Re: [tip:perf/core] perf/x86: Fix USER/KERNEL tagging of samples

H. Peter Anvin
2012-07-31T18:13:06Z

On 07/10/2012 02:48 AM, Ingo Molnar wrote:
>
> We could read out the current GDT [the SGDT instruction] instead
> of looking at gdt_page.
>
> Then we'd have to decode that descriptor, the limit. Decide
> whether the selector points to the GDT or LDT. All the fun x86
> legacies that we mostly forgot already after two decades of
> running the kernel in flat linear mode...
>

In 32-bit mode there are actually instructions that do that work for you.

-hpa

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