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SubjectRe: [PATCH 0/3] ftrace: handle kernel code remove

* Steven Rostedt <rostedt@goodmis.org> wrote:

> The dynamic ftrace feature keeps a table of all the places that call
> mcount to either disable them (replacing them with nops) or to enable
> them (calling some trace function).
>
> This table of functions is also displayed to the user interface to let
> users enable or disable specific functions. This allows users to only
> trace some functions within the kernel.
>
> When a module or init sections are removed, the pointers to their
> locations still exist in this table. To protect against faults and
> writing over other text, fault handling and code comparing is done.
> When the code is update, the code being replaced is calculated and
> compared to the actual text that is being replaced, if the code does
> not match what is expected to be there, the change is not made.
>
> There is a very small chance that the wrong text (or perhaps a data
> section) could match the call to mcount and an inappropriate
> modification could be made.
>
> This patch series adds ftrace_release, to allow a module to remove the
> pointers to the mcount callers in the module from this table.
>
> Also, __init has "notrace" added to it so that text in the init
> section are not traced. The trace currently can not be enabled until
> after init anyway, so this should not be a problem.

applied to tip/tracing/ftrace - thanks Steve! I merged it into
tip/master and started testing it.

Ingo


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