linux-kernel - [PATCH v2] tracing: fprobe: use ftrace if CONFIG_DYNAMIC_FTRACE_WITH

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Message-ID: <20251031024038.19176-1-dongml2@chinatelecom.cn>
Date: Fri, 31 Oct 2025 10:40:38 +0800
From: Menglong Dong <menglong8.dong@...il.com>
To: mhiramat@...nel.org
Cc: rostedt@...dmis.org,
	jolsa@...nel.org,
	mathieu.desnoyers@...icios.com,
	jiang.biao@...ux.dev,
	linux-kernel@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v2] tracing: fprobe: use ftrace if CONFIG_DYNAMIC_FTRACE_WITH_ARGS

For now, we will use ftrace for the fprobe if fp->exit_handler not exists
and CONFIG_DYNAMIC_FTRACE_WITH_REGS is enabled.

However, CONFIG_DYNAMIC_FTRACE_WITH_REGS is not supported by some arch,
such as arm. What we need in the fprobe is the function arguments, so we
can use ftrace for fprobe if CONFIG_DYNAMIC_FTRACE_WITH_ARGS is enabled.

Therefore, use ftrace if CONFIG_DYNAMIC_FTRACE_WITH_REGS or
CONFIG_DYNAMIC_FTRACE_WITH_ARGS enabled.

Signed-off-by: Menglong Dong <dongml2@...natelecom.cn>
---
v2:
- remove the definition of FPROBE_USE_FTRACE
---
 kernel/trace/fprobe.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index ecd623eef68b..742ad5a61d46 100644
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -44,6 +44,7 @@
 static struct hlist_head fprobe_table[FPROBE_TABLE_SIZE];
 static struct rhltable fprobe_ip_table;
 static DEFINE_MUTEX(fprobe_mutex);
+static struct fgraph_ops fprobe_graph_ops;
 
 static u32 fprobe_node_hashfn(const void *data, u32 len, u32 seed)
 {
@@ -254,7 +255,7 @@ static inline int __fprobe_kprobe_handler(unsigned long ip, unsigned long parent
 	return ret;
 }
 
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+#if defined(CONFIG_DYNAMIC_FTRACE_WITH_ARGS) || defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS)
 /* ftrace_ops callback, this processes fprobes which have only entry_handler. */
 static void fprobe_ftrace_entry(unsigned long ip, unsigned long parent_ip,
 	struct ftrace_ops *ops, struct ftrace_regs *fregs)
@@ -295,7 +296,7 @@ NOKPROBE_SYMBOL(fprobe_ftrace_entry);
 
 static struct ftrace_ops fprobe_ftrace_ops = {
 	.func	= fprobe_ftrace_entry,
-	.flags	= FTRACE_OPS_FL_SAVE_REGS,
+	.flags	= FTRACE_OPS_FL_SAVE_ARGS,
 };
 static int fprobe_ftrace_active;
 
@@ -335,6 +336,13 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
 {
 	return !fp->exit_handler;
 }
+
+static void fprobe_set_ips(unsigned long *ips, unsigned int cnt, int remove,
+			   int reset)
+{
+	ftrace_set_filter_ips(&fprobe_graph_ops.ops, ips, cnt, remove, reset);
+	ftrace_set_filter_ips(&fprobe_ftrace_ops, ips, cnt, remove, reset);
+}
 #else
 static int fprobe_ftrace_add_ips(unsigned long *addrs, int num)
 {
@@ -349,7 +357,13 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
 {
 	return false;
 }
-#endif
+
+static void fprobe_set_ips(unsigned long *ips, unsigned int cnt, int remove,
+			   int reset)
+{
+	ftrace_set_filter_ips(&fprobe_graph_ops.ops, ips, cnt, remove, reset);
+}
+#endif /* !CONFIG_DYNAMIC_FTRACE_WITH_ARGS && !CONFIG_DYNAMIC_FTRACE_WITH_REGS */
 
 /* fgraph_ops callback, this processes fprobes which have exit_handler. */
 static int fprobe_fgraph_entry(struct ftrace_graph_ent *trace, struct fgraph_ops *gops,
@@ -596,14 +610,8 @@ static int fprobe_module_callback(struct notifier_block *nb,
 	} while (node == ERR_PTR(-EAGAIN));
 	rhashtable_walk_exit(&iter);
 
-	if (alist.index > 0) {
-		ftrace_set_filter_ips(&fprobe_graph_ops.ops,
-				      alist.addrs, alist.index, 1, 0);
-#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
-		ftrace_set_filter_ips(&fprobe_ftrace_ops,
-				      alist.addrs, alist.index, 1, 0);
-#endif
-	}
+	if (alist.index > 0)
+		fprobe_set_ips(alist.addrs, alist.index, 1, 0);
 	mutex_unlock(&fprobe_mutex);
 
 	kfree(alist.addrs);
-- 
2.51.2