Hello Luca, I am not sure whether dlopen'ing an executable (and not a shared lib) is a supported feature of uClibc-ng... Man page of dlopen says it is for opening "shared lib". There has been a discussion on glibc bug tracker to widen the scope of dlopen and allow it to open executables ... but it seems Ulrich Drepper refused it, and then the discussion was revived and it still does not seem to hold a strong consensus. See https://sourceware.org/bugzilla/show_bug.cgi?id=11754 I didn't try, but I am guessing here that if it works, it is by accident. opening and mapping an ET_EXEC is needed indeed in the case of "standalone" (dynamic loader run as an executable and loading another executable given as argument). And the function used to do this, is also the one used by dlopen() to map the shared libs. I guess you are refering to https://elixir.bootlin.com/uclibc-ng/latest/source/ldso/ldso/dl-elf.c#L596 _dl_load_elf_shared_library is indeed used to load the ET_EXEC in the "ld.so used as an executable" from there: https://elixir.bootlin.com/uclibc-ng/latest/source/ldso/ldso/ldso.c#L601 And it is also called from https://elixir.bootlin.com/uclibc-ng/latest/source/ldso/ldso/dl-elf.c#L200 Which is itself called from dlopen: https://elixir.bootlin.com/uclibc-ng/latest/source/ldso/libdl/libdl.c#L372 So it seems the same function is used in 2 different contexts and that leads to the support of ET_EXEC which is valid in one context ... but I'm not sure it is valid in the other one (directly loading an ET_EXEC with dlopen). I hope this is clear. Maybe someone else can give a hint whether my guess is correct or not? Rich ? Waldemar ?

Thanks for the help. I guess there isn't a problem then. I didn't know that you can only load a "special" ET_DYN PIE elf, it makes sense though. FYI: I am investigating a problem relating NodeJS on ARM. And after some more investigating I found out that openssl tries to dlload itself again, for a reason I don't fully understand yet ("|Deliberately leak a reference to ourselves. This will force the library to remain loaded until the atexit() handler is run at process exit.|"). But since openssl is statically linked in node, it loads the binary again. Therefore this certainly isn't a uclibc problem.

I meanwhile found the problem, it is already known, and they did something about in the newest OpenSSL version. OpenSSL wants for be sure, that their cleanup routines on atexit are executed. However if it was loaded by dload and later closed by dlclose neccessary code is not available anymore on exit. To achieve this they do a (presumably second) dload on their library to keep it loaded. This makes no sense if it is dynamically compile time linked, but does not really harm. But when linked statically like in my case it does something invalid, which doesn't really hurt either, but on uclibc apparently leads to a printed error message. This might actually be a thing to consider for uclibc, not printing out an error, and only rely on the "normal" error handling mechanisms, like in this case dload returning NULL. Am 03.06.19 um 17:06 schrieb Rich Felker: -- Unsere Aussagen koennen Irrtuemer und Missverstaendnisse enthalten. Bitte pruefen Sie die Aussagen fuer Ihren Fall, bevor Sie Entscheidungen auf Grundlage dieser Aussagen treffen. Wiesemann & Theis GmbH, Porschestr. 12, D-42279 Wuppertal Geschaeftsfuehrer: Dipl.-Ing. Ruediger Theis Registergericht: Amtsgericht Wuppertal, HRB 6377 Infos zum Datenschutz: http://www.wut.de/datenschutz Tel. +49-202/2680-0, Fax +49-202/2680-265, http://www.wut.de

And just out of curiosity, are you sure that you are following all requirements described there: https://github.com/openssl/openssl/blob/df1f538f28c10f2954757164b17781040d2… ? Especially the "NOTES" part? On 6/3/19 5:34 PM, Yann Sionneau wrote: > For the record here are what I think are the corresponding threads: > > https://github.com/openssl/openssl/issues/654 > > https://github.com/curl/curl/issues/1055 > > It seems those thread end up pointing that OpenSSL have invalid > assumptions on atexit() in their code at least for Windows platform. > (for the 2nd link) > > This also seems to be of interest > https://github.com/openssl/openssl/issues/653 > > In any case, I think it is hard to dig deeper in this topic without > looking at the actual code and having more precise information about > what is linked with what, and how (static? dynamic ?). > > And see some crash dumps (stack trace). > > On 6/3/19 5:16 PM, Luca Lindhorst wrote: >> I meanwhile found the problem, it is already known, and they did >> something about in the newest OpenSSL version. OpenSSL wants for be >> sure, that their cleanup routines on atexit are executed. However if >> it was loaded by dload and later closed by dlclose neccessary code >> is not available anymore on exit. To achieve this they do a >> (presumably second) dload on their library to keep it loaded. This >> makes no sense if it is dynamically compile time linked, but does >> not really harm. But when linked statically like in my case it does >> something invalid, which doesn't really hurt either, but on uclibc >> apparently leads to a printed error message. >> >> This might actually be a thing to consider for uclibc, not printing >> out an error, and only rely on the "normal" error handling >> mechanisms, like in this case dload returning NULL. >> >> Am 03.06.19 um 17:06 schrieb Rich Felker: >>> On Mon, Jun 03, 2019 at 03:47:48PM +0200, Luca Lindhorst wrote: >>>> Thanks for the help. >>>> >>>> I guess there isn't a problem then. I didn't know that you can only >>>> load a "special" ET_DYN PIE elf, it makes sense though. >>>> >>>> FYI: I am investigating a problem relating NodeJS on ARM. And after >>>> some more investigating I found out that openssl tries to dlload >>>> itself again, for a reason I don't fully understand yet >>>> ("|Deliberately leak a reference to ourselves. This will force the >>>> library to remain loaded until the atexit() handler is run at >>>> process exit.|"). But since openssl is statically linked in node, it >>>> loads the binary again. >>>> >>>> Therefore this certainly isn't a uclibc problem. >>> I don't understand why it would dlopen the openssl binary rather than >>> libssl for this purpose. It should not be doing that, and there's >>> probably some other bug in openssl or in your integration of it that's >>> making it do that. It also might be something you could consider a bug >>> in uclibc -- attempting to dlopen the main program itself, rather than >>> some other executable, should probably give a handle to the existing >>> instance, rather than attempting to load it again. >>> >>> Rich >> -- Unsere Aussagen koennen Irrtuemer und Missverstaendnisse enthalten. >> Bitte pruefen Sie die Aussagen fuer Ihren Fall, bevor Sie >> Entscheidungen auf Grundlage dieser Aussagen treffen. >> Wiesemann & Theis GmbH, Porschestr. 12, D-42279 Wuppertal >> Geschaeftsfuehrer: Dipl.-Ing. Ruediger Theis >> Registergericht: Amtsgericht Wuppertal, HRB 6377 Infos zum >> Datenschutz: http://www.wut.de/datenschutz >> Tel. +49-202/2680-0, Fax +49-202/2680-265, http://www.wut.de > _______________________________________________ > devel mailing list > devel(a)uclibc-ng.org > https://mailman.uclibc-ng.org/cgi-bin/mailman/listinfo/devel