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From: Pavel Skripkin <paskripkin@gmail.com>
To: Dongliang Mu <mudongliangabcd@gmail.com>
Cc: alex.aring@gmail.com, "David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-wpan@vger.kernel.org, netdev@vger.kernel.org,
	stefan@datenfreihafen.org,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	syzbot+b80c9959009a9325cdff@syzkaller.appspotmail.com,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Greg KH <gregkh@linuxfoundation.org>
Subject: Re: Suggestions on how to debug kernel crashes where printk and gdb both does not work
Date: Mon, 14 Jun 2021 16:34:01 +0300	[thread overview]
Message-ID: <20210614163401.52807197@gmail.com> (raw)
In-Reply-To: <CAD-N9QUUCSpZjg5RwdKBNF7xx127E6fUowTZkUhm66C891Fpkg@mail.gmail.com>

On Mon, 14 Jun 2021 21:22:43 +0800
Dongliang Mu <mudongliangabcd@gmail.com> wrote:

> Dear kernel developers,
> 
> I was trying to debug the crash - memory leak in hwsim_add_one [1]
> recently. However, I encountered a disgusting issue: my breakpoint and
> printk/pr_alert in the functions that will be surely executed do not
> work. The stack trace is in the following. I wrote this email to ask
> for some suggestions on how to debug such cases?
> 
> Thanks very much. Looking forward to your reply.
> 

Hi, Dongliang!

This bug is not similar to others on the dashboard. I spent some time
debugging it a week ago. The main problem here, that memory
allocation happens in the boot time:

> [<ffffffff84359255>] kernel_init+0xc/0x1a7 init/main.c:1447

and reproducer simply tries to
free this data. You can use ftrace to look at it. Smth like this: 

$ echo 'hwsim_*' > $TRACE_DIR/set_ftrace_filter

would work.


With regards,
Pavel Skripkin

  reply	other threads:[~2021-06-14 13:34 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-14 13:22 Suggestions on how to debug kernel crashes where printk and gdb both does not work Dongliang Mu
2021-06-14 13:34 ` Pavel Skripkin [this message]
2021-06-14 14:19   ` Dongliang Mu
2021-06-14 14:25     ` Pavel Skripkin
2021-06-14 14:40       ` Dongliang Mu
2021-06-14 14:47         ` Pavel Skripkin
2021-06-14 15:04           ` Dongliang Mu
2021-06-14 20:30             ` Pavel Skripkin
2021-06-15 10:37               ` Dongliang Mu
2021-06-15 13:34                 ` Pavel Skripkin
2021-06-16  2:02                   ` Dongliang Mu
2021-06-16  2:11                     ` Dongliang Mu

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