[RFC][PATCH 12/14 v2] function_graph: Move graph notrace bit to shadow stack global var

From: Steven Rostedt
Date: Mon May 20 2019 - 10:25:06 EST


From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

The use of the task->trace_recursion for the logic used for the function
graph no-trace was a bit of an abuse of that variable. Now that there exists
global vars that are per stack for registered graph traces, use that instead.

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
kernel/trace/trace.h | 16 +++++++++-------
kernel/trace/trace_functions_graph.c | 10 ++++++----
2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index c466c8a1a8cf..da623dd71b0c 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -566,13 +566,6 @@ enum {
* can only be modified by current, we can reuse trace_recursion.
*/
TRACE_IRQ_BIT,
-
- /*
- * To implement set_graph_notrace, if this bit is set, we ignore
- * function graph tracing of called functions, until the return
- * function is called to clear it.
- */
- TRACE_GRAPH_NOTRACE_BIT,
};

#define trace_recursion_set(bit) do { (current)->trace_recursion |= (1<<(bit)); } while (0)
@@ -926,8 +919,17 @@ enum {

TRACE_GRAPH_DEPTH_START_BIT,
TRACE_GRAPH_DEPTH_END_BIT,
+
+ /*
+ * To implement set_graph_notrace, if this bit is set, we ignore
+ * function graph tracing of called functions, until the return
+ * function is called to clear it.
+ */
+ TRACE_GRAPH_NOTRACE_BIT,
};

+#define TRACE_GRAPH_NOTRACE (1 << TRACE_GRAPH_NOTRACE_BIT)
+
static inline unsigned long ftrace_graph_depth(unsigned long *task_var)
{
return (*task_var >> TRACE_GRAPH_DEPTH_START_BIT) & 3;
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 054ec91e5086..20ee84350f43 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -125,6 +125,7 @@ static inline int ftrace_graph_ignore_irqs(void)
int trace_graph_entry(struct ftrace_graph_ent *trace,
struct fgraph_ops *gops)
{
+ unsigned long *task_var = fgraph_get_task_var(gops);
struct trace_array *tr = gops->private;
struct trace_array_cpu *data;
unsigned long flags;
@@ -133,11 +134,11 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
int cpu;
int pc;

- if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT))
+ if (*task_var & TRACE_GRAPH_NOTRACE)
return 0;

if (ftrace_graph_notrace_addr(trace->func)) {
- trace_recursion_set(TRACE_GRAPH_NOTRACE_BIT);
+ *task_var |= TRACE_GRAPH_NOTRACE_BIT;
/*
* Need to return 1 to have the return called
* that will clear the NOTRACE bit.
@@ -239,6 +240,7 @@ void __trace_graph_return(struct trace_array *tr,
void trace_graph_return(struct ftrace_graph_ret *trace,
struct fgraph_ops *gops)
{
+ unsigned long *task_var = fgraph_get_task_var(gops);
struct trace_array *tr = gops->private;
struct trace_array_cpu *data;
unsigned long flags;
@@ -248,8 +250,8 @@ void trace_graph_return(struct ftrace_graph_ret *trace,

ftrace_graph_addr_finish(gops, trace);

- if (trace_recursion_test(TRACE_GRAPH_NOTRACE_BIT)) {
- trace_recursion_clear(TRACE_GRAPH_NOTRACE_BIT);
+ if (*task_var & TRACE_GRAPH_NOTRACE) {
+ *task_var &= ~TRACE_GRAPH_NOTRACE;
return;
}

--
2.20.1