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Message-Id: <1473947349-14521-6-git-send-email-mark.rutland@arm.com>
Date: Thu, 15 Sep 2016 14:49:06 +0100
From: Mark Rutland <mark.rutland@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: akpm@...ux-foundation.org,
ard.biesheuvel@...aro.org,
catalin.marinas@....com,
james.morse@....com,
keescook@...omium.org,
linux-kernel@...r.kernel.org,
lorenzo.pieralisi@....com,
luto@...nel.org,
mark.rutland@....com,
suzuki.poulose@....com,
takahiro.akashi@...aro.org,
will.deacon@....com,
kernel-hardening@...ts.openwall.com
Subject: [RFC PATCH 5/8] 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@....com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: James Morse <james.morse@....com>
Cc: Will Deacon <will.deacon@....com>
---
arch/arm64/include/asm/assembler.h | 19 +++++++++++++++----
arch/arm64/kernel/entry.S | 2 +-
2 files changed, 16 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index d5025c6..265fd81 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -193,14 +193,25 @@ 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 441420c..52b4241 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -206,7 +206,7 @@ alternative_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
--
1.9.1
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