Re: swsusp.S: meaningfull assembly labels

[Richard B. Johnson]

On Fri, 25 Jun 2004, Pavel Machek wrote:

> Hi!
>
> > > This introduces meaningfull labels instead of .L1234, meaning code is
> > > readable, kills alignment where unneccessary, and kills TLB flush that
> > > was only pure paranoia (and slows it down a lot on emulated
> > > systems). Please apply,
> > >
> > > 								Pavel
> > >
> > > --- linux-cvs//arch/i386/power/swsusp.S	2004-05-25 17:41:18.000000000 +0200
> > > +++ linux/arch/i386/power/swsusp.S	2004-06-24 14:39:01.000000000 +0200
> > > @@ -18,7 +18,7 @@
> > >  ENTRY(do_magic)
> > >  	pushl %ebx
> > >  	cmpl $0,8(%esp)
> > > -	jne .L1450
> > > +	jne resume
> > >  	call do_magic_suspend_1
> > >  	call save_processor_state
> > >
> ...
> > NO! You just made those labels public! The LOCAL symbols need to
> > begin with ".L".  Now, if you have a 'copy_loop' in another module,
> > linked with this, anywhere in the kernel, they will share the
> > same address -- not what you expected, I'm sure! The assembler
> > has some strange rules you need to understand. Use `nm` and you
> > will find that your new labels are in the object file!
>
> Are you sure? I thought theare not visible from other moduless unless
> "ENTRY()" is used.  See for example entry.S.
> 							Pavel

Well if you find a way to make those symbols disappear from the
object files without using ".L", please let me know. I spent
some considerable time beautifying multiple assembly-language
files on a recent project, only to find that it would fail to
link because of the "multiple symbol definition" errors. I
had to change everything back.

You can make labels like ".Lresume:" remain visible only in
the file. They don't need to be numbers. It may even be possible
to use labels like ".L_resume:", I haven't tried. Basically, if
they show up using `nm`, they can (read will) give you problems.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5570.56 BogoMips).
            Note 96.31% of all statistics are fiction.


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/