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Commit 8a57f484 authored by Dave Hansen's avatar Dave Hansen Committed by Ingo Molnar
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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: default avatarDave Hansen <dave.hansen@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180406205506.030DB6B6@viggo.jf.intel.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 606c7193

arch/x86/include/asm/pgtable_types.h

+16 −13
Original line number Diff line number Diff line
@@ -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 PAGE_KERNEL_IO		__pgprot(__PAGE_KERNEL_IO)

#define PAGE_KERNEL_IO_NOCACHE	__pgprot(__PAGE_KERNEL_IO_NOCACHE)

#define default_pgprot(x)	__pgprot((x) & __default_kernel_pte_mask)



#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;

arch/x86/mm/init.c

+6 −0
Original line number Diff line number Diff line
@@ -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");

arch/x86/mm/init_32.c

+7 −1
Original line number Diff line number Diff line
@@ -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;

arch/x86/mm/init_64.c

+5 −0
Original line number Diff line number Diff line
@@ -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;