Re: Changing __USING_TOPDOWN_VM to a runtime decision

[christos%astron.com@localhost (Christos Zoulas)]

In article <20131105144023.GC17911%mail.duskware.de@localhost>,
Martin Husemann  <martin%duskware.de@localhost> wrote:
>-=-=-=-=-=-
>
>Hey folks,
>
>I would like to change the current (mostly) compile time decision
>wether we will use top-down VA layout for userland processes to a
>runtime check.
>
>This allows emulations to disable it, and also allows MD code to recognize
>binaries not suitable for topdown VM layout and give those binaries the
>old layout.
>
>The latter point is what I actually need: on sparc64 we have compiled most
>code in the "medlow" code model, which does not allow big addresses. I am
>about to commit changes that switch this default and properly mark new
>binaries. To still allow running old binaries, I need something like the
>attached patch.
>
>The patch is mostly straight forward: I define a new flag EXEC_TOPDOWN_VM,
>initialized by default according to __USING_TOPDOWN_VM, but overridable
>by a MD function. This way the exec_package carries over the information,
>wether we will use topdown-vm for the to-be-loaded binary.
>
>Most other changes are mechanical, like pass through this information through
>a few uvm layers.
>
>For architectures already using topdown-VM, no change is intended.
>
>Comments?

I don't like the !!(expr) syntax, I'd prefer to hide the ugliness in a macro
that does (expr != 0) 

christos