On Thu, 10 Oct 2019 10:55:15 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> But we have an issue with the state of the module here, as it is still > set as MODULE_STATE_UNFORMED. Let's look at what happens if we have: > > > CPU0 CPU1 > ---- ---- > echo function > current_tracer > modprobe foo > enable foo functions to be traced > (foo function records not disabled) > echo nop > current_tracer > > disable all functions being > traced including foo functions > > arch calls set_all_modules_text_rw() > [skips UNFORMED modules, which foo still is ] > > set foo's text to read-only > foo's state to COMING > > tries to disable foo's functions > foo's text is read-only > > BUG trying to write to ro text!!! > > > Like I said, this is very subtle. It may no longer be a bug on x86 > with your patches, but it will bug on ARM or anything else that still > uses set_all_modules_text_rw() in the ftrace prepare code. I guess I should have commented this, but the big reason for the split between ftrace_module_init() and ftrace_module_enable() is that we add the nops when the module is still UNFORMED, but we only enable it when the module is COMING or beyond, and not UNFORMED. -- Steve
