[PATCH 1/5] MIPS: Introduce irq_stack

[Matt Redfearn]

Allocate a per-cpu irq stack for use within interrupt handlers.

Also add a utility function on_irq_stack to determine if a given stack
pointer is within the irq stack for that cpu.

Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxxxx>

---

 arch/mips/include/asm/irq.h    | 12 ++++++++++++
 arch/mips/kernel/asm-offsets.c |  1 +
 arch/mips/kernel/irq.c         | 11 +++++++++++
 3 files changed, 24 insertions(+)

diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index 6bf10e796553..956db6e201d1 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -17,6 +17,18 @@
 
 #include <irq.h>
 
+#define IRQ_STACK_SIZE			THREAD_SIZE
+
+extern void *irq_stack[NR_CPUS];
+
+static inline bool on_irq_stack(int cpu, unsigned long sp)
+{
+	unsigned long low = (unsigned long)irq_stack[cpu];
+	unsigned long high = low + IRQ_STACK_SIZE;
+
+	return (low <= sp && sp <= high);
+}
+
 #ifdef CONFIG_I8259
 static inline int irq_canonicalize(int irq)
 {
diff --git a/arch/mips/kernel/asm-offsets.c b/arch/mips/kernel/asm-offsets.c
index fae2f9447792..4be2763f835d 100644
--- a/arch/mips/kernel/asm-offsets.c
+++ b/arch/mips/kernel/asm-offsets.c
@@ -102,6 +102,7 @@ void output_thread_info_defines(void)
 	OFFSET(TI_REGS, thread_info, regs);
 	DEFINE(_THREAD_SIZE, THREAD_SIZE);
 	DEFINE(_THREAD_MASK, THREAD_MASK);
+	DEFINE(_IRQ_STACK_SIZE, IRQ_STACK_SIZE);
 	BLANK();
 }
 
diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
index f25f7eab7307..2b0a371b42af 100644
--- a/arch/mips/kernel/irq.c
+++ b/arch/mips/kernel/irq.c
@@ -25,6 +25,8 @@
 #include <linux/atomic.h>
 #include <asm/uaccess.h>
 
+void *irq_stack[NR_CPUS];
+
 /*
  * 'what should we do if we get a hw irq event on an illegal vector'.
  * each architecture has to answer this themselves.
@@ -58,6 +60,15 @@ void __init init_IRQ(void)
 		clear_c0_status(ST0_IM);
 
 	arch_init_irq();
+
+	for_each_possible_cpu(i) {
+		int irq_pages = IRQ_STACK_SIZE / PAGE_SIZE;
+		void *s = (void *)__get_free_pages(GFP_KERNEL, irq_pages);
+
+		irq_stack[i] = s;
+		pr_debug("CPU%d IRQ stack at 0x%p - 0x%p\n", i,
+			irq_stack[i], irq_stack[i] + IRQ_STACK_SIZE);
+	}
 }
 
 #ifdef CONFIG_DEBUG_STACKOVERFLOW
-- 
2.7.4