Use page present for pae pdpes

PATCH New Zachary Amsden 1 participant 1 message Aug 31, 2005

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Zachary Amsden

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2005-08-31 21:51 UTC #0 lore raw

PATCH 2/2 Use page present for pae pdpes

Ok, the use of "1 + " and subtraction of one for PAE PDPEs has confused many people now. Make it explicit what is going on and why anding with PAGE_MASK is a better idea to strip these bits.

Signed-off-by Zachary Amsden <[email protected]>

Depends-on: add-pgtable-allocation-notifiers
Index: linux-2.6.13/arch/i386/mm/pgtable.c
===================================================================

arch/i386/mm/pgtable.c +3 -3

@@ -247,14 +247,14 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 		if (!pmd)
 			goto out_oom;
 		SetPagePDE(virt_to_page(pmd));
-		set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
+		set_pgd(&pgd[i], __pgd(_PAGE_PRESENT | __pa(pmd)));
 	}
 	return pgd;
 
 out_oom:
 	for (i--; i >= 0; i--) {
 		ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
-		kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+		kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i]) & PAGE_MASK));
 	}
 	kmem_cache_free(pgd_cache, pgd);
 	return NULL;

@@ -268,7 +268,7 @@ void pgd_free(pgd_t *pgd)
 	if (PTRS_PER_PMD > 1)
 		for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
 			ClearPagePDE(pfn_to_page(pgd_val(pgd[i]) >> PAGE_SHIFT));
-			kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i])-1));
+			kmem_cache_free(pmd_cache, (void *)__va(pgd_val(pgd[i]) & PAGE_MASK));
 		}
 	/* in the non-PAE case, free_pgtables() clears user pgd entries */
 	kmem_cache_free(pgd_cache, pgd);

arch/i386/mm/init.c +1 -1

Index: linux-2.6.13/arch/i386/mm/init.c
===================================================================
@@ -387,7 +387,7 @@ void zap_low_mappings (void)
 	 */
 	for (i = 0; i < USER_PTRS_PER_PGD; i++)
 #ifdef CONFIG_X86_PAE
-		set_pgd(swapper_pg_dir+i, __pgd(1 + __pa(empty_zero_page)));
+		set_pgd(swapper_pg_dir+i, __pgd(_PAGE_PRESENT | __pa(empty_zero_page)));
 #else
 		set_pgd(swapper_pg_dir+i, __pgd(0));
 #endif