ELF auxiliary vector tags

[John Baldwin]

On Monday, September 11, 2017 12:05:02 PM Marcel Moolenaar wrote:
> 
> > On Sep 8, 2017, at 10:36 AM, John Baldwin <jhb at freebsd.org> wrote:
> 
> 
> > I know Justin changed time_t to 64-bit on 32-bit powerpc which effectively broke 32-bit powerpc earlier, but this change would break both 32-bit and 64-bit powerpc and is probably more disruptive (in theory some binaries might have worked with a wrong time_t, but renumber AT_STACKPROT, etc. will probably break every binary).
> 
> That probably depends on the byte order. I would think widening
> time_t on a big-endian machine is a lot more disruptive than
> doing it on a little-endian machine.
> 
> That said and along the lines of what @imp said:
> Maybe add a a MD macro (e.g. NO_MI_AUX_VECTORS) whose existence
> suppresses the MI definitions of AT_* so that MD headers can
> define their own?

Going forward I would like to standardize on common values for new vectors
added.  The current implementation of 'info auxv' for GDB assumes they
are the same on all architectures (and judging by the binutils / gdb bits
for Linux, Linux uses the same AT_* values on all platforms).  Are you
running powerpc binaries yourself?  The only person who I know is who has
replied (Justin) is fine with just pulling the tier-2 card on powerpc to
bring it inline with all the other platforms (which are already identical).

One suggestion was to set a value in AT_FLAGS (currently always set to zero)
that binaries could then use to detect the new layout on ppc.

-- 
John Baldwin