Re: [regression] x86/signal/64: Fix SS handling for signals delivered to 64-bit programs breaks dosemu

From: Andy Lutomirski
Date: Thu Aug 13 2015 - 11:43:49 EST

On Thu, Aug 13, 2015 at 8:37 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Aug 11, 2015 at 5:17 PM, Stas Sergeev <stsp@xxxxxxx> wrote:
>> I realize this patch may be good to have in general, but
>> breaking userspace without a single warning is a bit
>> discouraging. Seems like the old "we don't break userspace"
>> rule have gone.
> That rule hasn't gone anywhere.
> Does a plain revert just fix everything? Because if so, that's the
> right thing to do, and we can just re-visit this later.
> I don't understand why Andy and Ingo are even discussing this. What
> the f*ck, guys?

I'm trying to fix it without reverting. If that doesn't work, then we
revert. Yesterday, I thought I had a reasonably clean fix, but it
turned out that it only solved half of the problem.

If we revert, I think I need to check what will break due to the
revert. I need to check at least Wine, and we'll have to do something
about all the selftests that will start failing. I also need to check
CRIU, and IIRC CRIU has started using the new sigcontext SS in new

And, damnit, those selftests are *useful*. They've smoked out all
kinds of problems. That's part of the reason I'd prefer not to revert
if there's a better option.

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