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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>
This commit is contained in:
Mark Rutland 2016-11-03 20:23:12 +00:00 committed by Catalin Marinas
parent 57c82954e7
commit 1b7e2296a8
2 changed files with 16 additions and 5 deletions
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19
arch/arm64/include/asm/assembler.h
View File

@ -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
/*

2
arch/arm64/kernel/entry.S
View File

@ -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