linux-kernel - Re: [PATCH 08/28] nios2: MMU Fault handling

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Message-ID: <20140424152232.GD1735@arch.cereza>
Date:	Thu, 24 Apr 2014 12:22:32 -0300
From:	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>
To:	Ley Foon Tan <lftan@...era.com>
Cc:	Linux-Arch <linux-arch@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	cltang@...esourcery.com
Subject: Re: [PATCH 08/28] nios2: MMU Fault handling

On Apr 24, Ley Foon Tan wrote:
> On Tue, Apr 22, 2014 at 10:30 PM, Ezequiel Garcia
> <ezequiel.garcia@...e-electrons.com> wrote:
> > Hello Ley Foon,
> >
> > On Apr 18, Ley Foon Tan wrote:
> >> +
> >> +bad_area_nosemaphore:
> >> +     /* User mode accesses just cause a SIGSEGV */
> >> +     if (user_mode(regs)) {
> >
> > I found that it's useful to add some printing here, just as ARM
> > does. I carry this patch on my kernel:
> >
> > +               printk(KERN_INFO "%s: unhandled page fault (%d) at 0x%08lx, cause %ld\n",
> > +                      current->comm, SIGSEGV, address, cause);
> > +               show_regs(regs);
> >
> > Do you think we could do something like it? Maybe with a compile time option?
> Yes, this is useful debug message. I can add this.
> Prefer not to add new compile time option, I think this shouldn't
> happen frequently.

No, it shouldn't happen frequently. You can take a look at what ARM does.
They use a DEBUG_USER compile-time option, much more complex than my silly
proposal.
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
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