From: Joel Fernandes <joel@joelfernandes.org>
To: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
Networking <netdev@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
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>,
Jonathan Corbet <corbet@lwn.net>,
Karim Yaghmour <karim.yaghmour@opersys.com>,
Kees Cook <keescook@chromium.org>,
kernel-team@android.com,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
Manoj Rao <linux@manojrajarao.com>,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
Shuah Khan <shuah@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>, Yonghong Song <yhs@fb.com>
Subject: Re: [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel
Date: Tue, 19 Feb 2019 00:12:03 -0500 [thread overview]
Message-ID: <20190219051203.GD201007@google.com> (raw)
In-Reply-To: <CAK7LNATf4adEEqWko2YO46wHHi-Vvc+_LBjQGNnM7rt8GSOgZQ@mail.gmail.com>
On Tue, Feb 19, 2019 at 01:42:13PM +0900, Masahiro Yamada wrote:
[..]
> > > > 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?
> >
> >
> > Honestly, I was not tracking this thread
> > since I did not know I was responsible for this.
> >
> >
> > I just started to take a closer look, then immediately got scared.
> >
> > This version is not mature enough for the merge.
> >
> >
> >
> > First of all, this patch cannot be compiled out-of-tree (O= option).
> >
> >
> > I do not know why 0-day bot did not catch this apparent breakage.
> >
> >
> > $ make -j8 O=hoge
> > make[1]: Entering directory '/home/masahiro/workspace/bsp/linux/hoge'
> > GEN Makefile
> > Using .. as source for kernel
> > DESCEND objtool
> > CALL ../scripts/checksyscalls.sh
> > CHK include/generated/compile.h
> > make[2]: *** No rule to make target 'Module.symvers', needed by
> > 'kernel/kheaders_data.txz'. Stop.
> > make[2]: *** Waiting for unfinished jobs....
> > /home/masahiro/workspace/bsp/linux/Makefile:1043: recipe for target
> > 'kernel' failed
> > make[1]: *** [kernel] Error 2
> > make[1]: *** Waiting for unfinished jobs....
> > make[1]: Leaving directory '/home/masahiro/workspace/bsp/linux/hoge'
> > Makefile:152: recipe for target 'sub-make' failed
> > make: *** [sub-make] Error 2
>
>
>
>
> I saw this build error for in-tree building as well.
>
> We cannot build this from a pristine source tree.
>
> For example, I observed the build error in the following procedure.
>
> $ make mrproper
> $ make defconfig
> Set CONFIG_IKHEADERS_PROC=y
> $ make
>
>
>
>
> Module.symvers is generated in the modpost stage
> (the very last stage of build).
>
> But, vmlinux depends on kernel/kheaders_data.txz,
> which includes Module.symvers.
>
> So, this is not so simple since it is a circular dependency...
I guess I was not building a pristine tree either and missed this circular
dependency :-/ . Any ideas on how we can fix the Module.symvers issue? One
idea is to reserve the space in the binaries, but only populate the space
reserved in the binary *after* the modpost stage, once the archive is ready..
thanks,
- Joel
next prev parent reply other threads:[~2019-02-19 5:12 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-11 14:35 [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel Joel Fernandes (Google)
2019-02-11 14:36 ` [PATCH v2 2/2] Add selftests for module build using in-kernel headers Joel Fernandes (Google)
2019-02-13 22:50 ` [PATCH v2 1/2] Provide in-kernel headers for making it easy to extend the kernel Karim Yaghmour
2019-02-15 3:19 ` Alexei Starovoitov
2019-02-15 3:47 ` Joel Fernandes
2019-02-16 19:10 ` Manoj
2019-02-19 4:14 ` Masahiro Yamada
2019-02-19 4:28 ` Alexei Starovoitov
2019-02-19 4:34 ` Joel Fernandes
2019-02-19 4:42 ` Masahiro Yamada
2019-02-19 5:12 ` Joel Fernandes [this message]
2019-02-19 15:16 ` Joel Fernandes
2019-02-21 14:34 ` Masahiro Yamada
2019-02-21 15:29 ` Joel Fernandes
2019-03-25 13:49 ` Joel Fernandes
2019-03-27 17:31 ` Joel Fernandes
2019-04-03 7:48 ` Masahiro Yamada
2019-04-03 17:20 ` Joel Fernandes
2019-04-03 17:46 ` Daniel Colascione
2019-04-03 17:56 ` Joel Fernandes
2019-04-04 3:54 ` Masahiro Yamada
2019-02-19 6:05 Alexey Dobriyan
2019-02-19 17:25 ` Joel Fernandes
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