Re: [Xen-devel] [PATCH v3] kexec: implement STATUS hypercall to check if image is loaded

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Jan 18, 2017 at 03:19:49AM -0700, Jan Beulich wrote:
> >>> On 17.01.17 at 18:29, <eric.devolder@xxxxxxxxxx> wrote:
> > --- a/xen/common/kexec.c
> > +++ b/xen/common/kexec.c
> > @@ -1169,6 +1169,22 @@ static int kexec_unload(XEN_GUEST_HANDLE_PARAM(void) 
> > uarg)
> >      return kexec_do_unload(&unload);
> >  }
> >  
> > +static int kexec_status(XEN_GUEST_HANDLE_PARAM(void) uarg)
> > +{
> > +    xen_kexec_status_t status;
> > +    int base, bit;
> > +
> > +    if ( unlikely(copy_from_guest(&status, uarg, 1)) )
> > +        return -EFAULT;
> > +
> > +    /* No need to check KEXEC_FLAG_IN_PROGRESS. */
> > +
> > +    if ( kexec_load_get_bits(status.type, &base, &bit) )
> > +        return -EINVAL;
> > +
> > +    return test_bit(bit, &kexec_flags);
> 
> In the public header you promise to return zero or one here (unless
> an error occurs), which requires the use of !!. Please see x86's
> implementation of the function for how/when there can actually be
> other non-zero values returned here (in particular all ones, which
> would resolve to -EPERM).
> 
> > --- a/xen/include/public/kexec.h
> > +++ b/xen/include/public/kexec.h
> > @@ -227,6 +227,19 @@ typedef struct xen_kexec_unload {
> >  } xen_kexec_unload_t;
> >  DEFINE_XEN_GUEST_HANDLE(xen_kexec_unload_t);
> >  
> > +/*
> > + * Figure out whether we have an image loaded. A return value of
> > + * zero indicates no image loaded. A return value of one
> > + * indicates an image is loaded. A negative return value
> > + * indicates an error.
> > + *
> > + * Type must be one of KEXEC_TYPE_DEFAULT or KEXEC_TYPE_CRASH.
> > + */
> > +#define KEXEC_CMD_kexec_status 6
> > +typedef struct xen_kexec_status {
> > +    uint8_t type;
> > +} xen_kexec_status_t;
> > +DEFINE_XEN_GUEST_HANDLE(xen_kexec_status_t);
> >  #else /* __XEN_INTERFACE_VERSION__ < 0x00040400 */
> 
> There was a blank line above here before your addition, and you
> shouldn't eliminate it (making quickly scanning over the file harder).
> 
> I guess both items are simple enough to fix while committing.
> 

Oops, I already committed this patch with Andrew's review. A follow-up
patch is appreciated. Thanks.

Wei.

> Jan
> 

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