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From: "Dmitry V. Levin" <ldv@altlinux.org>
To: Andrey Savchenko <bircoph@altlinux.org>
Cc: Ivan Zakharyaschev <imz@altlinux.org>,
	bug-gnulib@gnu.org, Bruno Haible <bruno@clisp.org>
Subject: Re: [RFC PATCH] test-c-stack2.sh: skip if the platform sent SIGILL on an invalid address.
Date: Sat, 29 Dec 2018 17:31:40 +0300	[thread overview]
Message-ID: <20181229143140.GA21975@altlinux.org> (raw)
In-Reply-To: <20181229143111.6c78b9849a8a681a47a420a0@altlinux.org>

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On Sat, Dec 29, 2018 at 02:31:11PM +0300, Andrey Savchenko wrote:
> On Sat, 29 Dec 2018 12:17:32 +0100 Bruno Haible wrote:
> > > As for the SIGILL peculiarity, it has a reason in the Elbrus architecture. 
> > > ...
> > > And it's not a segmentation fault.
> > 
> > I believe you should make it signal a SIGSEGV or SIGBUS, not SIGILL, for
> > the following reasons:
> > 
> > * Look at the second table in
> >   http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html.
> >   It defines a couple of signal codes for SIGILL, SIGSEGV, and SIGBUS.
> >   It implies that SIGILL means an invalid instruction (and "illegal operand"
> >   means an invalid operand that is in the instruction stream).
> >   Whereas SIGSEGV and SIGBUS mean a problem with an instruction in combination
> >   with a memory address.
> > 
> > * The main users of SIGSEGV and SIGBUS are catching stack overflow, garbage
> >   collection, and similar (e.g. by use of GNU libsigsegv). The fact that
> >   you observe an incompatibility between your Linux adaptation and
> >   application programs that work fine across Linux/BSD/AIX/Solaris is a sure
> >   indication that you will encounter similar incompatibilities along the lines,
> >   until you fix that port, to produce SIGSEGV or SIGBUS instead of SIGILL.
> 
> This is not possible. Four generations of hardware are already
> manufactured and they use SIGILL for such cases. It may be fixed in
> future generations if CPU designers will agree to do so, but we
> have to deal with already produced and used in production hardware.

It's all up to the kernel what signal to generate in response
to that particular non-SIGSEGV kind of trap.

I agree with Bruno here, as long as the code in question causes SIGILL,
the architecture is not compatible and its users will suffer more
because of this unneeded incompatibility.


-- 
ldv

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  parent reply	other threads:[~2018-12-29 14:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-15 12:50 [RFC PATCH] test-c-stack2.sh: skip if the platform sent SIGILL on an invalid address Ivan Zakharyaschev
2018-12-20  2:24 ` Bruno Haible
2018-12-28 14:23   ` Ivan Zakharyaschev
2018-12-29 11:17     ` Bruno Haible
2018-12-29 11:31       ` Andrey Savchenko
2018-12-29 14:03         ` Bruno Haible
2018-12-29 14:31         ` Dmitry V. Levin [this message]
2018-12-29 14:54       ` Bruno Haible
2018-12-29 15:03       ` Ivan Zakharyaschev
2018-12-29 16:30         ` Dmitry V. Levin
2018-12-29 20:13         ` Ivan Zakharyaschev
2018-12-30  4:49           ` Bruno Haible
2018-12-29 13:54     ` Dmitry V. Levin
2018-12-29 15:15       ` Ivan Zakharyaschev

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