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    Subject[PATCH 4.9 32/74] s390: add optimized array_index_mask_nospec
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Martin Schwidefsky <schwidefsky@de.ibm.com>


    [ Upstream commit e2dd833389cc4069a96b57bdd24227b5f52288f5 ]

    Add an optimized version of the array_index_mask_nospec function for
    s390 based on a compare and a subtract with borrow.

    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/s390/include/asm/barrier.h | 24 ++++++++++++++++++++++++
    1 file changed, 24 insertions(+)

    --- a/arch/s390/include/asm/barrier.h
    +++ b/arch/s390/include/asm/barrier.h
    @@ -48,6 +48,30 @@ do { \
    #define __smp_mb__before_atomic() barrier()
    #define __smp_mb__after_atomic() barrier()

    +/**
    + * array_index_mask_nospec - generate a mask for array_idx() that is
    + * ~0UL when the bounds check succeeds and 0 otherwise
    + * @index: array element index
    + * @size: number of elements in array
    + */
    +#define array_index_mask_nospec array_index_mask_nospec
    +static inline unsigned long array_index_mask_nospec(unsigned long index,
    + unsigned long size)
    +{
    + unsigned long mask;
    +
    + if (__builtin_constant_p(size) && size > 0) {
    + asm(" clgr %2,%1\n"
    + " slbgr %0,%0\n"
    + :"=d" (mask) : "d" (size-1), "d" (index) :"cc");
    + return mask;
    + }
    + asm(" clgr %1,%2\n"
    + " slbgr %0,%0\n"
    + :"=d" (mask) : "d" (size), "d" (index) :"cc");
    + return ~mask;
    +}
    +
    #include <asm-generic/barrier.h>

    #endif /* __ASM_BARRIER_H */

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