On Dienstag, 8. Mai 2018 08:44:29 CEST Bert Wesarg wrote: > On Mon, May 7, 2018 at 10:24 PM, Milian Wolff <m...@milianw.de> wrote: > > On Montag, 7. Mai 2018 21:27:04 CEST Milian Wolff wrote: > >> On Mittwoch, 2. Mai 2018 13:23:03 CEST Bert Wesarg wrote: > >> > Dear Milian, > >> > > >> > I tried to remember why we choose the initial-exec model, but could > >> > not found any reasons. By reading > >> > https://www.akkadia.org/drepper/tls.pdf again, I would say > >> > "local-exec" is the right way to go here. Which should be the default > >> > for 'static' variables anyway. Can you please confirm, that this works > >> > for you. Its just important, that there are no calls to > >> > __tls_get_addr() in the asm output. > >> > >> No, with the default I do see __tls_get_addr in the asm output (i.e. > >> matches in Gparser.o). So probably, the default isn't OK to be used > >> everywhere.> > > And local-exec doesn't compile: > > > > /usr/bin/ld: x86_64/.libs/Ltrace.o: relocation R_X86_64_TPOFF32 against > > `tls_cache_destroyed' can not be used when making a shared object; > > recompile with -fPIC > > > > Adding -fPIC isn't enough. I think it's because libunwind's build system > > uses static libraries to generate the shared libraries. But that doesn't > > seem to be possible with local-exec, if I'm understanding it correctly. > > > > Using local-exec does remove the call to __tls_get_addr from the *.o files > > though. > > Ok, that was a dead end. Back to square zero. I found my old sandbox > regarding tls and dlopen. And it still passes the initial-exec test. > > Can you run 'make run' in the following archive. Note that I open the > lib with RTLD_LOCAL, which you do to, aren't you?
I use RTLD_NOW, but don't specify RTLD_GLOBAL. If I understand the docs correctly, the former shouldn't affect the latter, and thus I should use RTLD_LOCAL (or so I hope). At least, changing your RTLD_LAZY to RTLD_NOW doesn't change the results below. Regarding your code, some of it doesn't compile: ``` $ make -j1 makeobj[0]: Entering directory `/tmp/tls-dlopen' gcc -shared -fPIC -DTHEMODEL=local-exec -o libadapter-extern-local-exec.so adapter.c -Wl,-rpath,$PWD -L. -lmy_tls-local-exec /usr/bin/ld: /tmp/ccMCneah.o: relocation R_X86_64_TPOFF32 against symbol `my_tls' can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status make: [Makefile:25: libadapter-extern-local-exec.so] Error 1 (ignored) gcc -shared -fPIC -DTHEMODEL=local-exec -DTHESTATIC -o libadapter-static- local-exec.so adapter.c /usr/bin/ld: /tmp/ccuIgB2n.o: relocation R_X86_64_TPOFF32 against `my_tls' can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status make: [Makefile:25: libadapter-static-local-exec.so] Error 1 (ignored) makeobj[0]: Leaving directory `/tmp/tls-dlopen' ``` Output from running it locally: ``` $ make run makeobj[0]: Entering directory `/tmp/tls-dlopen' gcc -shared -fPIC -DTHEMODEL=local-exec -o libadapter-extern-local-exec.so adapter.c -Wl,-rpath,$PWD -L. -lmy_tls-local-exec gcc -shared -fPIC -DTHEMODEL=local-exec -DTHESTATIC -o libadapter-static- local-exec.so adapter.c /usr/bin/ld: /tmp/ccs45TyO.o: relocation R_X86_64_TPOFF32 against `my_tls' can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status make: [Makefile:25: libadapter-static-local-exec.so] Error 1 (ignored) /usr/bin/ld: /tmp/cc8X0n8N.o: relocation R_X86_64_TPOFF32 against symbol `my_tls' can not be used when making a shared object; recompile with -fPIC /usr/bin/ld: final link failed: Nonrepresentable section on output collect2: error: ld returned 1 exit status make: [Makefile:25: libadapter-extern-local-exec.so] Error 1 (ignored) ./main 1 1 2 2 extern global-dynamic: enter enter 1 1 exit enter 2 exit enter 2 exit exit static global-dynamic: enter 1 enter 1 exit enter 2 exit enter 2 exit exit extern local-dynamic: enter enter 1 1 exit enter 2 exit enter 2 exit exit static local-dynamic: enter 1 enter 1 exit enter 2 exit enter 2 exit exit extern initial-exec: enter 1 enter 1 exit enter 2 exit enter 2 exit exit static initial-exec: enter 1 enter 1 exit enter 2 exit enter 2 exit exit extern local-exec: Could not load THEMONITOR : Success Could not load theenter symbol : Success Could not load theexit symbol : Success 1 1 2 2 static local-exec: Could not load THEMONITOR : Success Could not load theenter symbol : Success Could not load theexit symbol : Success 1 1 2 2 makeobj[0]: Leaving directory `/tmp/tls-dlopen' ``` So indeed, it looks like initial-exec should be fine... Maybe it's because I don't load libunwind directly, but rather load a secondary library which in turn depends on libunwind. Once I have more time, I'll try to expand your test accordingly to see if that is what breaks it. Cheers -- Milian Wolff m...@milianw.de http://milianw.de
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