linux-kernel - Re: [PATCH 1/many] PROC macro to annotate functions in assembly files

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Date:	Thu, 18 Dec 2008 19:05:41 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Alexander van Heukelum <heukelum@...tmail.fm>
Cc:	Sam Ravnborg <sam@...nborg.org>, Jan Beulich <jbeulich@...ell.com>,
	linux-arch@...r.kernel.org,
	Alexander van Heukelum <heukelum@...lshack.com>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/many] PROC macro to annotate functions in assembly
	files

[Alexander van Heukelum - Thu, Dec 18, 2008 at 01:40:55PM +0100]
| 
| On Thu, 18 Dec 2008 15:03:25 +0300, "Cyrill Gorcunov"
| <gorcunov@...il.com> said:
| > On Thu, Dec 18, 2008 at 12:51 PM, Alexander van Heukelum
| > <heukelum@...tmail.fm> wrote:
| > [...]
| > >> >
| > >> > Sam, I think eventually we should get something like this:
| > >> >
| > >> > - KPROBE will be eliminated and explicit section descriptions
| > >> >   are to be used
| > >> > - ENTRY could be used / or renamed for something more descriptive
| > >> >   and being used aligned jmp targets or in case of procs with
| > >> >   shared body
| > >
| > > I don't think ENTRY should be used for nested procedures. If the
| > > author wants to do something like that, he better knew something
| > > about the assembler anyhow.
| > 
| > Author anyway have to knew something. We can't bring some kind
| > of lexical machine that eliminate this needing :)
| > 
| > >
| > >> > - PROC/ENDPROC are to replace old ENTRY/END for procs being called
| > >> >   mostly from C code
| > >
| > > Currently there is many different patterns. Some functions use ENTRY
| > > without END, some use ENTRY/ENDPROC, some use ENDPROC without annotation
| > > at the start...
| > 
| > Alexander, I was just trying to say Sam about what we're planning to get
| > at the end of all this procedure. I mean I know there are some issues to
| > be fixed first.
| 
| I understood, but I wanted to avoid the meme that this procedure is
| just ebout renaming ENTRY->PROC and END->ENDPROC ;).

I wish it would be just renaming :-)

| 
| > Fix me if I'm wrong.
| > 
| > >
| > >> So what prevents us from extending ENTRY/END instead of introducing
| > >> another set?
| > >
| > > ENTRY/END alone is not enough if one wants to be able to distinguish
| > > between code (functions) and non-executed data.
| > >
| > >> Let us try to extend what we have and not introduce something new.
| > >
| > > Agreed. I vote to complement the existing ENDPROC annotation with
| > > the proposed PROC annotation. Let's call that an extension, not
| > > something new ;). As it stands it is not impossible to go with
| > > ENTRY/ENDPROC for code and ENTRY/END for data. However, ENTRY
| > > implies alignment and the prefered alignment for code and data
| > > might differ.
| > 
| > If ENTRY will be used for data objects it shouldn't contain any kind of
| > alignment since in general we could have arrays of bytes, words and so
| > on.
| 
| I would suggest using sizeof(long) alignment for data.

Maybe we could use more flexible scheme? Lets imagine we could
need to use not sizeof(long) on x86-64 for example... say in
boot/compressed/head_64.S... say for boot_heap. Should we use
DATAENTRY here? Or it's planned to use DATAENTRY for global defs
only? Alexander, don't get me wrong I'm just starting to confuse
with ENRTY/PROC/DATAENTRY :)

Letme try to classify them a bit (like they would be used in future).
If we have them classified it would be easier to distinguish their
usage and how they should be implemented

- PROC/ENDPROC for "C" callers
	- they are: aligned, .global, .size and .type and @function
- DATA/ENDDATA for data objects
	- they are: aligned as sizeof(long), .global, .size

right?

| 
| Greetings,
|    Alexander
| -- 
|   Alexander van Heukelum
|   heukelum@...tmail.fm

		- Cyrill -

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