Re: [Xen-devel] ioctl handling in netbsd_privcmd_hypercall()

[Roger Pau Monnà <roger.pau@xxxxxxxxxxxxx>]

2012/1/18 Olaf Hering <olaf@xxxxxxxxx>:
>
> I was looking at the slightly broken error handling in the new
> xc_mem_paging_load() function and stumbled over the ioctl() handling in
> netbsd_privcmd_hypercall().
>
> Is ioctl() on NetBSD special? I would have expected it returns -1 on
> error and the caller can deal with errno if it actually wants to.
> But instead it returns the negative errno value or what the hypervisor
> returned.

I haven't done this code, so I don't know if there are some hidden
subtleties here, but according to NetBSD ioctl(2) man page[0], it
returns -1 on error and errno is set to indicate the error.

> static int netbsd_privcmd_hypercall(xc_interface *xch, xc_osdep_handle h, 
> privcmd_hypercall_t *hypercall)
> {
> Â Âint fd = (int)h;
> Â Âint error = ioctl(fd, IOCTL_PRIVCMD_HYPERCALL, hypercall);
>
> Â Âif (error < 0)
> Â Â Â Âreturn -errno;
> Â Âelse
> Â Â Â Âreturn hypercall->retval;
> }
>
> I think do_domctl() is supposed to return -1 on error and let the caller
> decide what to do. At least thats how its appearently done on Linux and
> Solaris.

[0] http://netbsd.gw.com/cgi-bin/man-cgi?ioctl+.amd64+NetBSD-current

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