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/config.h>
   7 #include <linux/mm.h>
   8 #include <linux/sched.h>
   9 #include <linux/highmem.h>
  10 #include <linux/module.h>
  11 #include <linux/slab.h>
  12 #include <asm/uaccess.h>
  13 #include <asm/processor.h>
  14 #include <asm/tlbflush.h>
  15 #include <asm/pgalloc.h>
  16 #include <asm/sections.h>
  17
  18 static DEFINE_SPINLOCK(cpa_lock);
  19 static struct list_head df_list = LIST_HEAD_INIT(df_list);
  20
  21
  22 pte_t *lookup_address(unsigned long address)
  23 {
  24         pgd_t *pgd = pgd_offset_k(address);
  25         pud_t *pud;
  26         pmd_t *pmd;
  27         if (pgd_none(*pgd))
  28                 return NULL;
  29         pud = pud_offset(pgd, address);
  30         if (pud_none(*pud))
  31                 return NULL;
  32         pmd = pmd_offset(pud, address);
  33         if (pmd_none(*pmd))
  34                 return NULL;
  35         if (pmd_large(*pmd))
  36                 return (pte_t *)pmd;
  37         return pte_offset_kernel(pmd, address);
  38 }
  39
  40 static struct page *split_large_page(unsigned long address, pgprot_t prot,
  41                                         pgprot_t ref_prot)
  42 {
  43         int i;
  44         unsigned long addr;
  45         struct page *base;
  46         pte_t *pbase;
  47
  48         spin_unlock_irq(&cpa_lock);
  49         base = alloc_pages(GFP_KERNEL, 0);
  50         spin_lock_irq(&cpa_lock);
  51         if (!base)
  52                 return NULL;
  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                set_pte(&pbase[i], pfn_pte(addr >> PAGE_SHIFT,
  59                                           addr == address ? prot : ref_prot));
  60         }
  61         return base;
  62 }
  63
  64 static void flush_kernel_map(void *dummy)
  65 {
  66         /* Could use CLFLUSH here if the CPU supports it (Hammer,P4) */
  67         if (boot_cpu_data.x86_model >= 4)
  68                 wbinvd();
  69         /* Flush all to work around Errata in early athlons regarding
  70          * large page flushing.
  71          */
  72         __flush_tlb_all();
  73 }
  74
  75 static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
  76 {
  77         struct page *page;
  78         unsigned long flags;
  79
  80         set_pte_atomic(kpte, pte);      /* change init_mm */
  81         if (PTRS_PER_PMD > 1)
  82                 return;
  83
  84         spin_lock_irqsave(&pgd_lock, flags);
  85         for (page = pgd_list; page; page = (struct page *)page->index) {
  86                 pgd_t *pgd;
  87                 pud_t *pud;
  88                 pmd_t *pmd;
  89                 pgd = (pgd_t *)page_address(page) + pgd_index(address);
  90                 pud = pud_offset(pgd, address);
  91                 pmd = pmd_offset(pud, address);
  92                 set_pte_atomic((pte_t *)pmd, pte);
  93         }
  94         spin_unlock_irqrestore(&pgd_lock, flags);
  95 }
  96
  97 /*
  98  * No more special protections in this 2/4MB area - revert to a
  99  * large page again.
 100  */
 101 static inline void revert_page(struct page *kpte_page, unsigned long address)
 102 {
 103         pgprot_t ref_prot;
 104         pte_t *linear;
 105
 106         ref_prot =
 107         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 108                 ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;
 109
 110         linear = (pte_t *)
 111                 pmd_offset(pud_offset(pgd_offset_k(address), address), address);
 112         set_pmd_pte(linear,  address,
 113                     pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
 114                             ref_prot));
 115 }
 116
 117 static int
 118 __change_page_attr(struct page *page, pgprot_t prot)
 119 {
 120         pte_t *kpte;
 121         unsigned long address;
 122         struct page *kpte_page;
 123
 124         BUG_ON(PageHighMem(page));
 125         address = (unsigned long)page_address(page);
 126
 127         kpte = lookup_address(address);
 128         if (!kpte)
 129                 return -EINVAL;
 130         kpte_page = virt_to_page(kpte);
 131         if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) {
 132                 if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 133                         set_pte_atomic(kpte, mk_pte(page, prot));
 134                 } else {
 135                         pgprot_t ref_prot;
 136                         struct page *split;
 137
 138                         ref_prot =
 139                         ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
 140                                 ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
 141                         split = split_large_page(address, prot, ref_prot);
 142                         if (!split)
 143                                 return -ENOMEM;
 144                         set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
 145                         kpte_page = split;
 146                 }
 147                 get_page(kpte_page);
 148         } else if ((pte_val(*kpte) & _PAGE_PSE) == 0) {
 149                 set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
 150                 __put_page(kpte_page);
 151         } else
 152                 BUG();
 153
 154         /*
 155          * If the pte was reserved, it means it was created at boot
 156          * time (not via split_large_page) and in turn we must not
 157          * replace it with a largepage.
 158          */
 159         if (!PageReserved(kpte_page)) {
 160                 /* memleak and potential failed 2M page regeneration */
 161                 BUG_ON(!page_count(kpte_page));
 162
 163                 if (cpu_has_pse && (page_count(kpte_page) == 1)) {
 164                         list_add(&kpte_page->lru, &df_list);
 165                         revert_page(kpte_page, address);
 166                 }
 167         }
 168         return 0;
 169 }
 170
 171 static inline void flush_map(void)
 172 {
 173         on_each_cpu(flush_kernel_map, NULL, 1, 1);
 174 }
 175
 176 /*
 177  * Change the page attributes of an page in the linear mapping.
 178  *
 179  * This should be used when a page is mapped with a different caching policy
 180  * than write-back somewhere - some CPUs do not like it when mappings with
 181  * different caching policies exist. This changes the page attributes of the
 182  * in kernel linear mapping too.
 183  *
 184  * The caller needs to ensure that there are no conflicting mappings elsewhere.
 185  * This function only deals with the kernel linear map.
 186  *
 187  * Caller must call global_flush_tlb() after this.
 188  */
 189 int change_page_attr(struct page *page, int numpages, pgprot_t prot)
 190 {
 191         int err = 0;
 192         int i;
 193         unsigned long flags;
 194
 195         spin_lock_irqsave(&cpa_lock, flags);
 196         for (i = 0; i < numpages; i++, page++) {
 197                 err = __change_page_attr(page, prot);
 198                 if (err)
 199                         break;
 200         }
 201         spin_unlock_irqrestore(&cpa_lock, flags);
 202         return err;
 203 }
 204
 205 void global_flush_tlb(void)
 206 {
 207         LIST_HEAD(l);
 208         struct page *pg, *next;
 209
 210         BUG_ON(irqs_disabled());
 211
 212         spin_lock_irq(&cpa_lock);
 213         list_splice_init(&df_list, &l);
 214         spin_unlock_irq(&cpa_lock);
 215         flush_map();
 216         list_for_each_entry_safe(pg, next, &l, lru)
 217                 __free_page(pg);
 218 }
 219
 220 #ifdef CONFIG_DEBUG_PAGEALLOC
 221 void kernel_map_pages(struct page *page, int numpages, int enable)
 222 {
 223         if (PageHighMem(page))
 224                 return;
 225         if (!enable)
 226                 mutex_debug_check_no_locks_freed(page_address(page),
 227                                                  numpages * PAGE_SIZE);
 228
 229         /* the return value is ignored - the calls cannot fail,
 230          * large pages are disabled at boot time.
 231          */
 232         change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
 233         /* we should perform an IPI and flush all tlbs,
 234          * but that can deadlock->flush only current cpu.
 235          */
 236         __flush_tlb_all();
 237 }
 238 #endif
 239
 240 EXPORT_SYMBOL(change_page_attr);
 241 EXPORT_SYMBOL(global_flush_tlb);