Re: [PATCH 1/3] x86: record relocation offset

H. Peter Anvin
2009-12-30T19:50:46Z

On 12/30/2009 05:15 AM, Arnaldo Carvalho de Melo wrote:
>
> I'm no expert on the intricacies of boot_params, but all the other hunks
> seems sensible, but can't we provide a non-perf specific way of getting
> the relocate_offset? I guess other tools would also love to have it.
>
> What about systemtap, don't they solve this in some other way? Frank?
>

I at one point proposed that boot_params should be exported in toto via
sysfs. This got rather brutally shut down as "it's just a debugging
feature" and got moved to debugfs (/debug/boot_params/data). However,
the entire boot_params structure is available there.

Regardless of the reporting method, the patch passing this in by
modifying the early assembly code, though, is more than a little
pointless. The kernel already knows where it is loaded -- obviously, by
sheer necessity -- and knows how it was itself configured, and as such
we can do this calculation in C code without modifying boot_params or
the early bootstrap.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.