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

[H. Peter Anvin]

Jeremy Fitzhardinge wrote:
> > Its loaded at __per_cpu_load but the symbols have addresses starting 
> > at 0.
>
> Yes, which leads to an odd-looking ELF file where the Phdrs aren't 
> sorted by virtual address order.  I'm wondering what would happen if a 
> bootloader that actually understood ELF files tried to load it as an 
> actual ELF file...

If it is implemented correctly, it will work.  It might trigger bugs in 
such loaders, however.

> > Hmmm.... we could add the relocation offset to __per_cpu_load? 
> > __per_cpu_load is used very sparingly. Basically only useful during 
> > early boot and when a new per cpu area has to be setup. In that case 
> > we want to copy from __per_cpu_load to the newly allocated percpu area.
>
> Yes, it should be fairly easy to manually relocate it by applying the 
> (load - link) offset to it.

Seems easy enough, and as already stated, this is not 
performance-critical so a few extra instructions is pretty much a non-issue.

	-hpa
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