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    Subject[PATCH v4 05/10] x86-64: Map the HPET NX
    Date
    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>
    ---
    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
    }

    --
    1.7.5.1


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