linux-kernel - Re: [PATCH] frv: fix build failure

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Date:   Wed, 6 Dec 2017 14:00:23 -0800
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] frv: fix build failure

On 12/03/2017 02:32 PM, Sudip Mukherjee wrote:
> On Mon, Nov 27, 2017 at 10:25:16AM -0800, Vineet Gupta wrote:
>> +CC linux-arch, Arnd
>>
>> On 11/23/2017 09:17 AM, Alexey Brodkin wrote:
>>> Hi Sudip,
>>>
>>> On Tue, 2017-11-21 at 22:10 +0000, Sudip Mukherjee wrote:
> 
> <snip>
> 
>> I understand the case/need for adding a weak/common abort() as a
>> quick fix for handling such cases, but perhaps we should not and
>> instead fix the rootcause. In this specific case, Claudiu mentioned
>> that gcc was generating abort due to something like this (flagging a
>> possible divide by zero due to
>> -fno-isolate-erroneous-paths-dereference.
>>
>> a;
>>
>> fn1() {
>>    switch (a)
>>    case 0:
>>    return 1 / a;
>> }
>>
>> Sudeep can you confirm that removing this hacking FRV build to not
>> have this toggle fixes the abort issue.
>>
>> So the offending code needs to be fixed as in the end when that code
>> path is taken system is hosed.
> 
> The above case that you mentioned is indeed the case here.
> mpihelp_divrem() in lib/mpi/mpih-div.c has this same divide by zero case.
> 
> So, what should be the actual fix here?

To remove the divide by zero.

Or atleast have a __weak abort() defined in common code so all arches benefit from 
it !

-Vineet