RFC ftrace: track dynamic ftrace update failures
Status from this message: applied to tip/tracing/ftrace, thanks Abhishek.
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- v1 RFC Latest3 patches 10 repliesApplied
Patches in v1 Applied
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/3 | ftrace: prevent freeing of all failed updatesinclude/ kernel/ | +47 | 4 replies | |
| 2/3 | ftrace: remove ftrace_ip_convertedarch/ arch/ arch/ +2 more | +0 | 1 reply | |
| 3/3 | ftrace: add debugfs entry 'failures'kernel/ | +39 | 1 reply |
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Cover letter [PATCH 0/3][RFC] ftrace: track dynamic ftrace update failures
Hi Steven/Ingo,
In dynamic ftrace any record which fails gets freed to be recycled. This happens normally during (although not limited to) tracing of init functions. In general, failures can happen due to multiple reason, such as external patching of kernel functions, instrumentation of the mcount calls-sites, hardware error etc. As an example, in the case of kprobes if a probe is installed on the mcount call site (before being converted to NOP or after) then eventually ftrace will detect it and free the corresponding record. Kprobes however will keep on single-sepping the instruction it installed the probe on.
These patches prevent freeing of records which have failed (except for init functions). This prevents re-recording of failed functions and allows tracking them so that they can be listed using a new debugfs file -> 'failures'. The main change here is preventing removal of ftrace records from ftace_hash. This way records can be looked up by their 'ip' at any time.
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Regards,
Abhishek Sagar