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.

Link: https://lkml.kernel.org/r/20211008091336.33616-8-jolsa@kernel.org
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 0158261..9999e29 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -326,6 +326,8 @@ 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, unsigned long addr);
+int modify_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr);
+
 #else
 struct ftrace_ops;
 # define ftrace_direct_func_count 0
@@ -365,6 +367,10 @@ static inline int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigne
 {
        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 a05b25f..3012034 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5543,6 +5543,68 @@ int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
        return err;
 }
 EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
+
+/**
+ * modify_ftrace_direct_multi - Modify an existing direct 'multi' call
+ * to call something else
+ * @ops: The address of the struct ftrace_ops object
+ * @addr: The address of the new trampoline to call at @ops functions
+ *
+ * This is used to unregister currently registered direct caller and
+ * register new one @addr on functions registered in @ops object.
+ *
+ * Note there's window between ftrace_shutdown and ftrace_startup calls
+ * where there will be no callbacks called.
+ *
+ * Returns: zero on success. Non zero on error, which includes:
+ *  -EINVAL - The @ops object was not properly registered.
+ */
+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.
+        *
+        * Note there is no callback called for @ops object after
+        * this ftrace_shutdown call until ftrace_startup is called
+        * later on.
+        */
+       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 */
 
 /**