linux-kernel - Re: [PATCH V6 08/33] csky: Process management and Signal

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Date:   Fri, 28 Sep 2018 21:10:47 +0800
From:   Guo Ren <ren_guo@...ky.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     akpm@...ux-foundation.org, arnd@...db.de,
        daniel.lezcano@...aro.org, davem@...emloft.net,
        gregkh@...uxfoundation.org, jason@...edaemon.net,
        marc.zyngier@....com, mark.rutland@....com,
        mchehab+samsung@...nel.org, peterz@...radead.org, robh@...nel.org,
        robh+dt@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        devicetree@...r.kernel.org, green.hu@...il.com
Subject: Re: [PATCH V6 08/33] csky: Process management and Signal

On Thu, Sep 27, 2018 at 09:50:43PM +0200, Eric W. Biederman wrote:
> Guo Ren <ren_guo@...ky.com> writes:
> 
> > --- /dev/null
> > +++ b/arch/csky/abiv2/fpu.c
> > +void fpu_fpe(struct pt_regs * regs)
> > +{
> > +	int sig;
> > +	unsigned int fesr;
> > +	siginfo_t info;
> > +
> > +	fesr = mfcr("cr<2, 2>");
> > +
> > +	if(fesr & FPE_ILLE){
> > +		info.si_code = ILL_ILLOPC;
> > +		sig = SIGILL;
> > +	}
> > +	else if(fesr & FPE_IDC){
> > +		info.si_code = ILL_ILLOPN;
> > +		sig = SIGILL;
> > +	}
> > +	else if(fesr & FPE_FEC){
> > +		sig = SIGFPE;
> > +		if(fesr & FPE_IOC){
> > +			info.si_code = FPE_FLTINV;
> > +		}
> > +		else if(fesr & FPE_DZC){
> > +			info.si_code = FPE_FLTDIV;
> > +		}
> > +		else if(fesr & FPE_UFC){
> > +			info.si_code = FPE_FLTUND;
> > +		}
> > +		else if(fesr & FPE_OFC){
> > +			info.si_code = FPE_FLTOVF;
> > +		}
> > +		else if(fesr & FPE_IXC){
> > +			info.si_code = FPE_FLTRES;
> > +		}
> > +		else {
> > +			info.si_code = NSIGFPE;
> > +		}
> > +	}
> > +	else {
> > +		info.si_code = NSIGFPE;
> > +		sig = SIGFPE;
> > +	}
> > +	info.si_signo = SIGFPE;
> > +	info.si_errno = 0;
> > +	info.si_addr = (void *)regs->pc;
> > +	force_sig_info(sig, &info, current);
> > +}
> 
> 
> This use of sending a signal is buggy.  It results in undefined values
> being copied to userspace.
> 
> Userspace should never be sent NSIGXXX as a si_code.  You can use
> FPE_FLTUNK for this default case.
Ok, thx for the tips. I'll fix it up in next patch-set.

> In new code please use force_sig_fault instead of force_sig_info in new
> code.  That saves you the trouble of messing with struct siginfo.
Ok, got it. Thx

Best Regards
 Guo Ren