Re: [Qemu-devel] [PATCH v2 5/5] linux-user: Add aarch64_be magic numbers to qemu-binfmt-conf.sh

[Michael Weiser]

Hi Laurent,

On Wed, Dec 20, 2017 at 04:56:41PM +0100, Laurent Vivier wrote:

> > Based on that I suspect that qemu-binfmt-conf.sh's current assignment of
> > armeb and aarch64 into the arm CPU family is over-optimistic as well.
> > So I'd suggest treating all of arm, armeb, aarch64 and aarch64_be as
> > separate families.
> So it's not like on intel/AMD where we can execute a 32bit binary on a
> 64bit kernel?

An aarch64 CPU is capable of running arm (i.e. aarch32) code. And I
think this is supported as a multilib setup on Linux. But not in mixed
endianess as far as I know.

Looking at the code again, I'm confused now: Wouldn't the current logic
treat an actual i386 machine as capable of running x86_64 binaries
natively and omit registering the handler for x86_64?

> > Incidentally: I noticed that armeb is missing from qemu_target_list. Is
> > that intentional?
> no. please fix it :)

Will do.

> > Okay?
> It looks good to me.

Based on the above I now lean towards the following assignments:

 arm_family=arm
[...]
-armeb_family=arm
+armeb_family=armeb
[...] 
 aarch64_family=arm
[...]
-aarch64_be_family=arm
+aarch64_be_family=armeb

This would be in line with what you recommended, how i386/x86_64 is
treated and reflects the principal platform capabilities.
-- 
Bye,
Michael