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: <18012.61822.197988.279764@cargo.ozlabs.ibm.com> Date: Wed, 30 May 2007 13:37:34 +1000 From: Paul Mackerras To: Steve Munroe Subject: Re: Saving to 32 bits of GPRs in signal context In-Reply-To: References: Cc: Ulrich Weigand , linuxppc-dev list , Anton Blanchard List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Steve Munroe writes: > But unless you take the time to write it up like a full ABI change you are > never sure that it IS compatible. And any change to the size/shape of > ucontext_t is an ABI change. There is no change to the size or shape of the ucontext_t. There is no change to the ABI at all, in the sense that everything that is currently guaranteed by the ABI is still guaranteed. An extra guarantee is added: the top 32 bits of the GPRs will not change unpredictably as long as you don't call a function and don't use setcontext or swapcontext to return from a signal handler. I think actually it would be useful to have the saving/restoring of the high 32 bits controlled by a prctl, so that programs have to ask explicitly for the new behaviour (and programs that don't want to use the high 32 bits don't incur the extra overhead). Paul.