linux-kernel - Re: [PATCH 1/2] kernel: add TAINT

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Date:	Sun, 9 Nov 2014 12:19:22 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Seth Jennings <sjenning@...hat.com>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Steven Rostedt <rostedt@...dmis.org>,
	live-patching@...r.kernel.org, kpatch@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] kernel: add TAINT_LIVEPATCH

On Thu, Nov 06, 2014 at 08:39:07AM -0600, Seth Jennings wrote:
> This adds a new taint flag to indicate when the kernel or a kernel
> module has been live patched.  This will provide a clean indication in
> bug reports that live patching was used.
> 
> Additionally, if the crash occurs in a live patched function, the live
> patch module will appear beside the patched function in the backtrace.
> 
> Signed-off-by: Seth Jennings <sjenning@...hat.com>
> ---
>  Documentation/oops-tracing.txt  | 2 ++
>  Documentation/sysctl/kernel.txt | 1 +
>  include/linux/kernel.h          | 1 +
>  kernel/panic.c                  | 2 ++
>  4 files changed, 6 insertions(+)
> 
> diff --git a/Documentation/oops-tracing.txt b/Documentation/oops-tracing.txt
> index beefb9f..f3ac05c 100644
> --- a/Documentation/oops-tracing.txt
> +++ b/Documentation/oops-tracing.txt
> @@ -270,6 +270,8 @@ characters, each representing a particular tainted value.
>  
>   15: 'L' if a soft lockup has previously occurred on the system.
>  
> + 16: 'K' if the kernel has been live patched.
> +
>  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/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
> index d7fc4ab..085f73b 100644
> --- a/Documentation/sysctl/kernel.txt
> +++ b/Documentation/sysctl/kernel.txt
> @@ -831,6 +831,7 @@ can be ORed together:
>  8192 - An unsigned module has been loaded in a kernel supporting module
>         signature.
>  16384 - A soft lockup has previously occurred on the system.
> +32768 - The kernel has been live patched.
>  
>  ==============================================================
>  
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 446d76a..a6aa2df 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -473,6 +473,7 @@ extern enum system_states {
>  #define TAINT_OOT_MODULE		12
>  #define TAINT_UNSIGNED_MODULE		13
>  #define TAINT_SOFTLOCKUP		14
> +#define TAINT_LIVEPATCH			15
>  
>  extern const char hex_asc[];
>  #define hex_asc_lo(x)	hex_asc[((x) & 0x0f)]

Note, this conflicts with a taint value that others are proposing for
something else, so be aware you might run into problems when you hit
linux-next.

thanks,

greg k-h
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