Re: segfaults in _dl_fixup since 4af6982

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 13/10/2021 07:58, Adhemerval Zanella wrote:
> 
> 
>> On 13 Oct 2021, at 06:19, Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>>
>> The 10/13/2021 08:42, Manuel Lauss via Libc-alpha wrote:
>>> [resend with libc-alpha]
>>> Hi Adhemerval,
>>>
>>> Your recent commit 4af6982e4c9fc465ffb7a54b794aaaa134241f05 ("elf: Fix
>>> elf_get_dynamic_info definition")  causes a lot (but not all) of my
>>> applications
>>> to segfault:
>>>
>>> Program received signal SIGSEGV, Segmentation fault.
>>> _dl_fixup (l=<optimized out>, reloc_arg=<optimized out>) at dl-runtime.c:146
>>> 146       return elf_machine_fixup_plt (l, result, refsym, sym, reloc,
>>> rel_addr, value);
>>> (gdb) bt
>>> #0  _dl_fixup (l=<optimized out>, reloc_arg=<optimized out>) at dl-runtime.c:146
>>> #1  0x00007ffff7fe251a in _dl_runtime_resolve_xsavec () at
>>> ../sysdeps/x86_64/dl-trampoline.h:126
>>> #2  0x000055555555634e in main (argc=1, argv=0x7fffffffd568) at
>>> iconvconfig.c:288
>>>
>>> Reverting the commit fixes the problem. Gcc, python, etc seem to be
>>> not affected, while for example iconvconfig and openssh are.
>>
>> on aarch64 buildbot i see
>>
>> FAIL: nptl/test-cond-printers
>> FAIL: nptl/test-condattr-printers
>> FAIL: nptl/test-mutex-printers
>> FAIL: nptl/test-mutexattr-printers
>> FAIL: nptl/test-rwlock-printers
>> FAIL: nptl/test-rwlockattr-printers
>>
>> and
>>
>> $ cat nptl/test-cond-printers.out
>> Error: Response does not match the expected pattern.
>> Command: start
>> Expected pattern: main
>> Response:  Temporary breakpoint 1 at 0xac4: file test-cond-printers.c, line 36.
>> Starting program: /work/glibc-aarch64-linux/build/build/nptl/test-cond-printers
>>
>> Program received signal SIGSEGV, Segmentation fault.
>> _dl_fixup (l=<optimized out>, reloc_arg=<optimized out>) at dl-runtime.c:146
>> 146       return elf_machine_fixup_plt (l, result, refsym, sym, reloc, rel_addr, value);
>> (gdb)
>>
>>
>> it seems to be a bind-now pie where PLT relocs are not yet
>> processed when __libc_start_main is called but PLTGOT is
>> already marked readonly so _dl_fixup crashes.
> 
> I will check this out.
> 

I am trying to reproduce it on aarch64-linux-gnu without much success (using
gcc 11.1.1 20210702 and ld 2.36.1.20210702). Neither ssh or iconvconfig fails
when running through the built glibc (using ubuntu 21.04 one).

Any idea on how to reproduce it?