Commit 5fe599e0 authored Sep 14, 2016 by Josh Poimboeuf Committed by Ingo Molnar Sep 15, 2016

x86/dumpstack: Add support for unwinding empty IRQ stacks



When an interrupt happens in entry code while running on a software IRQ
stack, and the IRQ stack was empty, regs->sp will contain the stack end
address (e.g., irq_stack_ptr).  If the regs are passed to dump_trace(),
get_stack_info() will report STACK_TYPE_UNKNOWN, causing dump_trace() to
return prematurely without trying to go to the next stack.

Update the bounds checking for software interrupt stacks so that the
ending address is now considered part of the stack.

This means that it's now possible for the 'walk_stack' callbacks --
print_context_stack() and print_context_stack_bp() -- to be called with
an empty stack.  But that's fine; they're already prepared to deal with
that due to their on_stack() checks.

Signed-off-by: Josh 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/5a5e5de92dcf11e8dc6b6e8e50ad7639d067830b.1473905218.git.jpoimboe@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent cb76c939

arch/x86/kernel/dumpstack_32.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -35,7 +35,11 @@ static bool in_hardirq_stack(unsigned long stack, struct stack_info info)
		unsigned long begin = (unsigned long )this_cpu_read(hardirq_stack);
		unsigned long *end = begin + (THREAD_SIZE / sizeof(long));

		if (stack < begin \|\| stack >= end)
		/*
		* This is a software stack, so 'end' can be a valid stack pointer.
		* It just means the stack is empty.
		*/
		if (stack < begin \|\| stack > end)
		return false;

		info->type = STACK_TYPE_IRQ;
		@@ -56,7 +60,11 @@ static bool in_softirq_stack(unsigned long stack, struct stack_info info)
		unsigned long begin = (unsigned long )this_cpu_read(softirq_stack);
		unsigned long *end = begin + (THREAD_SIZE / sizeof(long));

		if (stack < begin \|\| stack >= end)
		/*
		* This is a software stack, so 'end' can be a valid stack pointer.
		* It just means the stack is empty.
		*/
		if (stack < begin \|\| stack > end)
		return false;

		info->type = STACK_TYPE_SOFTIRQ;

arch/x86/kernel/dumpstack_64.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -90,7 +90,11 @@ static bool in_irq_stack(unsigned long stack, struct stack_info info)
		unsigned long end = (unsigned long )this_cpu_read(irq_stack_ptr);
		unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));

		if (stack < begin \|\| stack >= end)
		/*
		* This is a software stack, so 'end' can be a valid stack pointer.
		* It just means the stack is empty.
		*/
		if (stack < begin \|\| stack > end)
		return false;

		info->type = STACK_TYPE_IRQ;