arm64: irq: fix walking from irq stack to task stack

[cascardo/linux.git] / arch / arm64 / include / asm / irq.h

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index fa2a8d0..877c7e3 100644 (file)
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -19,7 +19,23 @@ 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.
+ * find the dummy-stack frame put down by el?_irq() in entry.S, which
+ * is structured as follows:
+ *
+ *       ------------
+ *       |          |  <- irq_stack_ptr
+ *   top ------------
+ *       |  elr_el1 |
+ *       ------------
+ *       |   x29    | <- irq_stack_ptr - 0x10
+ *       ------------
+ *       |   xzr    |
+ *       ------------
+ *       |   x19    | <- irq_stack_ptr - 0x20
+ *       ------------
+ *
+ * where x19 holds a copy of the task stack pointer.
+ *
  */
 #define IRQ_STACK_PTR(cpu) ((unsigned long)per_cpu(irq_stack, cpu) + IRQ_STACK_START_SP)
 
@@ -27,7 +43,7 @@ DECLARE_PER_CPU(unsigned long [IRQ_STACK_SIZE/sizeof(long)], irq_stack);
  * 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));
+#define IRQ_STACK_TO_TASK_STACK(ptr) *((unsigned long *)(ptr - 0x20));
 
 extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));