On Wed, 8 May 2019 23:02:33 +0800 "chengjian (D)" <cj.chengj...@huawei.com> wrote:
> function tracer uses ftrace_caller() and livepatch uses > ftrace_regs_caller(). > > I can modify my testcase to trigger this race condition. > > > #enable livepatch > insmod klp_unshare_files.ko > cat /sys/kernel/debug/tracing/enabled_functions > unshare_files (1) R I tramp: 0xffffffffc0008000 > (klp_ftrace_handler+0x0/0xa0) ->ftrace_ops_assist_func+0x0/0xf0 > [NOW, the rec caller is ftracer_regs_caller TRAMPOLINE] > > #function tracer > echo unshare_files > /sys/kernel/debug/tracing/set_ftrace_filter > echo function > /sys/kernel/debug/tracing/current_tracer > cat /sys/kernel/debug/tracing/enabled_functions > unshare_files (2) R I ->ftrace_ops_list_func+0x0/0x170 > [NOW, the rec caller is ftracer_regs_caller] > > > # disable livepatch > echo 0 > /sys/kernel/livepatch/klp_unshare_files/enabled > rmmod klp_unshare_files > > > cat /sys/kernel/debug/tracing/enabled_functions > unshare_files (1) tramp: 0xffffffffc0005000 > (function_trace_call+0x0/0x120) ->function_trace_call+0x0/0x120 > [NOW, the rec caller is ftrace_caller TRAMPOLINE] > > So, the caller switch from regs caller back to non regs caller > when disable the livepatch. Could this testcase cause the race > condition ? BUT, Nothing happened here. > > What will happen when the race triggers ? What can I do. > I still can't think of it. But since the merge window already opened, I'd like to have this patch sit in linux-next for a bit. That is, I would wait to pull it in for the next merge window, and not this one. -- Steve
