[PATCH] elf,nptl: Add -z lazy -z norelro to tests that need it

[Florian Weimer]

* Arsen Arsenović:

> Arsen Arsenović <arsen@gentoo.org> writes:
>
>> Hm.  Something went awry while I was debugging this.  I looked at a test
>> again just now and noticed that the symbols some of these tests were
>> crashing on came from libc (dlopen here) while loading constload2 (which
>> is dlopen'd from constload1).  The backtrace contains a PLT trampoline
>> which then fixups dlopen inside the RELRO segment.
>>
>> I take it dlopen@got[plt] is not supposed to be in the RELRO range?
>>
>> I could have sworn this failed when fixing up bar (void) as a result of
>> constload2 dlopening constload3... but maybe that was a different
>> failure.
>>
>> Let's put this patch on hold while I investigate further.
>>
>> FWIW, this should be easy to reproduce by building with CC='gcc
>> -Wl,-z,relro,-z,now' or so, I think.
>
> Ah, I think I see the issue:
>
>   ~/gnu/glibc/b2$ diff -u0 shlib.lds.-Wl,-z,{lazy,now},-z,relro 
>   --- shlib.lds.-Wl,-z,lazy,-z,relro	2023-03-04 19:54:42.977032934 +0100
>   +++ shlib.lds.-Wl,-z,now,-z,relro	2023-03-04 18:57:03.195010040 +0100
>   @@ -1 +1 @@
>   -/* Script for -shared -z combreloc -z separate-code */
>   +/* Script for -shared -z combreloc -z separate-code -z relro -z now */
>   @@ -153,3 +153,2 @@
>   -  .got            : { *(.got) *(.igot) }
>   -  . = DATA_SEGMENT_RELRO_END (SIZEOF (.got.plt) >= 24 ? 24 : 0, .);
>   -  .got.plt        : { *(.got.plt) *(.igot.plt) }
>   +  .got            : { *(.got.plt) *(.igot.plt) *(.got) *(.igot) }
>   +  . = DATA_SEGMENT_RELRO_END (0, .);
>   ~/gnu/glibc/b2 1 $ 
>
> The builds system assumes that all the flags used while building glibc
> use the same linker script, and that this will be the same linker script
> as the one that's used initially to generate shlib.lds.  This is not
> true when -z relro is set and -z {now,lazy} are being varied.
>
> This also explains why the problem only arose after we introduced
> -Wl,-z,now.

Interesting, thanks for looking into this.

Does the issue go away if you configure with --enable-bind-now?

That's what we are doing, and we don't see those test failures.

Florian