Re: [PATCH v12 2/7] linux: Introduce INTERNAL_VSYSCALL

[Florian Weimer <fweimer@redhat.com>]

* Evan Green:

> Add an INTERNAL_VSYSCALL() macro that makes a vDSO call, falling back to
> a regular syscall, but without setting errno. Instead, the return value
> is plumbed straight out of the macro.
>
> Signed-off-by: Evan Green <evan@rivosinc.com>
> ---
>
> (no changes since v10)
>
> Changes in v10:
>  - Introduced INTERNAL_VSYSCALL patch
>
>  sysdeps/unix/sysv/linux/sysdep-vdso.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
>
> diff --git a/sysdeps/unix/sysv/linux/sysdep-vdso.h b/sysdeps/unix/sysv/linux/sysdep-vdso.h
> index 189319ad98..f7d4b29b25 100644
> --- a/sysdeps/unix/sysv/linux/sysdep-vdso.h
> +++ b/sysdeps/unix/sysv/linux/sysdep-vdso.h
> @@ -53,4 +53,23 @@
>      sc_ret;								      \
>    })
>  
> +#define INTERNAL_VSYSCALL(name, nr, args...)				      \
> +  ({									      \
> +    __label__ out;							      \
> +    long int sc_ret;							      \
> +									      \
> +    __typeof (GLRO(dl_vdso_##name)) vdsop = GLRO(dl_vdso_##name);	      \
> +    if (vdsop != NULL)							      \
> +      {									      \
> +	sc_ret = INTERNAL_VSYSCALL_CALL (vdsop, nr, ##args);	      	      \
> +	if ((!INTERNAL_SYSCALL_ERROR_P (sc_ret)) ||			      \
> +	    (INTERNAL_SYSCALL_ERRNO (sc_ret) != ENOSYS))		      \
> +	  goto out;							      \
> +      }									      \
> +									      \
> +    sc_ret = INTERNAL_SYSCALL_CALL (name, ##args);		      	      \
> +  out:									      \
> +    sc_ret;								      \
> +  })
> +
>  #endif /* SYSDEP_VDSO_LINUX_H  */

I wonder if this is clearer without the label and with a conditional
expression instead?

Thanks,
Florian