Re: [PATCH 1/4] Initial support for GNU_PROPERTY_1_NEEDED

["H.J. Lu" <hjl.tools@gmail.com>]

On Mon, Jun 21, 2021 at 12:06 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu via Libc-alpha:
>
> > diff --git a/elf/elf.h b/elf/elf.h
> > index 2a62b98d4a..45b107fdcf 100644
> > --- a/elf/elf.h
> > +++ b/elf/elf.h
> > @@ -1310,6 +1310,23 @@ typedef struct
> >  /* No copy relocation on protected data symbol.  */
> >  #define GNU_PROPERTY_NO_COPY_ON_PROTECTED    2
> >
> > +/* A 4-byte unsigned integer property: A bit is set if it is set in all
> > +   relocatable inputs.  */
> > +#define GNU_PROPERTY_UINT32_AND_LO   0xb0000000
> > +#define GNU_PROPERTY_UINT32_AND_HI   0xb0007fff
> > +
> > +/* A 4-byte unsigned integer property: A bit is set if it is set in any
> > +   relocatable inputs.  */
> > +#define GNU_PROPERTY_UINT32_OR_LO    0xb0008000
> > +#define GNU_PROPERTY_UINT32_OR_HI    0xb000ffff
> > +
> > +/* The needed properties by the object file.  */
> > +#define GNU_PROPERTY_1_NEEDED                GNU_PROPERTY_UINT32_OR_LO
> > +
> > +/* Set if the object file requires canonical function pointers and
> > +   cannot be used with copy relocation.  */
> > +#define GNU_PROPERTY_1_NEEDED_SINGLE_GLOBAL_DEFINITION       (1U << 0)
> > +
> >  /* Processor-specific semantics, lo */
> >  #define GNU_PROPERTY_LOPROC                  0xc0000000
> >  /* Processor-specific semantics, hi */
>
> Please add a stable link to the full specification.

I will work on it.

> I think we need more bits: one bit to indicate the status (in this
> patch), and another bit to indicate linker support for this feature.
> And perhaps yet another to indicate incompatibility with this feature.
>

There is

#define GNU_PROPERTY_1_NEEDED                GNU_PROPERTY_UINT32_OR_LO

Since the setting on output is ORed from inputs, one bit is
sufficient.

-- 
H.J.