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[37.247.29.68]) by smtp.gmail.com with ESMTPSA id u26sm1501136lfi.307.2022.02.07.05.45.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Feb 2022 05:45:31 -0800 (PST) Message-ID: Date: Mon, 7 Feb 2022 14:45:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: Debugging ld.so in gdb Content-Language: en-US From: Jacob Kroon To: Florian Weimer , cltang@codesourcery.com, adhemerval.zanella@linaro.org Cc: Jacob Kroon via Gdb References: <29e0ef71-4706-9b0f-2a68-e12c54120d8e@gmail.com> <8735kypwcd.fsf@oldenburg.str.redhat.com> <87y22qognw.fsf@oldenburg.str.redhat.com> <87h79eobq1.fsf@oldenburg.str.redhat.com> <87czk2o967.fsf@oldenburg.str.redhat.com> <06f726f4-855e-239b-fd2c-8d0d57f45131@gmail.com> <878ruqo8o2.fsf@oldenburg.str.redhat.com> <8d9d02de-1a59-1f4d-dbcf-050b65abef29@gmail.com> <93cd41d6-e333-f31e-96bb-2f34a88f164f@gmail.com> <875ypqc2ma.fsf@oldenburg.str.redhat.com> <3e08e7c7-05f5-16f2-50cb-036687386997@gmail.com> <87wni6amk5.fsf@oldenburg.str.redhat.com> <4ea94b1b-71f5-3fbe-e18d-dff61ba3d835@gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 07 Feb 2022 13:45:35 -0000 On 2/7/22 14:39, Jacob Kroon wrote: > On 2/7/22 13:32, Jacob Kroon wrote: >> On 2/7/22 13:27, Florian Weimer wrote: >>> * Jacob Kroon: >>> >>>>> What I find really confusing is that this is not the result of a dlopen >>>>> call. I definitely would expect that the maps array contains *all* >>>>> objects that are being loaded. Clearly this is not the case here. >>>>> Somehow certain objects are missing, and then they get written into the >>>>> rpo array. >>>>> >>>>> Please try to find libjvm.so among the l_initfini arrays of the objects. >>>> >>>> I do find libjvm.so in a couple of the maps[]->l_initfini[]->l_name >>>> arrays, yes. >>> >>> Okay, and of course there is an assumption that those make it to the >>> maps. No wonder we run off the array. >>> >>>>> It must be present somewhere. I assume it's also on the main list, >>>>> which starts off at _rtld_global._dl_ns[0]._ns_loaded. >>>> >>>> Hmm how do I iterate over that data structure ? >>>> >>>> See below: >>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[0]->l_name >>>>> $186 = 0x7ffff7ff1d97 "" >>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[1]->l_name >>>>> $187 = 0x0 >>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded[2]->l_name >>>>> $188 = 0x0 >>>>> (gdb) print _rtld_global._dl_ns[0]._ns_loaded->l_name >>>>> $189 = 0x7ffff7ff1d97 "" >>>>> (gdb) print _rtld_global._dl_ns[1]._ns_loaded->l_name >>>>> Cannot access memory at address 0x8 >>>>> (gdb) print _rtld_global._dl_ns[2]._ns_loaded->l_name >>>>> Cannot access memory at address 0x8 >>> >>> It's a list chained by l_prev/l_next. >>> >> >> Ok, yes "libjvm.so" is there, in multiple entries. >> > > I managed to build glibc master, and yes it also crashes. Reverting the > suspicious commit: > > commit 15a0c5730d1d5aeb95f50c9ec7470640084feae8 > Author: Chung-Lin Tang > Date: Thu Oct 21 21:41:22 2021 +0800 > > elf: Fix slow DSO sorting behavior in dynamic loader (BZ #17645) > > fixes the crash. Adding a couple of more people. > And yes, using master (or host) glibc and running: $ GLIBC_TUNABLES="glibc.rtld.dynamic_sort=1" ldd mylib.so also works without crashing. Jacob