Messages in this thread | | | Date | Fri, 30 Aug 2013 13:48:55 -0700 | From | "H. Peter Anvin" <> | Subject | Re: x86-32: Early microcode loading stumbles over disabled DYNAMIC_FTRACE |
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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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