linux-kernel - Re: [PATCH v3 32/51] x86/dumpstack: simplify in_exception

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Message-ID: <20160815153458.7lochdewklrev3lz@treble>
Date:	Mon, 15 Aug 2016 10:34:58 -0500
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Brian Gerst <brgerst@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Byungchul Park <byungchul.park@....com>,
	Nilay Vaish <nilayvaish@...il.com>
Subject: Re: [PATCH v3 32/51] x86/dumpstack: simplify in_exception_stack()

On Sun, Aug 14, 2016 at 12:48:15AM -0700, Andy Lutomirski wrote:
> On Fri, Aug 12, 2016 at 7:28 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> > in_exception_stack() does some bad, bad things just so the unwinder can
> > print different values for different areas of the debug exception stack.
> >
> > There's no need to clarify where exactly on the stack it is.  Just print
> > "#DB" and be done with it.
> 
> I'm okay with the printing part, but you're also using this to prevent
> infinite looping.  Will this cause the unwind to fail if we go debug
> -> page fault -> debug or similar?

Yes, but that behavior already existed.  This patch doesn't change that;
it just makes it clearer what's going on.

-- 
Josh