From 7162431dcf72032835d369c8d7b51311df407938 Mon Sep 17 00:00:00 2001 From: Miroslav Benes Date: Wed, 16 Oct 2019 13:33:13 +0200 Subject: ftrace: Introduce PERMANENT ftrace_ops flag Livepatch uses ftrace for redirection to new patched functions. It means that if ftrace is disabled, all live patched functions are disabled as well. Toggling global 'ftrace_enabled' sysctl thus affect it directly. It is not a problem per se, because only administrator can set sysctl values, but it still may be surprising. Introduce PERMANENT ftrace_ops flag to amend this. If the FTRACE_OPS_FL_PERMANENT is set on any ftrace ops, the tracing cannot be disabled by disabling ftrace_enabled. Equally, a callback with the flag set cannot be registered if ftrace_enabled is disabled. Link: http://lkml.kernel.org/r/20191016113316.13415-2-mbenes@suse.cz Reviewed-by: Petr Mladek Reviewed-by: Kamalesh Babulal Signed-off-by: Miroslav Benes Signed-off-by: Steven Rostedt (VMware) --- include/linux/ftrace.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 8a8cb3c401b2..8385cafe4f9f 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -142,6 +142,8 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops); * PID - Is affected by set_ftrace_pid (allows filtering on those pids) * RCU - Set when the ops can only be called when RCU is watching. * TRACE_ARRAY - The ops->private points to a trace_array descriptor. + * PERMANENT - Set when the ops is permanent and should not be affected by + * ftrace_enabled. */ enum { FTRACE_OPS_FL_ENABLED = 1 << 0, @@ -160,6 +162,7 @@ enum { FTRACE_OPS_FL_PID = 1 << 13, FTRACE_OPS_FL_RCU = 1 << 14, FTRACE_OPS_FL_TRACE_ARRAY = 1 << 15, + FTRACE_OPS_FL_PERMANENT = 1 << 16, }; #ifdef CONFIG_DYNAMIC_FTRACE -- cgit v1.2.3