[PATCH][MIPS] Add linker emulation for N64 ABI with forced 32-bit symbols

Matt Thomas matt@3am-software.com
Sat Nov 17 19:31:00 GMT 2012


On Nov 15, 2012, at 2:08 PM, Richard Sandiford wrote:

> Huh.  I'm very much against the original change to the n64 TEXT_START_ADDR.
> See this previous discussion on the topic:
> 
>    http://sourceware.org/ml/binutils/2008-06/msg00285.html
> 
> The justification for changing TEXT_START_ADDR from a 32-bit value to a
> larger value was that it would show users if their code was non-portable,
> because anything that assumed 32-bit addresses would now fault.  But that
> seems to me like the tools lecturing to the user.  As I said in that thread,
> I think users who want to smoke out such portability problems (by making
> sure that the lower 4GB aren't mapped) should be the ones who need to do
> something special.

Gee, should we go back and stop making sure VA 0 is unmapped too?  Sure it helps find NULL pointer dereferences but isn't that the tools lecturing to the user as well?  Having the TEXT_START_ADDR at 5GB doesn't hurt anyone and will errant catch 32-bit deferences instead of allowing possible silent corruption.  Why is that a bad thing?

> I think we should simply revert to a 32-bit TEXT_START_ADDR for all
> n64 emulations.  This time I'm even in a position to approve it :-)

I strongly disagree.  Just because you can approve it doesn't mean you are right.  If you do make the change, NetBSD will still use the 5GB start address.  



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