linux-kernel - Re: [PATCH 0/2] printk: replace ringbuffer

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Date:   Wed, 05 Feb 2020 10:00:12 +0100
From:   John Ogness <john.ogness@...utronix.de>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     lijiang <lijiang@...hat.com>, Petr Mladek <pmladek@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <parri.andrea@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] printk: replace ringbuffer

On 2020-02-05, Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> wrote:
>>>> So there is a General protection fault. That's the type of a
>>>> problem that kills the boot for me as well (different backtrace,
>>>> tho).
>>> 
>>> Do you have CONFIG_RELOCATABLE and CONFIG_RANDOMIZE_BASE (KASLR)
>>> enabled?
>> 
>> Yes. These two options are enabled.
>> 
>> CONFIG_RELOCATABLE=y
>> CONFIG_RANDOMIZE_BASE=y
>
> So KASLR kills the boot for me. So does KASAN.

Sergey, thanks for looking into this already!

> John, do you see any of these problems on your test machine?

For x86 I have only been using qemu. (For hardware tests I use arm64-smp
in order to verify memory barriers.) With qemu-x86_64 I am unable to
reproduce the problem.

Lianbo, thanks for the report. Can you share your boot args? Anything
special in there (like log_buf_len=, earlyprintk, etc)?

Also, could you share your CONFIG_LOG_* and CONFIG_PRINTK_* options?

I will move to bare metal x86_64 and hopefully see it as well.

John