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

[Laurent Vivier]

Le 20/12/2017 à 16:37, Michael Weiser a écrit :
> 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.

So it's not like on intel/AMD where we can execute a 32bit binary on a
64bit kernel?

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

no. please fix it :)

> 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?
> 

It looks good to me.

Thanks,
Laurent