From: Masami Hiramatsu <mhiramat@kernel.org>
To: "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc: 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, Guenter Roeck <groeck@chromium.org>,
Jonathan Corbet <corbet@lwn.net>,
karim.yaghmour@opersys.com, Kees Cook <keescook@chromium.org>,
kernel-team@android.com, linux-doc@vger.kernel.org,
linux-kselftest@vger.kernel.org,
linux-trace-devel@vger.kernel.org,
Manoj Rao <linux@manojrajarao.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
mhiramat@kernel.org, paulmck@linux.vnet.ibm.com,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
qais.yousef@arm.com, rdunlap@infradead.org, rostedt@goodmis.org,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
yhs@fb.com
Subject: Re: [PATCH v3 1/2] Provide in-kernel headers for making it easy to extend the kernel
Date: Thu, 28 Feb 2019 17:34:44 +0900 [thread overview]
Message-ID: <20190228173444.54403795211d80ba540b61cb@kernel.org> (raw)
In-Reply-To: <20190227193748.132301-1-joel@joelfernandes.org>
Hi Joel,
On Wed, 27 Feb 2019 14:37:47 -0500
"Joel Fernandes (Google)" <joel@joelfernandes.org> wrote:
> Introduce in-kernel headers and other artifacts which are made available
> as an archive through proc (/proc/kheaders.tar.xz 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.
Hmm, isn't it easier to add kernel-headers package on Android?
> The feature is also buildable as a module just in case the user desires
> it not being part of the kernel image. This makes it possible to load
> and unload the headers on demand. A tracing program, or a kernel module
> builder can load the module, do its operations, and then unload the
> module to save kernel memory. The total memory needed is 3.8MB.
But it also requires to install build environment (tools etc.)
on the target system...
>
> The code to read the headers is based on /proc/config.gz code and uses
> the same technique to embed the headers.
>
> To build a module, the below steps have been tested on an x86 machine:
> modprobe kheaders
> rm -rf $HOME/headers
> mkdir -p $HOME/headers
> tar -xvf /proc/kheaders.tar.xz -C $HOME/headers >/dev/null
> cd my-kernel-module
> make -C $HOME/headers M=$(pwd) modules
> rmmod kheaders
It seems a bit complex, but no difference from compared with carrying
kheaders.tar.gz. I think we would better have a psudo filesystem
which can mount this compressed header file directly :) Then it becomes
simpler, like
modprobe headerfs
mkdir $HOME/headers
mount -t headerfs $HOME/headers
And this doesn't consume any disk-space.
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2019-02-28 8:34 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-27 19:37 [PATCH v3 1/2] Provide in-kernel headers for making it easy to extend the kernel Joel Fernandes (Google)
2019-02-27 19:37 ` [PATCH v3 2/2] Add selftests for module build using in-kernel headers Joel Fernandes (Google)
2019-02-28 2:17 ` [PATCH v3 1/2] Provide in-kernel headers for making it easy to extend the kernel Masahiro Yamada
2019-02-28 14:43 ` Joel Fernandes
2019-02-28 23:27 ` Joel Fernandes
2019-03-01 6:25 ` Masahiro Yamada
2019-03-01 17:19 ` Joel Fernandes
2019-03-02 2:13 ` Masahiro Yamada
2019-03-02 2:39 ` Joel Fernandes
2019-03-04 5:40 ` Masahiro Yamada
2019-02-28 8:34 ` Masami Hiramatsu [this message]
2019-02-28 15:00 ` Joel Fernandes
2019-02-28 15:30 ` Greg KH
2019-02-28 15:37 ` Joel Fernandes
2019-02-28 15:45 ` Greg KH
2019-02-28 15:59 ` Joel Fernandes
2019-02-28 16:09 ` Steven Rostedt
2019-03-01 2:28 ` Masami Hiramatsu
2019-03-01 3:26 ` Joel Fernandes
2019-03-01 7:03 ` Masami Hiramatsu
2019-03-01 17:21 ` Joel Fernandes
2019-03-01 11:05 ` Qais Yousef
2019-02-28 13:53 ` Qais Yousef
2019-02-28 14:47 ` Joel Fernandes
2019-02-28 16:04 ` Dietmar Eggemann
2019-02-28 16:22 ` Qais Yousef
2019-02-28 16:48 ` Qais Yousef
2019-02-28 18:36 ` Dietmar Eggemann
2019-02-28 19:10 ` Joel Fernandes
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190228173444.54403795211d80ba540b61cb@kernel.org \
--to=mhiramat@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=ast@kernel.org \
--cc=atishp04@gmail.com \
--cc=corbet@lwn.net \
--cc=dan.j.williams@intel.com \
--cc=dancol@google.com \
--cc=gregkh@linuxfoundation.org \
--cc=groeck@chromium.org \
--cc=joel@joelfernandes.org \
--cc=karim.yaghmour@opersys.com \
--cc=keescook@chromium.org \
--cc=kernel-team@android.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-kselftest@vger.kernel.org \
--cc=linux-trace-devel@vger.kernel.org \
--cc=linux@manojrajarao.com \
--cc=paulmck@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=qais.yousef@arm.com \
--cc=rdunlap@infradead.org \
--cc=rostedt@goodmis.org \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=yamada.masahiro@socionext.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).