From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.3 required=5.0 tests=MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 9196 invoked from network); 29 Oct 2020 14:18:35 -0000 Received: from mother.openwall.net (195.42.179.200) by inbox.vuxu.org with ESMTPUTF8; 29 Oct 2020 14:18:35 -0000 Received: (qmail 26597 invoked by uid 550); 29 Oct 2020 14:18:31 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 26579 invoked from network); 29 Oct 2020 14:18:31 -0000 Date: Thu, 29 Oct 2020 17:18:20 +0300 (MSK) From: Alexander Monakov To: musl@lists.openwall.com In-Reply-To: <87pn51ruii.fsf@oldenburg2.str.redhat.com> Message-ID: References: <20201029063448.GK534@brightrain.aerifal.cx> <20201029133839.GL534@brightrain.aerifal.cx> <87pn51ruii.fsf@oldenburg2.str.redhat.com> User-Agent: Alpine 2.20.13 (LNX 116 2015-12-14) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Subject: Re: [musl] More thoughts on wrapping signal handling On Thu, 29 Oct 2020, Florian Weimer wrote: > * Alexander Monakov: > > > On Thu, 29 Oct 2020, Alexander Monakov wrote: > > > >> On Thu, 29 Oct 2020, Rich Felker wrote: > >> > >> > Yes, I kinda hand-waved over this with the word "call", which I > >> > thought about annotating with (*). In the case of SA_ONSTACK you need > >> > a primitive to "call on new stack", and while the ucontext is mostly > >> > not meaningful/inspectable to the signal handler (because it's > >> > interrupting libc code), the saved signal mask is. You can have the > >> > caller restore it (in place of SYS_[rt_]sigreturn), but the natural > >> > common solution to all of these needs is having a sort of makecontext. > >> > >> Alternatively you could re-raise the signal to have the kernel re-deliver > >> it with the correctly regenerated ucontext (and on the right stack)? > >> Would that be undesirable for some reason? > > > > Ah, because there's no way to propagate siginfo struct. Sorry :) > > Yes, and that's why I think copying it into TLS space will not work, > either. Actually I regret rushing that email: clearly as we are talking about wrapped signal handlers, re-raising would call the wrapper, which would be perfectly capable of substituting saved siginfo. So I don't think propagating siginfo is more complicated with this re-raising approach. Alexander