[RFC PATCH v4 23/34] ftrace: notify kprobe when ftrace is initialized.

[Wang Nan]

Makes ftrace calls init_kprobes_on_ftrace() when ftrace_init()
finished. Before this call, marks kprobes on ftrace with
'KPROBE_FLAG_FTRACE_EARLY' instead of 'KPROBE_FLAG_FTRACE' to make
kprobe not to kprobe treats these kprobes as ftrace kprobes.

Following patches should convert such kprobes into kprobes on ftrace.

Signed-off-by: Wang Nan <wangnan0 at huawei.com>
---
 include/linux/kprobes.h | 11 +++++++++++
 kernel/kprobes.c        | 17 ++++++++++++++++-
 kernel/trace/ftrace.c   |  2 ++
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index bb2b2c6..96dc842 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -130,6 +130,8 @@ struct kprobe {
 				   * this flag is only for optimized_kprobe.
 				   */
 #define KPROBE_FLAG_FTRACE	8 /* probe is using ftrace */
+/* probe will use ftrace, but ftrace is not ready when registering */
+#define KPROBE_FLAG_FTRACE_EARLY	16
 
 /* Has this kprobe gone ? */
 static inline int kprobe_gone(struct kprobe *p)
@@ -269,6 +271,14 @@ extern void show_registers(struct pt_regs *regs);
 extern void kprobes_inc_nmissed_count(struct kprobe *p);
 extern bool arch_within_kprobe_blacklist(unsigned long addr);
 
+#if defined(CONFIG_EARLY_KPROBES) && defined(CONFIG_KPROBES_ON_FTRACE)
+extern void init_kprobes_on_ftrace(void);
+#else
+static inline void init_kprobes_on_ftrace(void)
+{
+}
+#endif // CONFIG_EARLY_KPROBES && CONFIG_KPROBES_ON_FTRACE
+
 #ifdef CONFIG_EARLY_KPROBES
 
 #define NR_EARLY_KPROBES_SLOTS	CONFIG_NR_EARLY_KPROBES_SLOTS
@@ -453,6 +463,7 @@ extern int proc_kprobes_optimization_handler(struct ctl_table *table,
 extern void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 				  struct ftrace_ops *ops, struct pt_regs *regs);
 extern int arch_prepare_kprobe_ftrace(struct kprobe *p);
+
 #endif
 
 int arch_check_ftrace_location(struct kprobe *p);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 4b7b20a..b5e13ba 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -69,6 +69,11 @@
 
 static int kprobes_initialized;
 static int kprobes_blacklist_initialized;
+#if defined(CONFIG_KPROBES_ON_FTRACE) && defined(CONFIG_EARLY_KPROBES)
+static bool kprobes_on_ftrace_initialized __read_mostly = false;
+#else
+# define kprobes_on_ftrace_initialized	false
+#endif
 
 bool kprobes_is_early(void)
 {
@@ -1497,7 +1502,10 @@ int __weak arch_check_ftrace_location(struct kprobe *p)
 		/* Given address is not on the instruction boundary */
 		if ((unsigned long)p->addr != ftrace_addr)
 			return -EILSEQ;
-		p->flags |= KPROBE_FLAG_FTRACE;
+		if (unlikely(!kprobes_on_ftrace_initialized))
+			p->flags |= KPROBE_FLAG_FTRACE_EARLY;
+		else
+			p->flags |= KPROBE_FLAG_FTRACE;
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
 		return -EINVAL;
 #endif
@@ -2574,3 +2582,10 @@ module_init(init_kprobes);
 
 /* defined in arch/.../kernel/kprobes.c */
 EXPORT_SYMBOL_GPL(jprobe_return);
+
+#if defined(CONFIG_KPROBES_ON_FTRACE) && defined(CONFIG_EARLY_KPROBES)
+void init_kprobes_on_ftrace(void)
+{
+	kprobes_on_ftrace_initialized = true;
+}
+#endif
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7fa88d0..5cb0269 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -23,6 +23,7 @@
 #include <linux/kthread.h>
 #include <linux/uaccess.h>
 #include <linux/bsearch.h>
+#include <linux/kprobes.h>
 #include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/sysctl.h>
@@ -5022,6 +5023,7 @@ void __init ftrace_init(void)
 	if (ret)
 		pr_warning("Failed to register trace ftrace module exit notifier\n");
 
+	init_kprobes_on_ftrace();
 	set_ftrace_early_filters();
 
 	return;
-- 
1.8.4