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Date: Wed, 12 Jul 2017 23:33:01 +0100
From: Mark Rutland <mark.rutland@....com>
To: ard.biesheuvel@...aro.org,
kernel-hardening@...ts.openwall.com,
linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Cc: akashi.takahiro@...aro.org,
catalin.marinas@....com,
dave.martin@....com,
james.morse@....com,
labbott@...oraproject.org,
will.deacon@....com,
keescook@...omium.org,
Mark Rutland <mark.rutland@....com>
Subject: [RFC PATCH 4/6] arm64: pass stack base to secondary_start_kernel
In subsequent patches, we'll want the base of the secondary stack in
secondary_start_kernel.
Pass the stack base down, as we do in the primary path, and add the
offset in secondary_start_kernel. Unfortunately, we can't encode
STACK_START_SP in an add immediate, so use a mov immedaite, which has
greater range.
This is far from a hot path, so the overhead shouldn't matter.
Signed-off-by: Mark Rutland <mark.rutland@....com>
---
arch/arm64/kernel/head.S | 3 ++-
arch/arm64/kernel/smp.c | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index a58ecda..db77cac 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -613,7 +613,8 @@ __secondary_switched:
adr_l x0, secondary_data
ldr x1, [x0, #CPU_BOOT_STACK] // get secondary_data.stack
- mov sp, x1
+ mov x3, #THREAD_START_SP
+ add sp, x1, x3
ldr x2, [x0, #CPU_BOOT_TASK]
msr tpidr_el1, x2
mov x29, #0
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 6e0e16a..269c957 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -154,7 +154,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
* page tables.
*/
secondary_data.task = idle;
- secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
+ secondary_data.stack = task_stack_page(idle);
update_cpu_boot_status(CPU_MMU_OFF);
__flush_dcache_area(&secondary_data, sizeof(secondary_data));
--
1.9.1
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