Re: V3 [PATCH] Add a C wrapper for prctl [BZ #25896]

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella Netto:

> On 10/11/22 09:03, Florian Weimer wrote:
>> * Adhemerval Zanella Netto:
>> 
>>> The previous syscalls.list entry marked the function as 5 argument one
>>> instead of variadic, so I think it would be better to add a way each
>>> ABI to use this instead of the variadic one. Something like:
>>>
>>>   #if PRCTL_VARIADIC_OK
>>>   int
>>>   __prctl (int option, ...)
>>>   {
>>>     va_list arg;
>>>     va_start (arg, option);
>>>     unsigned long int arg2 = va_arg (arg, unsigned long int);
>>>     unsigned long int arg3 = va_arg (arg, unsigned long int);
>>>     unsigned long int arg4 = va_arg (arg, unsigned long int);
>>>     unsigned long int arg5 = va_arg (arg, unsigned long int);
>>>     va_end (arg);
>>>     return INLINE_SYSCALL_CALL (prctl, option, arg2, arg3, arg4, arg5);
>>>   }
>>>   #else
>>>   int
>>>   __prctl (int option, int arg1, int arg2, int arg3, int arg4, int arg5)
>>>   {
>>>     return INLINE_SYSCALL_CALL (prctl, option, arg2, arg3, arg4, arg5);
>>>   }
>>>   #endif
>> 
>> (The arguments need to be unsigned long int.)
>> 
>> This is not easy to do in C because the GCC aliasing machinery performs
>> type checking (as it should).
>> 
>> We can probably use
>> 
>> #define prctl prctl_XXX
>> #define __prctl __prctl_XXX
>
> Yes, I did not include it but we already do it for non-LFS to LFS alias.
>
>> 
>> before including <sys/prctl.h>, but that's quite ugly.  Do you still
>> want me to proceed with the C version?
>
> I would, although it is not the simplest solution.

It's not too bad.  I'm going to make the internal __prctl prototype
non-variadic.

Thanks,
Florian