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Message-ID: <87h87r391i.fsf@oldenburg2.str.redhat.com>
Date: Fri, 12 Jul 2019 11:18:49 +0200
From: Florian Weimer <fweimer@...hat.com>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] Fix the use of sigaltstack to return to the saved main stack.

* Szabolcs Nagy:

> the comment does not make sense to me, the check is obviously
> not redundant.
>
> MINSIGSTKSZ is a libc api, has nothing to do with the kernel
>
> the kernel also defines a MINSIGSZTKSZ but musl is an
> abstraction layer higher, the linux limit should not be
> observable to users, only the limit defined by musl,
> which ensures not only that the kernel can deliver a
> signal but also reserves space of any current or future
> hackery the c runtime may need to do around signal handling,
> so that trivial c language signal handler is guaranteed
> to work.

Please keep in mind that the kernel stack requirements for delivering a
signal vary and tend to increase over time, with newer CPU generations
with larger register files.  It leads to bugs to pretend this value is
constant.

Thanks,
Florian

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