Re: [RFC PATCH glibc 1/3] glibc: Perform rseq(2) registration at C startup and thread creation (v18)

[Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>]

* Mathieu Desnoyers:

> Considering this, I wonder if we should be strict and e.g. do:
>
> const char *msg = NULL;
>
> switch (INTERNAL_SYSCALL_ERRNO (ret))
>   {
>   case ENOSYS:
>   case EPERM:
>     /* rseq system call is unavailable or not permitted.  */
>     __rseq_abi.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
>     break;
>   case EINVAL:
>     msg = "glibc fatal error: rseq already registered for this thread\n";
>     break;
>   case EBUSY:
>     msg = "glibc fatal error: rseq parameters are invalid";
>   case EFAULT:
>     msg = "glibc fatal error: rseq is an invalid address";
>     break;
>   default:
>     msg = "glibc fatal error: unexpected rseq errno";
>     break;
>   }
> if (msg)
>   __libc_fatal (msg);

Not sure if this is necessary.  I think it's the first fatal error with
that kind of verbosity, and it's an odd place to start, all things
considered.

> Also considering that __libc_fatal only takes a string as parameter,
> I wonder if there is a facility to print the errno string I could use
> instead of __libc_fatal () ?

I wouldn't get too creative here given that this failure happens so
early during startup, and initialization is somewhat incomplete.

Thanks,
Florian