linux-kernel - Re: sigaltstack breaks swapcontext()

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Date:	Thu, 7 Jan 2016 18:33:20 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: sigaltstack breaks swapcontext()

06.01.2016 22:53, Andy Lutomirski пишет:
> On Wed, Jan 6, 2016 at 11:31 AM, Stas Sergeev <stsp@...t.ru> wrote:
>> Exactly.
>> Do you think this can be ignored?
>> A man page should then be corrected with EPERM and the
>> above note removed, right?
>>
> I think it can be ignored.  I'd go the SS_FORCE route, though, to
> maintain POSIX compliance.
I think such a flag would be a wrong thing to do.
Allowing only SS_DISABLE (without any new flags) keeps
you still "compatible with posix", and anything beyond
SS_DISABLE in a sighandler is not needed.

So I think we only have the following options:
1. Remove the check and forget (if anything, glibc can
add the EPERM check to stay compatible with crap).
2. Allow only SS_DISABLE. This will mean a large patch,
touching all arches, but the bonus is the compatibility
with posix, that no one needs in this particular case.
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