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SubjectRe: [PATCH 05/10] efi/libstub: distinguish between native/mixed not 32/64 bit
On Sat, 14 Dec 2019 at 22:17, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> On Sat, Dec 14, 2019 at 08:27:50PM +0000, Ard Biesheuvel wrote:
> > On Sat, 14 Dec 2019 at 21:13, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > >
> > > On Sat, Dec 14, 2019 at 07:54:25PM +0000, Ard Biesheuvel wrote:
> > > > On Sat, 14 Dec 2019 at 20:49, Arvind Sankar <nivedita@alum.mit.edu> wrote:
> > > > >
> > > > > On Sat, Dec 14, 2019 at 02:46:27PM -0500, Arvind Sankar wrote:
> > > > > > On Sat, Dec 14, 2019 at 06:57:30PM +0100, Ard Biesheuvel wrote:
> > > > > > > +
> > > > > > > +#define efi_table_attr(table, attr, instance) ({ \
> > > > > > > + __typeof__(((table##_t *)0)->attr) __ret; \
> > > > > > > + if (efi_is_native()) { \
> > > > > > > + __ret = ((table##_t *)instance)->attr; \
> > > > > > > + } else { \
> > > > > > > + __typeof__(((table##_32_t *)0)->attr) at; \
> > > > > > > + at = (((table##_32_t *)(unsigned long)instance)->attr); \
> > > > > > > + __ret = (__typeof__(__ret))(unsigned long)at; \
> > > > > > > + } \
> > > > > > > + __ret; \
> > > > > > > +})
> > > > > >
> > Yes. I'm open to suggestions on how to improve this, but mixed mode is
> > somewhat of a maintenance burden, so if new future functionality needs
> > to leave mixed mode behind, I'm not too bothered.
> >
>
> Maybe just do
> if (sizeof(at) < sizeof(__ret))
> __ret = (__typeof__(__ret))(uintptr_t)at;
> else
> __ret = (__typeof__(__ret))at;
> That should cover most of the cases.

But the compiler will still be unhappy about the else clause if __ret
is a pointer type, since we'll be casting an u32 to a pointer,

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