linux-kernel - Re: [PATCH] Add TAINT_HARDWARE

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Message-Id: <20100621122145.76ebd7ac.akpm@linux-foundation.org>
Date:	Mon, 21 Jun 2010 12:21:45 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Prarit Bhargava <prarit@...hat.com>
Cc:	linux-kernel@...r.kernel.org,
	Randy Dunlap <randy.dunlap@...cle.com>, dzickus@...hat.com
Subject: Re: [PATCH] Add TAINT_HARDWARE_UNSUPPORTED flag

On Thu, 17 Jun 2010 15:54:09 -0400
Prarit Bhargava <prarit@...hat.com> wrote:

> 
> This patch is similar to Theordore Ts'o's TAINT_USER patch,
> linux-2.6 commit 34f5a39899f3f3e815da64f48ddb72942d86c366.
> 
> Individual distributions may enable "generic" features such as X86 support,
> PPC support, and driver support.
> 
> Some of the features that are enabled by these "generic" feature flags may
> not be considered supported by the individual distribution.
> 
> For example, a distribution may want to support PPC but not the Power5
> chipset, or the e1000e driver but not a card with a specific DeviceID because
> of known firmware issues.
> 
> Typically, one would push a config patch to enable and disable the feature and
> patch the distribution.  However, in some cases this is not feasible in order
> to preserve kabi and at the same time maintain parity with the upstream kernel.
> In some cases the distribution may want to allow booting of these features but
> explicitly notify a user that they are not "officially" supported.  It is also
> possible that the hardware is fixed via a firmware update at a later date,
> making it supported again.
> 
> It would be useful for a distribution to notify the installer and
> bug reporting applications, and notify users that the hardware they are using
> is unsupported during panic, oops, BUG(), and WARN().
> 
> This patch introduces the TAINT_HARDWARE_UNSUPPORTED flag for distributions
> to use.
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Signed-off-by: Don Zickus <dzickus@...hat.com>
> 
> diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
> index 6fe9001..e337b0a 100644
> --- a/Documentation/oops-tracing.txt
> +++ b/Documentation/oops-tracing.txt
> @@ -263,6 +263,8 @@ characters, each representing a particular tainted value.
>   12: 'I' if the kernel is working around a severe bug in the platform
>       firmware (BIOS or similar).
>  
> + 13: 'H' if the hardware is unsupported by the distribution
> +
>  The primary reason for the 'Tainted: ' string is to tell kernel
>  debuggers if this is a clean kernel or if anything unusual has
>  occurred.  Tainting is permanent: even if an offending module is
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 8317ec4..f722b0d 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -347,6 +347,7 @@ extern enum system_states {
>  #define TAINT_WARN			9
>  #define TAINT_CRAP			10
>  #define TAINT_FIRMWARE_WORKAROUND	11
> +#define TAINT_HARDWARE_UNSUPPORTED	12
>  
>  extern void dump_stack(void) __cold;
>  
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 3b16cd9..8d081ff 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -180,6 +180,7 @@ static const struct tnt tnts[] = {
>  	{ TAINT_WARN,			'W', ' ' },
>  	{ TAINT_CRAP,			'C', ' ' },
>  	{ TAINT_FIRMWARE_WORKAROUND,	'I', ' ' },
> +	{ TAINT_HARDWARE_UNSUPPORTED,	'H', ' ' },
>  };
>  
>  /**
> @@ -197,6 +198,7 @@ static const struct tnt tnts[] = {
>   *  'W' - Taint on warning.
>   *  'C' - modules from drivers/staging are loaded.
>   *  'I' - Working around severe firmware bug.
> + *  'H' - Hardware is unsupported.
>   *
>   *	The string is overwritten by the next call to print_tainted().
>   */
> @@ -243,6 +245,9 @@ void add_taint(unsigned flag)
>  	 */
>  	if (flag != TAINT_CRAP && flag != TAINT_WARN && __debug_locks_off())
>  		printk(KERN_WARNING "Disabling lock debugging due to kernel taint\n");
> +	if (flag == TAINT_HARDWARE_UNSUPPORTED)
> +		printk(KERN_CRIT
> +		       "WARNING: This system's hardware is unsupported.\n");
>  
>  	set_bit(flag, &tainted_mask);
>  }

That's pretty user-hostile.  What are they to do - throw the entire
computer away because it has the wrong type of mouse?

How about

void add_hardware_unsupported_taint(const char *hardware)
{
	printk(KERN_CRIT
	       "Hardware device %s is unsupported by this kernel's vendor\n",
		hardware);
	add_taint(TAINT_HARDWARE_UNSUPPORTED);
}

and

/*
 * Don't call add_taint(TAINT_HARDWARE_UNSUPPORTED) directly - use
 * add_hardware_unsupported_taint()
 */
#define TAINT_HARDWARE_UNSUPPORTED	12

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