From 73f9b911faa74ac5107879de05c9489c419f41bb Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Sat, 26 Mar 2022 11:27:05 +0900
Subject: kprobes: Use rethook for kretprobe if possible

Use rethook for kretprobe function return hooking if the arch sets
CONFIG_HAVE_RETHOOK=y. In this case, CONFIG_KRETPROBE_ON_RETHOOK is
set to 'y' automatically, and the kretprobe internal data fields
switches to use rethook. If not, it continues to use kretprobe
specific function return hooks.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164826162556.2455864.12255833167233452047.stgit@devnote2
---
 include/linux/kprobes.h | 51 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

(limited to 'include/linux')

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 312ff997c743..157168769fc2 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -28,6 +28,7 @@
 #include <linux/ftrace.h>
 #include <linux/refcount.h>
 #include <linux/freelist.h>
+#include <linux/rethook.h>
 #include <asm/kprobes.h>
 
 #ifdef CONFIG_KPROBES
@@ -149,13 +150,20 @@ struct kretprobe {
 	int maxactive;
 	int nmissed;
 	size_t data_size;
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+	struct rethook *rh;
+#else
 	struct freelist_head freelist;
 	struct kretprobe_holder *rph;
+#endif
 };
 
 #define KRETPROBE_MAX_DATA_SIZE	4096
 
 struct kretprobe_instance {
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+	struct rethook_node node;
+#else
 	union {
 		struct freelist_node freelist;
 		struct rcu_head rcu;
@@ -164,6 +172,7 @@ struct kretprobe_instance {
 	struct kretprobe_holder *rph;
 	kprobe_opcode_t *ret_addr;
 	void *fp;
+#endif
 	char data[];
 };
 
@@ -186,10 +195,24 @@ extern void kprobe_busy_begin(void);
 extern void kprobe_busy_end(void);
 
 #ifdef CONFIG_KRETPROBES
-extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
-				   struct pt_regs *regs);
+/* Check whether @p is used for implementing a trampoline. */
 extern int arch_trampoline_kprobe(struct kprobe *p);
 
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance *ri)
+{
+	RCU_LOCKDEP_WARN(!rcu_read_lock_any_held(),
+		"Kretprobe is accessed from instance under preemptive context");
+
+	return (struct kretprobe *)READ_ONCE(ri->node.rethook->data);
+}
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+	return ri->node.ret_addr;
+}
+#else
+extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
+				   struct pt_regs *regs);
 void arch_kretprobe_fixup_return(struct pt_regs *regs,
 				 kprobe_opcode_t *correct_ret_addr);
 
@@ -232,6 +255,12 @@ static nokprobe_inline struct kretprobe *get_kretprobe(struct kretprobe_instance
 	return READ_ONCE(ri->rph->rp);
 }
 
+static nokprobe_inline unsigned long get_kretprobe_retaddr(struct kretprobe_instance *ri)
+{
+	return (unsigned long)ri->ret_addr;
+}
+#endif /* CONFIG_KRETPROBE_ON_RETHOOK */
+
 #else /* !CONFIG_KRETPROBES */
 static inline void arch_prepare_kretprobe(struct kretprobe *rp,
 					struct pt_regs *regs)
@@ -395,7 +424,11 @@ void unregister_kretprobe(struct kretprobe *rp);
 int register_kretprobes(struct kretprobe **rps, int num);
 void unregister_kretprobes(struct kretprobe **rps, int num);
 
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+#define kprobe_flush_task(tk)	do {} while (0)
+#else
 void kprobe_flush_task(struct task_struct *tk);
+#endif
 
 void kprobe_free_init_mem(void);
 
@@ -509,6 +542,19 @@ static inline bool is_kprobe_optinsn_slot(unsigned long addr)
 #endif /* !CONFIG_OPTPROBES */
 
 #ifdef CONFIG_KRETPROBES
+#ifdef CONFIG_KRETPROBE_ON_RETHOOK
+static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
+{
+	return is_rethook_trampoline(addr);
+}
+
+static nokprobe_inline
+unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
+				      struct llist_node **cur)
+{
+	return rethook_find_ret_addr(tsk, (unsigned long)fp, cur);
+}
+#else
 static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 {
 	return (void *)addr == kretprobe_trampoline_addr();
@@ -516,6 +562,7 @@ static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 
 unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp,
 				      struct llist_node **cur);
+#endif
 #else
 static nokprobe_inline bool is_kretprobe_trampoline(unsigned long addr)
 {
-- 
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