RE: [PATCH-for-4.17] xen: fix generated code for calling hypercall handlers

[Henry Wang <Henry.Wang@arm.com>]

Hi Juergen and Jan,

> -----Original Message-----
> From: Jan Beulich <jbeulich@suse.com>
> Subject: Re: [PATCH-for-4.17] xen: fix generated code for calling hypercall
> handlers
> 
> On 03.11.2022 17:36, Juergen Gross wrote:
> > The code generated for the call_handlers_*() macros needs to avoid
> > undefined behavior when multiple handlers share the same priority.
> > The issue is the hypercall number being unverified fed into the macros
> > and then used to set a mask via "mask = 1ULL << <hypercall-number>".
> >
> > Avoid a shift amount of more than 63 by setting mask to zero in case
> > the hypercall number is too large.
> >
> > Fixes: eca1f00d0227 ("xen: generate hypercall interface related code")
> > Signed-off-by: Juergen Gross <jgross@suse.com>
> 
> Reviewed-by: Jan Beulich <jbeulich@suse.com>

Release-acked-by: Henry Wang <Henry.Wang@arm.com>

With...

> albeit preferably with ...
> 
> > --- a/xen/scripts/gen_hypercall.awk
> > +++ b/xen/scripts/gen_hypercall.awk
> > @@ -263,7 +263,7 @@ END {
> >          printf("#define call_handlers_%s(num, ret, a1, a2, a3, a4, a5) \\\n",
> ca);
> >          printf("({ \\\n");
> >          if (need_mask)
> > -            printf("    uint64_t mask = 1ULL << num; \\\n");
> > +            printf("    uint64_t mask = (num > 63) ? 0 : 1ULL << num; \\\n");
> 
> ... "num" also properly parenthesized (this is part of a macro definition
> in the output after all). Easy enough to take care of while committing.

...Jan's comment fixed (or agreement to let the committer fix on commit).

Kind regards,
Henry

> 
> Jan