From mboxrd@z Thu Jan 1 00:00:00 1970 From: compudj@krystal.dyndns.org (Mathieu Desnoyers) Date: Mon, 18 Apr 2011 21:18:36 -0400 Subject: [ltt-dev] [UST] Text relocations in 0.12 In-Reply-To: <20110416232432.GA22197@starquasia> References: <20110416232432.GA22197@starquasia> Message-ID: * Jon Bernard (jbernard at debian.org) wrote: > As I prepared the 0.12 release for Debian, I noticed that libust.so was > not PIC: > > $ readelf -d libust/.libs/libust.so.0.0.0 | grep TEXTREL > 0x0000000000000016 (TEXTREL) 0x0 > > Since all of the objects in libust are built with -fPIC, I thought > perhaps there was some assembly added between 0.11 and 0.12 that > contained text relocations. I bisected the two tags down to the > offending commit: > > eb5d20c68aaf73661ffc02ba8fea3683c0358702 > > Within that commit, it seems to be a problem in include/ust/marker.h > with these lines: > > @@ -129,7 +124,12 @@ struct marker { > [...] > + /*".section __markers_ptrs\n\t"*/ \ > + ".section __markers_ptrs,\"a\", at progbits\n\t" \ > > If I make the __markers_ptrs section writable, with: > > ".section __markers_ptrs,\"aw\"\n\t > > TEXTREL goes away and everything seems okay, tests pass. Is this > a correct solution? I don't understand why the section must be writable > to avoid relocations, can anyone explain? Oh.. I think I see. __markers_ptrs contains pointers to another section that must be populated by the dynamic linker (thus at runtime). If the section is read-only, the linker cannot update them at load time, so a relocation table is probably needed. I'll fix this in the git tree. It will be there in the next release. Thanks! Mathieu > > Cheers > > Jon > > _______________________________________________ > ltt-dev mailing list > ltt-dev at lists.casi.polymtl.ca > http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev > -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com