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Commit 4950d6d4 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
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x86/dumpstack: Remove 64-byte gap at end of irq stack 



There has been a 64-byte gap at the end of the irq stack for at least 12
years.  It predates git history, and I can't find any good reason for
it.  Remove it.  What's the worst that could happen?

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/14f9281c5475cc44af95945ea7546bff2e3836db.1471535549.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8b927d73

arch/x86/kernel/cpu/common.c

+1 −1
Original line number Diff line number Diff line
@@ -1281,7 +1281,7 @@ DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned = 
EXPORT_PER_CPU_SYMBOL(current_task);



DEFINE_PER_CPU(char *, irq_stack_ptr) =

	init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;

	init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE;



DEFINE_PER_CPU(unsigned int, irq_count) __visible = -1;

arch/x86/kernel/dumpstack_64.c

+3 −6
Original line number Diff line number Diff line
@@ -103,9 +103,6 @@ in_irq_stack(unsigned long *stack, unsigned long *irq_stack, 
	return (stack >= irq_stack && stack < irq_stack_end);

}



static const unsigned long irq_stack_size =

	(IRQ_STACK_SIZE - 64) / sizeof(unsigned long);



enum stack_type {

	STACK_IS_UNKNOWN,

	STACK_IS_NORMAL,
@@ -133,7 +130,7 @@ analyze_stack(int cpu, struct task_struct *task, unsigned long *stack, 
		return STACK_IS_NORMAL;



	*stack_end = irq_stack;

	irq_stack = irq_stack - irq_stack_size;

	irq_stack -= (IRQ_STACK_SIZE / sizeof(long));



	if (in_irq_stack(stack, irq_stack, *stack_end))

		return STACK_IS_IRQ;
@@ -257,7 +254,7 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs, 
	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     = irq_stack_end - (IRQ_STACK_SIZE / sizeof(long));



	/*

	 * Debugging aid: "show_stack(NULL, NULL);" prints the

arch/x86/kernel/setup_percpu.c

+1 −1
Original line number Diff line number Diff line
@@ -246,7 +246,7 @@ void __init setup_per_cpu_areas(void) 
#ifdef CONFIG_X86_64

		per_cpu(irq_stack_ptr, cpu) =

			per_cpu(irq_stack_union.irq_stack, cpu) +

			IRQ_STACK_SIZE - 64;

			IRQ_STACK_SIZE;

#endif

#ifdef CONFIG_NUMA

		per_cpu(x86_cpu_to_node_map, cpu) =