Re: [PATCH 2/2] livepatch: Fix the bug if the function name is larger than KSYM_NAME_LEN-1
From: Petr Mladek
Date: Tue Apr 14 2015 - 12:27:40 EST
On Tue 2015-04-14 23:55:36, Minfei Huang wrote:
> On 04/14/15 at 10:11P, Josh Poimboeuf wrote:
> > On Tue, Apr 14, 2015 at 01:45:49PM +0800, Minfei Huang wrote:
> > > On 04/14/15 at 12:32P, Josh Poimboeuf wrote:
> > > > On Tue, Apr 14, 2015 at 01:29:50PM +0800, Minfei Huang wrote:
> > > > >
> > > > > For end user, they may know litter about restriction of kallsyms and
> > > > > livepatch. How can they know the restriction that function name is
> > > > > limited to 127?
> > > >
> > > > As I mentioned above, I think kallsyms.c should fail the build if it
> > > > encounters a symbol longer than KSYM_NAME_LEN.
> > > >
> > >
> > > I dont think it is a good idea to handle this case like that. The
> > > function name is only for human recognization. Why the compiler fails
> > > to build it?
> > Well, the function name isn't only for human recognition. kpatch-build
> > generates patch modules automatically. It assumes that the compiled
> > function name matches the kallsyms name. And I'd guess that a lot of
> > other code (both in-kernel and user space tools) make the same
> > assumption.
> > Not to mention that most humans would also make the same assumption...
> Yes. The assumption is correct for most case.
> It is significance for livepatch to support extra module, because in my
> opinion kernel is more stable than the third module.
> So it is more important, if the livepatch can patch all sorts of patch.
> For dynamic function name, I think it is simple to avoid it.
Do you have some really existing module with such a crazy long
function names or is this debate pure theoretical, please?
Also have you tested your patch and tried to apply livepatch
for some really exiting module, please? I ask because it won't
be trivial to create such a patch. Also the patch would work
only for the one running system.
> Usually, we will use ominity to handle a bunch of machines. So it is
> simple, if we use script to get the function address and build the patch.
> Josh, is there any chance to accept my patches? It may be important
> somewhile that system can not restart without schedule to reload the
> > --
> > Josh
> To unsubscribe from this list: send the line "unsubscribe live-patching" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/