Re: [PATCH 4/6] ftrace, x86: make kernel text writable only for conversions

Pavel Machek
2009-02-28T22:07:50Z

> > > The very old text poke code I had for this just used a dynamic
> > > mapping elsewhere instead to modify the code. That's much less
> > > intrusive than changing the complete mappings. Any reason you can't use
> > > that too?
> >
> > Is it legal to have two mappings of same page with different
> > attributes? IIRC some processors did not like that...
>
> If you mean PAT caching attributes: correct it is not legal in x86 and
> causes problems including data corruption.

Aha, PAT is what I remembered on x86-64.

> If you mean other attributes like large page vs small page: it's normally legal,
> with a few exceptions.

...but is it okay on other architectures, like sparc, with funky cache
setups?
Pavel
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