Messages in this thread | | | From | Song Shuai <> | Date | Tue, 22 Nov 2022 02:28:25 +0000 | Subject | Re: [PATCH] ftrace: avoid replacing the list func with itself |
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Song Shuai <suagrfillet@gmail.com> 于2022年10月26日周三 13:20写道: > > The list func (ftrace_ops_list_func) will be patched first > before the transition between old and new calls are set, > which fixed the race described in this commit `59338f75`. > > While ftrace_trace_function changes from the list func to a > ftrace_ops func, like unregistering the klp_ops to leave the only > global_ops in ftrace_ops_list, the ftrace_[regs]_call will be > replaced with the list func although it already exists. So there > should be a condition to avoid this. > > This patch backups saved_ftrace_func by saved_ftrace_func_old > which will be compared with the list func before trying to patch it. > Ping...
Thanks, Song > Signed-off-by: Song Shuai <suagrfillet@gmail.com> > --- > kernel/trace/ftrace.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index bc921a3f7ea8..56b1a42e1937 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -2755,6 +2755,8 @@ void __weak ftrace_arch_code_modify_post_process(void) > { > } > > +static ftrace_func_t saved_ftrace_func_old; > + > void ftrace_modify_all_code(int command) > { > int update = command & FTRACE_UPDATE_TRACE_FUNC; > @@ -2774,7 +2776,7 @@ void ftrace_modify_all_code(int command) > * to make sure the ops are having the right functions > * traced. > */ > - if (update) { > + if (update && saved_ftrace_func_old != ftrace_ops_list_func) { > err = ftrace_update_ftrace_func(ftrace_ops_list_func); > if (FTRACE_WARN_ON(err)) > return; > @@ -2918,6 +2920,7 @@ static void ftrace_trampoline_free(struct ftrace_ops *ops) > static void ftrace_startup_enable(int command) > { > if (saved_ftrace_func != ftrace_trace_function) { > + saved_ftrace_func_old = saved_ftrace_func; > saved_ftrace_func = ftrace_trace_function; > command |= FTRACE_UPDATE_TRACE_FUNC; > } > @@ -3007,6 +3010,7 @@ int ftrace_shutdown(struct ftrace_ops *ops, int command) > ops->flags &= ~FTRACE_OPS_FL_ENABLED; > > if (saved_ftrace_func != ftrace_trace_function) { > + saved_ftrace_func_old = saved_ftrace_func; > saved_ftrace_func = ftrace_trace_function; > command |= FTRACE_UPDATE_TRACE_FUNC; > } > @@ -8321,6 +8325,7 @@ static void ftrace_startup_sysctl(void) > > /* Force update next time */ > saved_ftrace_func = NULL; > + saved_ftrace_func_old = NULL; > /* ftrace_start_up is true if we want ftrace running */ > if (ftrace_start_up) { > command = FTRACE_UPDATE_CALLS; > -- > 2.20.1 >
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