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 03:18:34PM +0100, Laurent Vivier wrote:

> > +aarch64_be_magic='\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7'
> > +aarch64_be_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
> > +aarch64_be_family=arm

> You need a different family, something like "armbe", to let
> qemu_set_binfmts() registers aarch64_be on aarch64 and vice-versa.

> The principle is binaries of a given family can be executed natively on
> the host of the same family, so we don't want to register a binfmt
> handler. Is that the case between aarch64 and arch64_be?

Right, while the CPU certainly is capable of switching endianess on the
fly I'm not sure if there is any multilib/multiarch userland setup and
kernel interface that would support mixed little/big-endianess of
arm or aarch64 binaries. Even if, it would likely need further detection
in the script to make sure it's there.

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.

Incidentally: I noticed that armeb is missing from qemu_target_list. Is
that intentional?

How about the following changes, maybe split into two patches "add
armeb" and "separate ARM CPU families"?

diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
index d69953525c..69ebfe7a6e 100755
--- a/scripts/qemu-binfmt-conf.sh
+++ b/scripts/qemu-binfmt-conf.sh
@@ -2,7 +2,7 @@
 # enable automatic i386/ARM/M68K/MIPS/SPARC/PPC/s390/HPPA
 # program execution by the kernel
 
-qemu_target_list="i386 i486 alpha arm sparc32plus ppc ppc64 ppc64le m68k \
+qemu_target_list="i386 i486 alpha arm armeb sparc32plus ppc ppc64 ppc64le m68k 
\
 mips mipsel mipsn32 mipsn32el mips64 mips64el \
 sh4 sh4eb s390x aarch64 aarch64_be hppa"
 
@@ -24,7 +24,7 @@ arm_family=arm
 
 
armeb_magic='\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28'
 
armeb_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
-armeb_family=arm
+armeb_family=armeb
 
 
sparc_magic='\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x02'
 
sparc_mask='\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
@@ -90,11 +90,11 @@ s390x_family=s390x
 
 
aarch64_magic='\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7\x00'
 
aarch64_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff'
-aarch64_family=arm
+aarch64_family=aarch64
 
 
aarch64_be_magic='\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xb7'
 
aarch64_be_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
-aarch64_be_family=arm
+aarch64_be_family=aarch64_be
 
 
hppa_magic='\x7f\x45\x4c\x46\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x0f'
 
hppa_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'

Okay?
-- 
bye, Michael