } else
 165                 BUG();
 166
 167         /*
 168          * If the pte was reserved, it means it was created at boot
 169          * time (not via split_large_page) and in turn we must not
 170          * replace it with a largepage.
 171          */
 172         if (!PageReserved(kpte_page)) {
 173                 if (cpu_has_pse && (page_private(kpte_page) == 0)) {
 174                         ClearPagePrivate(kpte_page);
 175                         list_add(&kpte_page->lru, &df_list);
 176                         revert_page(kpte_page, address);
 177                 }
 178         }
 179         return 0;
 180 }
 181
 182 static inline void flush_map(void *adr)
 183 {
 184         on_each_cpu(flush_kernel_map, adr, 1, 1);
 185 }
 186
 187 /*
 188  * Change the page attributes of an page in the linear mapping.
 189  *
 190  * This should be used when a page is mapped with a different caching policy
 191  * than write-back somewhere - some CPUs do not like it when mappings with
 192  * different caching policies exist. This changes the page attributes of the
 193  * in kernel linear mapping too.
 194  *
 195  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 196  * This function only deals with the kernel linear map.
 197  *
 198  * Caller must call global_flush_tlb() after this.
 199  */
 200 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 201 {
 202         int err = 0;
 203         int i;
 204         unsigned long flags;
 205
 206         spin_lock_irqsave(&cpa_lock, flags);
 207         for (i = 0; i < numpages; i++, page++) {
 208                 err = __change_page_attr(page, prot);
 209                 if (err)
 210                         break;
 211         }
 212         spin_unlock_irqrestore(&cpa_lock, flags);
 213         return err;
 214 }
 215
 216 void global_flush_tlb(void)
 217 {
 218         struct list_head l;
 219         struct page *pg, *next;
 220
 221         BUG_ON(irqs_disabled());
 222
 223         spin_lock_irq(&cpa_lock);
 224         list_replace_init(&df_list, &l);
 225         spin_unlock_irq(&cpa_lock);
 226         if (!cpu_has_clflush)
 227                 flush_map(0);
 228         list_for_each_entry_safe(pg, next, &l, lru) {
 229                 if (cpu_has_clflush)
 230                         flush_map(page_address(pg));
 231                 __free_page(pg);
 232         }
 233 }
 234
 235 #ifdef CONFIG_DEBUG_PAGEALLOC
 236 void kernel_map_pages(struct page *page, int numpages, int enable)
 237 {
 238         if (PageHighMem(page))
 239                 return;
 240         if (!enable)
 241                 debug_check_no_locks_freed(page_address(page),
 242                                            numpages * PAGE_SIZE);
 243
 244         /* the return value is ignored - the calls cannot fail,
 245          * large pages are disabled at boot time.
 246          */
 247         change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 248         /* we should perform an IPI and flush all tlbs,
 249          * but that can deadlock->flush only current cpu.
 250          */
 251         __flush_tlb_all();
 252 }
 253 #endif
 254
 255 EXPORT_SYMBOL(change_page_attr);
 256 EXPORT_SYMBOL(global_flush_tlb);