Messages in this thread | | | Date | Mon, 8 Feb 2016 12:58:10 -0500 | From | Jessica Yu <> | Subject | Re: Fix ordering of ftrace/livepatch calls on module load and unload |
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+++ Josh Poimboeuf [08/02/16 11:48 -0600]: >On Fri, Feb 05, 2016 at 10:08:15PM -0500, Jessica Yu wrote: >> As explained here [1], livepatch modules are failing to initialize properly >> because the ftrace coming module notifier (which calls >> ftrace_module_enable()) runs *after* the livepatch module notifier (which >> enables the patch(es)). Thus livepatch attempts to apply patches to >> modules before ftrace_module_enable() is even called for the corresponding >> module(s). As a result, patch modules break. Ftrace code must run before >> livepatch on module load, and the reverse is true on module unload. >> >> For ftrace and livepatch, order of initialization (plus exit/cleanup code) is >> important for loading and unloading modules, and using module notifiers to >> perform this work is not ideal since it is not always clear what gets called >> when. In this patchset, dependence on the module notifier call chain is removed >> in favor of hard coding the corresponding function calls in the module loader. >> This promotes better code visibility and ensures that ftrace and livepatch code >> get called in the correct order on patch module load and unload. >> >> Tested the changes with a test livepatch module that patches 9p and nilfs2, >> and verified that the issue described in [1] is fixed. > >Since Rusty agreed to your suggested changes for splitting up >complete_formation() and for setting mod->state = MODULE_STATE_GOING >before calling the going notifiers in the error path, can you do a v4 >with those changes? They should probably be split up like: > >1. split up complete_formation() >2. set MODULE_STATE_GOING before calling going notifiers in error path >3. remove ftrace module notifier >4. remove livepatch module notifier
Sure, I'll do that.
Jessica
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