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

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Message-ID: <55CCF733.70507@list.ru>
Date:	Thu, 13 Aug 2015 22:59:47 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [regression] x86/signal/64: Fix SS handling for signals delivered
 to 64-bit programs breaks dosemu

13.08.2015 22:37, Linus Torvalds пишет:
> On Thu, Aug 13, 2015 at 12:13 PM, Stas Sergeev <stsp@...t.ru> wrote:
>> As for the compilation failure - I am surprised you even care.
>> I thought the "we don't break userspace" covers only run-time,
>> not compile-time. Oh well.
> I definitely care.
>
> Compile issues may be slightly lower on my radar, but the basic rule
> should be that upgrading a kernel shouldn't cause problems.
It doesn't: fedora provides a "sanitized up" version of sigcontext.h
in /usr/include/bits, which comes from glibc-headers-2.21-7.fc22.x86_64.
So it seems the "sanitized up" headers come from glibc, which
means all other distros would have that too.

> The only exception is for stuff that gets very intimate with the
> kernel itself - ie things like external modules etc. Those we don't
> really try to cater to, or care about.
>
> Things that actually include internal kernel headers tend to have just
> themselves to blame and historically we really didn't care very much
> (long long ago we had issues with ext3fs-tools etc until those kinds
> of things just ended up making their own copies).
>
> But the point of the uabi headers was that even _that_ is supposed to
> actually work, at least for the limited case of those headers.. So if
> a uabi header change causes problems, we really *should* care, because
> otherwise, what was the point of that whole uabi rework, really?
I thought this is mainly to help glibc and distributors to
provide a sanitized-up versions.
If it was for something else, then this "something else" didn't
reach the user PCs yet. :) Fedora-22 still has the sanitized
version in the glibc-headers package, so no compilation break
because of your change was ever actually observed.
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