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