linux-kernel - Re: [PATCH] ARCv2: intc: untangle SMP, MCIP and IDU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1475861484.2874.44.camel@synopsys.com>
Date:   Fri, 7 Oct 2016 17:31:46 +0000
From:   Alexey Brodkin <Alexey.Brodkin@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yuriy.Kolerov@...opsys.com" <Yuriy.Kolerov@...opsys.com>,
        "Vladislav.Zakharov@...opsys.com" <Vladislav.Zakharov@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
Subject: Re: [PATCH] ARCv2: intc: untangle SMP, MCIP and IDU

Hi Vineet,

On Thu, 2016-10-06 at 10:10 -0700, Vineet Gupta wrote:
> On 10/06/2016 02:10 AM, Alexey Brodkin wrote:
> > 
> > > 
> > > +struct mcip_bcr {
> > > +#ifdef CONFIG_CPU_BIG_ENDIAN
> > > +		unsigned int pad3:8,
> > > +			     idu:1, llm:1, num_cores:6,
> > > +			     iocoh:1,  gfrc:1, dbg:1, pad2:1,
> > > +			     msg:1, sem:1, ipi:1, pad:1,
> > > +			     ver:8;
> > > +#else
> > > +		unsigned int ver:8,
> > > +			     pad:1, ipi:1, sem:1, msg:1,
> > > +			     pad2:1, dbg:1, gfrc:1, iocoh:1,
> > > +			     num_cores:6, llm:1, idu:1,
> > > +			     pad3:8;
> > > +#endif
> > > +};
> > 
> > IMHO we should stop using this kind of constructions because they
> > are ugly and what's more important not portable.
> 
> They are ugly I agree - but not portable - really ? The whole point is to make
> this work on BE w/o changing the src code - this details remains hidden in an
> obscure header.

That's what I learned the hard way.
At least I was beaten a couple of times yet in both Linux kernel community and
U-Boot
one.

> > Even though we have it now working for both LE and BE configurations
> > it won't work for 64-bit cores. We'll need to add ifdeffed 32-bit paddings
> > then which will make that construction even more ugly.
> 
> When we get to 64-bit a lot things would have to change - and possibly the aux reg
> layout. There is no way to make this exact code 64-bit ready !

Probably but as of now I believe use of offsets for bit-fields is the safest
approach which makes code ugly as well but at least that way we reduce risk
of erroneous copy-paste in "mirrored" part.

-Alexey