Re: post-ExitBootServices memory protection of RT_Data (ARM)

[Michael Zimmermann <sigmaepsilon92@gmail.com>]

> The LinuxLoader is a poorly maintained hack, and it is badly broken on
AARCH64
I'm actually just using the shutdown code from linux loader. I wrote my
own, very complete loader which does definitely work in terms of correct
loading and argument passing.

> Does the system have an L2 cache which may need invalidation/disabling.
I doubt that this is the problem because I can even load the soc vendor's
linux bootloader first(to a available addr) which fully works(usb, mmc,
...). and from there I can fastboot boot linux - which then just doesn't
work depending on the loading addr.

I'll ask him to do more tests like reading back data, loading other stuff
to that location to prevent problems linux might have with other memory
locations passed by atags, etc.


On Fri, Sep 2, 2016 at 11:02 PM, Ard Biesheuvel <ard.biesheuvel@linaro.org>
wrote:

> On 2 September 2016 at 21:45, Michael Zimmermann
> <sigmaepsilon92@gmail.com> wrote:
> > If I understand this correctly this is just some MMU feature, right?
> > I'm talking about a pure ARM(with atag's) linux kernel which is not UEFI
> > aware.
> >
> > Also the LinuxLoader disables almost everything(MMU, caches, it calls
> > exitbootservices etc).
> >
> > I really can't explain technically what UEFI could have done to
> accomplish
> > this protection with the MMU being disabled.
> >
>
> No, the kernel is entered with the MMU and caches off. The LinuxLoader
> is a poorly maintained hack, and it is badly broken on AARCH64. On
> ARM, however, it should still work. Does the system have an L2 cache
> which may need invalidation/disabling?
>