Re: [PATCH v5 1/3] Provide in-kernel headers to make extending kernel easier

From: Joel Fernandes <joel@joelfernandes.org>
To: "Enrico Weigelt, metux IT consult" <lkml@metux.net>
Cc: Olof Johansson <olof@lixom.net>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Qais Yousef <qais.yousef@arm.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Manoj Rao <linux@manojrajarao.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Alexei Starovoitov <ast@kernel.org>,
	atish patra <atishp04@gmail.com>,
	Daniel Colascione <dancol@google.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Guenter Roeck <groeck@chromium.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Karim Yaghmour <karim.yaghmour@opersys.com>,
	Kees Cook <keescook@chromium.org>,
	Android Kernel Team <kernel-team@android.com>,
	"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	linux-trace-devel@vger.kernel.org,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Shuah Khan <shuah@kernel.org>, Yonghong Song <yhs@fb.com>
Subject: Re: [PATCH v5 1/3] Provide in-kernel headers to make extending kernel easier
Date: Mon, 15 Apr 2019 09:52:49 -0400	[thread overview]
Message-ID: <20190415135249.GA205801@google.com> (raw)
In-Reply-To: <463a08cb-d1ac-b750-c699-8242c2c20fd2@metux.net>

On Mon, Apr 15, 2019 at 11:41:18AM +0200, Enrico Weigelt, metux IT consult wrote:
[snip]
> > This patch seems to have been met with a lot of responses in the tone> of "this is not an appealing solution".
> 
> Personally, having generic helpers for putting blobs into /proc files
> (like config.gz) sound appealing. But I'm not sure whether doing that
> w/ kernel headers this way is a good solution. Actually, I'm even not
> sure whether raw kernel headers are at all are a good way. (can't we
> use compiler-generated debug info ?)

We can't use compiler generated debug info for this.

As discussed previously here, eBPF tools need kernel headers, DWARF and
compiler debug information wont help:
https://lkml.org/lkml/2019/3/11/1358
https://lkml.org/lkml/2019/3/11/1363

> > Usually what we do at times like this is that we say "Yeah, this is a> problem that should be solved, but this solution doesn't seem to be>
> the right one and we would need to maintain it forever as part of the>
> ABI. Let's wait until a better solution is found." With time,> sometimes
> a better solution becomes obvious, or circumstances change> enough to
> allow for some different approach, or someone has a new idea> from a
> different perspective that solves the same problem.
> ACK. For now, this is an Android-only debug tool, just needed there
> because of it's unusual partitioning/deployment mechanisms - on usual
> GNU/Linux distros, we just have the kheaders in the file system.
> (and even on my small embedded devices, I either run the DUTs via NFS,
> 9P2k, initrd, etc or just deploy kernel and headers into the filesystem)
> 
> As Android already is in it's own universe, why can't that stuff remain
> incubated there, until we have more field experience w/ it and more time
> to rethink the whole idea very carefully ?

Well, we follow mostly an upstream first process.

> The patch is pretty small, so it's trivial cherry-pick, in case somebody
> outside Android universe wants to use it.

It could break very easily if things upstream change in some way, and adds a
lot of maintenance burden, besides I don't see a good reason it should not be
upstreamed tbh.

thanks,

 - Joel