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

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Date:	Thu, 13 Aug 2015 17:27:09 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Raymond Jennings <shentino@...il.com>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	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

On Thu, Aug 13, 2015 at 5:17 PM, Stas Sergeev <stsp@...t.ru> wrote:
>
> For example because you can as well do:
> prctl(ARCH_SET_SIGNAL_SS, 0)
> which will mean "restore ss in sighandler to its current value",

I really think a prctl() is the wrong thing to do.

If you want a signal handler to save/restore segments, I think it
should be a SA_xyz flag to sigaction() (the way we have SA_RESTART
etc).  And off by default because of the obvious compatibility issues.

                Linus
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