text: /* pgalloc.c: page directory & page table allocation
   *
   * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version
   * 2 of the License, or (at your option) any later version.
   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/mm.h>
  #include <linux/highmem.h>
  #include <linux/quicklist.h>
  #include <asm/pgalloc.h>
  #include <asm/page.h>
  #include <asm/cacheflush.h>
  
  pgd_t swapper_pg_dir[PTRS_PER_PGD] __attribute__((aligned(PAGE_SIZE)));
  
  pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
  {
  	pte_t *pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT);
  	if (pte)
  		clear_page(pte);
  	return pte;
  }
  
  pgtable_t pte_alloc_one(struct mm_struct *mm, unsigned long address)
  {
  	struct page *page;
  
  #ifdef CONFIG_HIGHPTE
  	page = alloc_pages(GFP_KERNEL|__GFP_HIGHMEM|__GFP_REPEAT, 0);
  #else
  	page = alloc_pages(GFP_KERNEL|__GFP_REPEAT, 0);
  #endif
  	if (page) {
  		clear_highpage(page);
  		pgtable_page_ctor(page);
  		flush_dcache_page(page);
  	}
  	return page;
  }
  
  void __set_pmd(pmd_t *pmdptr, unsigned long pmd)
  {
  	unsigned long *__ste_p = pmdptr->ste;
  	int loop;
  
  	if (!pmd) {
  		memset(__ste_p, 0, PME_SIZE);
  	}
  	else {
  		BUG_ON(pmd & (0x3f00 | xAMPRx_SS | 0xe));
  
  		for (loop = PME_SIZE; loop > 0; loop -= 4) {
  			*__ste_p++ = pmd;
  			pmd += __frv_PT_SIZE;
  		}
  	}
  
  	frv_dcache_writeback((unsigned long) pmdptr, (unsigned long) (pmdptr + 1));
  }
  
  /*
   * List of all pgd's needed for non-PAE so it can invalidate entries
   * in both cached and uncached pgd's; not needed for PAE since the
   * kernel pmd is shared. If PAE were not to share the pmd a similar
   * tactic would be needed. This is essentially codepath-based locking
   * against pageattr.c; it is the unique case in which a valid change
   * of kernel pagetables can't be lazily synchronized by vmalloc faults.
   * vmalloc faults work because attached pagetables are never freed.
   * If the locking proves to be non-performant, a ticketing scheme with
   * checks at dup_mmap(), exec(), and other mmlist addition points
   * could be used. The locking scheme was chosen on the basis of
   * manfred's recommendations and having no core impact whatsoever.
   * -- wli
   */
  DEFINE_SPINLOCK(pgd_lock);
  struct page *pgd_list;
  
  static inline void pgd_list_add(pgd_t *pgd)
  {
  	struct page *page = virt_to_page(pgd);
  	page->index = (unsigned long) pgd_list;
  	if (pgd_list)
  		set_page_private(pgd_list, (unsigned long) &page->index);
  	pgd_list = page;
  	set_page_private(page, (unsigned long)&pgd_list);
  }
  
  static inline void pgd_list_del(pgd_t *pgd)
  {
  	struct page *next, **pprev, *page = virt_to_page(pgd);
  	next = (struct page *) page->index;
  	pprev = (struct page **) page_private(page);
  	*pprev = next;
  	if (next)
  		set_page_private(next, (unsigned long) pprev);
  }
  
  void pgd_ctor(void *pgd)
  {
  	unsigned long flags;
  
  	if (PTRS_PER_PMD == 1)
  		spin_lock_irqsave(&pgd_lock, flags);
  
  	memcpy((pgd_t *) pgd + USER_PGDS_IN_LAST_PML4,
  	       swapper_pg_dir + USER_PGDS_IN_LAST_PML4,
  	       (PTRS_PER_PGD - USER_PGDS_IN_LAST_PML4) * sizeof(pgd_t));
  
  	if (PTRS_PER_PMD > 1)
  		return;
  
  	pgd_list_add(pgd);
  	spin_unlock_irqrestore(&pgd_lock, flags);
  	memset(pgd, 0, USER_PGDS_IN_LAST_PML4 * sizeof(pgd_t));
  }
  
  /* never called when PTRS_PER_PMD > 1 */
  void pgd_dtor(void *pgd)
  {
  	unsigned long flags; /* can be called from interrupt context */
  
  	spin_lock_irqsave(&pgd_lock, flags);
  	pgd_list_del(pgd);
  	spin_unlock_irqrestore(&pgd_lock, flags);
  }
  
  pgd_t *pgd_alloc(struct mm_struct *mm)
  {
  	pgd_t *pgd;
  
  	pgd = quicklist_alloc(0, GFP_KERNEL, pgd_ctor);
  	if (!pgd)
  		return pgd;
  
  	return pgd;
  }
  
  void pgd_free(struct mm_struct *mm, pgd_t *pgd)
  {
  	/* in the non-PAE case, clear_page_tables() clears user pgd entries */
   	quicklist_free(0, pgd_dtor, pgd);
  }
  
  void __init pgtable_cache_init(void)
  {
  }
  
  void check_pgt_cache(void)
  {
  	quicklist_trim(0, pgd_dtor, 25, 16);
  }
  
  