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From: Alexander Monakov <amonakov@ispras.ru>
To: musl@lists.openwall.com
Subject: Re: [musl] More thoughts on wrapping signal handling
Date: Thu, 29 Oct 2020 17:18:20 +0300 (MSK)	[thread overview]
Message-ID: <alpine.LNX.2.20.13.2010291714030.2454@monopod.intra.ispras.ru> (raw)
In-Reply-To: <87pn51ruii.fsf@oldenburg2.str.redhat.com>

On Thu, 29 Oct 2020, Florian Weimer wrote:

> * Alexander Monakov:
> 
> > On Thu, 29 Oct 2020, Alexander Monakov wrote:
> >
> >> On Thu, 29 Oct 2020, Rich Felker wrote:
> >> 
> >> > Yes, I kinda hand-waved over this with the word "call", which I
> >> > thought about annotating with (*). In the case of SA_ONSTACK you need
> >> > a primitive to "call on new stack", and while the ucontext is mostly
> >> > not meaningful/inspectable to the signal handler (because it's
> >> > interrupting libc code), the saved signal mask is. You can have the
> >> > caller restore it (in place of SYS_[rt_]sigreturn), but the natural
> >> > common solution to all of these needs is having a sort of makecontext.
> >> 
> >> Alternatively you could re-raise the signal to have the kernel re-deliver
> >> it with the correctly regenerated ucontext (and on the right stack)?
> >> Would that be undesirable for some reason?
> >
> > Ah, because there's no way to propagate siginfo struct. Sorry :)
> 
> Yes, and that's why I think copying it into TLS space will not work,
> either.

Actually I regret rushing that email: clearly as we are talking about wrapped
signal handlers, re-raising would call the wrapper, which would be perfectly
capable of substituting saved siginfo.

So I don't think propagating siginfo is more complicated with this re-raising
approach.

Alexander

  reply	other threads:[~2020-10-29 14:18 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-29  6:34 Rich Felker
2020-10-29 11:45 ` Alexey Izbyshev
2020-10-29 13:38   ` Rich Felker
2020-10-29 13:51     ` Alexander Monakov
2020-10-29 14:02       ` Alexander Monakov
2020-10-29 14:12         ` Florian Weimer
2020-10-29 14:18           ` Alexander Monakov [this message]
2020-10-29 14:28             ` Rich Felker
2020-10-31 17:33     ` Alexey Izbyshev
2020-10-29 14:21 ` Szabolcs Nagy
2020-10-29 14:43   ` Rich Felker

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