Re: [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel

From: Joel Fernandes <joel@joelfernandes.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	ast@kernel.org, atishp04@gmail.com, dancol@google.com,
	Dan Williams <dan.j.williams@intel.com>,
	gregkh@linuxfoundation.org, Jonathan Corbet <corbet@lwn.net>,
	karim.yaghmour@opersys.com, Kees Cook <keescook@chromium.org>,
	linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
	Manoj Rao <linux@manojrajarao.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	rdunlap@infradead.org
Subject: Re: [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel
Date: Wed, 27 Mar 2019 13:31:03 -0400	[thread overview]
Message-ID: <20190327173103.GA205980@google.com> (raw)
In-Reply-To: <20190325134947.GA187133@google.com>

On Mon, Mar 25, 2019 at 09:49:47AM -0400, Joel Fernandes wrote:
> On Thu, Feb 14, 2019 at 07:19:29PM -0800, Alexei Starovoitov wrote:
> > On Mon, Feb 11, 2019 at 09:35:59AM -0500, Joel Fernandes (Google) wrote:
> > > Introduce in-kernel headers and other artifacts which are made available
> > > as an archive through proc (/proc/kheaders.txz file). This archive makes
> > > it possible to build kernel modules, run eBPF programs, and other
> > > tracing programs that need to extend the kernel for tracing purposes
> > > without any dependency on the file system having headers and build
> > > artifacts.
> > > 
> > > On Android and embedded systems, it is common to switch kernels but not
> > > have kernel headers available on the file system. Raw kernel headers
> > > also cannot be copied into the filesystem like they can be on other
> > > distros, due to licensing and other issues. There's no linux-headers
> > > package on Android. Further once a different kernel is booted, any
> > > headers stored on the file system will no longer be useful. By storing
> > > the headers as a compressed archive within the kernel, we can avoid these
> > > issues that have been a hindrance for a long time.
> > 
> > The set looks good to me and since the main use case is building bpf progs
> > I can route it via bpf-next tree if there are no objections.
> > Masahiro, could you please ack it?
> 
> FYI, Masahiro's comments were all address by v5:
> https://lore.kernel.org/patchwork/project/lkml/list/?series=387311
> 
> I believe aren't more outstanding concerns. Could we consider it for v5.2?

Just to highlight the problem, today I booted v5.0 on an emulated Android
device for some testing, that didn't have a set of prebuilt headers that we
have been packaging on well known kernels, to get around this issue. This
caused great pain and issues with what I was doing. I know me and many others
really want this. With this I can boot an emulated Android device with
IKCONFIG_PROC=y and run BCC with that that. Also I want to do the BCC side of
the development, but first want to know if we can merge this upstream.

Masahiro, I believe due diligence has been done in solidifying it as posted
in the v5.  Anything else we need to do here? Are you with the patches?

thanks!

 - Joel