linux-kernel - Re: [GIT PULL v4.5] Fix INT1 recursion with unregistered breakpoints

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Message-ID: <CALCETrXhWXXRk0CgYiGfCMTXwxAjHvNKDZ+N7fOvh08==DK55A@mail.gmail.com>
Date:	Mon, 11 Jan 2016 16:49:02 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Jeff Merkey <linux.mdb@...il.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>, Jiri Olsa <jolsa@...nel.org>
Subject: Re: [GIT PULL v4.5] Fix INT1 recursion with unregistered breakpoints

On Mon, Jan 11, 2016 at 4:44 PM, Jeff Merkey <linux.mdb@...il.com> wrote:
> Hi Thomas,
>
> I agree with #2, we should clear the breakpoint.  As for #1, if
> there's an execute breakpoint it MUST be cleared or it will just fire
> off again when it sees the iretd from the int1 exception handler.  I
> do use the breakpoint API Thomas, this showed up while debugging and
> testing the API with "lazy debug register switching".
>
> So do you want me to expand the patch and clear the breakpoint?  Just
> give the word and I'll get busy and GIT -R- DONE.

It seems to me that you're papering over some issue instead of fixing
the root cause.  If you're using the API, then either you're doing it
wrong or the API is broken.  Can you figure out which and fix it?

--Andy