From: Andrey Konovalov <andreyknvl@google.com>
To: Dmitry Vyukov <dvyukov@google.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: syzkaller <syzkaller@googlegroups.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Petr Mladek <pmladek@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ondrej Mosnacek <omosnace@redhat.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: Re: [PATCH v2] twist: allow converting pr_devel()/pr_debug() into snprintf()
Date: Mon, 8 Jun 2020 13:31:13 +0200 [thread overview]
Message-ID: <CAAeHK+x+rcxLdN+xw-QGi8-3T+89X+WHpZUUsOco3u58t=Z15A@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+Z58Z8u1g8SBy-i1WxLMrdmXvggsLFAhfbLc8D=uffPyA@mail.gmail.com>
On Mon, Jun 8, 2020 at 9:48 AM 'Dmitry Vyukov' via syzkaller
<syzkaller@googlegroups.com> wrote:
>
> On Fri, May 29, 2020 at 3:27 PM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
> >
> > Hello, Dmitry.
> >
> > Linus is asking me to avoid build-time switching based on kernel config options,
> > and is suggesting me to use boot-time switching based on boot-config file feature
> > (which is available since 5.6). I have several concerns about use of boot-config file
> > feature in syzkaller.
> >
> > (1) To use boot-config file, syzkaller will need to add "bootconfig" option
> > to the kernel command line. This will be doable by patching
> > https://github.com/google/syzkaller/tree/master/dashboard/config/ *.cmdline
> > files.
>
> Hello Tetsuo,
>
> Yes, command line arguments are easily changeable. Please send pull
> requests to syzkaller, if you want to change something.
>
>
> > (2) The boot-config file is embedded into initramfs file. Since syzkaller builds
> > kernels with almost-allyesconfig, booting syzkaller kernels do not require
> > initramfs for loading kernel modules needed for mounting the root partition.
> > In fact, according to "unexpected kernel reboot" report which contains boot messages,
> > I can't find "Unpacking initramfs..." message. It seems that syzkaller kernels do not
> > use initramfs file.
> >
> > Is it possible for syzkaller to enforce performing steps for creating an initramfs,
> > embedding the boot-config file
> > ( https://www.kernel.org/doc/html/latest/admin-guide/bootconfig.html#boot-kernel-with-a-boot-config),
> > and loading that initramfs whenever booting the syzkaller kernels?
> > By the way, I do worry that people forget to perform these steps when they do
> > their tests without asking syzbot...
>
> I think we have some confusion between syzkaller and syzbot here.
> syzkaller itself does not enforce/require any kernel configuration,
> hardware nor use or not use of initramfs. In fact, qemu VM type
> supports initramfs today. Or syzkaller can work with bare machines
> where all setup is up to the user.
> syzbot is just one deployment of syzkaller with a particular
> configuration/hardware.
>
> If this feature is useful for any linux kernel fuzzing, then we need
> to have a plan for all users and setups.
>
> And, yes, an additional context is kernel developers reproducing bugs.
> Not all of them may be happy about any additional steps, nor will
> follow them.
>
> Answering your question, syzkaller can do some sanity checking of the
> provided machine/kernel and reject working with it. If you tell me
> what exactly needs to be checked, I can think where this code should
> go.
> However, again, I am not sure if one is using, say, Android phones and
> they don't envision use of initramfs, then what?
>
> For syzbot, the build happens here:
> https://github.com/google/syzkaller/blob/7751efd04aebb07bc82b5c0e8eeaca07be1ae112/pkg/build/linux.go#L72
> I don't know if initramfs is supported with GCE machines and what
> exactly is required.
>
>
> > (3) Since syzkaller keeps track of "kernel tree", "commit of the kernel tree", and
> > "commit of the syzkaller tree" in order to guarantee reproducibility, it would be
> > possible to identify the "your-config" file used for tools/bootconfig/bootconfig
> > command. But since "#syz test" command currently accepts only "kernel tree" and
> > "commit of the kernel tree" arguments, we might fail to use intended "your-config"
> > file when doing reproducibility test. Can syzbot solve this concern?
>
> Most likely it's possible.
FTR, there's https://github.com/google/syzkaller/issues/1611 filed for this.
>
> > (4) Of course, "your-config" file would not change so frequently, but "#syz test" command
> > relies on external file in "syzkaller tree" makes it impossible to try different
> > configuration when I have to ask syzbot to test. (Since I don't have hardware which
> > syzbot is reporting problems, I have to ask syzbot when I can't reproduce the problem
> > in my environment.)
> >
> > https://syzkaller.appspot.com/text?tag=Patch&x=135f254a100000 is an example of
> > need to enforce CONFIG_DEBUG_INFO_BTF=n in order to workaround build failure during
> > "#syz test" command. If we bring "which twist options should be enabled" to an external
> > boot-config file, I can't ask syzbot to try different twist options (except directly
> > patching the kernel source which handles "which twist options should be enabled").
> > Can syzbot solve this concern?
>
> The CONFIG_DEBUG_INFO_BTF relates to build config. This can't be
> solved during boot, right? So what is the relation?
>
> > (5) Anything else?
>
> Reading:
> https://www.kernel.org/doc/html/latest/admin-guide/bootconfig.html#boot-kernel-with-a-boot-config
> It seems that boot config is just a more complex way to provide
> command line arguments. syzbot already supports command line
> arguments, and it looks much simpler and no additional work required.
> Why do we want to use boot config?
>
> Next quarter we will be additionally busy with interns, so I can't
> promise any time availability for syzbot improvements. But pull
> requests are welcome.
>
> --
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next prev parent reply other threads:[~2020-06-08 11:31 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-24 14:50 [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN_DEBUG) Tetsuo Handa
2020-05-24 17:38 ` Joe Perches
2020-05-24 19:18 ` Ondrej Mosnacek
2020-05-25 5:03 ` Tetsuo Handa
2020-05-25 6:07 ` Joe Perches
2020-05-25 7:38 ` Dmitry Vyukov
2020-05-25 8:42 ` Petr Mladek
2020-05-25 9:11 ` Sergey Senozhatsky
2020-05-25 10:43 ` Tetsuo Handa
2020-05-27 8:37 ` Petr Mladek
2020-05-27 10:13 ` Tetsuo Handa
2020-05-27 15:55 ` Petr Mladek
2020-05-27 23:33 ` Tetsuo Handa
2020-05-28 6:56 ` [PATCH v2] twist: allow converting pr_devel()/pr_debug() into snprintf() Tetsuo Handa
2020-05-28 11:06 ` Petr Mladek
2020-05-28 15:16 ` Tetsuo Handa
2020-05-28 19:10 ` Andrew Morton
2020-05-28 19:50 ` Linus Torvalds
2020-05-28 20:01 ` Linus Torvalds
2020-05-29 0:07 ` Tetsuo Handa
2020-05-29 0:28 ` Linus Torvalds
2020-05-29 2:13 ` Tetsuo Handa
2020-05-29 2:24 ` Linus Torvalds
2020-05-29 4:47 ` Tetsuo Handa
2020-05-29 13:26 ` Tetsuo Handa
2020-06-03 11:03 ` twist: allow disabling reboot request Tetsuo Handa
2020-06-03 12:44 ` Petr Mladek
2020-06-03 13:35 ` Tetsuo Handa
2020-06-04 10:21 ` Petr Mladek
2020-06-08 7:48 ` [PATCH v2] twist: allow converting pr_devel()/pr_debug() into snprintf() Dmitry Vyukov
2020-06-08 10:30 ` Tetsuo Handa
2020-06-08 11:31 ` Andrey Konovalov [this message]
2020-05-29 8:17 ` Petr Mladek
2020-06-08 16:39 ` Geert Uytterhoeven
2020-05-28 10:59 ` [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN_DEBUG) Petr Mladek
2020-05-28 11:33 ` Tetsuo Handa
2020-05-28 12:14 ` Petr Mladek
2020-05-28 14:13 ` Tetsuo Handa
2020-05-28 17:08 ` Joe Perches
2020-05-29 2:04 ` Sergey Senozhatsky
2020-05-29 5:06 ` Tetsuo Handa
2020-05-27 9:59 ` kbuild test robot
2020-05-27 13:41 ` Tetsuo Handa
2020-05-27 12:37 ` kbuild test robot
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