Re: [PATCH] [RFC][PATCH] kvm: kvmtrace: kvmtrace_format for supporting big_endian

[Avi Kivity <avi@qumranet.com>]

Tan, Li wrote:
> -----Original Message-----
> From: Avi Kivity [mailto:avi@qumranet.com] 
> Sent: 2008年5月21日 0:23
> To: Tan, Li
> Cc: kvm@vger.kernel.org
> Subject: Re: [PATCH] [RFC][PATCH] kvm: kvmtrace: kvmtrace_format for supporting big_endian
>
> Tan, Li wrote:
>   
>> From 9d39264bdfb00a1a717074e486a948a578547c50 Mon Sep 17 00:00:00 2001
>> From: Tan Li <li.tan@intel.com>
>> Date: Tue, 20 May 2008 09:14:41 +0800
>> Subject: [PATCH] [RFC][PATCH] kvm: kvmtrace: kvmtrace_format for
>> supporting big_endian
>>
>> Currently kvmtrace is not portable, and prevent from copying a trace
>> file from big-endian target to little-endian workstation for analysis.
>>
>> In the patch, kvmtrace_format reads and checks the magic number from
>> trace log. if needed, then change bytes order of all fields in records
>> followed.
>>
>>  
>> +def reverse_bytes(origin, bytes_cnt):
>> +	i = 0
>> +	rtn = 0L
>> +	while i < bytes_cnt:
>> +		i = i + 1
>> +	        b = origin & 0xff
>> +		origin = origin >> 8
>> +		rtn = (rtn << 8) + b
>> +	return rtn
>> +
>> +def reverse_int(origin):
>> +	return reverse_bytes(origin, 4)
>> +
>> +def reverse_qword(origin):
>> +	return reverse_bytes(origin, 8)
>> +
>>  def sighand(x,y):
>>      global interrupted
>>      interrupted = 1
>> @@ -100,18 +116,40 @@ D2REC  = "II"
>>  D3REC  = "III"
>>  D4REC  = "IIII"
>>  D5REC  = "IIIII"
>> +KMAGIC  = "I"
>>   
>>     
>
> The python struct module supports reading big-endian and little-endian 
> data.  So you can simply switch the format strings if you have the wrong 
> endianness.
>
>   
> [tan] thanks for your comments. Then it looks like:
> def reverse_int(origin):
>         s = struct.pack('<I', origin)
>         return struct.unpack('>I', s)
>
> def reverse_qword(origin):
>         s = struct.pack('<Q', origin)
>         return struct.unpack('>Q', s)
>   

I meant, you can change the definitions of D3REC, D4REC, etc. and not
worry about reversing once you've decoded the magic word.

-- 
error compiling committee.c: too many arguments to function