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Message-ID: <20250729102813.1531457-3-jolsa@kernel.org>
Date: Tue, 29 Jul 2025 12:28:05 +0200
From: Jiri Olsa <jolsa@...nel.org>
To: Steven Rostedt <rostedt@...nel.org>,
Florent Revest <revest@...gle.com>,
Mark Rutland <mark.rutland@....com>
Cc: bpf@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-trace-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Menglong Dong <menglong8.dong@...il.com>
Subject: [RFC 02/10] ftrace: Add register_ftrace_direct_hash function
Adding register_ftrace_direct_hash function that registers
all entries (ip -> direct) provided in hash argument.
The difference to current register_ftrace_direct is
- hash argument that allows to register multiple ip -> direct
entries at once
- we can call register_ftrace_direct_hash multiple times on the
same ftrace_ops object, becase after first registration with
register_ftrace_function_nolock, it uses ftrace_update_ops to
update the ftrace_ops object
This change will allow us to have simple ftrace_ops for all bpf
direct interface users in following changes.
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
include/linux/ftrace.h | 7 +++
kernel/trace/ftrace.c | 123 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 130 insertions(+)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index b672ca15f265..e45bcc9de53b 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -526,6 +526,8 @@ int unregister_ftrace_direct(struct ftrace_ops *ops, unsigned long addr,
int modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr);
int modify_ftrace_direct_nolock(struct ftrace_ops *ops, unsigned long addr);
+int register_ftrace_direct_hash(struct ftrace_ops *ops, struct ftrace_hash *hash);
+
void ftrace_stub_direct_tramp(void);
#else
@@ -552,6 +554,11 @@ static inline int modify_ftrace_direct_nolock(struct ftrace_ops *ops, unsigned l
return -ENODEV;
}
+int register_ftrace_direct_hash(struct ftrace_ops *ops, struct ftrace_hash *hash)
+{
+ return -ENODEV;
+}
+
/*
* This must be implemented by the architecture.
* It is the way the ftrace direct_ops helper, when called
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5b8f565a1258..1dbb113f4e9c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6219,6 +6219,129 @@ int modify_ftrace_direct(struct ftrace_ops *ops, unsigned long addr)
return err;
}
EXPORT_SYMBOL_GPL(modify_ftrace_direct);
+
+static unsigned long hash_count(struct ftrace_hash *hash)
+{
+ return hash ? hash->count : 0;
+}
+
+/**
+ * hash_add - adds two struct ftrace_hash and returns the result
+ * @a: struct ftrace_hash object
+ * @b: struct ftrace_hash object
+ *
+ * Returns struct ftrace_hash object on success, NULL on error.
+ */
+static struct ftrace_hash *hash_add(struct ftrace_hash *a, struct ftrace_hash *b)
+{
+ struct ftrace_func_entry *entry;
+ struct ftrace_hash *add;
+ int size, i;
+
+ size = hash_count(a) + hash_count(b);
+ if (size > 32)
+ size = 32;
+
+ add = alloc_and_copy_ftrace_hash(fls(size), a);
+ if (!add)
+ goto error;
+
+ size = 1 << b->size_bits;
+ for (i = 0; i < size; i++) {
+ hlist_for_each_entry(entry, &b->buckets[i], hlist) {
+ if (add_hash_entry_direct(add, entry->ip, entry->direct) == NULL)
+ goto error;
+ }
+ }
+ return add;
+
+ error:
+ free_ftrace_hash(add);
+ return NULL;
+}
+
+static void call_direct_funcs_hash(unsigned long ip, unsigned long pip,
+ struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+ unsigned long addr;
+
+ addr = ftrace_find_rec_direct(ip);
+ if (!addr)
+ return;
+
+ arch_ftrace_set_direct_caller(fregs, addr);
+}
+
+int register_ftrace_direct_hash(struct ftrace_ops *ops, struct ftrace_hash *hash)
+{
+ struct ftrace_hash *filter_hash = NULL, *new_hash = NULL, *free_hash = NULL;
+ struct ftrace_func_entry *entry;
+ int i, size, err;
+ bool reg;
+
+ if (!hash_count(hash))
+ return 0;
+
+ mutex_lock(&direct_mutex);
+
+ /* Make sure requested entry is not already registered. */
+ size = 1 << hash->size_bits;
+ for (i = 0; i < size; i++) {
+ hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
+ if (__ftrace_lookup_ip(direct_functions, entry->ip))
+ goto out_unlock;
+ }
+ }
+
+ filter_hash = ops->func_hash ? ops->func_hash->filter_hash : NULL;
+
+ /* If there's nothing in filter_hash we need to register the ops. */
+ reg = hash_count(filter_hash) == 0;
+ if (reg) {
+ if (ops->func || ops->trampoline)
+ goto out_unlock;
+ if (ops->flags & FTRACE_OPS_FL_ENABLED)
+ goto out_unlock;
+ }
+
+ filter_hash = hash_add(filter_hash, hash);
+ if (!filter_hash)
+ goto out_unlock;
+
+ new_hash = hash_add(direct_functions, hash);
+ if (!new_hash)
+ goto out_unlock;
+
+ free_hash = direct_functions;
+ rcu_assign_pointer(direct_functions, new_hash);
+ new_hash = NULL;
+
+ if (reg) {
+ ops->func = call_direct_funcs_hash;
+ ops->flags = MULTI_FLAGS;
+ ops->trampoline = FTRACE_REGS_ADDR;
+ ops->local_hash.filter_hash = filter_hash;
+
+ err = register_ftrace_function_nolock(ops);
+ if (!err)
+ filter_hash = NULL;
+ } else {
+ err = ftrace_update_ops(ops, filter_hash, EMPTY_HASH);
+ }
+
+ out_unlock:
+ mutex_unlock(&direct_mutex);
+
+ if (free_hash && free_hash != EMPTY_HASH)
+ call_rcu_tasks(&free_hash->rcu, register_ftrace_direct_cb);
+
+ if (filter_hash)
+ free_ftrace_hash(filter_hash);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(register_ftrace_direct_hash);
+
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
/**
--
2.50.1
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