From 8a57f4849f4fa22ed18a941164a214083fc020a2 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Fri, 6 Apr 2018 13:55:06 -0700 Subject: [PATCH] x86/mm: Introduce "default" kernel PTE mask The __PAGE_KERNEL_* page permissions are "raw". They contain bits that may or may not be supported on the current processor. They need to be filtered by a mask (currently __supported_pte_mask) to turn them into a value that we can actually set in a PTE. These __PAGE_KERNEL_* values all contain _PAGE_GLOBAL. But, with PTI, we want to be able to support _PAGE_GLOBAL (have the bit set in __supported_pte_mask) but not have it appear in any of these masks by default. This patch creates a new mask, __default_kernel_pte_mask, and applies it when creating all of the PAGE_KERNEL_* masks. This makes PAGE_KERNEL_* safe to use anywhere (they only contain supported bits). It also ensures that PAGE_KERNEL_* contains _PAGE_GLOBAL on PTI=n kernels but clears _PAGE_GLOBAL when PTI=y. We also make __default_kernel_pte_mask a non-GPL exported symbol because there are plenty of driver-available interfaces that take PAGE_KERNEL_* permissions. Signed-off-by: Dave Hansen Cc: Andrea Arcangeli Cc: Andy Lutomirski Cc: Arjan van de Ven Cc: Borislav Petkov Cc: Dan Williams Cc: David Woodhouse Cc: Greg Kroah-Hartman Cc: Hugh Dickins Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Kees Cook Cc: Linus Torvalds Cc: Nadav Amit Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-mm@kvack.org Link: http://lkml.kernel.org/r/20180406205506.030DB6B6@viggo.jf.intel.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/pgtable_types.h | 27 +++++++++++++++------------ arch/x86/mm/init.c | 6 ++++++ arch/x86/mm/init_32.c | 8 +++++++- arch/x86/mm/init_64.c | 5 +++++ 4 files changed, 33 insertions(+), 13 deletions(-) diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index acfe755562a6..1e5a40673953 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -196,19 +196,21 @@ enum page_cache_mode { #define __PAGE_KERNEL_NOENC (__PAGE_KERNEL) #define __PAGE_KERNEL_NOENC_WP (__PAGE_KERNEL_WP) -#define PAGE_KERNEL __pgprot(__PAGE_KERNEL | _PAGE_ENC) -#define PAGE_KERNEL_NOENC __pgprot(__PAGE_KERNEL) -#define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO | _PAGE_ENC) -#define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC | _PAGE_ENC) -#define PAGE_KERNEL_EXEC_NOENC __pgprot(__PAGE_KERNEL_EXEC) -#define PAGE_KERNEL_RX __pgprot(__PAGE_KERNEL_RX | _PAGE_ENC) -#define PAGE_KERNEL_NOCACHE __pgprot(__PAGE_KERNEL_NOCACHE | _PAGE_ENC) -#define PAGE_KERNEL_LARGE __pgprot(__PAGE_KERNEL_LARGE | _PAGE_ENC) -#define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC | _PAGE_ENC) -#define PAGE_KERNEL_VVAR __pgprot(__PAGE_KERNEL_VVAR | _PAGE_ENC) +#define default_pgprot(x) __pgprot((x) & __default_kernel_pte_mask) -#define PAGE_KERNEL_IO __pgprot(__PAGE_KERNEL_IO) -#define PAGE_KERNEL_IO_NOCACHE __pgprot(__PAGE_KERNEL_IO_NOCACHE) +#define PAGE_KERNEL default_pgprot(__PAGE_KERNEL | _PAGE_ENC) +#define PAGE_KERNEL_NOENC default_pgprot(__PAGE_KERNEL) +#define PAGE_KERNEL_RO default_pgprot(__PAGE_KERNEL_RO | _PAGE_ENC) +#define PAGE_KERNEL_EXEC default_pgprot(__PAGE_KERNEL_EXEC | _PAGE_ENC) +#define PAGE_KERNEL_EXEC_NOENC default_pgprot(__PAGE_KERNEL_EXEC) +#define PAGE_KERNEL_RX default_pgprot(__PAGE_KERNEL_RX | _PAGE_ENC) +#define PAGE_KERNEL_NOCACHE default_pgprot(__PAGE_KERNEL_NOCACHE | _PAGE_ENC) +#define PAGE_KERNEL_LARGE default_pgprot(__PAGE_KERNEL_LARGE | _PAGE_ENC) +#define PAGE_KERNEL_LARGE_EXEC default_pgprot(__PAGE_KERNEL_LARGE_EXEC | _PAGE_ENC) +#define PAGE_KERNEL_VVAR default_pgprot(__PAGE_KERNEL_VVAR | _PAGE_ENC) + +#define PAGE_KERNEL_IO default_pgprot(__PAGE_KERNEL_IO) +#define PAGE_KERNEL_IO_NOCACHE default_pgprot(__PAGE_KERNEL_IO_NOCACHE) #endif /* __ASSEMBLY__ */ @@ -483,6 +485,7 @@ static inline pgprot_t pgprot_large_2_4k(pgprot_t pgprot) typedef struct page *pgtable_t; extern pteval_t __supported_pte_mask; +extern pteval_t __default_kernel_pte_mask; extern void set_nx(void); extern int nx_enabled; diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 82f5252c723a..583a88c8a6ee 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -190,6 +190,12 @@ static void __init probe_page_size_mask(void) enable_global_pages(); } + /* By the default is everything supported: */ + __default_kernel_pte_mask = __supported_pte_mask; + /* Except when with PTI where the kernel is mostly non-Global: */ + if (cpu_feature_enabled(X86_FEATURE_PTI)) + __default_kernel_pte_mask &= ~_PAGE_GLOBAL; + /* Enable 1 GB linear kernel mappings if available: */ if (direct_gbpages && boot_cpu_has(X86_FEATURE_GBPAGES)) { printk(KERN_INFO "Using GB pages for direct mapping\n"); diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 396e1f0151ac..07cdc2ed4965 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -558,8 +558,14 @@ static void __init pagetable_init(void) permanent_kmaps_init(pgd_base); } -pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL); +#define DEFAULT_PTE_MASK ~(_PAGE_NX | _PAGE_GLOBAL) +/* Bits supported by the hardware: */ +pteval_t __supported_pte_mask __read_mostly = DEFAULT_PTE_MASK; +/* Bits allowed in normal kernel mappings: */ +pteval_t __default_kernel_pte_mask __read_mostly = DEFAULT_PTE_MASK; EXPORT_SYMBOL_GPL(__supported_pte_mask); +/* Used in PAGE_KERNEL_* macros which are reasonably used out-of-tree: */ +EXPORT_SYMBOL(__default_kernel_pte_mask); /* user-defined highmem size */ static unsigned int highmem_pages = -1; diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 45241de66785..e6c52dbbf649 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -65,8 +65,13 @@ * around without checking the pgd every time. */ +/* Bits supported by the hardware: */ pteval_t __supported_pte_mask __read_mostly = ~0; +/* Bits allowed in normal kernel mappings: */ +pteval_t __default_kernel_pte_mask __read_mostly = ~0; EXPORT_SYMBOL_GPL(__supported_pte_mask); +/* Used in PAGE_KERNEL_* macros which are reasonably used out-of-tree: */ +EXPORT_SYMBOL(__default_kernel_pte_mask); int force_personality32;