From 8624c1f66f0fef640d0e044ddf1eb60e77e76df6 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 6 Jun 2017 14:31:31 +0300 Subject: [PATCH] x86/mm: Add support for 5-level paging for KASLR With 5-level paging randomization happens on P4D level instead of PUD. Maximum amount of physical memory also bumped to 52-bits for 5-level paging. Signed-off-by: Kirill A. Shutemov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Kees Cook Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-arch@vger.kernel.org Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20170606113133.22974-13-kirill.shutemov@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/mm/kaslr.c | 81 ++++++++++++++++++++++++++++++++++----------- 1 file changed, 62 insertions(+), 19 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index aed206475aa7..af599167fe3c 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -6,12 +6,12 @@ * * Entropy is generated using the KASLR early boot functions now shared in * the lib directory (originally written by Kees Cook). Randomization is - * done on PGD & PUD page table levels to increase possible addresses. The - * physical memory mapping code was adapted to support PUD level virtual - * addresses. This implementation on the best configuration provides 30,000 - * possible virtual addresses in average for each memory region. An additional - * low memory page is used to ensure each CPU can start with a PGD aligned - * virtual address (for realmode). + * done on PGD & P4D/PUD page table levels to increase possible addresses. + * The physical memory mapping code was adapted to support P4D/PUD level + * virtual addresses. This implementation on the best configuration provides + * 30,000 possible virtual addresses in average for each memory region. + * An additional low memory page is used to ensure each CPU can start with + * a PGD aligned virtual address (for realmode). * * The order of each memory region is not changed. The feature looks at * the available space for the regions based on different configuration @@ -70,7 +70,7 @@ static __initdata struct kaslr_memory_region { unsigned long *base; unsigned long size_tb; } kaslr_regions[] = { - { &page_offset_base, 64/* Maximum */ }, + { &page_offset_base, 1 << (__PHYSICAL_MASK_SHIFT - TB_SHIFT) /* Maximum */ }, { &vmalloc_base, VMALLOC_SIZE_TB }, { &vmemmap_base, 1 }, }; @@ -142,7 +142,10 @@ void __init kernel_randomize_memory(void) */ entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i); prandom_bytes_state(&rand_state, &rand, sizeof(rand)); - entropy = (rand % (entropy + 1)) & PUD_MASK; + if (IS_ENABLED(CONFIG_X86_5LEVEL)) + entropy = (rand % (entropy + 1)) & P4D_MASK; + else + entropy = (rand % (entropy + 1)) & PUD_MASK; vaddr += entropy; *kaslr_regions[i].base = vaddr; @@ -151,27 +154,21 @@ void __init kernel_randomize_memory(void) * randomization alignment. */ vaddr += get_padding(&kaslr_regions[i]); - vaddr = round_up(vaddr + 1, PUD_SIZE); + if (IS_ENABLED(CONFIG_X86_5LEVEL)) + vaddr = round_up(vaddr + 1, P4D_SIZE); + else + vaddr = round_up(vaddr + 1, PUD_SIZE); remain_entropy -= entropy; } } -/* - * Create PGD aligned trampoline table to allow real mode initialization - * of additional CPUs. Consume only 1 low memory page. - */ -void __meminit init_trampoline(void) +static void __meminit init_trampoline_pud(void) { unsigned long paddr, paddr_next; pgd_t *pgd; pud_t *pud_page, *pud_page_tramp; int i; - if (!kaslr_memory_enabled()) { - init_trampoline_default(); - return; - } - pud_page_tramp = alloc_low_page(); paddr = 0; @@ -192,3 +189,49 @@ void __meminit init_trampoline(void) set_pgd(&trampoline_pgd_entry, __pgd(_KERNPG_TABLE | __pa(pud_page_tramp))); } + +static void __meminit init_trampoline_p4d(void) +{ + unsigned long paddr, paddr_next; + pgd_t *pgd; + p4d_t *p4d_page, *p4d_page_tramp; + int i; + + p4d_page_tramp = alloc_low_page(); + + paddr = 0; + pgd = pgd_offset_k((unsigned long)__va(paddr)); + p4d_page = (p4d_t *) pgd_page_vaddr(*pgd); + + for (i = p4d_index(paddr); i < PTRS_PER_P4D; i++, paddr = paddr_next) { + p4d_t *p4d, *p4d_tramp; + unsigned long vaddr = (unsigned long)__va(paddr); + + p4d_tramp = p4d_page_tramp + p4d_index(paddr); + p4d = p4d_page + p4d_index(vaddr); + paddr_next = (paddr & P4D_MASK) + P4D_SIZE; + + *p4d_tramp = *p4d; + } + + set_pgd(&trampoline_pgd_entry, + __pgd(_KERNPG_TABLE | __pa(p4d_page_tramp))); +} + +/* + * Create PGD aligned trampoline table to allow real mode initialization + * of additional CPUs. Consume only 1 low memory page. + */ +void __meminit init_trampoline(void) +{ + + if (!kaslr_memory_enabled()) { + init_trampoline_default(); + return; + } + + if (IS_ENABLED(CONFIG_X86_5LEVEL)) + init_trampoline_p4d(); + else + init_trampoline_pud(); +} -- 2.20.1