From 84013bf58a18c1d26ee77dad2ad67452f2a73252 Mon Sep 17 00:00:00 2001
From: Mark Rutland <mark.rutland@arm.com>
Date: Thu, 20 Jul 2017 14:01:01 +0100
Subject: [PATCH 19/51] arm64: unwind: avoid percpu indirection for irq stack

Git-commit: 096683724cb2eb95fea759a2580996df1039fdd0
Patch-mainline: v4.14-rc1
References: bsc#1068032

Our IRQ_STACK_PTR() and on_irq_stack() helpers both take a cpu argument,
used to generate a percpu address. In all cases, they are passed
{raw_,}smp_processor_id(), so this parameter is redundant.

Since {raw_,}smp_processor_id() use a percpu variable internally, this
approach means we generate a percpu offset to find the current cpu, then
use this to index an array of percpu offsets, which we then use to find
the current CPU's IRQ stack pointer. Thus, most of the work is
redundant.

Instead, we can consistently use raw_cpu_ptr() to generate the CPU's
irq_stack pointer by simply adding the percpu offset to the irq_stack
address, which is simpler in both respects.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 arch/arm64/include/asm/irq.h   | 6 +++---
 arch/arm64/kernel/ptrace.c     | 2 +-
 arch/arm64/kernel/stacktrace.c | 4 ++--
 arch/arm64/kernel/traps.c      | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index b77197d941fc..6d6f85e4923e 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -32,7 +32,7 @@ DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
  * from kernel_entry can be found.
  *
  */
-#define IRQ_STACK_PTR(cpu) ((unsigned long)per_cpu(irq_stack, cpu) + IRQ_STACK_START_SP)
+#define IRQ_STACK_PTR() ((unsigned long)raw_cpu_ptr(irq_stack) + IRQ_STACK_START_SP)
 
 /*
  * The offset from irq_stack_ptr where entry.S will store the original
@@ -47,10 +47,10 @@ static inline int nr_legacy_irqs(void)
 	return 0;
 }
 
-static inline bool on_irq_stack(unsigned long sp, int cpu)
+static inline bool on_irq_stack(unsigned long sp)
 {
 	/* variable names the same as kernel/stacktrace.c */
-	unsigned long low = (unsigned long)per_cpu(irq_stack, cpu);
+	unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack);
 	unsigned long high = low + IRQ_STACK_START_SP;
 
 	return (low <= sp && sp <= high);
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index c142459a88f3..465926f0d965 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -127,7 +127,7 @@ static bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
 {
 	return ((addr & ~(THREAD_SIZE - 1))  ==
 		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))) ||
-		on_irq_stack(addr, raw_smp_processor_id());
+		on_irq_stack(addr);
 }
 
 /**
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index feac80c22f61..745b71329292 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -54,13 +54,13 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
 	 * non-preemptible context.
 	 */
 	if (tsk == current && !preemptible())
-		irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
+		irq_stack_ptr = IRQ_STACK_PTR();
 	else
 		irq_stack_ptr = 0;
 
 	low  = frame->sp;
 	/* irq stacks are not THREAD_SIZE aligned */
-	if (on_irq_stack(frame->sp, raw_smp_processor_id()))
+	if (on_irq_stack(frame->sp))
 		high = irq_stack_ptr;
 	else
 		high = ALIGN(low, THREAD_SIZE) - 0x20;
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 0805b44f986a..c8bdbb46b1fb 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -159,7 +159,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	 * non-preemptible context.
 	 */
 	if (tsk == current && !preemptible())
-		irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
+		irq_stack_ptr = IRQ_STACK_PTR();
 	else
 		irq_stack_ptr = 0;
 
-- 
2.11.0