musl - Re: Re: Powerpc Linux 'scv' system call ABI proposal take 2

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Message-Id: <1587540390.vde84z8edw.astroid@bobo.none>
Date: Wed, 22 Apr 2020 17:31:07 +1000
From: Nicholas Piggin <npiggin@...il.com>
To: Florian Weimer <fw@...eb.enyo.de>
Cc: Adhemerval Zanella <adhemerval.zanella@...aro.org>, Rich Felker
	<dalias@...c.org>, David Laight <David.Laight@...LAB.COM>,
	"libc-alpha@...rceware.org" <libc-alpha@...rceware.org>,
	"libc-dev@...ts.llvm.org" <libc-dev@...ts.llvm.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	musl@...ts.openwall.com, Segher Boessenkool <segher@...nel.crashing.org>
Subject: Re: Re: Powerpc Linux 'scv' system call ABI proposal take 2

Excerpts from Florian Weimer's message of April 22, 2020 5:15 pm:
> * Nicholas Piggin:
> 
>> Another option would be to use a different signal. I don't see that any 
>> are more suitable.
> 
> SIGSYS comes to my mind.  But I don't know how exclusively it is
> associated with seccomp these days.

SIGSYS is entirely seccomp now. There looks like a single obscure MIPS 
user of it in Linux that's not seccomp, but it would be entirely new for 
powerpc (or any of the common platforms, arm, x86 etc).

So I would be disinclined to use SIGSYS unless there are no other better 
signal types, and we don't want to use SIGILL for some good reason -- is 
there a good reason to add complexity for userspace by differentiating 
these two situations?

Thanks,
Nick

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