From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <17551.16830.186314.247458@cargo.ozlabs.ibm.com> Date: Wed, 14 Jun 2006 08:52:46 +1000 From: Paul Mackerras To: David Woodhouse Subject: Re: 32 bit userland on G5 In-Reply-To: <1150202709.12423.21.camel@hades.cambridge.redhat.com> References: <1150194348.9208.33.camel@johannes> <1150202709.12423.21.camel@hades.cambridge.redhat.com> Cc: linuxppc-dev list , Johannes Berg List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , David Woodhouse writes: > Why? Just because older hardware wasn't capable of enforcing the > permissions, that doesn't mean that we shouldn't enforce them now. Historically the PPC32 ELF ABI has used an executable PLT, containing instructions constructed at runtime, located next to the BSS, and without the corresponding program header entry indicating execute permission. Alan Modra devised a new way of doing the PLT which doesn't require it to be executable, but of course it is only used in programs that have been built since the new method went into the toolchain (in fact all of the .o files being linked have to have been compiled with the new method in order for it to be used). So if you are absolutely sure that every program you will ever want to run on your kernel has been built with an up-to-date toolchain, you can turn on enforcement of execute permissions for 32-bit processes. It would be a "courageous" step (in the Yes Minister sense :) for a distro to do it, IMHO. Paul.