arch/x86_64/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/io.h>
  15
  16 static inline pte_t *lookup_address(unsigned long address)
  17 {
  18         pgd_t *pgd = pgd_offset_k(address);
  19         pud_t *pud;
  20         pmd_t *pmd;
  21         pte_t *pte;
  22         if (pgd_none(*pgd))
  23                 return NULL;
  24         pud = pud_offset(pgd, address);
  25         if (!pud_present(*pud))
  26                 return NULL;
  27         pmd = pmd_offset(pud, address);
  28         if (!pmd_present(*pmd))
  29                 return NULL;
  30         if (pmd_large(*pmd))
  31                 return (pte_t *)pmd;
  32         pte = pte_offset_kernel(pmd, address);
  33         if (pte && !pte_present(*pte))
  34                 pte = NULL;
  35         return pte;
  36 }
  37
  38 static struct page *split_large_page(unsigned long address, pgprot_t prot,
  39                                      pgprot_t ref_prot)
  40 {
  41         int i;
  42         unsigned long addr;
  43         struct page *base = alloc_pages(GFP_KERNEL, 0);
  44         pte_t *pbase;
  45         if (!base)
  46                 return NULL;
  47         /*
  48          * page_private is used to track the number of entries in
  49          * the page table page have non standard attributes.
  50          */
  51         SetPagePrivate(base);
  52         page_private(base) = 0;
  53
  54         address = __pa(address);
  55         addr = address & LARGE_PAGE_MASK;
  56         pbase = (pte_t *)page_address(base);
  57         for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
  58                 pbase[i] = pfn_pte(addr >> PAGE_SHIFT,
  59                                    addr == address ? prot : ref_prot);
  60         }
  61         return base;
  62 }
  63
  64
  65 static void flush_kernel_map(void *address)
  66 {
  67         if (0 && address && cpu_has_clflush) {
  68                 /* is this worth it? */
  69                 int i;
  70                 for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
  71                         asm volatile("clflush (%0)" :: "r" (address + i));
  72         } else
  73                 asm volatile("wbinvd":::"memory");
  74         if (address)
  75                 __flush_tlb_one(address);
  76         else
  77                 __flush_tlb_all();
  78 }
  79
  80
  81 static inline void flush_map(unsigned long address)
  82 {
  83         on_each_cpu(flush_kernel_map, (void *)address, 1, 1);
  84 }
  85
  86 static struct page *deferred_pages; /* protected by init_mm.mmap_sem */
  87
  88 static inline void save_page(struct page *fpage)
  89 {
  90         fpage->lru.next = (struct list_head *)deferred_pages;
  91         deferred_pages = fpage;
  92 }
  93
  94 /*
  95  * No more special protections in this 2/4MB area - revert to a
  96  * large page again.
  97  */
  98 static void revert_page(unsigned long address, pgprot_t ref_prot)
  99 {
 100         pgd_t *pgd;
 101         pud_t *pud;
 102         pmd_t *pmd;
 103         pte_t large_pte;
 104
 105         pgd = pgd_offset_k(address);
 106         BUG_ON(pgd_none(*pgd));
 107         pud = pud_offset(pgd,address);
 108         BUG_ON(pud_none(*pud));
 109         pmd = pmd_offset(pud, address);
 110         BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
 111         pgprot_val(ref_prot) |= _PAGE_PSE;
 112         large_pte = mk_pte_phys(__pa(address) & LARGE_PAGE_MASK, ref_prot);
 113         set_pte((pte_t *)pmd, large_pte);
 114 }
 115
 116 static int
 117 __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
 118                                    pgprot_t ref_prot)
 119 {
 120         pte_t *kpte;
 121         struct page *kpte_page;
 122         unsigned kpte_flags;
 123         pgprot_t ref_prot2;
 124         kpte = lookup_address(address);
 125         if (!kpte) return 0;
 126         kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
 127         kpte_flags = pte_val(*kpte);
 128         if (pgprot_val(prot) != pgprot_val(ref_prot)) {
 129                 if ((kpte_flags & _PAGE_PSE) == 0) {
 130                         set_pte(kpte, pfn_pte(pfn, prot));
 131                 } else {
 132                         /*
 133                          * split_large_page will take the reference for this
 134                          * change_page_attr on the split page.
 135                          */
 136
 137                         struct page *split;
 138                         ref_prot2 = __pgprot(pgprot_val(pte_pgprot(*lookup_address(address))) & ~(1<<_PAGE_BIT_PSE));
 139
 140                         split = split_large_page(address, prot, ref_prot2);
 141                         if (!split)
 142                                 return -ENOMEM;
 143                         set_pte(kpte,mk_pte(split, ref_prot2));
 144                         kpte_page = split;
 145                 }
 146                 page_private(kpte_page)++;
 147         } else if ((kpte_flags & _PAGE_PSE) == 0) {
 148                 set_pte(kpte, pfn_pte(pfn, ref_prot));
 149                 BUG_ON(page_private(kpte_page) == 0);
 150                 page_private(kpte_page)--;
 151         } else
 152                 BUG();
 153
 154         /* on x86-64 the direct mapping set at boot is not using 4k pages */
 155         BUG_ON(PageReserved(kpte_page));
 156
 157         if (page_private(kpte_page) == 0) {
 158                 save_page(kpte_page);
 159                 revert_page(address, ref_prot);
 160         }
 161         return 0;
 162 }
 163
 164 /*
 165  * Change the page attributes of an page in the linear mapping.
 166  *
 167  * This should be used when a page is mapped with a different caching policy
 168  * than write-back somewhere - some CPUs do not like it when mappings with
 169  * different caching policies exist. This changes the page attributes of the
 170  * in kernel linear mapping too.
 171  *
 172  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 173  * This function only deals with the kernel linear map.
 174  *
 175  * Caller must call global_flush_tlb() after this.
 176  */
 177 int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
 178 {
 179         int err = 0;
 180         int i;
 181
 182         down_write(&init_mm.mmap_sem);
 183         for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
 184                 unsigned long pfn = __pa(address) >> PAGE_SHIFT;
 185
 186                 err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
 187                 if (err)
 188                         break;
 189                 /* Handle kernel mapping too which aliases part of the
 190                  * lowmem */
 191                 if (__pa(address) < KERNEL_TEXT_SIZE) {
 192                         unsigned long addr2;
 193                         pgprot_t prot2 = prot;
 194                         addr2 = __START_KERNEL_map + __pa(address);
 195                         pgprot_val(prot2) &= ~_PAGE_NX;
 196                         err = __change_page_attr(addr2, pfn, prot2, PAGE_KERNEL_EXEC);
 197                 }
 198         }
 199         up_write(&init_mm.mmap_sem);
 200         return err;
 201 }
 202
 203 /* Don't call this for MMIO areas that may not have a mem_map entry */
 204 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 205 {
 206         unsigned long addr = (unsigned long)page_address(page);
 207         return change_page_attr_addr(addr, numpages, prot);
 208 }
 209
 210 void global_flush_tlb(void)
 211 {
 212         struct page *dpage;
 213
 214         down_read(&init_mm.mmap_sem);
 215         dpage = xchg(&deferred_pages, NULL);
 216         up_read(&init_mm.mmap_sem);
 217
 218         flush_map((dpage && !dpage->lru.next) ? (unsigned long)page_address(dpage) : 0);
 219         while (dpage) {
 220                 struct page *tmp = dpage;
 221                 dpage = (struct page *)dpage->lru.next;
 222                 ClearPagePrivate(tmp);
 223                 __free_page(tmp);
 224         }
 225 }
 226
 227 EXPORT_SYMBOL(change_page_attr);
 228 EXPORT_SYMBOL(global_flush_tlb);