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pageattr_64.c

/* 
 * Copyright 2002 Andi Kleen, SuSE Labs. 
 * Thanks to Ben LaHaise for precious feedback.
 */ 

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

pte_t *lookup_address(unsigned long address)
{ 
      pgd_t *pgd = pgd_offset_k(address);
      pud_t *pud;
      pmd_t *pmd;
      pte_t *pte;
      if (pgd_none(*pgd))
            return NULL;
      pud = pud_offset(pgd, address);
      if (!pud_present(*pud))
            return NULL; 
      pmd = pmd_offset(pud, address);
      if (!pmd_present(*pmd))
            return NULL; 
      if (pmd_large(*pmd))
            return (pte_t *)pmd;
      pte = pte_offset_kernel(pmd, address);
      if (pte && !pte_present(*pte))
            pte = NULL; 
      return pte;
} 

static struct page *split_large_page(unsigned long address, pgprot_t prot,
                             pgprot_t ref_prot)
{ 
      int i; 
      unsigned long addr;
      struct page *base = alloc_pages(GFP_KERNEL, 0);
      pte_t *pbase;
      if (!base) 
            return NULL;
      /*
       * page_private is used to track the number of entries in
       * the page table page have non standard attributes.
       */
      SetPagePrivate(base);
      page_private(base) = 0;

      address = __pa(address);
      addr = address & LARGE_PAGE_MASK; 
      pbase = (pte_t *)page_address(base);
      for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
            pbase[i] = pfn_pte(addr >> PAGE_SHIFT, 
                           addr == address ? prot : ref_prot);
      }
      return base;
} 

void clflush_cache_range(void *adr, int size)
{
      int i;
      for (i = 0; i < size; i += boot_cpu_data.x86_clflush_size)
            clflush(adr+i);
}

static void flush_kernel_map(void *arg)
{
      struct list_head *l = (struct list_head *)arg;
      struct page *pg;

      /* When clflush is available always use it because it is
         much cheaper than WBINVD. */
      /* clflush is still broken. Disable for now. */
      if (1 || !cpu_has_clflush)
            asm volatile("wbinvd" ::: "memory");
      else list_for_each_entry(pg, l, lru) {
            void *adr = page_address(pg);
            clflush_cache_range(adr, PAGE_SIZE);
      }
      __flush_tlb_all();
}

static inline void flush_map(struct list_head *l)
{     
      on_each_cpu(flush_kernel_map, l, 1, 1);
}

static LIST_HEAD(deferred_pages); /* protected by init_mm.mmap_sem */

static inline void save_page(struct page *fpage)
{
      if (!test_and_set_bit(PG_arch_1, &fpage->flags))
            list_add(&fpage->lru, &deferred_pages);
}

/* 
 * No more special protections in this 2/4MB area - revert to a
 * large page again. 
 */
static void revert_page(unsigned long address, pgprot_t ref_prot)
{
      pgd_t *pgd;
      pud_t *pud;
      pmd_t *pmd;
      pte_t large_pte;
      unsigned long pfn;

      pgd = pgd_offset_k(address);
      BUG_ON(pgd_none(*pgd));
      pud = pud_offset(pgd,address);
      BUG_ON(pud_none(*pud));
      pmd = pmd_offset(pud, address);
      BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
      pfn = (__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT;
      large_pte = pfn_pte(pfn, ref_prot);
      large_pte = pte_mkhuge(large_pte);
      set_pte((pte_t *)pmd, large_pte);
}      

static int
__change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
                           pgprot_t ref_prot)
{ 
      pte_t *kpte; 
      struct page *kpte_page;
      pgprot_t ref_prot2;

      kpte = lookup_address(address);
      if (!kpte) return 0;
      kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
      BUG_ON(PageLRU(kpte_page));
      BUG_ON(PageCompound(kpte_page));
      if (pgprot_val(prot) != pgprot_val(ref_prot)) { 
            if (!pte_huge(*kpte)) {
                  set_pte(kpte, pfn_pte(pfn, prot));
            } else {
                  /*
                   * split_large_page will take the reference for this
                   * change_page_attr on the split page.
                   */
                  struct page *split;
                  ref_prot2 = pte_pgprot(pte_clrhuge(*kpte));
                  split = split_large_page(address, prot, ref_prot2);
                  if (!split)
                        return -ENOMEM;
                  pgprot_val(ref_prot2) &= ~_PAGE_NX;
                  set_pte(kpte, mk_pte(split, ref_prot2));
                  kpte_page = split;
            }
            page_private(kpte_page)++;
      } else if (!pte_huge(*kpte)) {
            set_pte(kpte, pfn_pte(pfn, ref_prot));
            BUG_ON(page_private(kpte_page) == 0);
            page_private(kpte_page)--;
      } else
            BUG();

      /* on x86-64 the direct mapping set at boot is not using 4k pages */
      BUG_ON(PageReserved(kpte_page));

      save_page(kpte_page);
      if (page_private(kpte_page) == 0)
            revert_page(address, ref_prot);
      return 0;
} 

/*
 * Change the page attributes of an page in the linear mapping.
 *
 * This should be used when a page is mapped with a different caching policy
 * than write-back somewhere - some CPUs do not like it when mappings with
 * different caching policies exist. This changes the page attributes of the
 * in kernel linear mapping too.
 * 
 * The caller needs to ensure that there are no conflicting mappings elsewhere.
 * This function only deals with the kernel linear map.
 * 
 * Caller must call global_flush_tlb() after this.
 */
int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
{
      int err = 0, kernel_map = 0;
      int i; 

      if (address >= __START_KERNEL_map
          && address < __START_KERNEL_map + KERNEL_TEXT_SIZE) {
            address = (unsigned long)__va(__pa(address));
            kernel_map = 1;
      }

      down_write(&init_mm.mmap_sem);
      for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
            unsigned long pfn = __pa(address) >> PAGE_SHIFT;

            if (!kernel_map || pte_present(pfn_pte(0, prot))) {
                  err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
                  if (err)
                        break;
            }
            /* Handle kernel mapping too which aliases part of the
             * lowmem */
            if (__pa(address) < KERNEL_TEXT_SIZE) {
                  unsigned long addr2;
                  pgprot_t prot2;
                  addr2 = __START_KERNEL_map + __pa(address);
                  /* Make sure the kernel mappings stay executable */
                  prot2 = pte_pgprot(pte_mkexec(pfn_pte(0, prot)));
                  err = __change_page_attr(addr2, pfn, prot2,
                                     PAGE_KERNEL_EXEC);
            } 
      }     
      up_write(&init_mm.mmap_sem); 
      return err;
}

/* Don't call this for MMIO areas that may not have a mem_map entry */
int change_page_attr(struct page *page, int numpages, pgprot_t prot)
{
      unsigned long addr = (unsigned long)page_address(page);
      return change_page_attr_addr(addr, numpages, prot);
}

void global_flush_tlb(void)
{ 
      struct page *pg, *next;
      struct list_head l;

      /*
       * Write-protect the semaphore, to exclude two contexts
       * doing a list_replace_init() call in parallel and to
       * exclude new additions to the deferred_pages list:
       */
      down_write(&init_mm.mmap_sem);
      list_replace_init(&deferred_pages, &l);
      up_write(&init_mm.mmap_sem);

      flush_map(&l);

      list_for_each_entry_safe(pg, next, &l, lru) {
            list_del(&pg->lru);
            clear_bit(PG_arch_1, &pg->flags);
            if (page_private(pg) != 0)
                  continue;
            ClearPagePrivate(pg);
            __free_page(pg);
      } 
} 

EXPORT_SYMBOL(change_page_attr);
EXPORT_SYMBOL(global_flush_tlb);

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