Message-ID: <20190415135249.GA205801@google.com>
Date:   Mon, 15 Apr 2019 09:52:49 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
Cc:     Olof Johansson <olof@...om.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Qais Yousef <qais.yousef@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Manoj Rao <linux@...ojrajarao.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexei Starovoitov <ast@...nel.org>,
        atish patra <atishp04@...il.com>,
        Daniel Colascione <dancol@...gle.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Guenter Roeck <groeck@...omium.org>,
        Jonathan Corbet <corbet@....net>,
        Karim Yaghmour <karim.yaghmour@...rsys.com>,
        Kees Cook <keescook@...omium.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        linux-trace-devel@...r.kernel.org,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Shuah Khan <shuah@...nel.org>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH v5 1/3] Provide in-kernel headers to make extending
 kernel easier

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

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