svn commit: r226343 - head/sys/vm

[David Schultz]

On Thu, Oct 13, 2011, Marcel Moolenaar wrote:
> 
> On Oct 13, 2011, at 2:07 PM, John Baldwin wrote:
> >> 
> >> That's really besides the point. ABI changes are made deliberately
> >> and ABIs must be well-documented for anyone to adhere to it. You
> >> can't post hoc wave your hand and say that at some unspecified time
> >> in the past the ABI changed: at what precise time does "supported
> >> by hardware mean" and how does that tie to a major FreeBSD version?
> >> 
> >> Point in case: the JDK 1.4.x still works on FreeBSD 9.x (i386), so
> >> the ABI really hasn't changed at all in that respect.
> > 
> > I think if you booted a FreeBSD 9.x i386 PAE kernel you'd find that the
> > jdk did not work.  That will be true for any i386 PAE kernel back to
> > when PG_NX support was introduced.
> 
> That's bad.

Recent binutils support a PT_GNU_HEAP flag in the ELF header that
controls whether heap allocations are executable by default.  In
Linux, the flag can be set using an ld option or the execstack(8)
command.  That seems like a better way to go than breaking old
JVMs or disabling the security feature.