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

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Date:	Tue, 11 Nov 2014 08:54:50 -0600
From:	Seth Jennings <sjenning@...hat.com>
To:	Greg KH <gregkh@...uxfoundation.org>
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 Sun, Nov 09, 2014 at 12:19:22PM -0800, Greg KH wrote:
> 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 for the notice.  I'll continue rebasing the patchset against the
latest -next and if the other proposal(s) gets in first, I'll change.

Seth

> 
> thanks,
> 
> greg k-h
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