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    Subject[PATCH 4.9 43/66] arm64: assembler: introduce ldr_this_cpu
    Date
    4.9-stable review patch.  If anyone has any objections, please let me know.

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

    From: Mark Rutland <mark.rutland@arm.com>

    Commit 1b7e2296a822dfd2349960addc42a139360ce769 upstream.

    Shortly we will want to load a percpu variable in the return from
    userspace path. We can save an instruction by folding the addition of
    the percpu offset into the load instruction, and this patch adds a new
    helper to do so.

    At the same time, we clean up this_cpu_ptr for consistency. As with
    {adr,ldr,str}_l, we change the template to take the destination register
    first, and name this dst. Secondly, we rename the macro to adr_this_cpu,
    following the scheme of adr_l, and matching the newly added
    ldr_this_cpu.

    Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    Tested-by: Laura Abbott <labbott@redhat.com>
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Cc: James Morse <james.morse@arm.com>
    Cc: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
    Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/arm64/include/asm/assembler.h | 19 +++++++++++++++----
    arch/arm64/kernel/entry.S | 2 +-
    2 files changed, 16 insertions(+), 5 deletions(-)

    --- a/arch/arm64/include/asm/assembler.h
    +++ b/arch/arm64/include/asm/assembler.h
    @@ -239,14 +239,25 @@ lr .req x30 // link register
    .endm

    /*
    + * @dst: Result of per_cpu(sym, smp_processor_id())
    * @sym: The name of the per-cpu variable
    - * @reg: Result of per_cpu(sym, smp_processor_id())
    * @tmp: scratch register
    */
    - .macro this_cpu_ptr, sym, reg, tmp
    - adr_l \reg, \sym
    + .macro adr_this_cpu, dst, sym, tmp
    + adr_l \dst, \sym
    mrs \tmp, tpidr_el1
    - add \reg, \reg, \tmp
    + add \dst, \dst, \tmp
    + .endm
    +
    + /*
    + * @dst: Result of READ_ONCE(per_cpu(sym, smp_processor_id()))
    + * @sym: The name of the per-cpu variable
    + * @tmp: scratch register
    + */
    + .macro ldr_this_cpu dst, sym, tmp
    + adr_l \dst, \sym
    + mrs \tmp, tpidr_el1
    + ldr \dst, [\dst, \tmp]
    .endm

    /*
    --- a/arch/arm64/kernel/entry.S
    +++ b/arch/arm64/kernel/entry.S
    @@ -243,7 +243,7 @@ alternative_insn eret, nop, ARM64_UNMAP_
    cmp x25, tsk
    b.ne 9998f

    - this_cpu_ptr irq_stack, x25, x26
    + adr_this_cpu x25, irq_stack, x26
    mov x26, #IRQ_STACK_START_SP
    add x26, x25, x26


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