linux-kernel - [PATCH] kernel/trace: Remove function callback casts

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Date:   Sun, 14 Jun 2020 09:01:54 +0200
From:   Oscar Carter <oscar.carter@....com>
To:     Kees Cook <keescook@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org,
        Oscar Carter <oscar.carter@....com>
Subject: [PATCH] kernel/trace: Remove function callback casts

In an effort to enable -Wcast-function-type in the top-level Makefile to
support Control Flow Integrity builds, remove all the function callback
casts.

To do this, use the ftrace_ops_list_func function as a wrapper when the
arch not supports ftrace ops instead of the use of a function cast.

Signed-off-by: Oscar Carter <oscar.carter@....com>
---
 kernel/trace/ftrace.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c163c3531faf..ed1efc0e3a25 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -119,13 +119,12 @@ struct ftrace_ops __rcu *ftrace_ops_list __read_mostly = &ftrace_list_end;
 ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 struct ftrace_ops global_ops;

-#if ARCH_SUPPORTS_FTRACE_OPS
 static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
 				 struct ftrace_ops *op, struct pt_regs *regs);
-#else
+
+#if !ARCH_SUPPORTS_FTRACE_OPS
 /* See comment below, where ftrace_ops_list_func is defined */
 static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip);
-#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops)
 #endif

 static inline void ftrace_ops_init(struct ftrace_ops *ops)
@@ -6860,6 +6859,12 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
 }
 NOKPROBE_SYMBOL(ftrace_ops_list_func);
 #else
+static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
+				 struct ftrace_ops *op, struct pt_regs *regs)
+{
+	ftrace_ops_no_ops(ip, parent_ip);
+}
+
 static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
 {
 	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
--
2.20.1