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 2124 invoked from network); 7 Sep 2023 13:29:05 -0000 Received: from second.openwall.net (193.110.157.125) by inbox.vuxu.org with ESMTPUTF8; 7 Sep 2023 13:29:05 -0000 Received: (qmail 5703 invoked by uid 550); 7 Sep 2023 13:29:02 -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 5657 invoked from network); 7 Sep 2023 13:29:01 -0000 Date: Thu, 7 Sep 2023 09:28:52 -0400 From: Rich Felker To: musl@lists.openwall.com Cc: Peter Williams Message-ID: <20230907132851.GC4163@brightrain.aerifal.cx> References: <1db459153e3f7be32cb469509c272977b9c2b381.camel@newton.cx> <20230907124828.GB4163@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230907124828.GB4163@brightrain.aerifal.cx> User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] aarch64 sigsetjmp relocation truncation bug, maybe (Re-adding the OP to CC) On Thu, Sep 07, 2023 at 08:48:28AM -0400, Rich Felker wrote: > On Thu, Sep 07, 2023 at 05:08:13AM +0200, Markus Wichmann wrote: > > Am Wed, Sep 06, 2023 at 08:46:32PM -0400 schrieb Peter Williams: > > > If I'm understanding correctly, the complaint is that a branch in > > > sigsetjmp that invokes setjmp is too far away from the definition of > > > setjmp. My very handwavey idea is that maybe for some reason my program > > > is causing the linker to want to locate setjmp() and sigsetjmp() really > > > far away from each other. If that's right, perhaps it would be possible > > > to modify the assembler code to be able to handle such a situation? > > > > I'm guessing the same. Pretty much all architectures have shorter > > conditional than unconditional branches. That is why branches to other > > files (technically to other sections) should always be unconditional. I > > am attaching a simple patch that should help with the situation. > > > > Ciao, > > Markus > > > From dd227e22a5337d54e1cb0838410bca6672c76c43 Mon Sep 17 00:00:00 2001 > > From: Markus Wichmann > > Date: Thu, 7 Sep 2023 05:01:23 +0200 > > Subject: [PATCH] Make branch to external symbol unconditional. > > > > Conditional branches have a shorter branch length than unconditional > > ones, and almost all ABIs require unconditional branches to external > > symbols. Otherwise linkers may create broken binaries. > > --- > > src/signal/aarch64/sigsetjmp.s | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/src/signal/aarch64/sigsetjmp.s b/src/signal/aarch64/sigsetjmp..s > > index 75910c43..9a28e395 100644 > > --- a/src/signal/aarch64/sigsetjmp.s > > +++ b/src/signal/aarch64/sigsetjmp.s > > @@ -4,7 +4,7 @@ > > .type __sigsetjmp,%function > > sigsetjmp: > > __sigsetjmp: > > - cbz x1,setjmp > > + cbz x1,1f > > > > str x30,[x0,#176] > > str x19,[x0,#176+8+8] > > @@ -19,3 +19,5 @@ __sigsetjmp: > > > > .hidden __sigsetjmp_tail > > b __sigsetjmp_tail > > + > > +1: b setjmp > > -- > > 2.39.2 > > Are you sure this is the actual problem? I think it's that the aarch64 > (and several other archs) version of sigsetjmp is wrongly using the > public setjmp symbol whose definition is possibly provided by a PLT > thunk in the main program, rather than either setjmp@PLT (which would > necessarily be the right local call point to use) or the hidden > ___setjmp symbol that exists for this purpose (which i386, for > example, uses). Hmm, no, that seems to be a separate issue. The reported issue is indeed a large static link where PLT stuff should not come into play. So I think the cbz limited-range is indeed the issue. Rich