linux-kernel - [PATCH 7/8] ftrace: Add multi direct modify interface

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Message-Id: <20210831095017.412311-8-jolsa@kernel.org>
Date:   Tue, 31 Aug 2021 11:50:16 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Steven Rostedt (VMware)" <rostedt@...dmis.org>
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH 7/8] ftrace: Add multi direct modify interface

Adding interface to modify registered direct function
for ftrace_ops. Adding following function:

   modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)

The function changes the currently registered direct
function for all attached functions.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 include/linux/ftrace.h |  6 ++++++
 kernel/trace/ftrace.c  | 43 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e40b5201c16e..f3ba6366f7af 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -318,6 +318,8 @@ int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
 unsigned long ftrace_find_rec_direct(unsigned long ip);
 int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
 int unregister_ftrace_direct_multi(struct ftrace_ops *ops);
+int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
+
 #else
 struct ftrace_ops;
 # define ftrace_direct_func_count 0
@@ -357,6 +359,10 @@ static inline int unregister_ftrace_direct_multi(struct ftrace_ops *ops)
 {
 	return -ENODEV;
 }
+static inline int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 #ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7243769493c9..59940a6a907c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5518,6 +5518,49 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops)
 	return err;
 }
 EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
+
+int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+	struct ftrace_hash *hash = ops->func_hash->filter_hash;
+	struct ftrace_func_entry *entry, *iter;
+	int i, size;
+	int err;
+
+	if (check_direct_multi(ops))
+		return -EINVAL;
+	if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
+		return -EINVAL;
+
+	mutex_lock(&direct_mutex);
+	mutex_lock(&ftrace_lock);
+
+	/*
+	 * Shutdown the ops, change 'direct' pointer for each
+	 * ops entry in direct_functions hash and startup the
+	 * ops back again.
+	 */
+	err = ftrace_shutdown(ops, 0);
+	if (err)
+		goto out_unlock;
+
+	size = 1 << hash->size_bits;
+	for (i = 0; i < size; i++) {
+		hlist_for_each_entry(iter, &hash->buckets[i], hlist) {
+			entry = __ftrace_lookup_ip(direct_functions, iter->ip);
+			if (!entry)
+				continue;
+			entry->direct = addr;
+		}
+	}
+
+	err = ftrace_startup(ops, 0);
+
+ out_unlock:
+	mutex_unlock(&ftrace_lock);
+	mutex_unlock(&direct_mutex);
+	return err;
+}
+EXPORT_SYMBOL_GPL(modify_ftrace_direct_multi);
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 /**
-- 
2.31.1