(2015/01/19 20:21), Wang Nan wrote: > On 2015/1/19 17:05, Masami Hiramatsu wrote: >> Hi Wang, >> >> I've found a problem on this patch, since kprobes calls unoptioize_kprobe >> with kprobes_all_disarmed=true when trying to disable all kprobes, this >> cause a serious problem. >> >> Moreover, I couldn't reproduce your reported bug on my 3.19-rc4 kernel. >> Could you test it again? >> > > I tested it again based on 3.19-rc5 and found that the problem still exists. > My testing is based on QEMU. > > First I tested my kprobeopt for ARM, then on x86_64. The test results are > pasted > at the bottom of this mail. Commands after 'gdb attaches to QEMU' is my > actions > on a gdb console attached to QEMU; commands after 'inside virtual machine' is > what I do in Linux run under QEMU.
Thank you for the reporting. So, now I know what happened, the problem is "debugfs/kprobes/enabled doesn't work correctly on optimized kprobes". Please make update the patch description. I also reproduced the bug without gdb. Here is the log. ---- [root@localhost ~]# cd /sys/kernel/debug/tracing/ [root@localhost tracing]# echo p do_fork+5 > kprobe_events # setup new event [root@localhost tracing]# echo $$ > set_ftrace_pid # trace only this process [root@localhost tracing]# echo 1 > events/kprobes/p_do_fork_5/enable # enable it [root@localhost tracing]# cat trace # check the trace data # tracer: nop # # entries-in-buffer/entries-written: 1/1 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | bash-3883 [006] d... 279.799023: p_do_fork_5: (do_fork+0x5/0x360) # OK, now tracing [root@localhost tracing]# cat ../kprobes/list ffffffff810bc1c5 k do_fork+0x5 [OPTIMIZED] # and it is actually optimized [root@localhost tracing]# echo 0 > ../kprobes/enabled # disable *ALL* kprobes [root@localhost tracing]# echo > trace # clear events [root@localhost tracing]# cat trace # this should show empty buffer # tracer: nop # # entries-in-buffer/entries-written: 1/1 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | bash-3883 [006] d... 337.770785: p_do_fork_5: (do_fork+0x5/0x360) # But still tracing! [root@localhost tracing]# cat trace # Check again # tracer: nop # # entries-in-buffer/entries-written: 2/2 #P:8 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | bash-3883 [006] d... 337.770785: p_do_fork_5: (do_fork+0x5/0x360) bash-3883 [006] d... 345.592178: p_do_fork_5: (do_fork+0x5/0x360) # We are tracing!! So, after global disabling kprobes, ALL kprobes event should be disabled, but not. OK, I think your first patch is better than the second one, but not enough. What we should do is use kprobes_all_disarmed for force option like below. unoptimize_kprobe(p, kprobes_all_disarmed); /* Try to unoptimize */ We also would better to check the flag in unregistering path for skipping unneeded disarming process when kprobes globally disarmed. 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/