Messages in this thread | | | Date | Wed, 14 Feb 2018 11:34:07 -0600 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 1/3] jump_label: Warn on failed jump_label patch |
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On Wed, Feb 14, 2018 at 12:18:20PM -0500, Jason Baron wrote: > > > On 02/14/2018 12:01 PM, Steven Rostedt wrote: > > On Wed, 14 Feb 2018 10:40:41 -0600 > > Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > > >> When the jump label code encounters an address which isn't recognized by > >> kernel_text_address(), it just silently fails. > >> > >> This can be dangerous because jump labels are used in a variety of > >> places, and are generally expected to work. Convert the silent failure > >> to a warning. > > > > I made ftrace function tracing work on init code, can we do the same > > with tracepoints (aka jump labels)? > > > > jump labels do work on init code, except they don't work on it after it > has been freed :) > > It uses 'kernel_text_address()', which will return true for init code if > system_state < SYSTEM_RUNNING. See: core_kernel_text(). > > So I'm guessing that the warnings here are coming from init code that > has already been freed. Are we sure that these warnings are coming from > init code that hasn't already been freed?
Ah, I see. I missed that 'system_state < SYSTEM_RUNNING' check. It was nicely hidden. :-)
So I guess patches 2 & 3 can be dropped, as those tracepoints can still be used during boot.
And in patch 1 the warning conditions need to be tweaked a bit to exclude the __init case.
-- Josh
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