Messages in this thread Patch in this message | | | From | Song Shuai <> | Subject | [PATCH] ftrace: avoid replacing the list func with itself | Date | Wed, 26 Oct 2022 21:20:39 +0800 |
| |
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.
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
| |