Re: [Xen-devel] [PATCH 2/4] libxc: Provide access to internal handles

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, May 14, 2018 at 06:08:57PM +0100, Ian Jackson wrote:
> In order to support auditing of qemu depriv, my audit tool wants to
> know the fd of a privcmd handle on which it can easily make
> hypercalls.  xencall provides such a handle, but has no cooked
> facilities for making hypercalls.  So I open a libxc handle.  That
> means I need to get the privcmd fd out of the libxc handle.
> 
> ISTM that it is best to do this by providing an interface to get the
> underlying library handles for a libxc handle.  This kind of interface
> is quite common elsewhere and has not caused problems.
> 
> libxc is not a stable API so the downside risk of providing this
> access is not significant.
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> ---
>  tools/libxc/include/xenctrl.h | 10 ++++++++++
>  tools/libxc/xc_private.c      |  5 +++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> index 408fa1c..d7733aa 100644
> --- a/tools/libxc/include/xenctrl.h
> +++ b/tools/libxc/include/xenctrl.h
> @@ -183,6 +183,16 @@ enum xc_open_flags {
>   */
>  int xc_interface_close(xc_interface *xch);
>  
> +/**
> + * Return the handles which xch has opened and will use for
> + * hypercalls, foreign memory accesses and device model operations.
> + * These may be used with the corresponding libraries so long as the
> + * xch itself remains open.
> + */
> +struct xencall_handle *xc_interface_xcall_handle(xc_interface *xch);
> +struct xenforeignmemory_handle *xc_interface_fmem_handle(xc_interface *xch);
> +struct xendevicemodel_handle *xc_interface_dmod_handle(xc_interface *xch);

You introduce 3 prototypes but there's only one function being defined
below. Is this patch missing some chunks or I'm missing something
myself?

> +xencall_handle *xc_interface_xcall_handle(xc_interface *xch)
> +{
> +    return xch->xcall;
> +}
> +
>  static pthread_key_t errbuf_pkey;
>  static pthread_once_t errbuf_pkey_once = PTHREAD_ONCE_INIT;

Thanks.

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