[PATCH] elf: Make string tunables startup-only

[Adhemerval Zanella Netto]

On 18/06/26 04:59, Andreas Schwab wrote:
> On Jun 17 2026, Adhemerval Zanella wrote:
> 
>> @@ -460,6 +461,12 @@ __tunable_get_val (tunable_id_t id, void *valp, tunable_callback_t callback)
>>  	}
>>      case TUNABLE_TYPE_STRING:
>>  	{
>> +	  /* String tunables reference the environment block and are only
>> +	     valid during early startup; once sealed they must not be read. */
>> +	  if (__glibc_unlikely (cur->sealed))
>> +	    _dl_fatal_printf ("Inconsistency detected: trying to read the %s "
>> +			      "string tunable after process initialization\n",
>> +			      cur->name);
> 
> Why do you need the sealed member?  Wouldn't it be enough to check for
> NULL in strval?
> 

It would prevent to use a TUNABLE_GET{_FULL} without first checking TUNABLE_IS_INITIALIZED.
I can change all TUNABLE_GET{_FULL} usage to do so, but I don't see this much as 
improvement. The internal ABI is already a bit clunky.