segfaults in _dl_fixup since 4af6982

[Adhemerval Zanella]

On 13/10/2021 10:55, Manuel Lauss wrote:
> Applied this patch on top of git head, still same error.
> 
> Manuel

Sigh, it seems I got the elf_get_dynamic_info() sideways.  Could you check
this slight modified patch? It is x86_64 only for now.

And I am puzzled why I am not seeing any issues in the environments I am
checking...

> 
> On Wed, Oct 13, 2021 at 3:47 PM Adhemerval Zanella
> <adhemerval.zanella@linaro.org> wrote:
>>
>>
>>
>> On 13/10/2021 08:56, Adhemerval Zanella wrote:
>>>
>>>
>>> On 13/10/2021 08:44, Adhemerval Zanella wrote:
>>>>
>>>>
>>>> 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?
>>>>
>>>
>>> Sigh... I think this is another fallback of RTLD_BOOTSTRAP.  I fixed the
>>> elf_get_dynamic_info(), but there are lot of more usage that changes
>>> the semantic of the nested functions (specifically on elf/do-rel.h
>>> and dl-machine.h).
>>>
>>> I will try to fix, I think we should define RTLD_BOOTSTRAP before the
>>> fist dynamic-link.h in rtld.
>>>
>>
>> Could you check if the attached patch fixes it?  The rtld.c now should get
>> all the required function with the expected semantic (RTLD_BOOTSTRAP defined).
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-elf-Fix-dynamic-link.h-usage-on-rtld.c.patch
Type: text/x-patch
Size: 22504 bytes
Desc: not available
URL: <https://sourceware.org/pipermail/libc-alpha/attachments/20211013/9aabdc28/attachment-0001.bin>