linux-kernel - Re: [RFC] taint: add module firmware crash taint support

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Date:   Fri, 8 May 2020 02:18:44 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     jeyu@...nel.org
Cc:     akpm@...ux-foundation.org, arnd@...db.de, rostedt@...dmis.org,
        mingo@...hat.com, aquini@...hat.com, cai@....pw, dyoung@...hat.com,
        bhe@...hat.com, peterz@...radead.org, tglx@...utronix.de,
        gpiccoli@...onical.com, pmladek@...e.com, tiwai@...e.de,
        schlad@...e.de, andriy.shevchenko@...ux.intel.com,
        keescook@...omium.org, daniel.vetter@...ll.ch, will@...nel.org,
        mchehab+samsung@...nel.org, kvalo@...eaurora.org,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        nborisov@...e.com
Subject: Re: [RFC] taint: add module firmware crash taint support

On Fri, May 08, 2020 at 02:14:38AM +0000, Luis Chamberlain wrote:
> Device driver firmware can crash, and sometimes, this can leave your
> system in a state which makes the device or subsystem completely
> useless. Detecting this by inspecting /proc/sys/kernel/tainted instead
> of scraping some magical words from the kernel log, which is driver
> specific, is much easier. So instead provide a helper which lets drivers
> annotate this.
> 
> Once this happens, scrapers can easily scrape modules taint flags.
> This will taint both the kernel and respective calling module.
> 
> The new helper module_firmware_crashed() uses LOCKDEP_STILL_OK as
> this fact should in no way shape or form affect lockdep. This taint
> is device driver specific.
> 
> Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
> ---
> 
> Below is the full diff stat of manual inspection throughout the kernel
> when this happens. My methodology is to just scrape for "crash" and
> then study the driver a bit to see if indeed it seems like that the
> firmware crashes there. In *many* cases there is even infrastructure
> for this, so this is sometimes clearly obvious. Some other times it
> required a bit of deciphering.
> 
> The diff stat below is what I have so far, however the patch below
> only includes the drivers that start with Q, as they were a source of
> inspiration for this, and to make this RFC easier to read.
> 
> If this seems sensible, I can follow up with the kernel helper first,
> and then tackle each subsystem independently.
> 
> I purposely skipped review of remoteproc and virtualization. That should
> require its own separate careful review and considerations.
> 

I should also note that another motivation for this is it is *very*
common for support issues to creep up, where the issues at hand are
firmware related. Easily ruling out a firmware crash, and later devising
tooling which captures this, can help with support.

  Luis