From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACA3F30B988; Wed, 2 Jul 2025 14:56:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751468167; cv=none; b=g72RbpJyPyBb4m+DZVV2liQDALRl9CV8+We4kjPAuLzIn7nTH0AaRYsQalFZdoiLb7G7fjqoD81U+lf41siItNLwDP8NlRJKvHheh8isRApHGn95ptf8qD0P0VzcXzTtQBody2SaYeEGNBDKuHSCcAvLYxduD61oCbRLxZ5y6Kg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751468167; c=relaxed/simple; bh=jPSExSFTuCmZYyW1vpV6frVat4xvr0IfGJRia6zEiEM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XhkpBVr7N4owY3tH6jIk348F3uix3e83VjpK0ZdozdGtLFpy8x5Wp7PDFr7Q3kUfEJJ6eZeoz5bnj0vvxPqIbcV4Bd9JIeKuqKRPzkCvPa60z5aoismMX69snpnb0K/NyW8S2z5u6a5acD+YduC+JCusY1MBPCIX0/yYeT7TBPk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TwmzkYlw; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TwmzkYlw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3090DC4CEE7; Wed, 2 Jul 2025 14:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751468167; bh=jPSExSFTuCmZYyW1vpV6frVat4xvr0IfGJRia6zEiEM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TwmzkYlwB9IXoWYiTTPlsJR9akZk93fcjgJg6GoqsidFL3/va22HeolW4AtWm6WBR qDORl0UL2v1tX9sqxupC621a9pK4Po/zcfQTqQ93FeFqHU4lIAO82OY2azKmqOSw6z juJ/kKe+A4Jyr4MHP2RmWZD28BsxqVQZ+8LkLAN4S8sP5+TyuHDl+lj1cwEoeV3J87 BQibCF8oi7FhXWzO7FypDa15h26jMsH+ynDLuonuhHj21WNBRSAc3WQRozq20sQCTr IZTy2epyswxYsioCWK9zFS7c4uUgKPWmtHtAR49sUt6LgUHTa8moooBkgVSEkuRE+G jQGOPhmB+QPIQ== Date: Wed, 2 Jul 2025 07:56:06 -0700 From: Kees Cook To: Steven Rostedt Cc: Linus Torvalds , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, x86@kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Josh Poimboeuf , Peter Zijlstra , Ingo Molnar , Jiri Olsa , Namhyung Kim , Thomas Gleixner , Andrii Nakryiko , Indu Bhagat , "Jose E. Marchesi" , Beau Belgrave , Jens Remus , Andrew Morton , Jens Axboe , Florian Weimer Subject: Re: [PATCH v12 00/14] unwind_user: x86: Deferred unwinding infrastructure Message-ID: <202507020751.CB3EFC2D@keescook> References: <20250701005321.942306427@goodmis.org> <20250630224539.3ccf38b0@gandalf.local.home> <202507011547.D291476BE1@keescook> <20250701192619.20eb2a58@gandalf.local.home> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250701192619.20eb2a58@gandalf.local.home> On Tue, Jul 01, 2025 at 07:26:19PM -0400, Steven Rostedt wrote: > On Tue, 1 Jul 2025 15:49:23 -0700 Kees Cook wrote: > > Okay, I've read the cover letter and this wiki page, but I am dense: why > > does the _kernel_ want to do this? Shouldn't it only be userspace that > > cares about userspace unwinding? I don't use perf, ftrace, and ebpf > > enough to make this obvious to me, I guess. ;) > [...] > Anyway, yeah, it's something that has a ton of interest, as it's the way > for tools like perf to give nice graphs of where user space bottlenecks > exist. Right! Yeah, I know it's very wanted -- I wasn't saying "don't this in the kernel", but quite literally, "*I* am missing something about why this is so important." :) And thank you, now I see: the sampling-based profiling of userspace must happen via the kernel. -- Kees Cook