Simple question about powerpc kernel source.

Simple question about powerpc kernel source.

[HongWoo Lee]

Hi all,

I have something to ask for the ppc kernel source.

#define LOADADDR(rn,name)           \
    lis     rn,name##@highest;      \
    ori     rn,rn,name##@higher;    \
    rldicr  rn,rn,32,31;            \
    oris    rn,rn,name##@h;         \
    ori     rn,rn,name##@l

Is ## used for concatenation. I'm not sure because it is just meaningless.
If so what on earth is the result of concatenating ?

And is there a good reference to understand powerpc asm ?
I'm reading Power ISA, but I can't find @highest, @higher and ##.
It would be good to know the reference book.

Thanks in advance.


Regards,
HongWoo.

Re: Simple question about powerpc kernel source.

[Benjamin Herrenschmidt]

On Mon, 2009-07-20 at 18:00 +0900, HongWoo Lee wrote:
> Hi all,
> 
> I have something to ask for the ppc kernel source.
> 
> #define LOADADDR(rn,name)           \
>     lis     rn,name##@highest;      \
>     ori     rn,rn,name##@higher;    \
>     rldicr  rn,rn,32,31;            \
>     oris    rn,rn,name##@h;         \
>     ori     rn,rn,name##@l
> 
> Is ## used for concatenation. I'm not sure because it is just meaningless.
> If so what on earth is the result of concatenating ?
> 
> And is there a good reference to understand powerpc asm ?
> I'm reading Power ISA, but I can't find @highest, @higher and ##.
> It would be good to know the reference book.

You already asked pretty much the same question with the subject "Simple
question about powerpc asm" and it was already replied to.

Cheers,
Ben.

Re: Simple question about powerpc kernel source.

[HongWoo Lee]

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-------- Original Message  --------
Subject: Re: Simple question about powerpc kernel source.
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: HongWoo Lee <hongwoo7@gmail.com>
Cc: linuxppc-dev@lists.ozlabs.org
Date: Mon Jul 20 2009 19:02:38 GMT+0900
> On Mon, 2009-07-20 at 18:00 +0900, HongWoo Lee wrote:
>   
>> Hi all,
>>
>> I have something to ask for the ppc kernel source.
>>
>> #define LOADADDR(rn,name)           \
>>     lis     rn,name##@highest;      \
>>     ori     rn,rn,name##@higher;    \
>>     rldicr  rn,rn,32,31;            \
>>     oris    rn,rn,name##@h;         \
>>     ori     rn,rn,name##@l
>>
>> Is ## used for concatenation. I'm not sure because it is just meaningless.
>> If so what on earth is the result of concatenating ?
>>
>> And is there a good reference to understand powerpc asm ?
>> I'm reading Power ISA, but I can't find @highest, @higher and ##.
>> It would be good to know the reference book.
>>     
>
> You already asked pretty much the same question with the subject "Simple
> question about powerpc asm" and it was already replied to.
>
> Cheers,
> Ben.
>
>
>   

Thank you, Ben.

First, I aleady understood about @highest, @higher, @h and @l.
For now, what I want to know is about "##" in the below code.

#define LOADADDR(rn,name)           \
    lis     rn,name##@highest;      \
    ori     rn,rn,name##@higher;    \
    rldicr  rn,rn,32,31;            \
    oris    rn,rn,name##@h;         \
    ori     rn,rn,name##@l


And I don't want to ask every detail.
So I want to know the manual or document which describes the detail.


Regards,
HongWoo.


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Re: Simple question about powerpc kernel source.

[Benjamin Herrenschmidt]

On Tue, 2009-07-21 at 09:15 +0900, HongWoo Lee wrote:
> First, I aleady understood about @highest, @higher, @h and @l. 
> For now, what I want to know is about "##" in the below code. 
> 
> #define LOADADDR(rn,name)           \
>     lis     rn,name##@highest;      \
>     ori     rn,rn,name##@higher;    \
>     rldicr  rn,rn,32,31;            \
>     oris    rn,rn,name##@h;         \
>     ori     rn,rn,name##@l
> 
> And I don't want to ask every detail. 
> So I want to know the manual or document which describes the detail. 

Well, it's just concatenation...

Ie, if you do LOADADDR(rn, .myfunction) it will turn to

   lis     rn,.myfunction@highest;
   ori     rn,rn,.myfunction@higher;
   rldicr  rn,rn,32,31;
   oris    rn,rn,.myfunction@h;
   ori     rn,rn,.myfunction@l
> 
Which means putting the address of .myfunction into register rn.

Cheers,
Ben.