Re: [Xen-devel] [PATCH 2/4] xen/arm: initialize access

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 16 Oct 2018, Tamas K Lengyel wrote:
> On Mon, Oct 15, 2018 at 7:14 PM Stefano Stabellini
> <sstabellini@xxxxxxxxxx> wrote:
> >
> > On Mon, 15 Oct 2018, Tamas K Lengyel wrote:
> > > On Mon, Oct 15, 2018 at 3:57 AM Stefano Stabellini
> > > <sstabellini@xxxxxxxxxx> wrote:
> > > >
> > > > Initialize variable *access before returning it back to the caller.
> > > >
> > > > Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
> > > > ---
> > > >  xen/arch/arm/mem_access.c | 1 +
> > > >  1 file changed, 1 insertion(+)
> > > >
> > > > diff --git a/xen/arch/arm/mem_access.c b/xen/arch/arm/mem_access.c
> > > > index ba4ec78..10ab308 100644
> > > > --- a/xen/arch/arm/mem_access.c
> > > > +++ b/xen/arch/arm/mem_access.c
> > > > @@ -47,6 +47,7 @@ static int __p2m_get_mem_access(struct domain *d, 
> > > > gfn_t gfn,
> > > >      };
> > > >
> > > >      ASSERT(p2m_is_locked(p2m));
> > > > +    *access = XENMEM_access_n;
> > >
> > >  Why XENMEM_access_n and why set this at all here?
> >
> > Hi Tamas,
> >
> > Yes, I missed an explanation. Initializing variables before passing them
> > as parameter or as a return value to a function is a safety
> > certification requirement. Also, it makes the code a bit nicer.
> >
> > In the specific case of this function, *access is initialized before
> > returning in all cases but the return -ESRCH case. I thought the nicer
> > way to make sure *access is always initialized, making the code more
> > robust, would be to initialize *access at the beginning of the function
> > with a restrictive value.
> 
> Got it, thanks, Please use p2m->default_access for this instead to be
> consistent with similar code at other spots.

OK, no prob

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