Re: [XEN PATCH for-4.14] tools/xen-ucode: fix error code propagation of microcode load operation

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Igor Druzhinin writes ("[PATCH] tools/xen-ucode: fix error code propagation of 
microcode load operation"):
> Otherwise it's impossible to know the reason for a fault or blob rejection
> inside the automation.
...
>          fprintf(stderr, "Failed to update microcode. (err: %s)\n",
>                  strerror(errno));

This part is fine.

> +        ret = errno;
>      xc_interface_close(xch);
...
>      }
>      close(fd);
>  
> -    return 0;
> +    return ret;

Unfortunately I don't think this is right.  errno might not fit into a
return value.  Returning nonzero on microcode loading error would
definitely be right, but ...

... oh I have just read the rest of this file.

I think what is missing here is simply `return errno' (and the braces)
There is no need to call xc_interface_close, or munmap, if we are
about to exit.

I think fixing the lost error return is 4.14 material, so I have
added that to the subject line.

Paul, would you Release-ack a patch that replaced every `return errno'
with (say) exit(12) ?  Otherwise, fixing this program not to try to
fit errno into an exit status is future work.  Also I notice that the
program exits 0 if invoked wrongly.  Unhelpful!  I would want to fix
that too.

Ian.