PowerPC paxtest results w/ gcc-4.1

Matt Sealey matt at genesi-usa.com
Mon Aug 14 21:50:53 EST 2006

> Of course, that won't make all that much difference on your 
> Cube, because the G4 CPU doesn't have hardware support for 
> non-executable pages (any readable page is executable)

I don't think this is true?

Book I compatible PowerPC's have had a "no-executable" bit in
the page protection flags since the dark ages.. see page 7-38
and 7-39 of the 'Programming Environments Manual for 32-Bit
Microprocessors'.. this document predates even the G3.

As far as the documentation goes, you can make the page
readable and writable to the LSU, but the N bit causes the
instruction fetch to cause a machine check. That's pretty
"not-executable" to me at least :)

Matt Sealey <matt at genesi-usa.com>
Manager, Genesi, Developer Relations

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