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ftrace: Create set_ftrace_notrace_pid to not trace tasks

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There's currently a way to select a task that should only be traced by
functions, but there's no way to select a task not to be traced by the
function tracer. Add a set_ftrace_notrace_pid file that acts the same as
set_ftrace_pid (and is also affected by function-fork), but the task pids in
this file will not be traced even if they are listed in the set_ftrace_pid
file. This makes it easy for tools like trace-cmd to "hide" itself from the
function tracer when it is recording other tasks.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware)
2020-03-19 23:19:06 -04:00
parent 717e3f5ebc
commit b3b1e6eded
4 changed files with 180 additions and 35 deletions
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2
kernel/trace/trace.h
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@@ -331,6 +331,7 @@ struct trace_array {
#ifdef CONFIG_FUNCTION_TRACER
struct ftrace_ops *ops;
struct trace_pid_list __rcu *function_pids;
struct trace_pid_list __rcu *function_no_pids;
#ifdef CONFIG_DYNAMIC_FTRACE
/* All of these are protected by the ftrace_lock */
struct list_head func_probes;
@@ -782,6 +783,7 @@ extern int pid_max;
bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,
pid_t search_pid);
bool trace_ignore_this_task(struct trace_pid_list *filtered_pids,
struct trace_pid_list *filtered_no_pids,
struct task_struct *task);
void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
struct task_struct *self,