arm64: Modify stack trace and dump for use with irq_stack

This patch allows unwind_frame() to traverse from interrupt stack to task
stack correctly. It requires data from a dummy stack frame, created
during irq_stack_entry(), added by a later patch.

A similar approach is taken to modify dump_backtrace(), which expects to
find struct pt_regs underneath any call to functions marked __exception.
When on an irq_stack, the struct pt_regs is stored on the old task stack,
the location of which is stored in the dummy stack frame.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[james.morse: merged two patches, reworked for per_cpu irq_stacks, and
 no alignment guarantees, added irq_stack definitions]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index 8e8d30684392..e2f3f135a3bc 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -1,10 +1,32 @@
 #ifndef __ASM_IRQ_H
 #define __ASM_IRQ_H
 
+#define IRQ_STACK_SIZE			THREAD_SIZE
+#define IRQ_STACK_START_SP		THREAD_START_SP
+
+#ifndef __ASSEMBLER__
+
+#include <linux/percpu.h>
+
 #include <asm-generic/irq.h>
+#include <asm/thread_info.h>
 
 struct pt_regs;
 
+DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
+
+/*
+ * The highest address on the stack, and the first to be used. Used to
+ * find the dummy-stack frame put down by el?_irq() in entry.S.
+ */
+#define IRQ_STACK_PTR(cpu) ((unsigned long)per_cpu(irq_stack, cpu) + IRQ_STACK_START_SP)
+
+/*
+ * The offset from irq_stack_ptr where entry.S will store the original
+ * stack pointer. Used by unwind_frame() and dump_backtrace().
+ */
+#define IRQ_STACK_TO_TASK_STACK(ptr) *((unsigned long *)(ptr - 0x10));
+
 extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 
 static inline int nr_legacy_irqs(void)
@@ -12,4 +34,14 @@ static inline int nr_legacy_irqs(void)
 	return 0;
 }
 
+static inline bool on_irq_stack(unsigned long sp, int cpu)
+{
+	/* variable names the same as kernel/stacktrace.c */
+	unsigned long low = (unsigned long)per_cpu(irq_stack, cpu);
+	unsigned long high = low + IRQ_STACK_START_SP;
+
+	return (low <= sp && sp <= high);
+}
+
+#endif /* !__ASSEMBLER__ */
 #endif