From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH] [RFC] fix kernel crash (protection id trap) when Date: Mon, 22 Dec 2008 16:46:30 -0600 Message-ID: <1229985990.3345.47.camel@localhost.localdomain> References: <20081219212906.GG8945@bombadil.infradead.org> <20081221152017.102C84F19@hiauly1.hia.nrc.ca> <20081221222005.GB30144@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain Cc: John David Anglin , deller@gmx.de, linux-parisc@vger.kernel.org To: Kyle McMartin Return-path: In-Reply-To: <20081221222005.GB30144@bombadil.infradead.org> List-ID: List-Id: linux-parisc.vger.kernel.org On Sun, 2008-12-21 at 17:20 -0500, Kyle McMartin wrote: > On Sun, Dec 21, 2008 at 10:20:16AM -0500, John David Anglin wrote: > > > Honestly, I can't decide whether to apply this. It really should never > > > happen in the kernel, since the kernel can guarantee it won't get the > > > access rights failure (highest privilege level, and can set %sr and > > > %protid to whatever it wants.) > > > > I believe this change should be applied because we enable P and the > > hardware can generate the exception. Yes, it should never happen, but > > the coding to prevent this occurring is very subtle. > > > > If we're going to paper over a bug like this, we might as well just turn > the P-bit off... I'm afraid you can't. The invisibility of the kernel space from user space relies on this, as does quite a lot of the page protections. James