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    Subject[PATCH 4.19 302/346] powerpc: Fix incorrect stw{, ux, u, x} instructions in __set_pte_at
    Date
    From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

    commit d85be8a49e733dcd23674aa6202870d54bf5600d upstream.

    The placeholder for instruction selection should use the second
    argument's operand, which is %1, not %0. This could generate incorrect
    assembly code if the memory addressing of operand %0 is a different
    form from that of operand %1.

    Also remove the %Un placeholder because having %Un placeholders
    for two operands which are based on the same local var (ptep) doesn't
    make much sense. By the way, it doesn't change the current behaviour
    because "<>" constraint is missing for the associated "=m".

    [chleroy: revised commit log iaw segher's comments and removed %U0]

    Fixes: 9bf2b5cdc5fe ("powerpc: Fixes for CONFIG_PTE_64BIT for SMP support")
    Cc: <stable@vger.kernel.org> # v2.6.28+
    Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
    Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
    Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/96354bd77977a6a933fe9020da57629007fdb920.1603358942.git.christophe.leroy@csgroup.eu
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/powerpc/include/asm/book3s/32/pgtable.h | 4 ++--
    arch/powerpc/include/asm/nohash/pgtable.h | 4 ++--
    2 files changed, 4 insertions(+), 4 deletions(-)

    --- a/arch/powerpc/include/asm/book3s/32/pgtable.h
    +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
    @@ -434,9 +434,9 @@ static inline void __set_pte_at(struct m
    if (pte_val(*ptep) & _PAGE_HASHPTE)
    flush_hash_entry(mm, ptep, addr);
    __asm__ __volatile__("\
    - stw%U0%X0 %2,%0\n\
    + stw%X0 %2,%0\n\
    eieio\n\
    - stw%U0%X0 %L2,%1"
    + stw%X1 %L2,%1"
    : "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
    : "r" (pte) : "memory");

    --- a/arch/powerpc/include/asm/nohash/pgtable.h
    +++ b/arch/powerpc/include/asm/nohash/pgtable.h
    @@ -151,9 +151,9 @@ static inline void __set_pte_at(struct m
    */
    if (IS_ENABLED(CONFIG_PPC32) && IS_ENABLED(CONFIG_PTE_64BIT) && !percpu) {
    __asm__ __volatile__("\
    - stw%U0%X0 %2,%0\n\
    + stw%X0 %2,%0\n\
    eieio\n\
    - stw%U0%X0 %L2,%1"
    + stw%X1 %L2,%1"
    : "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
    : "r" (pte) : "memory");
    return;

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