Re: [PATCH][RFC] jump_labels/x86: Use either 5 byte or 2 byte jumps

H. Peter Anvin
2011-10-07T22:03:51Z

On 10/07/2011 03:00 PM, Steven Rostedt wrote:
>
> Ouch, quite shaken by k.org? I guess I should have substituted go blind
> with being hacked.
>

Well, yes, but I would have said exactly the same thing before.

> The thing is, it may be as simple as an out of tree module screwing up
> the jump table. Or worse, gcc not doing things that we did not expect.
> If this is the case, jump labels can be disabled from modifying code.
>
> But if we just want to do the BUG() case, this will be a big hammer to
> the code and we just prevent any further progress until the issue is
> addressed. Which may be tell people to disable jump labels in their
> code, or use a different compiler.

That is EXACTLY what should happen. Something is wrong to the point of
the kernel is *known* to be executing the wrong code. That is an
extremely serious condition and should be treated as such.

If you want, you could have a debug option to demote this to WARN, but I
really don't want to see it by default.

-hpa