[PATCH v3] tracing: fprobe: use ftrace if CONFIG_DYNAMIC_FTRACE_WITH_ARGS

[PATCH v3] tracing: fprobe: use ftrace if CONFIG_DYNAMIC_FTRACE_WITH_ARGS

[Menglong Dong]

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@chinatelecom.cn>
---
v3:
- fix the build warning when CONFIG_MODULES not enabled

v2:
- remove the definition of FPROBE_USE_FTRACE
---
 kernel/trace/fprobe.c | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index ecd623eef68b..0b1ee8e585f2 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 +336,15 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
 {
 	return !fp->exit_handler;
 }
+
+#ifdef CONFIG_MODULES
+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);
+}
+#endif
 #else
 static int fprobe_ftrace_add_ips(unsigned long *addrs, int num)
 {
@@ -349,7 +359,15 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
 {
 	return false;
 }
+
+#ifdef CONFIG_MODULES
+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
+#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 +614,8 @@ 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

Re: [PATCH v3] tracing: fprobe: use ftrace if CONFIG_DYNAMIC_FTRACE_WITH_ARGS

[Masami Hiramatsu]

On Mon,  3 Nov 2025 14:34:34 +0800
Menglong Dong <menglong8.dong@gmail.com> wrote:

> 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.
> 

Looks good to me. Thanks!

> Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
> ---
> v3:
> - fix the build warning when CONFIG_MODULES not enabled
> 
> v2:
> - remove the definition of FPROBE_USE_FTRACE
> ---
>  kernel/trace/fprobe.c | 32 ++++++++++++++++++++++----------
>  1 file changed, 22 insertions(+), 10 deletions(-)
> 
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index ecd623eef68b..0b1ee8e585f2 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 +336,15 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
>  {
>  	return !fp->exit_handler;
>  }
> +
> +#ifdef CONFIG_MODULES
> +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);
> +}
> +#endif
>  #else
>  static int fprobe_ftrace_add_ips(unsigned long *addrs, int num)
>  {
> @@ -349,7 +359,15 @@ static bool fprobe_is_ftrace(struct fprobe *fp)
>  {
>  	return false;
>  }
> +
> +#ifdef CONFIG_MODULES
> +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
> +#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 +614,8 @@ 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
> 


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