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SubjectRe: [crash, bisected] Re: [PATCH 3/4] x86_64: Fold pda into per cpu area
Eric W. Biederman wrote:
> Mike Travis <travis@sgi.com> 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.

Mike


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