arm64: assembler: introduce ldr_this_cpu

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>

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 28bfe6132eb69240648aee4ce754dfaaee2b4aa0..128a9ca06c8adc12dbc1c137bf327880f709dec5 100644 (file)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -202,14 +202,25 @@ 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
 
 /*

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 223d54a4d66b44acdc19e02243ea3d238cf56603..2d4c83bc1f811b030b8adebe030965c05166c04c 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -200,7 +200,7 @@ alternative_else_nop_endif
        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