linux-kernel - [PATCH 03/12] ftrace: Do not bother checking per CPU "disabled" flag

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250502205348.303564071@goodmis.org>
Date: Fri, 02 May 2025 16:51:50 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 03/12] ftrace: Do not bother checking per CPU "disabled" flag

From: Steven Rostedt <rostedt@...dmis.org>

The per CPU "disabled" value was the original way to disable tracing when
the tracing subsystem was first created. Today, the ring buffer
infrastructure has its own way to disable tracing. In fact, things have
changed so much since 2008 that many things ignore the disable flag.

There's no reason for the function tracer to check it, if tracing is
disabled, the ring buffer will not record the event anyway.

Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_functions.c | 16 +++-------------
 1 file changed, 3 insertions(+), 13 deletions(-)

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 98ccf3f00c51..bd153219a712 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -209,7 +209,6 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
 		    struct ftrace_ops *op, struct ftrace_regs *fregs)
 {
 	struct trace_array *tr = op->private;
-	struct trace_array_cpu *data;
 	unsigned int trace_ctx;
 	int bit;
 
@@ -224,9 +223,7 @@ function_trace_call(unsigned long ip, unsigned long parent_ip,
 
 	trace_ctx = tracing_gen_ctx_dec();
 
-	data = this_cpu_ptr(tr->array_buffer.data);
-	if (!atomic_read(&data->disabled))
-		trace_function(tr, ip, parent_ip, trace_ctx, NULL);
+	trace_function(tr, ip, parent_ip, trace_ctx, NULL);
 
 	ftrace_test_recursion_unlock(bit);
 }
@@ -236,10 +233,8 @@ function_args_trace_call(unsigned long ip, unsigned long parent_ip,
 			 struct ftrace_ops *op, struct ftrace_regs *fregs)
 {
 	struct trace_array *tr = op->private;
-	struct trace_array_cpu *data;
 	unsigned int trace_ctx;
 	int bit;
-	int cpu;
 
 	if (unlikely(!tr->function_enabled))
 		return;
@@ -250,10 +245,7 @@ function_args_trace_call(unsigned long ip, unsigned long parent_ip,
 
 	trace_ctx = tracing_gen_ctx();
 
-	cpu = smp_processor_id();
-	data = per_cpu_ptr(tr->array_buffer.data, cpu);
-	if (!atomic_read(&data->disabled))
-		trace_function(tr, ip, parent_ip, trace_ctx, fregs);
+	trace_function(tr, ip, parent_ip, trace_ctx, fregs);
 
 	ftrace_test_recursion_unlock(bit);
 }
@@ -352,7 +344,6 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
 {
 	struct trace_func_repeats *last_info;
 	struct trace_array *tr = op->private;
-	struct trace_array_cpu *data;
 	unsigned int trace_ctx;
 	int bit;
 
@@ -364,8 +355,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip,
 		return;
 
 	parent_ip = function_get_true_parent_ip(parent_ip, fregs);
-	data = this_cpu_ptr(tr->array_buffer.data);
-	if (atomic_read(&data->disabled))
+	if (!tracer_tracing_is_on(tr))
 		goto out;
 
 	/*
-- 
2.47.2