From d9e9a6418065bb376e5de8d93ce346939b9a37a6 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Mon, 4 Dec 2017 15:07:39 +0100 Subject: [PATCH] x86/mm/pti: Allocate a separate user PGD Kernel page table isolation requires to have two PGDs. One for the kernel, which contains the full kernel mapping plus the user space mapping and one for user space which contains the user space mappings and the minimal set of kernel mappings which are required by the architecture to be able to transition from and to user space. Add the necessary preliminaries. [ tglx: Split out from the big kaiser dump. EFI fixup from Kirill ] Signed-off-by: Dave Hansen Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/pgalloc.h | 11 +++++++++++ arch/x86/kernel/head_64.S | 30 +++++++++++++++++++++++++++--- arch/x86/mm/pgtable.c | 5 +++-- arch/x86/platform/efi/efi_64.c | 5 ++++- 4 files changed, 45 insertions(+), 6 deletions(-) diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h index 4b5e1eafada7..aff42e1da6ee 100644 --- a/arch/x86/include/asm/pgalloc.h +++ b/arch/x86/include/asm/pgalloc.h @@ -30,6 +30,17 @@ static inline void paravirt_release_p4d(unsigned long pfn) {} */ extern gfp_t __userpte_alloc_gfp; +#ifdef CONFIG_PAGE_TABLE_ISOLATION +/* + * Instead of one PGD, we acquire two PGDs. Being order-1, it is + * both 8k in size and 8k-aligned. That lets us just flip bit 12 + * in a pointer to swap between the two 4k halves. + */ +#define PGD_ALLOCATION_ORDER 1 +#else +#define PGD_ALLOCATION_ORDER 0 +#endif + /* * Allocate and free page tables. */ diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 7dca675fe78d..04a625f0fcda 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -341,6 +341,27 @@ GLOBAL(early_recursion_flag) .balign PAGE_SIZE; \ GLOBAL(name) +#ifdef CONFIG_PAGE_TABLE_ISOLATION +/* + * Each PGD needs to be 8k long and 8k aligned. We do not + * ever go out to userspace with these, so we do not + * strictly *need* the second page, but this allows us to + * have a single set_pgd() implementation that does not + * need to worry about whether it has 4k or 8k to work + * with. + * + * This ensures PGDs are 8k long: + */ +#define PTI_USER_PGD_FILL 512 +/* This ensures they are 8k-aligned: */ +#define NEXT_PGD_PAGE(name) \ + .balign 2 * PAGE_SIZE; \ +GLOBAL(name) +#else +#define NEXT_PGD_PAGE(name) NEXT_PAGE(name) +#define PTI_USER_PGD_FILL 0 +#endif + /* Automate the creation of 1 to 1 mapping pmd entries */ #define PMDS(START, PERM, COUNT) \ i = 0 ; \ @@ -350,13 +371,14 @@ GLOBAL(name) .endr __INITDATA -NEXT_PAGE(early_top_pgt) +NEXT_PGD_PAGE(early_top_pgt) .fill 511,8,0 #ifdef CONFIG_X86_5LEVEL .quad level4_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC #else .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC #endif + .fill PTI_USER_PGD_FILL,8,0 NEXT_PAGE(early_dynamic_pgts) .fill 512*EARLY_DYNAMIC_PAGE_TABLES,8,0 @@ -364,13 +386,14 @@ NEXT_PAGE(early_dynamic_pgts) .data #if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH) -NEXT_PAGE(init_top_pgt) +NEXT_PGD_PAGE(init_top_pgt) .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .org init_top_pgt + PGD_PAGE_OFFSET*8, 0 .quad level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC .org init_top_pgt + PGD_START_KERNEL*8, 0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ .quad level3_kernel_pgt - __START_KERNEL_map + _PAGE_TABLE_NOENC + .fill PTI_USER_PGD_FILL,8,0 NEXT_PAGE(level3_ident_pgt) .quad level2_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC @@ -381,8 +404,9 @@ NEXT_PAGE(level2_ident_pgt) */ PMDS(0, __PAGE_KERNEL_IDENT_LARGE_EXEC, PTRS_PER_PMD) #else -NEXT_PAGE(init_top_pgt) +NEXT_PGD_PAGE(init_top_pgt) .fill 512,8,0 + .fill PTI_USER_PGD_FILL,8,0 #endif #ifdef CONFIG_X86_5LEVEL diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c index 17ebc5a978cc..9b7bcbd33cc2 100644 --- a/arch/x86/mm/pgtable.c +++ b/arch/x86/mm/pgtable.c @@ -355,14 +355,15 @@ static inline void _pgd_free(pgd_t *pgd) kmem_cache_free(pgd_cache, pgd); } #else + static inline pgd_t *_pgd_alloc(void) { - return (pgd_t *)__get_free_page(PGALLOC_GFP); + return (pgd_t *)__get_free_pages(PGALLOC_GFP, PGD_ALLOCATION_ORDER); } static inline void _pgd_free(pgd_t *pgd) { - free_page((unsigned long)pgd); + free_pages((unsigned long)pgd, PGD_ALLOCATION_ORDER); } #endif /* CONFIG_X86_PAE */ diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 20fb31579b69..39c4b35ac7a4 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -195,6 +195,9 @@ static pgd_t *efi_pgd; * because we want to avoid inserting EFI region mappings (EFI_VA_END * to EFI_VA_START) into the standard kernel page tables. Everything * else can be shared, see efi_sync_low_kernel_mappings(). + * + * We don't want the pgd on the pgd_list and cannot use pgd_alloc() for the + * allocation. */ int __init efi_alloc_page_tables(void) { @@ -207,7 +210,7 @@ int __init efi_alloc_page_tables(void) return 0; gfp_mask = GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO; - efi_pgd = (pgd_t *)__get_free_page(gfp_mask); + efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER); if (!efi_pgd) return -ENOMEM;