Re: [PATCH 6/10] lguest code: the little linux hypervisor.

[Zachary Amsden]

Rusty Russell wrote:
> On Fri, 2007-02-09 at 01:35 -0800, Andrew Morton wrote:
>   
> > On Fri, 09 Feb 2007 20:20:27 +1100 Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote:
> >
> >     
> > > +#define log(...)					\
> > > +	do {						\
> > > +		mm_segment_t oldfs = get_fs();		\
> > > +		char buf[100];				\
> > > +		sprintf(buf, "lguest:" __VA_ARGS__);	\
> > > +		set_fs(KERNEL_DS);			\
> > > +		sys_write(1, buf, strlen(buf));		\
> > > +		set_fs(oldfs);				\
> > > +	} while(0)
> > >       
> > Due to gcc shortcomings, each instance of this will chew an additional 100
> > bytes of stack.  Unless they fixed it recently.  Is a bit of a timebomb.  I
> > guess ksaprintf() could be used.
> >
> > It also looks a bit, umm, innovative.
> >     
>
> It's also unused 8)
>
> It's an extremely useful macro for doing grossly invasive logging of the
> guest.  I'll drop it if you prefer.
>   

Yes, it is a bit, umm, innovative.  If it is going to be kept, even if 
just for devel logging, you should disable interrupts around it.  
Changing segments is not a normal thing to do.

Zach
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