Re: [PATCH 7/8] ftrace: Add multi direct modify interface
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2021-09-14 21:41:43
Also in:
lkml
On Tue, 31 Aug 2021 11:50:16 +0200 Jiri Olsa [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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@kernel.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_CALLSdiff --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); +
Needs kernel doc comments.
+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);This needs to be commented that there's going to be a rather large time frame that there will be no callbacks happening while this update occurs. A better solution, that prevents having to do this, is to first change the function fentry's to call the ftrace list loop function, that calls the ftrace_ops list, and will call the direct call via the ops in the loop. Have the ops->func call the new direct function (all will be immediately affected). Update the entries, and then switch from the loop back to the direct caller. -- Steve
+ 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 */
/**