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suspend.c

/*
 * Suspend support specific for i386 - temporary page tables
 *
 * Distribute under GPLv2
 *
 * Copyright (c) 2006 Rafael J. Wysocki <rjw@sisk.pl>
 */

#include <linux/suspend.h>
#include <linux/bootmem.h>

#include <asm/system.h>
#include <asm/page.h>
#include <asm/pgtable.h>

/* Defined in arch/i386/power/swsusp.S */
extern int restore_image(void);

/* References to section boundaries */
extern const void __nosave_begin, __nosave_end;

/* Pointer to the temporary resume page tables */
pgd_t *resume_pg_dir;

/* The following three functions are based on the analogous code in
 * arch/i386/mm/init.c
 */

/*
 * Create a middle page table on a resume-safe page and put a pointer to it in
 * the given global directory entry.  This only returns the gd entry
 * in non-PAE compilation mode, since the middle layer is folded.
 */
static pmd_t *resume_one_md_table_init(pgd_t *pgd)
{
      pud_t *pud;
      pmd_t *pmd_table;

#ifdef CONFIG_X86_PAE
      pmd_table = (pmd_t *)get_safe_page(GFP_ATOMIC);
      if (!pmd_table)
            return NULL;

      set_pgd(pgd, __pgd(__pa(pmd_table) | _PAGE_PRESENT));
      pud = pud_offset(pgd, 0);

      BUG_ON(pmd_table != pmd_offset(pud, 0));
#else
      pud = pud_offset(pgd, 0);
      pmd_table = pmd_offset(pud, 0);
#endif

      return pmd_table;
}

/*
 * Create a page table on a resume-safe page and place a pointer to it in
 * a middle page directory entry.
 */
static pte_t *resume_one_page_table_init(pmd_t *pmd)
{
      if (pmd_none(*pmd)) {
            pte_t *page_table = (pte_t *)get_safe_page(GFP_ATOMIC);
            if (!page_table)
                  return NULL;

            set_pmd(pmd, __pmd(__pa(page_table) | _PAGE_TABLE));

            BUG_ON(page_table != pte_offset_kernel(pmd, 0));

            return page_table;
      }

      return pte_offset_kernel(pmd, 0);
}

/*
 * This maps the physical memory to kernel virtual address space, a total
 * of max_low_pfn pages, by creating page tables starting from address
 * PAGE_OFFSET.  The page tables are allocated out of resume-safe pages.
 */
static int resume_physical_mapping_init(pgd_t *pgd_base)
{
      unsigned long pfn;
      pgd_t *pgd;
      pmd_t *pmd;
      pte_t *pte;
      int pgd_idx, pmd_idx;

      pgd_idx = pgd_index(PAGE_OFFSET);
      pgd = pgd_base + pgd_idx;
      pfn = 0;

      for (; pgd_idx < PTRS_PER_PGD; pgd++, pgd_idx++) {
            pmd = resume_one_md_table_init(pgd);
            if (!pmd)
                  return -ENOMEM;

            if (pfn >= max_low_pfn)
                  continue;

            for (pmd_idx = 0; pmd_idx < PTRS_PER_PMD; pmd++, pmd_idx++) {
                  if (pfn >= max_low_pfn)
                        break;

                  /* Map with big pages if possible, otherwise create
                   * normal page tables.
                   * NOTE: We can mark everything as executable here
                   */
                  if (cpu_has_pse) {
                        set_pmd(pmd, pfn_pmd(pfn, PAGE_KERNEL_LARGE_EXEC));
                        pfn += PTRS_PER_PTE;
                  } else {
                        pte_t *max_pte;

                        pte = resume_one_page_table_init(pmd);
                        if (!pte)
                              return -ENOMEM;

                        max_pte = pte + PTRS_PER_PTE;
                        for (; pte < max_pte; pte++, pfn++) {
                              if (pfn >= max_low_pfn)
                                    break;

                              set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
                        }
                  }
            }
      }
      return 0;
}

static inline void resume_init_first_level_page_table(pgd_t *pg_dir)
{
#ifdef CONFIG_X86_PAE
      int i;

      /* Init entries of the first-level page table to the zero page */
      for (i = 0; i < PTRS_PER_PGD; i++)
            set_pgd(pg_dir + i,
                  __pgd(__pa(empty_zero_page) | _PAGE_PRESENT));
#endif
}

int swsusp_arch_resume(void)
{
      int error;

      resume_pg_dir = (pgd_t *)get_safe_page(GFP_ATOMIC);
      if (!resume_pg_dir)
            return -ENOMEM;

      resume_init_first_level_page_table(resume_pg_dir);
      error = resume_physical_mapping_init(resume_pg_dir);
      if (error)
            return error;

      /* We have got enough memory and from now on we cannot recover */
      restore_image();
      return 0;
}

/*
 *    pfn_is_nosave - check if given pfn is in the 'nosave' section
 */

int pfn_is_nosave(unsigned long pfn)
{
      unsigned long nosave_begin_pfn = __pa_symbol(&__nosave_begin) >> PAGE_SHIFT;
      unsigned long nosave_end_pfn = PAGE_ALIGN(__pa_symbol(&__nosave_end)) >> PAGE_SHIFT;
      return (pfn >= nosave_begin_pfn) && (pfn < nosave_end_pfn);
}

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