Messages in this thread Patch in this message | | | Subject | [RFC][PATCH 03/10] x86/mm: introduce "default" kernel PTE mask | From | Dave Hansen <> | Date | Thu, 22 Feb 2018 12:36:56 -0800 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
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.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Kees Cook <keescook@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Juergen Gross <jgross@suse.com> Cc: x86@kernel.org Cc: Nadav Amit <namit@vmware.com> ---
b/arch/x86/include/asm/pgtable_types.h | 29 ++++++++++++++++------------- b/arch/x86/mm/init.c | 6 ++++++ b/arch/x86/mm/init_32.c | 7 ++++++- b/arch/x86/mm/init_64.c | 4 ++++ 4 files changed, 32 insertions(+), 14 deletions(-)
diff -puN arch/x86/include/asm/pgtable_types.h~KERN-pgprot-default arch/x86/include/asm/pgtable_types.h --- a/arch/x86/include/asm/pgtable_types.h~KERN-pgprot-default 2018-02-22 12:36:18.608036554 -0800 +++ b/arch/x86/include/asm/pgtable_types.h 2018-02-22 12:36:18.617036554 -0800 @@ -145,6 +145,7 @@ enum page_cache_mode { _PAGE_CACHE_MODE_WP = 5, _PAGE_CACHE_MODE_NUM = 8 }; +extern unsigned long __default_kernel_pte_mask; #endif #define _PAGE_CACHE_MASK (_PAGE_PAT | _PAGE_PCD | _PAGE_PWT) @@ -197,20 +198,22 @@ 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_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL | _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_VSYSCALL default_pgprot(__PAGE_KERNEL_VSYSCALL | _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__ */ diff -puN arch/x86/mm/init_32.c~KERN-pgprot-default arch/x86/mm/init_32.c --- a/arch/x86/mm/init_32.c~KERN-pgprot-default 2018-02-22 12:36:18.610036554 -0800 +++ b/arch/x86/mm/init_32.c 2018-02-22 12:36:18.618036554 -0800 @@ -543,8 +543,13 @@ 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); +EXPORT_SYMBOL_GPL(__default_kernel_pte_mask); /* user-defined highmem size */ static unsigned int highmem_pages = -1; diff -puN arch/x86/mm/init_64.c~KERN-pgprot-default arch/x86/mm/init_64.c --- a/arch/x86/mm/init_64.c~KERN-pgprot-default 2018-02-22 12:36:18.612036554 -0800 +++ b/arch/x86/mm/init_64.c 2018-02-22 12:36:18.618036554 -0800 @@ -65,8 +65,12 @@ * 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); +EXPORT_SYMBOL_GPL(__default_kernel_pte_mask); int force_personality32; diff -puN arch/x86/mm/init.c~KERN-pgprot-default arch/x86/mm/init.c --- a/arch/x86/mm/init.c~KERN-pgprot-default 2018-02-22 12:36:18.614036554 -0800 +++ b/arch/x86/mm/init.c 2018-02-22 12:36:18.619036554 -0800 @@ -190,6 +190,12 @@ static void __init probe_page_size_mask( 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"); _
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