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