* Andy Lutomirski <[email protected]> wrote:
> On Fri, Jul 17, 2015 at 9:47 AM, Josh Poimboeuf <[email protected]> wrote:
> > These patches fix many of the warnings reported by stackvalidate.
> > They're based on top of the "Compile-time stack validation" v7 patch set
> > [1].
> >
> > They've been compile-tested and boot tested in a VM, but I haven't
> > attempted any meaningful testing for most of them. This should give an
> > idea of what kinds of changes I think are needed.
> >
> > [1] https://lkml.kernel.org/r/[email protected]
> >
>
> Nothing here looks all that bad, but I think the extra frame pointers
> staring us in the face (as opposed to the ones that gcc adds
> transparently) might serve as added incentive to suck it up and get
> CFI unwinding working.
So there are two aspects to frame pointers staring us in the face:
- Syntactically there's extra debuginfo cruft added to the source code.
Not good but very fixable: I already made a couple of suggestions of
how to trim all that in a way that improves general readability as well over
what we have today.
- Instruction wise in the generated code. I'm afraid the 'transparent' frame
pointers added by GCC are staring me in the face in perf top/report
disassembly
output just as much! ;-)
But naming details aside, I like the direction of these patches a lot better
than
that of any previous debuginfo approach, because the approach is very proactive.
( Which it really has to be, given that deep down these patches are motivated
by
enabling more complex models of live kernel patching. But that's a win-win. )
Once the cleanliness of the annotations is improved and we have a reasonable
path
towards having no warnings on a regular kernel build, I plan on starting to
apply
the patches.
So if anyone has any deep objections that were kept close to the vest so far,
please holler now.
Thanks,
Ingo
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