Re: SDIV / UDIV Question
[Adding Jonny] On Thu, Oct 10, 2013 at 06:04:41AM +0100, Wang, Yalin wrote: > Oh , I see , > Thanks for your clarification ! > So R-class cores will not run linux ? R-class cores can run Linux, but I don't reckon we touch SCTLR.DZ. I've added Jonny, so he can clarify the behaviour here. (I'm also not sure which cores have these instructions either). Will > -Original Message- > From: Will Deacon [mailto:will.dea...@arm.com] > Sent: Wednesday, October 09, 2013 6:54 PM > To: Wang, Yalin > Cc: 'linux-arm-msm-ow...@vger.kernel.org'; linux-kernel@vger.kernel.org > Subject: Re: SDIV / UDIV Question > > On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: > > I have a question about sdiv/ udiv instructions : > > In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as > > undefined exception or just return zero (decided by implementation) . > > > > So in kernel , should we need register a undef hook to Get this > > undef exception and send SIGFPE to user space Process ? > > As far as I can see, this can only happen for R-class cores, based on > SCTLR.DZ. > > Will > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: SDIV / UDIV Question
[Adding Jonny] On Thu, Oct 10, 2013 at 06:04:41AM +0100, Wang, Yalin wrote: Oh , I see , Thanks for your clarification ! So R-class cores will not run linux ? R-class cores can run Linux, but I don't reckon we touch SCTLR.DZ. I've added Jonny, so he can clarify the behaviour here. (I'm also not sure which cores have these instructions either). Will -Original Message- From: Will Deacon [mailto:will.dea...@arm.com] Sent: Wednesday, October 09, 2013 6:54 PM To: Wang, Yalin Cc: 'linux-arm-msm-ow...@vger.kernel.org'; linux-kernel@vger.kernel.org Subject: Re: SDIV / UDIV Question On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: I have a question about sdiv/ udiv instructions : In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as undefined exception or just return zero (decided by implementation) . So in kernel , should we need register a undef hook to Get this undef exception and send SIGFPE to user space Process ? As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. Will -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: SDIV / UDIV Question
Hi Will , Oh , I see , Thanks for your clarification ! So R-class cores will not run linux ? This means we don't need care about this . Am I right ? Thank you . -Original Message- From: Will Deacon [mailto:will.dea...@arm.com] Sent: Wednesday, October 09, 2013 6:54 PM To: Wang, Yalin Cc: 'linux-arm-msm-ow...@vger.kernel.org'; linux-kernel@vger.kernel.org Subject: Re: SDIV / UDIV Question On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: > I have a question about sdiv/ udiv instructions : > In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as > undefined exception or just return zero (decided by implementation) . > > So in kernel , should we need register a undef hook to Get this > undef exception and send SIGFPE to user space Process ? As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: SDIV / UDIV Question
On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: > I have a question about sdiv/ udiv instructions : > In armv7 A/R TRM, it said sdiv/udiv will cause > Divide by zero as undefined exception or just return zero > (decided by implementation) . > > So in kernel , should we need register a undef hook to > Get this undef exception and send SIGFPE to user space > Process ? As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: SDIV / UDIV Question
On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: I have a question about sdiv/ udiv instructions : In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as undefined exception or just return zero (decided by implementation) . So in kernel , should we need register a undef hook to Get this undef exception and send SIGFPE to user space Process ? As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. Will -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
RE: SDIV / UDIV Question
Hi Will , Oh , I see , Thanks for your clarification ! So R-class cores will not run linux ? This means we don't need care about this . Am I right ? Thank you . -Original Message- From: Will Deacon [mailto:will.dea...@arm.com] Sent: Wednesday, October 09, 2013 6:54 PM To: Wang, Yalin Cc: 'linux-arm-msm-ow...@vger.kernel.org'; linux-kernel@vger.kernel.org Subject: Re: SDIV / UDIV Question On Wed, Oct 09, 2013 at 08:08:05AM +0100, Wang, Yalin wrote: I have a question about sdiv/ udiv instructions : In armv7 A/R TRM, it said sdiv/udiv will cause Divide by zero as undefined exception or just return zero (decided by implementation) . So in kernel , should we need register a undef hook to Get this undef exception and send SIGFPE to user space Process ? As far as I can see, this can only happen for R-class cores, based on SCTLR.DZ. Will -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
