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Peter Anvin" , Paul Turner , linux-api , Christian Brauner Message-ID: <1481331967.14276.1594824846736.JavaMail.zimbra@efficios.com> In-Reply-To: <87mu4028uk.fsf@oldenburg2.str.redhat.com> References: <20200714030348.6214-1-mathieu.desnoyers@efficios.com> <87a7028d5u.fsf@oldenburg2.str.redhat.com> <2452161.11491.1594732791558.JavaMail.zimbra@efficios.com> <71f08b3a-56f5-0e0f-53b0-cc680f7e8181@redhat.com> <2053637148.14136.1594818777608.JavaMail.zimbra@efficios.com> <87y2nk29rp.fsf@oldenburg2.str.redhat.com> <882700738.14181.1594819884049.JavaMail.zimbra@efficios.com> <87mu4028uk.fsf@oldenburg2.str.redhat.com> Subject: Re: [RFC PATCH 2/4] rseq: Allow extending struct rseq MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.26.124] X-Mailer: Zimbra 8.8.15_GA_3955 (ZimbraWebClient - FF78 (Linux)/8.8.15_GA_3953) Thread-Topic: rseq: Allow extending struct rseq Thread-Index: GU+HWQn+q08bfey6uiSkHPIIjdE8lw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- On Jul 15, 2020, at 9:42 AM, Florian Weimer fweimer@redhat.com wrote: > * Mathieu Desnoyers: > [...] >> How would this allow early-rseq-adopter libraries to interact with >> glibc ? > > Under all extension proposals I've seen so far, early adopters are > essentially incompatible with glibc rseq registration. I don't think > you can have it both ways. The basic question I'm not sure about is whether we are allowed to increase the size and alignement of __rseq_abi from e.g. glibc 2.32 to glibc 2.33. If not, then we just need to find another way to extend struct rseq, e.g. by adding a pointer to another extended structure in the padding space we have at the end of struct rseq. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com