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Re: [Qemu-devel] [PATCH] linux-user, s390x: ignore OS ABI value in ELF h


From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-devel] [PATCH] linux-user, s390x: ignore OS ABI value in ELF header
Date: Sun, 12 Nov 2017 14:24:43 -0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0

On 11/12/2017 06:23 AM, Laurent Vivier wrote:
> Le 12/11/2017 à 07:56, Thomas Huth a écrit :
>> Am Fri, 10 Nov 2017 20:49:35 +0100
>> schrieb Laurent Vivier <address@hidden>:
>>
>>> I have this error:
>>> bash: /sbin/ldconfig: cannot execute binary file: Exec format error
>>>
>>> because /sbin/ldconfig is:
>>> ELF 64-bit MSB executable, IBM S/390, version 1 (GNU/Linux),
>>> statically linked, for GNU/Linux 3.2.0,
>>> BuildID[sha1]=90b64604014aafac9c1a0623b1cf447281d1a382, stripped
>>>
>>> OS ABI is GNU/linux
>>>
>>> "/bin/ls" works well:
>>>
>>> ELF 64-bit MSB shared object, IBM S/390, version 1 (SYSV),
>>> dynamically linked, interpreter /lib/ld64.so.1, for GNU/Linux 3.2.0,
>>> BuildID[sha1]=be9b19143d4657678846f6e5277383071fc1059a, stripped
>>>
>>> OS ABI is SYSV
>>>
>>> To be able to execute ldconfig, this patch modifies s390x binfmt mask
>>> to ignore the OS ABI value (EI_OSABI, byte 7).
>>>
>>> Signed-off-by: Laurent Vivier <address@hidden>
>>> ---
>>>  scripts/qemu-binfmt-conf.sh | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/scripts/qemu-binfmt-conf.sh b/scripts/qemu-binfmt-conf.sh
>>> index 8afc3eb5bb..e2e1b7544d 100755
>>> --- a/scripts/qemu-binfmt-conf.sh
>>> +++ b/scripts/qemu-binfmt-conf.sh
>>> @@ -85,7 +85,7 @@
>>> sh4eb_mask='\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff
>>> sh4eb_family=sh4 
>>>  
>>> s390x_magic='\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x16'
>>> -s390x_mask='\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
>>> +s390x_mask='\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff'
>>
>> If I've got that right, the OSABI field should either be 0 for
>> "No extensions or unspecified" (which is then printed  by "file"
>> as SYSV) or 3 for "GNU/Linux".
>> Thus wouldn't it be better to use a mask of 0xfc here instead, so
>> that we refuse at least everything with a value > 3 here?
> No, because with this mask you allow HPUX and NetBSD (See
> /usr/include/elf.h), I don't think it's really better. The simplest way
> to manage this is to ignore the field. A better way should be to have
> two binfmt entries, one for SYSV and one for GNU/Linux, but as our goal
> is to run linux binaries on linux system, is it worth it?

This was my first thought when I reviewed your patch, this indeed looks
cleaner and would be self-explanatory.

Regards,

Phil.



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