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Re: [Qemu-devel] [PATCH 1/5] target-tile: Firstly add to qemu with minim

From: Chen Gang S
Subject: Re: [Qemu-devel] [PATCH 1/5] target-tile: Firstly add to qemu with minimized features
Date: Tue, 17 Feb 2015 11:18:40 +0800
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

And of cause, it is not the excuse to let me stop:

 - I shall integrate binutils disassembler firstly in my own branch for
   the related test and learning.

 - According to binutils disassembler implementation, I shall write
   translate.c step by step.

 - After finish translate.c, I shall send related patch to qemu mailing
   list without binutils disassembler integration.

For me, I guess, it is legal.


On 2/17/15 11:11, Chen Gang S wrote:
> On 2/17/15 10:48, Chen Gang S wrote:
>> On 2/17/15 08:11, Chris Metcalf wrote:
>>> On 2/16/2015 6:46 PM, Peter Maydell wrote:
>>>> On 17 February 2015 at 08:08, Chen Gang S <address@hidden> wrote:
>>>>> On 2/16/15 23:24, Max Filippov wrote:
>>>>>> Disassembler is not a crucial part of QEMU target.
>>>>> For me, it is necessary. We need disassemble target binary instructions
>>>>> (recognize them), then translate them into tcg instructions which are
>>>>> grouped by Translate Block.
>>>> No, Max is correct. What QEMU calls the "disassembler" is just
>>>> used for debug logging: it is code that goes from target binary
>>>> instructions to printed display of assembly language instructions.
>>>> This is completely separate code from the code in target-*/translate.c
>>>> which decodes target binary instructions and emits TCG opcodes.
>>>> That code is generally called the translator or the decoder, and
>>>> it is always written from scratch specifically for QEMU. Don't
>>>> try to reuse code from binutils there.
>>> The kernel disassembly that Chen Gang is looking at is basically just an
>>> instruction recognizer; it doesn't even include text strings for opcodes,
>>> for example.  But my guess is that it is exactly the right starting building
>>> block for decoding target binary instructions.
>> Excuse me, I am not quite familiar with the GPL license, so I guess we
>> are misunderstanding with each other.
>>  - it is necessary to disassemble/decode target binary instructions.
>>  - I want to write the decoder in translate.c according to binutils/
>>    kernel disassembler (also need consider about "BFD_RELOC" and
>>    "!__KERNEL__ && !__LIBC__").
>>  - If I reference to binutils source code, I am not quite sure whether I
>>    break the license or not (is it illegal?).
> Originally, I really wanted to print the disassembly code, although I
> knew it is optional (not necessary), just like all of you said (and
> originally, I was not quite sure DISASM_ONLY, either).
> Thanks.

Chen Gang

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