linux-kernel - Re: [PATCH v8 10/12] unwind_user/sframe: Enable debugging in uaccess regions

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Message-ID: <orpxec72lzxzkwhcu3gateqbcw6cdlojxvxmvopa2jxr67d4az@rvgfflvrbzk5>
Date: Tue, 8 Jul 2025 07:34:36 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>, 
	Steven Rostedt <rostedt@...nel.org>, linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	bpf@...r.kernel.org, x86@...nel.org, Masami Hiramatsu <mhiramat@...nel.org>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Peter Zijlstra <peterz@...radead.org>, 
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Andrii Nakryiko <andrii@...nel.org>, 
	Indu Bhagat <indu.bhagat@...cle.com>, "Jose E. Marchesi" <jemarch@....org>, 
	Beau Belgrave <beaub@...ux.microsoft.com>, Jens Remus <jremus@...ux.ibm.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Jens Axboe <axboe@...nel.dk>, 
	Florian Weimer <fweimer@...hat.com>, Sam James <sam@...too.org>
Subject: Re: [PATCH v8 10/12] unwind_user/sframe: Enable debugging in uaccess
 regions

On Tue, Jul 08, 2025 at 09:23:51AM -0400, Steven Rostedt wrote:
> On Mon, 7 Jul 2025 20:38:35 -0700
> Linus Torvalds <torvalds@...ux-foundation.org> wrote:
> 
> > On Mon, 7 Jul 2025 at 19:12, Steven Rostedt <rostedt@...nel.org> wrote:
> 
> > This patch is disgusting, in other words. It's wrong. STOP IT.
> > 
> 
> No problem, I can easily drop it.
> 
> I just took Josh's PoC patches and posted them. This particular series
> still needs a bit of work. That's one of the reasons I split it out of the
> other series. The core series is at the stage for acceptance and looking
> for feedback from other maintainers. This series is still a work in
> progress. Others have asked me to post them so they can start playing with
> it.
> 
> We still need to come up with a system call with a robust API to allow the
> dynamic linker to tell the kernel where the SFrames are for the libraries
> it loads. Hence the "DO NOT APPLY" patch at the end (which I just noticed the
> subject text got dropped when I pulled it into git from patchwork and sent
> out this version, at least the change long still suggest it shouldn't be
> applied).
> 
> But I will remove this patch from the queue. I never even used this
> debugging. What I did was inject trace_printk() all over the place to make
> sure it was working as expected.

I had found those debug printks really useful for debugging
corrupt/missing .sframe data, but yeah, this patch is ridiculously bad.
Sorry for putting that out into the world ;-)

And those are all error paths, so it's rather pointless to do that whole
uaccess disable/enable/disable dance.

So yeah, drop it for now and I can replace it with something better
later on.

-- 
Josh