linux-kernel - [PATCH] ftrace: Remove unused global 'ftrace_direct_func

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Date: Tue,  7 May 2024 00:33:05 +0100
From: linux@...blig.org
To: rostedt@...dmis.org,
	mhiramat@...nel.org
Cc: linux-trace-kernel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Dr. David Alan Gilbert" <linux@...blig.org>
Subject: [PATCH] ftrace: Remove unused global 'ftrace_direct_func_count'

From: "Dr. David Alan Gilbert" <linux@...blig.org>

Commit 8788ca164eb4b ("ftrace: Remove the legacy _ftrace_direct API")
stopped setting the 'ftrace_direct_func_count' variable, but left
it around.  Clean it up.

Signed-off-by: Dr. David Alan Gilbert <linux@...blig.org>
---
 include/linux/ftrace.h |  2 --
 kernel/trace/fgraph.c  | 11 -----------
 kernel/trace/ftrace.c  |  1 -
 3 files changed, 14 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index b01cca36147ff..e3a83ebd1b333 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -413,7 +413,6 @@ struct ftrace_func_entry {
 };
 
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
-extern int ftrace_direct_func_count;
 unsigned long ftrace_find_rec_direct(unsigned long ip);
 int register_ftrace_direct(struct ftrace_ops *ops, unsigned long addr);
 int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr,
@@ -425,7 +424,6 @@ void ftrace_stub_direct_tramp(void);
 
 #else
 struct ftrace_ops;
-# define ftrace_direct_func_count 0
 static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
 {
 	return 0;
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index c83c005e654e3..a130b2d898f7c 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -125,17 +125,6 @@ int function_graph_enter(unsigned long ret, unsigned long func,
 {
 	struct ftrace_graph_ent trace;
 
-#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
-	/*
-	 * Skip graph tracing if the return location is served by direct trampoline,
-	 * since call sequence and return addresses are unpredictable anyway.
-	 * Ex: BPF trampoline may call original function and may skip frame
-	 * depending on type of BPF programs attached.
-	 */
-	if (ftrace_direct_func_count &&
-	    ftrace_find_rec_direct(ret - MCOUNT_INSN_SIZE))
-		return -EBUSY;
-#endif
 	trace.func = func;
 	trace.depth = ++current->curr_ret_depth;
 
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b18b4ece3d7c9..adf34167c3418 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2538,7 +2538,6 @@ ftrace_find_unique_ops(struct dyn_ftrace *rec)
 /* Protected by rcu_tasks for reading, and direct_mutex for writing */
 static struct ftrace_hash __rcu *direct_functions = EMPTY_HASH;
 static DEFINE_MUTEX(direct_mutex);
-int ftrace_direct_func_count;
 
 /*
  * Search the direct_functions hash to see if the given instruction pointer
-- 
2.45.0