linux-kernel - [RFC PATCH 3/5] kprobe: Simplify prepare_kprobe() by dropping redundant version

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Date:   Wed,  9 Jun 2021 19:50:17 +0900
From:   Punit Agrawal <punitagrawal@...il.com>
To:     mhiramat@...nel.org, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, davem@...emloft.net
Cc:     Punit Agrawal <punitagrawal@...il.com>,
        linux-kernel@...r.kernel.org, guoren@...nel.org,
        linux-csky@...r.kernel.org
Subject: [RFC PATCH 3/5] kprobe: Simplify prepare_kprobe() by dropping redundant version

The function prepare_kprobe() is called during kprobe registration and
is responsible for ensuring any architecture related preparation for
the kprobe is done before returning.

One of two versions of prepare_kprobe() is chosen depending on the
availability of KPROBE_ON_FTRACE in the kernel configuration.

Simplify the code by dropping the version when KPROBE_ON_FTRACE is not
selected - instead relying on kprobe_ftrace() to return false when
KPROBE_ON_FTRACE is not set.

No functional change.

Signed-off-by: Punit Agrawal <punitagrawal@...il.com>
---
 include/linux/kprobes.h |  5 +++++
 kernel/kprobes.c        | 23 +++++++++--------------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 1883a4a9f16a..771013bab18a 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -362,6 +362,11 @@ static inline void wait_for_kprobe_optimizer(void) { }
 extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 				  struct ftrace_ops *ops, struct ftrace_regs *fregs);
 extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
+#else
+static inline int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	return -EINVAL;
+}
 #endif
 
 int arch_check_ftrace_location(struct kprobe *p);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 1a11d3c411bf..54d37d4ab897 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1022,15 +1022,6 @@ static struct ftrace_ops kprobe_ipmodify_ops __read_mostly = {
 static int kprobe_ipmodify_enabled;
 static int kprobe_ftrace_enabled;
 
-/* Must ensure p->addr is really on ftrace */
-static int prepare_kprobe(struct kprobe *p)
-{
-	if (!kprobe_ftrace(p))
-		return arch_prepare_kprobe(p);
-
-	return arch_prepare_kprobe_ftrace(p);
-}
-
 /* Caller must lock kprobe_mutex */
 static int __arm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 			       int *cnt)
@@ -1102,11 +1093,6 @@ static int disarm_kprobe_ftrace(struct kprobe *p)
 		ipmodify ? &kprobe_ipmodify_enabled : &kprobe_ftrace_enabled);
 }
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
-static inline int prepare_kprobe(struct kprobe *p)
-{
-	return arch_prepare_kprobe(p);
-}
-
 static inline int arm_kprobe_ftrace(struct kprobe *p)
 {
 	return -ENODEV;
@@ -1118,6 +1104,15 @@ static inline int disarm_kprobe_ftrace(struct kprobe *p)
 }
 #endif
 
+static int prepare_kprobe(struct kprobe *p)
+{
+	/* Must ensure p->addr is really on ftrace */
+	if (kprobe_ftrace(p))
+		return arch_prepare_kprobe_ftrace(p);
+
+	return arch_prepare_kprobe(p);
+}
+
 /* Arm a kprobe with text_mutex */
 static int arm_kprobe(struct kprobe *kp)
 {
-- 
2.30.2