linux-kernel - Re: Re：Re: [PATCH] powerpc: Fix a bug in __div64

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Message-ID: <20200823001101.GO28786@gate.crashing.org>
Date:   Sat, 22 Aug 2020 19:11:01 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Guohua Zhong <zhongguohua1@...wei.com>
Cc:     christophe.leroy@...roup.eu, nixiaoming@...wei.com,
        wangle6@...wei.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        paulus@...ba.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: Re：Re: [PATCH] powerpc: Fix a bug in __div64_32 if divisor is zero

On Sun, Aug 23, 2020 at 12:54:33AM +0800, Guohua Zhong wrote:
> Yet, I have noticed that there is no checking of 'base' in these functions.
> But I am not sure how to check is better.As we know that the result is 
> undefined when divisor is zero. It maybe good to print error and dump stack.
>  Let the process to know that the divisor is zero by sending SIGFPE. 

That is now what the PowerPC integer divide insns do: they just leave
the result undefined (and they can set the overflow flag then, but no
one uses that).


Segher