linux-kernel - Re: [PATCH, RFC] x86: also CFI-annotate certain inline asm()s

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Date:	Mon, 10 Nov 2014 10:10:01 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Anvin <hpa@...or.com>, Jan Beulich <JBeulich@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Tony Jones <tonyj@...e.de>
Subject: Re: [PATCH, RFC] x86: also CFI-annotate certain inline asm()s

On Mon, Nov 10, 2014 at 9:56 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> So no. A very strong NACK. The code was too ugly to live, there is no good
> stated reason for it, and the only reason I can even remotely imagine is
> wrong and complete crap anyway (ie making the CFI annotations a correctness
> issue by introducing other infrastructure that depends on it always being
> right).

Btw, the sane thing to do is to make your infrastructure just say "If
my frame walker hits a push/pop without CFI information, I'll just add
it myself".

Yes, that involved having to actuall ylook at the instruction. Tough
shit. Just do it right. There aren't that many push/pop patterns.
Don't make the kernel more fragile by introducing these kinds of hacky
macros-from-hell.

Improve the debugger, don't make kernel code worse because your
out-of-tree debugging infrastructure is too broken to live.

                      Linus
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