[PATCH] kprobes: fix compiler warning for !CONFIG_KPROBES_ON_FTRACE

[Muchun Song]

Fix compiler warning(as show below) for !CONFIG_KPROBES_ON_FTRACE.

kernel/kprobes.c: In function 'kill_kprobe':
kernel/kprobes.c:1116:33: warning: statement with no effect
[-Wunused-value]
 1116 | #define disarm_kprobe_ftrace(p) (-ENODEV)
      |                                 ^
kernel/kprobes.c:2154:3: note: in expansion of macro
'disarm_kprobe_ftrace'
 2154 |   disarm_kprobe_ftrace(p);

Link: https://lore.kernel.org/r/20200805142136.0331f7ea@xxxxxxxxxxxxxxxx

Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Fixes: 0cb2f1372baa ("kprobes: Fix NULL pointer dereference at kprobe_ftrace_handler")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
---
 kernel/kprobes.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 503add629599..d36e2b017588 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1114,9 +1114,20 @@ static int disarm_kprobe_ftrace(struct kprobe *p)
 		ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
 }
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
-#define prepare_kprobe(p)	arch_prepare_kprobe(p)
-#define arm_kprobe_ftrace(p)	(-ENODEV)
-#define disarm_kprobe_ftrace(p)	(-ENODEV)
+static inline int prepare_kprobe(struct kprobe *p)
+{
+	return arch_prepare_kprobe(p);
+}
+
+static inline int arm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
+
+static inline int disarm_kprobe_ftrace(struct kprobe *p)
+{
+	return -ENODEV;
+}
 #endif
 
 /* Arm a kprobe with text_mutex */
-- 
2.11.0