Re: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpuarea

[Jeremy Fitzhardinge]

Mike Travis wrote:
> Eric W. Biederman wrote:
>   
> > Mike Travis <travis@xxxxxxx> writes:
> >     
> ...
>   
> > > Can we generate a new symbol which would account for LOAD_OFFSET?
> > >       
> > Ouch.  Absolute symbols indeed.  On the 32bit kernel that may play havoc
> > with the relocatable kernel, although we have had similar absolute logic
> > for the last year. With __per_cpu_start and __per_cpu_end so it may
> > not be a problem.
> >
> > To initialize the percpu data you do want to talk to the virtual address
> > at __per_coup_load.  But it is absolute Ugh.  
> >
> > It might be worth saying something like.
> > .data.percpu.start : AT(.data.percpu.dummy - LOAD_OFFSET) {
> > 	DATA(0)                   
> > 	. = ALIGN(align);
> >         __per_cpu_load = . ;                   
> > }
> > To make __per_cpu_load a relative symbol. ld has a bad habit of taking
> > symbols out of empty sections and making them absolute.  Which is why
> > I added the DATA(0).
> >
> > Still I don't think that would be the 64bit problem.
> >
> > Eric
> >     
>
> FYI, I did try this out and it caused the bootloader to scramble the
> loaded data.  The first corruption I found was the .x86cpuvendor.init
> section contained all zeroes.

Well, that's what appeared to be happening with the pre-initialized GDT 
as well, so I'm not sure that's a new symptom.

   J
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