Re: Re: ftrace/kprobes: Warning when insmod two modules
(2014/04/22 14:29), Takao Indoh wrote: > (2014/04/22 12:51), Rusty Russell wrote: >> Steven Rostedt writes: >>> On Mon, 24 Mar 2014 20:26:05 +0900 >>> Masami Hiramatsu wrote: >>> >>> Thank you for reporting with this pretty backtrace :) Steven, I think this is not the kprobe bug but ftrace (and perhaps, module). >>> >>> Looks to be more of a module issue than a ftrace issue. >>> If the ftrace can set loading module text read only before the module subsystem expected, I think it should be protected by the module subsystem itself (e.g. set_all_modules_text_ro(rw) skips the modules which is MODULE_STATE_COMING) >>> >>> Does this patch fix it? >>> >>> In-review-off-by: Steven Rostedt >> >> Sorry, was on paternity leave. >> >> I'm always nervous about adding more states, since every place which >> examines the state has to be audited. >> >> We set the mod->state to MOD_STATE_COMING in complete_formation; >> why don't we set NX there instead? It also makes more sense to >> set NX before we hit parse_args() which can execute code in the module. >> >> In fact, we should probably call the notifier there too, so people >> can breakpoint/tracepoint/etc parameter calls. >> >> Of course, this means that we set NX before the notifier; does anything >> break? > > This does not work. ftrace_process_locs() is called from the notifier, > and it tries to change its text like this. > > load_module > blocking_notifier_call_chain > ftrace_module_notify_enter > ftrace_init_module > ftrace_process_locs > sort > ftrace_swap_ips > > But the text is already RO, so it causes panic. We need to call notifier > before setting it RO. Or should we unset RO temporarily in > ftrace_process_locs()? Perhaps, IMHO, ftrace needs to change the module RW in ftrace_init_module and makes it RO after modifying the module text. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: Re: ftrace/kprobes: Warning when insmod two modules
(2014/04/22 14:29), Takao Indoh wrote: (2014/04/22 12:51), Rusty Russell wrote: Steven Rostedt rost...@goodmis.org writes: On Mon, 24 Mar 2014 20:26:05 +0900 Masami Hiramatsu masami.hiramatsu...@hitachi.com wrote: Thank you for reporting with this pretty backtrace :) Steven, I think this is not the kprobe bug but ftrace (and perhaps, module). Looks to be more of a module issue than a ftrace issue. If the ftrace can set loading module text read only before the module subsystem expected, I think it should be protected by the module subsystem itself (e.g. set_all_modules_text_ro(rw) skips the modules which is MODULE_STATE_COMING) Does this patch fix it? In-review-off-by: Steven Rostedt rost...@goodmis.org Sorry, was on paternity leave. I'm always nervous about adding more states, since every place which examines the state has to be audited. We set the mod-state to MOD_STATE_COMING in complete_formation; why don't we set NX there instead? It also makes more sense to set NX before we hit parse_args() which can execute code in the module. In fact, we should probably call the notifier there too, so people can breakpoint/tracepoint/etc parameter calls. Of course, this means that we set NX before the notifier; does anything break? This does not work. ftrace_process_locs() is called from the notifier, and it tries to change its text like this. load_module blocking_notifier_call_chain ftrace_module_notify_enter ftrace_init_module ftrace_process_locs sort ftrace_swap_ips But the text is already RO, so it causes panic. We need to call notifier before setting it RO. Or should we unset RO temporarily in ftrace_process_locs()? Perhaps, IMHO, ftrace needs to change the module RW in ftrace_init_module and makes it RO after modifying the module text. Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
