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pgd.c

/*
 *  linux/arch/arm/mm/pgd.c
 *
 *  Copyright (C) 1998-2005 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/mm.h>
#include <linux/gfp.h>
#include <linux/highmem.h>

#include <asm/pgalloc.h>
#include <asm/page.h>
#include <asm/tlbflush.h>

#include "mm.h"

/*
 * need to get a 16k page for level 1
 */
pgd_t *pgd_alloc(struct mm_struct *mm)
{
      pgd_t *new_pgd, *init_pgd;
      pmd_t *new_pmd, *init_pmd;
      pte_t *new_pte, *init_pte;

      new_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL, 2);
      if (!new_pgd)
            goto no_pgd;

      memset(new_pgd, 0, USER_PTRS_PER_PGD * sizeof(pgd_t));

      /*
       * Copy over the kernel and IO PGD entries
       */
      init_pgd = pgd_offset_k(0);
      memcpy(new_pgd + USER_PTRS_PER_PGD, init_pgd + USER_PTRS_PER_PGD,
                   (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));

      clean_dcache_area(new_pgd, PTRS_PER_PGD * sizeof(pgd_t));

      if (!vectors_high()) {
            /*
             * On ARM, first page must always be allocated since it
             * contains the machine vectors.
             */
            new_pmd = pmd_alloc(mm, new_pgd, 0);
            if (!new_pmd)
                  goto no_pmd;

            new_pte = pte_alloc_map(mm, NULL, new_pmd, 0);
            if (!new_pte)
                  goto no_pte;

            init_pmd = pmd_offset(init_pgd, 0);
            init_pte = pte_offset_map(init_pmd, 0);
            set_pte_ext(new_pte, *init_pte, 0);
            pte_unmap(init_pte);
            pte_unmap(new_pte);
      }

      return new_pgd;

no_pte:
      pmd_free(mm, new_pmd);
no_pmd:
      free_pages((unsigned long)new_pgd, 2);
no_pgd:
      return NULL;
}

void pgd_free(struct mm_struct *mm, pgd_t *pgd_base)
{
      pgd_t *pgd;
      pmd_t *pmd;
      pgtable_t pte;

      if (!pgd_base)
            return;

      pgd = pgd_base + pgd_index(0);
      if (pgd_none_or_clear_bad(pgd))
            goto no_pgd;

      pmd = pmd_offset(pgd, 0);
      if (pmd_none_or_clear_bad(pmd))
            goto no_pmd;

      pte = pmd_pgtable(*pmd);
      pmd_clear(pmd);
      pte_free(mm, pte);
no_pmd:
      pgd_clear(pgd);
      pmd_free(mm, pmd);
no_pgd:
      free_pages((unsigned long) pgd_base, 2);
}

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