[PATCH 5.8 354/464] ftrace: Fix ftrace_trace_task return value

From: Greg Kroah-Hartman
Date: Mon Aug 17 2020 - 11:42:50 EST


From: Josef Bacik <josef@xxxxxxxxxxxxxx>

[ Upstream commit c58b6b0372de0d4cd0536d6585addd1b36b151ae ]

I was attempting to use pid filtering with function_graph, but it wasn't
allowing anything to make it through. Turns out ftrace_trace_task
returns false if ftrace_ignore_pid is not-empty, which isn't correct
anymore. We're now setting it to FTRACE_PID_IGNORE if we need to ignore
that pid, otherwise it's set to the pid (which is weird considering the
name) or to FTRACE_PID_TRACE. Fix the check to check for !=
FTRACE_PID_IGNORE. With this we can now use function_graph with pid
filtering.

Link: https://lkml.kernel.org/r/20200725005048.1790-1-josef@xxxxxxxxxxxxxx

Fixes: 717e3f5ebc82 ("ftrace: Make function trace pid filtering a bit more exact")
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/trace/ftrace.c | 3 ---
kernel/trace/trace.h | 7 ++++++-
2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 1903b80db6ebc..7d879fae3777f 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -139,9 +139,6 @@ static inline void ftrace_ops_init(struct ftrace_ops *ops)
#endif
}

-#define FTRACE_PID_IGNORE -1
-#define FTRACE_PID_TRACE -2
-
static void ftrace_pid_func(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *op, struct pt_regs *regs)
{
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f21607f871891..610d21355526d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1103,6 +1103,10 @@ print_graph_function_flags(struct trace_iterator *iter, u32 flags)
extern struct list_head ftrace_pids;

#ifdef CONFIG_FUNCTION_TRACER
+
+#define FTRACE_PID_IGNORE -1
+#define FTRACE_PID_TRACE -2
+
struct ftrace_func_command {
struct list_head list;
char *name;
@@ -1114,7 +1118,8 @@ struct ftrace_func_command {
extern bool ftrace_filter_param __initdata;
static inline int ftrace_trace_task(struct trace_array *tr)
{
- return !this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid);
+ return this_cpu_read(tr->array_buffer.data->ftrace_ignore_pid) !=
+ FTRACE_PID_IGNORE;
}
extern int ftrace_is_dead(void);
int ftrace_create_function_files(struct trace_array *tr,
--
2.25.1