1 files changed, 84 insertions, 15 deletions

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index d3746efb060..1ba945eb628 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -270,6 +270,8 @@ static __ref void unmap_low_page(void *adr)
 	early_iounmap(adr, PAGE_SIZE);
 }
 
+static int physical_mapping_iter;
+
 static unsigned long __meminit
 phys_pte_init(pte_t *pte_page, unsigned long addr, unsigned long end)
 {
@@ -290,16 +292,19 @@ phys_pte_init(pte_t *pte_page, unsigned long addr, unsigned long end)
 		}
 
 		if (pte_val(*pte))
-			continue;
+			goto repeat_set_pte;
 
 		if (0)
 			printk("   pte=%p addr=%lx pte=%016lx\n",
 			       pte, addr, pfn_pte(addr >> PAGE_SHIFT, PAGE_KERNEL).pte);
+		pages++;
+repeat_set_pte:
 		set_pte(pte, pfn_pte(addr >> PAGE_SHIFT, PAGE_KERNEL));
 		last_map_addr = (addr & PAGE_MASK) + PAGE_SIZE;
-		pages++;
 	}
-	update_page_count(PG_LEVEL_4K, pages);
+
+	if (physical_mapping_iter == 1)
+		update_page_count(PG_LEVEL_4K, pages);
 
 	return last_map_addr;
 }
@@ -318,7 +323,6 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end,
 {
 	unsigned long pages = 0;
 	unsigned long last_map_addr = end;
-	unsigned long start = address;
 
 	int i = pmd_index(address);
 
@@ -341,15 +345,14 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end,
 				last_map_addr = phys_pte_update(pmd, address,
 								end);
 				spin_unlock(&init_mm.page_table_lock);
+				continue;
 			}
-			/* Count entries we're using from level2_ident_pgt */
-			if (start == 0)
-				pages++;
-			continue;
+			goto repeat_set_pte;
 		}
 
 		if (page_size_mask & (1<<PG_LEVEL_2M)) {
 			pages++;
+repeat_set_pte:
 			spin_lock(&init_mm.page_table_lock);
 			set_pte((pte_t *)pmd,
 				pfn_pte(address >> PAGE_SHIFT, PAGE_KERNEL_LARGE));
@@ -366,7 +369,8 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end,
 		pmd_populate_kernel(&init_mm, pmd, __va(pte_phys));
 		spin_unlock(&init_mm.page_table_lock);
 	}
-	update_page_count(PG_LEVEL_2M, pages);
+	if (physical_mapping_iter == 1)
+		update_page_count(PG_LEVEL_2M, pages);
 	return last_map_addr;
 }
 
@@ -405,14 +409,18 @@ phys_pud_init(pud_t *pud_page, unsigned long addr, unsigned long end,
 		}
 
 		if (pud_val(*pud)) {
-			if (!pud_large(*pud))
+			if (!pud_large(*pud)) {
 				last_map_addr = phys_pmd_update(pud, addr, end,
 							 page_size_mask);
-			continue;
+				continue;
+			}
+
+			goto repeat_set_pte;
 		}
 
 		if (page_size_mask & (1<<PG_LEVEL_1G)) {
 			pages++;
+repeat_set_pte:
 			spin_lock(&init_mm.page_table_lock);
 			set_pte((pte_t *)pud,
 				pfn_pte(addr >> PAGE_SHIFT, PAGE_KERNEL_LARGE));
@@ -430,7 +438,9 @@ phys_pud_init(pud_t *pud_page, unsigned long addr, unsigned long end,
 		spin_unlock(&init_mm.page_table_lock);
 	}
 	__flush_tlb_all();
-	update_page_count(PG_LEVEL_1G, pages);
+
+	if (physical_mapping_iter == 1)
+		update_page_count(PG_LEVEL_1G, pages);
 
 	return last_map_addr;
 }
@@ -494,15 +504,54 @@ static void __init init_gbpages(void)
 		direct_gbpages = 0;
 }
 
+static int is_kernel(unsigned long pfn)
+{
+	unsigned long pg_addresss = pfn << PAGE_SHIFT;
+
+	if (pg_addresss >= (unsigned long) __pa(_text) &&
+	    pg_addresss <= (unsigned long) __pa(_end))
+		return 1;
+
+	return 0;
+}
+
 static unsigned long __init kernel_physical_mapping_init(unsigned long start,
 						unsigned long end,
 						unsigned long page_size_mask)
 {
 
-	unsigned long next, last_map_addr = end;
+	unsigned long next, last_map_addr;
+	u64 cached_supported_pte_mask = __supported_pte_mask;
+	unsigned long cache_start = start;
+	unsigned long cache_end = end;
+
+	/*
+	 * First iteration will setup identity mapping using large/small pages
+	 * based on page_size_mask, with other attributes same as set by
+	 * the early code in head_64.S
+	 *
+	 * Second iteration will setup the appropriate attributes
+	 * as desired for the kernel identity mapping.
+	 *
+	 * This two pass mechanism conforms to the TLB app note which says:
+	 *
+	 *     "Software should not write to a paging-structure entry in a way
+	 *      that would change, for any linear address, both the page size
+	 *      and either the page frame or attributes."
+	 *
+	 * For now, only difference between very early PTE attributes used in
+	 * head_64.S and here is _PAGE_NX.
+	 */
+	BUILD_BUG_ON((__PAGE_KERNEL_LARGE & ~__PAGE_KERNEL_IDENT_LARGE_EXEC)
+		     != _PAGE_NX);
+	__supported_pte_mask &= ~(_PAGE_NX);
+	physical_mapping_iter = 1;
 
-	start = (unsigned long)__va(start);
-	end = (unsigned long)__va(end);
+repeat:
+	last_map_addr = cache_end;
+
+	start = (unsigned long)__va(cache_start);
+	end = (unsigned long)__va(cache_end);
 
 	for (; start < end; start = next) {
 		pgd_t *pgd = pgd_offset_k(start);
@@ -514,11 +563,21 @@ static unsigned long __init kernel_physical_mapping_init(unsigned long start,
 			next = end;
 
 		if (pgd_val(*pgd)) {
+			/*
+			 * Static identity mappings will be overwritten
+			 * with run-time mappings. For example, this allows
+			 * the static 0-1GB identity mapping to be mapped
+			 * non-executable with this.
+			 */
+			if (is_kernel(pte_pfn(*((pte_t *) pgd))))
+				goto realloc;
+
 			last_map_addr = phys_pud_update(pgd, __pa(start),
 						 __pa(end), page_size_mask);
 			continue;
 		}
 
+realloc:
 		pud = alloc_low_page(&pud_phys);
 		last_map_addr = phys_pud_init(pud, __pa(start), __pa(next),
 						 page_size_mask);
@@ -528,6 +587,16 @@ static unsigned long __init kernel_physical_mapping_init(unsigned long start,
 		pgd_populate(&init_mm, pgd, __va(pud_phys));
 		spin_unlock(&init_mm.page_table_lock);
 	}
+	__flush_tlb_all();
+
+	if (physical_mapping_iter == 1) {
+		physical_mapping_iter = 2;
+		/*
+		 * Second iteration will set the actual desired PTE attributes.
+		 */
+		__supported_pte_mask = cached_supported_pte_mask;
+		goto repeat;
+	}
 
 	return last_map_addr;
 }