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         paravirt_alloc_pt(page_to_pfn(base));
  64         for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
  65                set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
  66                                           addr == address ? prot : ref_prot));
  67         }
  68         return base;
  69 }
  70
  71 static void cache_flush_page(struct page *p)
  72 {
  73         unsigned long adr = (unsigned long)page_address(p);
  74         int i;
  75         for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
  76                 asm volatile("clflush (%0)" :: "r" (adr + i));
  77 }
  78
  79 static void flush_kernel_map(void *arg)
  80 {
  81         struct list_head *lh = (struct list_head *)arg;
  82         struct page *p;
  83
  84         /* High level code is not ready for clflush yet */
  85         if (0 && cpu_has_clflush) {
  86                 list_for_each_entry (p, lh, lru)
  87                         cache_flush_page(p);
  88         } else if (boot_cpu_data.x86_model >= 4)
  89                 wbinvd();
  90
  91         /* Flush all to work around Errata in early athlons regarding
  92          * large page flushing.
  93          */
  94         __flush_tlb_all();
  95 }
  96
  97 static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
  98 {
  99         struct page *page;
 100         unsigned long flags;
 101
 102         set_pte_atomic(kpte, pte);      /* change init_mm */
 103         if (SHARED_KERNEL_PMD)
 104                 return;
 105
 106         spin_lock_irqsave(&pgd_lock, flags);
 107         for (page = pgd_list; page; page = (struct page *)page->index) {
 108                 pgd_t *pgd;
 109                 pud_t *pud;
 110                 pmd_t *pmd;
 111                 pgd = (pgd_t *)page_address(page) + pgd_index(address);
 112                 pud = pud_offset(pgd, address);
 113                 pmd = pmd_offset(pud, address);
 114                 set_pte_atomic((pte_t *)pmd, pte);
 115         }
 116         spin_unlock_irqrestore(&pgd_lock, flags);
 117 }
 118
 119 /*
 120  * No more special protections in this 2/4MB area - revert to a
 121  * large page again.
 122  */
 123 static inline void revert_page(struct page *kpte_page, unsigned long address)
 124 {
 125         pgprot_t ref_prot;
 126         pte_t *linear;
 127
 128         ref_prot =
 129         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 130                 ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;
 131
 132         linear = (pte_t *)
 133                 pmd_offset(pud_offset(pgd_offset_k(address), address), address);
 134         set_pmd_pte(linear,  address,
 135                     pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
 136                             ref_prot));
 137 }
 138
 139 static int
 140 __change_page_attr(struct page *page, pgprot_t prot)
 141 {
 142         pte_t *kpte;
 143         unsigned long address;
 144         struct page *kpte_page;
 145
 146         BUG_ON(PageHighMem(page));
 147         address = (unsigned long)page_address(page);
 148
 149         kpte = lookup_address(address);
 150         if (!kpte)
 151                 return -EINVAL;
 152         kpte_page = virt_to_page(kpte);
 153         if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) {
 154                 if (!pte_huge(*kpte)) {
 155                         set_pte_atomic(kpte, mk_pte(page, prot));
 156                 } else {
 157                         pgprot_t ref_prot;
 158                         struct page *split;
 159
 160                         ref_prot =
 161                         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 162                                 ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
 163                         split = split_large_page(address, prot, ref_prot);
 164                         if (!split)
 165                                 return -ENOMEM;
 166                         set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
 167                         kpte_page = split;
 168                 }
 169                 page_private(kpte_page)++;
 170         } else if (!pte_huge(*kpte)) {
 171                 set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
 172                 BUG_ON(page_private(kpte_page) == 0);
 173                 page_private(kpte_page)--;
 174         } else
 175                 BUG();
 176
 177         /*
 178          * If the pte was reserved, it means it was created at boot
 179          * time (not via split_large_page) and in turn we must not
 180          * replace it with a largepage.
 181          */
 182         if (!PageReserved(kpte_page)) {
 183                 if (cpu_has_pse && (page_private(kpte_page) == 0)) {
 184                         ClearPagePrivate(kpte_page);
 185                         paravirt_release_pt(page_to_pfn(kpte_page));
 186                         list_add(&kpte_page->lru, &df_list);
 187                         revert_page(kpte_page, address);
 188                 }
 189         }
 190         return 0;
 191 }
 192
 193 static inline void flush_map(struct list_head *l)
 194 {
 195         on_each_cpu(flush_kernel_map, l, 1, 1);
 196 }
 197
 198 /*
 199  * Change the page attributes of an page in the linear mapping.
 200  *
 201  * This should be used when a page is mapped with a different caching policy
 202  * than write-back somewhere - some CPUs do not like it when mappings with
 203  * different caching policies exist. This changes the page attributes of the
 204  * in kernel linear mapping too.
 205  *
 206  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 207  * This function only deals with the kernel linear map.
 208  *
 209  * Caller must call global_flush_tlb() after this.
 210  */
 211 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 212 {
 213         int err = 0;
 214         int i;
 215         unsigned long flags;
 216
 217         spin_lock_irqsave(&cpa_lock, flags);
 218         for (i = 0; i < numpages; i++, page++) {
 219                 err = __change_page_attr(page, prot);
 220                 if (err)
 221                         break;
 222         }
 223         spin_unlock_irqrestore(&cpa_lock, flags);
 224         return err;
 225 }
 226
 227 void global_flush_tlb(void)
 228 {
 229         struct list_head l;
 230         struct page *pg, *next;
 231
 232         BUG_ON(irqs_disabled());
 233
 234         spin_lock_irq(&cpa_lock);
 235         list_replace_init(&df_list, &l);
 236         spin_unlock_irq(&cpa_lock);
 237         flush_map(&l);
 238         list_for_each_entry_safe(pg, next, &l, lru) {
 239                 __free_page(pg);
 240         }
 241 }
 242
 243 #ifdef CONFIG_DEBUG_PAGEALLOC
 244 void kernel_map_pages(struct page *page, int numpages, int enable)
 245 {
 246         if (PageHighMem(page))
 247                 return;
 248         if (!enable)
 249                 debug_check_no_locks_freed(page_address(page),
 250                                            numpages * PAGE_SIZE);
 251
 252         /* the return value is ignored - the calls cannot fail,
 253          * large pages are disabled at boot time.
 254          */
 255         change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 256         /* we should perform an IPI and flush all tlbs,
 257          * but that can deadlock->flush only current cpu.
 258          */
 259         __flush_tlb_all();
 260 }
 261 #endif
 262
 263 EXPORT_SYMBOL(change_page_attr);
 264 EXPORT_SYMBOL(global_flush_tlb);