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SubjectRe: x86-32: Early microcode loading stumbles over disabled DYNAMIC_FTRACE
On 08/30/2013 10:03 AM, Steven Rostedt wrote:
> On Fri, 30 Aug 2013 09:35:18 -0700
> "H. Peter Anvin" <hpa@zytor.com> wrote:
>
>> On 08/30/2013 08:51 AM, Steven Rostedt wrote:
>>>
>>> It does when dynamic tracing is enabled. But this issue is with static
>>> tracing, there's no code modification, thus all functions call
>>> mcount/__fentry__ and we need to look at a variable to determine if we
>>> should trace or not.
>>>
>>
>> And of course global variables are a no-no without special handling in
>> pre-paging mode. Sigh.
>>
>> You *could* bail out of the calling address is < PAGE_OFFSET.
>>
>
> We could do that too, as static tracing already gives us high overhead,
> I'm not sure how much more overhead another check like this even
> matters.
>
> Who uses static tracing? I only use it to test that it still works ;-)
>

Anyway... can we add this to the static tracing code? It is two
instructions and is only needed on x86-32. For performance, use dynamic.

-hpa




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