Re: [PATCH] x86/debug: Remove perpetually broken, unmaintainable dwarf annotations

[Jan Beulich]

>>> On 28.05.15 at 13:20, <mingo@xxxxxxxxxx> wrote:
> * Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> Not sure why assembly code should look like C code. It's a matter of taste 
>> perhaps, and I can see your point, but I'm also not really eager to do 
> changes 
>> just to match other people's taste. And just like above - certainly not 
>> something for this patch I would think.
> 
> Yeah, no, so this isn't going to work that way.
> 
> On one hand you want dwarf annotations mostly for the out of tree 
> dwarf-unwinding 
> stack backtraces patch on SUSE kernels, while for the upstream kernel it's 
> mostly 
> just unreadable gunk in some of the most security sensitive code paths of 
> the 
> kernel, which only gets in the way of readability.
> 
> But on the other hand you are unwilling to (or don't have the time to) do a 
> proper 
> job of making this palatable for upstream.
> 
> That's unacceptable from the upstream kernel's POV, so instead of limping 
> forward 
> I'll do the attached patch: it gets rid of the unmaintainable dwarf mess 
> from low 
> level x86 assembly code. This isn't a new concern, a couple of years ago we 
> almost 
> did this.

I can understand your motivation, yet I still view it as rather sad that
you move this way. Indeed I don't have the time to do major rework
in this area, but I don't think you can blame me for not having tried to
at least investigate and eliminate breakage when I found such (which,
as you say, happens every now and then). Yet I do recall people
indicating that the unwind data can be useful for other than the
out-of-tree live stack unwinder. I.e. those will be broken along with
that code which we're _forced_ to maintain out-of-tree.

> and meanwhile you can keep a revert of this patch ported to SUSE kernels in 
> whatever fashion you prefer.

Funny suggestion - I don't think that's reasonable for us to do. Or if
we were to, we could as well invest in doing the re-work you're asking
for; I don't think anyone will have the time to do either.

Jan

--
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/