Re: [Xen-devel] [RFC PATCH 2/7] x86/boot: Remove gratuitous call back into low-memory code

[David Woodhouse <dwmw2@xxxxxxxxxxxxx>]

On Thu, 2019-05-02 at 10:23 +0100, Andrew Cooper wrote:
> ...this reasoning is bogus.  We're either accessing the data itself, or
> the memcpy function, but there is no possible way to programatically
> avoid "wrong" access into the trampoline, because we're still accessing it.

Just to be clear, now I'm back at a real computer: yes there is a way
to avoid "wrong" access into the trampoline from the 64-bit C code.
It's the 6th patch in my series, for which this one is a necessary
preliminary cleanup.

http://git.infradead.org/users/dwmw2/xen.git/commitdiff/f54044fb3ad5d

It rips out all those horrid bootsym() pointer gymnastics in the 64-bit 
code, except for the limited cases where we really do need to put
things in place for the permanently AP/wakeup trampolines.

It puts all these boot-discovered variables into their own section,
then copies them back into the Xen image when the 16-bit boot code has
finished running, to be accessed from there ever after.

Which also paves the way for the no-real-mode boot not actually putting
*anything* into low memory during boot at all.

This allows us to clean up the EFI code to stop having to do that, too.

Attachment: smime.p7s
Description: S/MIME cryptographic signature

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel