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pageattr_32.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/pgalloc.h>
#include <asm/sections.h>

static DEFINE_SPINLOCK(cpa_lock);
static struct list_head df_list = LIST_HEAD_INIT(df_list);


pte_t *lookup_address(unsigned long address) 
{ 
      pgd_t *pgd = pgd_offset_k(address);
      pud_t *pud;
      pmd_t *pmd;
      if (pgd_none(*pgd))
            return NULL;
      pud = pud_offset(pgd, address);
      if (pud_none(*pud))
            return NULL;
      pmd = pmd_offset(pud, address);
      if (pmd_none(*pmd))
            return NULL;
      if (pmd_large(*pmd))
            return (pte_t *)pmd;
        return pte_offset_kernel(pmd, address);
} 

static struct page *split_large_page(unsigned long address, pgprot_t prot,
                              pgprot_t ref_prot)
{ 
      int i; 
      unsigned long addr;
      struct page *base;
      pte_t *pbase;

      spin_unlock_irq(&cpa_lock);
      base = alloc_pages(GFP_KERNEL, 0);
      spin_lock_irq(&cpa_lock);
      if (!base) 
            return NULL;

      /*
       * page_private is used to track the number of entries in
       * the page table page that have non standard attributes.
       */
      SetPagePrivate(base);
      page_private(base) = 0;

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

static void cache_flush_page(struct page *p)
{ 
      void *adr = page_address(p);
      int i;
      for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size)
            clflush(adr+i);
}

static void flush_kernel_map(void *arg)
{
      struct list_head *lh = (struct list_head *)arg;
      struct page *p;

      /* High level code is not ready for clflush yet */
      if (0 && cpu_has_clflush) {
            list_for_each_entry (p, lh, lru)
                  cache_flush_page(p);
      } else if (boot_cpu_data.x86_model >= 4)
            wbinvd();

      /* Flush all to work around Errata in early athlons regarding 
       * large page flushing. 
       */
      __flush_tlb_all();      
}

static void set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte) 
{ 
      struct page *page;
      unsigned long flags;

      set_pte_atomic(kpte, pte);    /* change init_mm */
      if (SHARED_KERNEL_PMD)
            return;

      spin_lock_irqsave(&pgd_lock, flags);
      for (page = pgd_list; page; page = (struct page *)page->index) {
            pgd_t *pgd;
            pud_t *pud;
            pmd_t *pmd;
            pgd = (pgd_t *)page_address(page) + pgd_index(address);
            pud = pud_offset(pgd, address);
            pmd = pmd_offset(pud, address);
            set_pte_atomic((pte_t *)pmd, pte);
      }
      spin_unlock_irqrestore(&pgd_lock, flags);
}

/* 
 * No more special protections in this 2/4MB area - revert to a
 * large page again. 
 */
static inline void revert_page(struct page *kpte_page, unsigned long address)
{
      pgprot_t ref_prot;
      pte_t *linear;

      ref_prot =
      ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
            ? PAGE_KERNEL_LARGE_EXEC : PAGE_KERNEL_LARGE;

      linear = (pte_t *)
            pmd_offset(pud_offset(pgd_offset_k(address), address), address);
      set_pmd_pte(linear,  address,
                pfn_pte((__pa(address) & LARGE_PAGE_MASK) >> PAGE_SHIFT,
                      ref_prot));
}

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

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

      BUG_ON(PageHighMem(page));
      address = (unsigned long)page_address(page);

      kpte = lookup_address(address);
      if (!kpte)
            return -EINVAL;
      kpte_page = virt_to_page(kpte);
      BUG_ON(PageLRU(kpte_page));
      BUG_ON(PageCompound(kpte_page));

      if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) { 
            if (!pte_huge(*kpte)) {
                  set_pte_atomic(kpte, mk_pte(page, prot)); 
            } else {
                  pgprot_t ref_prot;
                  struct page *split;

                  ref_prot =
                  ((address & LARGE_PAGE_MASK) < (unsigned long)&_etext)
                        ? PAGE_KERNEL_EXEC : PAGE_KERNEL;
                  split = split_large_page(address, prot, ref_prot);
                  if (!split)
                        return -ENOMEM;
                  set_pmd_pte(kpte,address,mk_pte(split, ref_prot));
                  kpte_page = split;
            }
            page_private(kpte_page)++;
      } else if (!pte_huge(*kpte)) {
            set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
            BUG_ON(page_private(kpte_page) == 0);
            page_private(kpte_page)--;
      } else
            BUG();

      /*
       * If the pte was reserved, it means it was created at boot
       * time (not via split_large_page) and in turn we must not
       * replace it with a largepage.
       */

      save_page(kpte_page);
      if (!PageReserved(kpte_page)) {
            if (cpu_has_pse && (page_private(kpte_page) == 0)) {
                  paravirt_release_pt(page_to_pfn(kpte_page));
                  revert_page(kpte_page, address);
            }
      }
      return 0;
} 

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

/*
 * 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(struct page *page, int numpages, pgprot_t prot)
{
      int err = 0; 
      int i; 
      unsigned long flags;

      spin_lock_irqsave(&cpa_lock, flags);
      for (i = 0; i < numpages; i++, page++) { 
            err = __change_page_attr(page, prot);
            if (err) 
                  break; 
      }     
      spin_unlock_irqrestore(&cpa_lock, flags);
      return err;
}

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

      BUG_ON(irqs_disabled());

      spin_lock_irq(&cpa_lock);
      list_replace_init(&df_list, &l);
      spin_unlock_irq(&cpa_lock);
      flush_map(&l);
      list_for_each_entry_safe(pg, next, &l, lru) {
            list_del(&pg->lru);
            clear_bit(PG_arch_1, &pg->flags);
            if (PageReserved(pg) || !cpu_has_pse || page_private(pg) != 0)
                  continue;
            ClearPagePrivate(pg);
            __free_page(pg);
      }
}

#ifdef CONFIG_DEBUG_PAGEALLOC
void kernel_map_pages(struct page *page, int numpages, int enable)
{
      if (PageHighMem(page))
            return;
      if (!enable)
            debug_check_no_locks_freed(page_address(page),
                                 numpages * PAGE_SIZE);

      /* the return value is ignored - the calls cannot fail,
       * large pages are disabled at boot time.
       */
      change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
      /* we should perform an IPI and flush all tlbs,
       * but that can deadlock->flush only current cpu.
       */
      __flush_tlb_all();
}
#endif

EXPORT_SYMBOL(change_page_attr);
EXPORT_SYMBOL(global_flush_tlb);

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