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    Subject[tip:x86/vdso] x86-64: Map the HPET NX
    Commit-ID:  d319bb79afa4039bda6f85661d6bf0c13299ce93
    Gitweb: http://git.kernel.org/tip/d319bb79afa4039bda6f85661d6bf0c13299ce93
    Author: Andy Lutomirski <luto@mit.edu>
    AuthorDate: Sun, 5 Jun 2011 13:50:21 -0400
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Sun, 5 Jun 2011 21:30:33 +0200

    x86-64: Map the HPET NX

    Currently the HPET mapping is a user-accessible syscall
    instruction at a fixed address some of the time.

    A sufficiently determined hacker might be able to guess when.

    Signed-off-by: Andy Lutomirski <luto@mit.edu>
    Cc: Jesper Juhl <jj@chaosbits.net>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Arjan van de Ven <arjan@infradead.org>
    Cc: Jan Beulich <JBeulich@novell.com>
    Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
    Cc: Mikael Pettersson <mikpe@it.uu.se>
    Cc: Andi Kleen <andi@firstfloor.org>
    Cc: Brian Gerst <brgerst@gmail.com>
    Cc: Louis Rilling <Louis.Rilling@kerlabs.com>
    Cc: Valdis.Kletnieks@vt.edu
    Cc: pageexec@freemail.hu
    Link: http://lkml.kernel.org/r/ab41b525a4ca346b1ca1145d16fb8d181861a8aa.1307292171.git.luto@mit.edu
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    arch/x86/include/asm/pgtable_types.h | 4 ++--
    arch/x86/kernel/hpet.c | 2 +-
    2 files changed, 3 insertions(+), 3 deletions(-)

    diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
    index 6a29aed6..013286a 100644
    --- a/arch/x86/include/asm/pgtable_types.h
    +++ b/arch/x86/include/asm/pgtable_types.h
    @@ -107,8 +107,8 @@
    #define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD | _PAGE_PWT)
    #define __PAGE_KERNEL_UC_MINUS (__PAGE_KERNEL | _PAGE_PCD)
    #define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER)
    -#define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD | _PAGE_PWT)
    #define __PAGE_KERNEL_VVAR (__PAGE_KERNEL_RO | _PAGE_USER)
    +#define __PAGE_KERNEL_VVAR_NOCACHE (__PAGE_KERNEL_VVAR | _PAGE_PCD | _PAGE_PWT)
    #define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE)
    #define __PAGE_KERNEL_LARGE_NOCACHE (__PAGE_KERNEL | _PAGE_CACHE_UC | _PAGE_PSE)
    #define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE)
    @@ -130,8 +130,8 @@
    #define PAGE_KERNEL_LARGE_NOCACHE __pgprot(__PAGE_KERNEL_LARGE_NOCACHE)
    #define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC)
    #define PAGE_KERNEL_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL)
    -#define PAGE_KERNEL_VSYSCALL_NOCACHE __pgprot(__PAGE_KERNEL_VSYSCALL_NOCACHE)
    #define PAGE_KERNEL_VVAR __pgprot(__PAGE_KERNEL_VVAR)
    +#define PAGE_KERNEL_VVAR_NOCACHE __pgprot(__PAGE_KERNEL_VVAR_NOCACHE)

    #define PAGE_KERNEL_IO __pgprot(__PAGE_KERNEL_IO)
    #define PAGE_KERNEL_IO_NOCACHE __pgprot(__PAGE_KERNEL_IO_NOCACHE)
    diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
    index 6781765..e9f5605 100644
    --- a/arch/x86/kernel/hpet.c
    +++ b/arch/x86/kernel/hpet.c
    @@ -71,7 +71,7 @@ static inline void hpet_set_mapping(void)
    {
    hpet_virt_address = ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
    #ifdef CONFIG_X86_64
    - __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VSYSCALL_NOCACHE);
    + __set_fixmap(VSYSCALL_HPET, hpet_address, PAGE_KERNEL_VVAR_NOCACHE);
    #endif
    }


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