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 *dummy)
  71 {
  72         /* Could use CLFLUSH here if the CPU supports it (Hammer,P4) */
  73         if (boot_cpu_data.x86_model >= 4)
  74                 wbinvd();
  75         /* Flush all to work around Errata in early athlons regarding
  76          * large page flushing.
  77          */
  78         __flush_tlb_all();
  79 }
  80
  81 static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
  82 {
  83         struct page *page;
  84         unsigned long flags;
  85
  86         set_pte_atomic(kpte, pte);      /* change init_mm */
  87         if (PTRS_PER_PMD > 1)
  88                 return;
  89
  90         spin_lock_irqsave(&pgd_lock, flags);
  91         for (page = pgd_list; page; page = (struct page *)page->index) {
  92                 pgd_t *pgd;
  93                 pud_t *pud;
  94                 pmd_t *pmd;
  95                 pgd = (pgd_t *)page_address(page) + pgd_index(address);
  96                 pud = pud_offset(pgd, address);
  97                 pmd = pmd_offset(pud, address);
  98                 set_pte_atomic((pte_t *)pmd, pte);
  99         }
 100         spin_unlock_irqrestore(&pgd_lock, flags);
 101 }
 102
 103 /*
 104  * No more special protections in this 2/4MB area - revert to a
 105  * large page again.
 106  */
 107 static inline void revert_page(struct page *kpte_page, unsigned long address)
 108 {
 109         pgprot_t ref_prot;
 110         pte_t *linear;
 111
 112         ref_prot =
 113         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 114                 ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;
 115
 116         linear = (pte_t *)
 117                 pmd_offset(pud_offset(pgd_offset_k(address), address), address);
 118         set_pmd_pte(linear,  address,
 119                     pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
 120                             ref_prot));
 121 }
 122
 123 static int
 124 __change_page_attr(struct page *page, pgprot_t prot)
 125 {
 126         pte_t *kpte;
 127         unsigned long address;
 128         struct page *kpte_page;
 129
 130         BUG_ON(PageHighMem(page));
 131         address = (unsigned long)page_address(page);
 132
 133         kpte = lookup_address(address);
 134         if (!kpte)
 135                 return -EINVAL;
 136         kpte_page = virt_to_page(kpte);
 137         if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) {
 138                 if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 139                         set_pte_atomic(kpte, mk_pte(page, prot));
 140                 } else {
 141                         pgprot_t ref_prot;
 142                         struct page *split;
 143
 144                         ref_prot =
 145                         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 146                                 ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
 147                         split = split_large_page(address, prot, ref_prot);
 148                         if (!split)
 149                                 return -ENOMEM;
 150                         set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
 151                         kpte_page = split;
 152                 }
 153                 page_private(kpte_page)++;
 154         } else if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 155                 set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
 156                 BUG_ON(page_private(kpte_page) == 0);
 157                 page_private(kpte_page)--;
 158         } else
 159                 BUG();
 160
 161         /*
 162          * If the pte was reserved, it means it was created at boot
 163          * time (not via split_large_page) and in turn we must not
 164          * replace it with a largepage.
 165          */
 166         if (!PageReserved(kpte_page)) {
 167                 if (cpu_has_pse && (page_private(kpte_page) == 0)) {
 168                         ClearPagePrivate(kpte_page);
 169                         list_add(&kpte_page->lru, &df_list);
 170                         revert_page(kpte_page, address);
 171                 }
 172         }
 173         return 0;
 174 }
 175
 176 static inline void flush_map(void)
 177 {
 178         on_each_cpu(flush_kernel_map, NULL, 1, 1);
 179 }
 180
 181 /*
 182  * Change the page attributes of an page in the linear mapping.
 183  *
 184  * This should be used when a page is mapped with a different caching policy
 185  * than write-back somewhere - some CPUs do not like it when mappings with
 186  * different caching policies exist. This changes the page attributes of the
 187  * in kernel linear mapping too.
 188  *
 189  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 190  * This function only deals with the kernel linear map.
 191  *
 192  * Caller must call global_flush_tlb() after this.
 193  */
 194 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 195 {
 196         int err = 0;
 197         int i;
 198         unsigned long flags;
 199
 200         spin_lock_irqsave(&cpa_lock, flags);
 201         for (i = 0; i < numpages; i++, page++) {
 202                 err = __change_page_attr(page, prot);
 203                 if (err)
 204                         break;
 205         }
 206         spin_unlock_irqrestore(&cpa_lock, flags);
 207         return err;
 208 }
 209
 210 void global_flush_tlb(void)
 211 {
 212         struct list_head l;
 213         struct page *pg, *next;
 214
 215         BUG_ON(irqs_disabled());
 216
 217         spin_lock_irq(&cpa_lock);
 218         list_replace_init(&df_list, &l);
 219         spin_unlock_irq(&cpa_lock);
 220         flush_map();
 221         list_for_each_entry_safe(pg, next, &l, lru)
 222                 __free_page(pg);
 223 }
 224
 225 #ifdef CONFIG_DEBUG_PAGEALLOC
 226 void kernel_map_pages(struct page *page, int numpages, int enable)
 227 {
 228         if (PageHighMem(page))
 229                 return;
 230         if (!enable)
 231                 debug_check_no_locks_freed(page_address(page),
 232                                            numpages * PAGE_SIZE);
 233
 234         /* the return value is ignored - the calls cannot fail,
 235          * large pages are disabled at boot time.
 236          */
 237         change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 238         /* we should perform an IPI and flush all tlbs,
 239          * but that can deadlock->flush only current cpu.
 240          */
 241         __flush_tlb_all();
 242 }
 243 #endif
 244
 245 EXPORT_SYMBOL(change_page_attr);
 246 EXPORT_SYMBOL(global_flush_tlb);