[PATCH v4 08/57] x86/dumpstack: fix irq stack bounds calculation in show_stack_log_lvl()

[Josh Poimboeuf]

The percpu irq_stack_ptr variable has a 64-byte gap from the end of the
allocated irq stack area, so subtracting IRQ_STACK_SIZE from it actually
results in a value 64 bytes before the beginning of the stack.  Use
IRQ_USABLE_STACK_SIZE instead.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 arch/x86/kernel/dumpstack_64.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 7ea6ed0..0fdd371 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -253,8 +253,8 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	preempt_disable();
 	cpu = smp_processor_id();
 
-	irq_stack_end	= (unsigned long *)(per_cpu(irq_stack_ptr, cpu));
-	irq_stack	= (unsigned long *)(per_cpu(irq_stack_ptr, cpu) - IRQ_STACK_SIZE);
+	irq_stack_end = (unsigned long *)(per_cpu(irq_stack_ptr, cpu));
+	irq_stack     = irq_stack_end - (IRQ_USABLE_STACK_SIZE / sizeof(long));
 
 	/*
 	 * Debugging aid: "show_stack(NULL, NULL);" prints the
-- 
2.7.4