[PATCH] elf: Fix elf_get_dynamic_info definition

[Florian Weimer]

* Adhemerval Zanella:

> On 12/10/2021 03:35, Florian Weimer wrote:
>> * Adhemerval Zanella via Libc-alpha:
>> 
>>> +  if (check)
>>> +    {
>>> +      /* Only the bind now flags are allowed.  */
>>> +      assert (info[VERSYMIDX (DT_FLAGS_1)] == NULL
>>> +	      || (info[VERSYMIDX (DT_FLAGS_1)]->d_un.d_val & ~DF_1_NOW) == 0);
>>> +      /* Flags must not be set for ld.so.  */
>>> +      assert (info[DT_FLAGS] == NULL
>>> +	      || (info[DT_FLAGS]->d_un.d_val & ~DF_BIND_NOW) == 0);
>>> +# ifdef STATIC_PIE_BOOTSTRAP
>>> +      assert (info[DT_RUNPATH] == NULL);
>>> +      assert (info[DT_RPATH] == NULL);
>>> +# endif
>>> +    }
>> 
>> Why is a conditional check required?  Is this an optimization?
>> 
>
> Because these asserts are only meaningful for the loader itself, but 
> this function is used by setup_vdso() as well.  Enabling it regardless
> leads to:

Please add a comment mentioning this.

In the long run, we should replace these asserts with a build-time
check.  I hesitate to add more tests based on readelf output, though.