[RFC PATCH 3/4] tracing: Add disable_bpf trace option to ignore eBPF for fetchargs

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Add a trace option "disable_bpf" to disable BPF execution for fetchargs,
forcing the execution to fallback to the interpreter loop. This is useful
for evaluating BPF compilation performance impact.

Assisted-by: Antigravity:gemini-3.5-flash
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/trace/trace.c            |    7 +++++++
 kernel/trace/trace.h            |    8 ++++++++
 kernel/trace/trace_probe_tmpl.h |    2 +-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c9e182d40059..7c0f7b629fcb 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9940,6 +9940,13 @@ struct trace_array *trace_get_global_array(void)
 }
 #endif
 
+#ifdef CONFIG_BPF_SYSCALL
+bool trace_probe_bpf_disabled(void)
+{
+	return !!(global_trace.trace_flags & TRACE_ITER(DISABLE_BPF));
+}
+#endif
+
 void __init early_trace_init(void)
 {
 	if (tracepoint_printk) {
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 80fe152af1dd..bf83680e0ba7 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1503,6 +1503,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
 		C(PAUSE_ON_TRACE,	"pause-on-trace"),	\
 		C(HASH_PTR,		"hash-ptr"),	/* Print hashed pointer */ \
 		C(BITMASK_LIST,		"bitmask-list"),	\
+		C(DISABLE_BPF,		"disable_bpf"),		\
 		FUNCTION_FLAGS					\
 		FGRAPH_FLAGS					\
 		STACK_FLAGS					\
@@ -2505,4 +2506,11 @@ static inline int rv_init_interface(void)
 		_args;							\
 	})
 
+#ifdef CONFIG_BPF_SYSCALL
+bool trace_probe_bpf_disabled(void);
+#else
+static inline bool trace_probe_bpf_disabled(void) { return false; }
+#endif
+
 #endif /* _LINUX_KERNEL_TRACE_H */
+
diff --git a/kernel/trace/trace_probe_tmpl.h b/kernel/trace/trace_probe_tmpl.h
index 6ca2dfe59a0f..015208aefbaf 100644
--- a/kernel/trace/trace_probe_tmpl.h
+++ b/kernel/trace/trace_probe_tmpl.h
@@ -274,7 +274,7 @@ store_trace_args(void *data, struct trace_probe *tp, void *rec, void *edata,
 	int ret, i;
 
 #ifdef CONFIG_BPF_SYSCALL
-	if (tp->prog) {
+	if (tp->prog && !trace_probe_bpf_disabled()) {
 		struct fetch_bpf_ctx ctx = {
 			.rec = rec,
 			.edata = edata,