Re: [PATCH][Fix] Prevent swsusp from corrupting page translation tables during resume on x86-64

Pavel Machek
2005-09-25T22:09:38Z

Hi!

> The following patch fixes Bug #4959. It creates temporary page translation
> tables located in the page frames that are not overwritten by swsusp while copying
> the image.
>
> The temporary page translation tables are generally based on the existing ones
> with the exception that the mappings using 4KB pages are replaced with the
> equivalent mappings that use 2MB pages only. The temporary page tables are
> only used for copying the image.

Would not it be simpler to create them from scratch? mm/init.c has
some handy functions, they should be applicable. [init_memory_mapping,
phys_pud_init]. Perhaps even initialize only simple direct mapping,
and place virt_to_phys() at strategic places?
Pavel

> +static int __duplicate_page_tables(pgd_t *src_pgd, pgd_t *pgd, unsigned long map_offset)
> +{
> + pud_t *src_pud, *pud;
> + pmd_t *src_pmd, *pmd;
> + pte_t *src_pte;
> + int i, j, k;
> +
> + pr_debug("Duplicating pagetables for the map 0x%016lx at 0x%016lx\n",
> + map_offset, (unsigned long)src_pgd);
> + i = pgd_index(map_offset);
> + j = pud_index(map_offset);
> + k = pmd_index(map_offset);
> + src_pgd += i;
> + pgd += i;
> + for (; pgd_val(*src_pgd) && i < PTRS_PER_PGD; i++, src_pgd++, pgd++) {
> + pud = (pud_t *)get_usable_page(GFP_ATOMIC);
> + if (!pud)
> + return -ENOMEM;
> + pgd_val(*pgd) = (pgd_val(*src_pgd) & ~__PGTABLE_MASK) |
> + __pa((unsigned long)pud);
> + pud += j;
> + src_pud = (pud_t *)__va(pgd_val(*src_pgd) & __PGTABLE_MASK) + j;
> + for (; pud_val(*src_pud) && j < PTRS_PER_PUD; j++, src_pud++, pud++) {
> + pmd = (pmd_t *)get_usable_page(GFP_ATOMIC);
> + if (!pmd)
> + return -ENOMEM;
> + pud_val(*pud) = (pud_val(*src_pud) & ~__PGTABLE_MASK) |
> + __pa((unsigned long)pmd);
> + pmd += k;
> + src_pmd = (pmd_t *)__va(pud_val(*src_pud) & __PGTABLE_MASK) + k;
> + for (; pmd_val(*src_pmd) && k < PTRS_PER_PMD; k++, src_pmd++, pmd++)
> + if (pmd_val(*src_pmd) & _PAGE_PSE) /* 2MB page */
> + pmd_val(*pmd) = pmd_val(*src_pmd);
> + else { /* 4KB page table -> 2MB page */
> + src_pte = __va(pmd_val(*src_pmd) & __PGTABLE_MASK);
> + pmd_val(*pmd) = ((pmd_val(*src_pmd) & ~__PGTABLE_MASK) |
> + _PAGE_PSE) |
> + (pte_val(*src_pte) & __PGTABLE_PSE_MASK);
> + }
> + k = 0;
> + }
> + j = 0;
> + }
> + return 0;
> +}

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