[for-next][PATCH 18/27] function_graph: Move graph notrace bit to shadow stack global var

From: Steven Rostedt
Date: Tue Jun 04 2024 - 10:47:28 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.

Link: https://lore.kernel.org/linux-trace-kernel/171509107907.162236.6564679266777519065.stgit@devnote2
Link: https://lore.kernel.org/linux-trace-kernel/20240603190823.796709456@xxxxxxxxxxx

Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Cc: Florent Revest <revest@xxxxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: bpf <bpf@xxxxxxxxxxxxxxx>
Cc: Sven Schnelle <svens@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Alan Maguire <alan.maguire@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Guo Ren <guoren@xxxxxxxxxx>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
include/linux/trace_recursion.h | 7 -------
kernel/trace/trace.h | 9 +++++++++
kernel/trace/trace_functions_graph.c | 10 ++++++----
3 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index fdfb6f66718a..ae04054a1be3 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -44,13 +44,6 @@ enum {
*/
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,
-
/* Used to prevent recursion recording from recursing. */
TRACE_RECORD_RECURSION_BIT,
};
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 82d879dc63ff..b37402e3f0c9 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -919,8 +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 66cce73e94f8..13d0387ac6a6 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -130,6 +130,7 @@ 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;
@@ -138,7 +139,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
int ret;
int cpu;

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

/*
@@ -149,7 +150,7 @@ int trace_graph_entry(struct ftrace_graph_ent *trace,
* returning from the function.
*/
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.
@@ -240,6 +241,7 @@ 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;
@@ -249,8 +251,8 @@ 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;
}

--
2.43.0