In the first pass, kernel physical mapping will be setup using large or small pages but uses the same PTE attributes as that of the early PTE attributes setup by early boot code in head_[32|64].S After flushing TLB's, we go through the second pass, which setups the direct mapped PTE's with the appropriate attributes (like NX, GLOBAL etc) which are runtime detectable. 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." Signed-off-by: Suresh Siddha --- Index: tip/arch/x86/mm/init_32.c =================================================================== --- tip.orig/arch/x86/mm/init_32.c 2008-09-22 15:59:31.000000000 -0700 +++ tip/arch/x86/mm/init_32.c 2008-09-22 15:59:37.000000000 -0700 @@ -196,11 +196,30 @@ pgd_t *pgd; pmd_t *pmd; pte_t *pte; - unsigned pages_2m = 0, pages_4k = 0; + unsigned pages_2m, pages_4k; + int mapping_iter; + + /* + * First iteration will setup identity mapping using large/small pages + * based on use_pse, with other attributes same as set by + * the early code in head_32.S + * + * Second iteration will setup the appropriate attributes (NX, GLOBAL..) + * 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." + */ + mapping_iter = 1; if (!cpu_has_pse) use_pse = 0; +repeat: + pages_2m = pages_4k = 0; pfn = start_pfn; pgd_idx = pgd_index((pfn<> 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; } @@ -371,7 +376,6 @@ { unsigned long pages = 0; unsigned long last_map_addr = end; - unsigned long start = address; int i = pmd_index(address); @@ -394,15 +398,14 @@ 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<> PAGE_SHIFT, PAGE_KERNEL_LARGE)); @@ -419,7 +422,8 @@ 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; } @@ -458,14 +462,18 @@ } 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<> PAGE_SHIFT, PAGE_KERNEL_LARGE)); @@ -483,7 +491,9 @@ 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; } @@ -547,15 +557,54 @@ 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); @@ -567,11 +616,21 @@ 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); @@ -581,6 +640,16 @@ 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; } -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/