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 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 static void cache_flush_page(void *adr)
  65 {
  66         int i;
  67         for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
  68                 asm volatile("clflush (%0)" :: "r" (adr + i));
  69 }
  70
  71 static void flush_kernel_map(void *arg)
  72 {
  73         struct list_head *l = (struct list_head *)arg;
  74         struct page *pg;
  75
  76         /* When clflush is available always use it because it is
  77            much cheaper than WBINVD. */
  78         if (!cpu_has_clflush)
  79                 asm volatile("wbinvd" ::: "memory");
  80         else list_for_each_entry(pg, l, lru) {
  81                 void *adr = page_address(pg);
  82                 cache_flush_page(adr);
  83         }
  84         __flush_tlb_all();
  85 }
  86
  87 static inline void flush_map(struct list_head *l)
  88 {
  89         on_each_cpu(flush_kernel_map, l, 1, 1);
  90 }
  91
  92 static LIST_HEAD(deferred_pages); /* protected by init_mm.mmap_sem */
  93
  94 static inline void save_page(struct page *fpage)
  95 {
  96         if (!test_and_set_bit(PG_arch_1, &fpage->flags))
  97                 list_add(&fpage->lru, &deferred_pages);
  98 }
  99
 100 /*
 101  * No more special protections in this 2/4MB area - revert to a
 102  * large page again.
 103  */
 104 static void revert_page(unsigned long address, pgprot_t ref_prot)
 105 {
 106         pgd_t *pgd;
 107         pud_t *pud;
 108         pmd_t *pmd;
 109         pte_t large_pte;
 110         unsigned long pfn;
 111
 112         pgd = pgd_offset_k(address);
 113         BUG_ON(pgd_none(*pgd));
 114         pud = pud_offset(pgd,address);
 115         BUG_ON(pud_none(*pud));
 116         pmd = pmd_offset(pud, address);
 117         BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
 118         pfn = (__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT;
 119         large_pte = pfn_pte(pfn, ref_prot);
 120         large_pte = pte_mkhuge(large_pte);
 121         set_pte((pte_t *)pmd, large_pte);
 122 }
 123
 124 static int
 125 __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
 126                                    pgprot_t ref_prot)
 127 {
 128         pte_t *kpte;
 129         struct page *kpte_page;
 130         pgprot_t ref_prot2;
 131
 132         kpte = lookup_address(address);
 133         if (!kpte) return 0;
 134         kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
 135         BUG_ON(PageLRU(kpte_page));
 136         BUG_ON(PageCompound(kpte_page));
 137         if (pgprot_val(prot) != pgprot_val(ref_prot)) {
 138                 if (!pte_huge(*kpte)) {
 139                         set_pte(kpte, pfn_pte(pfn, prot));
 140                 } else {
 141                         /*
 142                          * split_large_page will take the reference for this
 143                          * change_page_attr on the split page.
 144                          */
 145                         struct page *split;
 146                         ref_prot2 = pte_pgprot(pte_clrhuge(*kpte));
 147                         split = split_large_page(address, prot, ref_prot2);
 148                         if (!split)
 149                                 return -ENOMEM;
 150                         set_pte(kpte, mk_pte(split, ref_prot2));
 151                         kpte_page = split;
 152                 }
 153                 page_private(kpte_page)++;
 154         } else if (!pte_huge(*kpte)) {
 155                 set_pte(kpte, pfn_pte(pfn, ref_prot));
 156                 BUG_ON(page_private(kpte_page) == 0);
 157                 page_private(kpte_page)--;
 158         } else
 159                 BUG();
 160
 161         /* on x86-64 the direct mapping set at boot is not using 4k pages */
 162         BUG_ON(PageReserved(kpte_page));
 163
 164         save_page(kpte_page);
 165         if (page_private(kpte_page) == 0)
 166                 revert_page(address, ref_prot);
 167         return 0;
 168 }
 169
 170 /*
 171  * Change the page attributes of an page in the linear mapping.
 172  *
 173  * This should be used when a page is mapped with a different caching policy
 174  * than write-back somewhere - some CPUs do not like it when mappings with
 175  * different caching policies exist. This changes the page attributes of the
 176  * in kernel linear mapping too.
 177  *
 178  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 179  * This function only deals with the kernel linear map.
 180  *
 181  * Caller must call global_flush_tlb() after this.
 182  */
 183 int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
 184 {
 185         int err = 0, kernel_map = 0;
 186         int i;
 187
 188         if (address >= __START_KERNEL_map
 189             && address < __START_KERNEL_map + KERNEL_TEXT_SIZE) {
 190                 address = (unsigned long)__va(__pa(address));
 191                 kernel_map = 1;
 192         }
 193
 194         down_write(&init_mm.mmap_sem);
 195         for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
 196                 unsigned long pfn = __pa(address) >> PAGE_SHIFT;
 197
 198                 if (!kernel_map || pte_present(pfn_pte(0, prot))) {
 199                         err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
 200                         if (err)
 201                                 break;
 202                 }
 203                 /* Handle kernel mapping too which aliases part of the
 204                  * lowmem */
 205                 if (__pa(address) < KERNEL_TEXT_SIZE) {
 206                         unsigned long addr2;
 207                         pgprot_t prot2;
 208                         addr2 = __START_KERNEL_map + __pa(address);
 209                         /* Make sure the kernel mappings stay executable */
 210                         prot2 = pte_pgprot(pte_mkexec(pfn_pte(0, prot)));
 211                         err = __change_page_attr(addr2, pfn, prot2,
 212                                                  PAGE_KERNEL_EXEC);
 213                 }
 214         }
 215         up_write(&init_mm.mmap_sem);
 216         return err;
 217 }
 218
 219 /* Don't call this for MMIO areas that may not have a mem_map entry */
 220 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 221 {
 222         unsigned long addr = (unsigned long)page_address(page);
 223         return change_page_attr_addr(addr, numpages, prot);
 224 }
 225
 226 void global_flush_tlb(void)
 227 {
 228         struct page *pg, *next;
 229         struct list_head l;
 230
 231         down_read(&init_mm.mmap_sem);
 232         list_replace_init(&deferred_pages, &l);
 233         up_read(&init_mm.mmap_sem);
 234
 235         flush_map(&l);
 236
 237         list_for_each_entry_safe(pg, next, &l, lru) {
 238                 list_del(&pg->lru);
 239                 clear_bit(PG_arch_1, &pg->flags);
 240                 if (page_private(pg) != 0)
 241                         continue;
 242                 ClearPagePrivate(pg);
 243                 __free_page(pg);
 244         }
 245 }
 246
 247 EXPORT_SYMBOL(change_page_attr);
 248 EXPORT_SYMBOL(global_flush_tlb);