Adding update_ftrace_direct_add function that adds all entries
(ip -> addr) provided in hash argument to direct ftrace ops
and updates its attachments.
The difference to current register_ftrace_direct is
- hash argument that allows to register multiple ip -> direct
entries at once
- we can call update_ftrace_direct_add 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@kernel.org>
---
include/linux/ftrace.h | 7 +++
kernel/trace/ftrace.c | 128 +++++++++++++++++++++++++++++++++++++++++
2 files changed, 135 insertions(+)
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index c0a72fcae1f6..5cf151cb8e6d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -543,6 +543,8 @@ 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 update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash);
+
void ftrace_stub_direct_tramp(void);
#else
@@ -569,6 +571,11 @@ static inline int modify_ftrace_direct_nolock(struct ftrace_ops *ops, unsigned l
return -ENODEV;
}
+static inline int update_ftrace_direct_add(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 84aee9096a9e..ec7d93460dac 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6249,6 +6249,134 @@ 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;
+}
+
+int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash)
+{
+ struct ftrace_hash *old_direct_functions = NULL, *new_direct_functions;
+ struct ftrace_hash *old_filter_hash, *new_filter_hash = NULL;
+ struct ftrace_func_entry *entry;
+ int i, size, err = -EINVAL;
+ bool reg;
+
+ if (!hash_count(hash))
+ return -EINVAL;
+
+ mutex_lock(&direct_mutex);
+
+ /* Make sure requested entries are 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;
+ }
+ }
+
+ old_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(old_filter_hash) == 0;
+ if (reg) {
+ if (ops->func || ops->trampoline)
+ goto out_unlock;
+ if (ops->flags & FTRACE_OPS_FL_ENABLED)
+ goto out_unlock;
+ }
+
+ err = -ENOMEM;
+ new_filter_hash = hash_add(old_filter_hash, hash);
+ if (!new_filter_hash)
+ goto out_unlock;
+
+ new_direct_functions = hash_add(direct_functions, hash);
+ if (!new_direct_functions)
+ goto out_unlock;
+
+ old_direct_functions = direct_functions;
+ rcu_assign_pointer(direct_functions, new_direct_functions);
+
+ if (reg) {
+ ops->func = call_direct_funcs;
+ ops->flags |= MULTI_FLAGS;
+ ops->trampoline = FTRACE_REGS_ADDR;
+ ops->local_hash.filter_hash = new_filter_hash;
+
+ err = register_ftrace_function_nolock(ops);
+ if (err) {
+ /* restore old filter on error */
+ ops->local_hash.filter_hash = old_filter_hash;
+
+ /* cleanup for possible another register call */
+ ops->func = NULL;
+ ops->trampoline = 0;
+ } else {
+ new_filter_hash = old_filter_hash;
+ }
+ } else {
+ err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
+ /*
+ * new_filter_hash is dup-ed, so we need to release it anyway,
+ * old_filter_hash either stays on error or is already released
+ */
+ }
+
+ if (err) {
+ /* reset direct_functions and free the new one */
+ rcu_assign_pointer(direct_functions, old_direct_functions);
+ old_direct_functions = new_direct_functions;
+ }
+
+ out_unlock:
+ mutex_unlock(&direct_mutex);
+
+ if (old_direct_functions && old_direct_functions != EMPTY_HASH)
+ call_rcu_tasks(&old_direct_functions->rcu, register_ftrace_direct_cb);
+ if (new_filter_hash)
+ free_ftrace_hash(new_filter_hash);
+
+ return err;
+}
+
#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
/**
--
2.52.0On Mon, 15 Dec 2025 22:13:57 +0100
Jiri Olsa <jolsa@kernel.org> wrote:
> +/**
> + * 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;
You can just return NULL here, as add is NULL.
> +
> + 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;
Could remove the error and have:
if (add_hash_entry_direct(add, entry->ip, entry->direct) == NULL) {
free_ftrace_hash(add);
return NULL;
}
> + }
> + }
> + return add;
> +
> + error:
> + free_ftrace_hash(add);
> + return NULL;
> +}
> +
Non static functions require a kerneldoc header.
> +int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash)
> +{
> + struct ftrace_hash *old_direct_functions = NULL, *new_direct_functions;
> + struct ftrace_hash *old_filter_hash, *new_filter_hash = NULL;
BTW, I prefer to not double up on variables. That is to have each on
their own lines. Makes it easier to read for me.
> + struct ftrace_func_entry *entry;
> + int i, size, err = -EINVAL;
Even here.
> + bool reg;
> +
> + if (!hash_count(hash))
> + return -EINVAL;
> +
> + mutex_lock(&direct_mutex);
> +
> + /* Make sure requested entries are not already registered. */
> + size = 1 << hash->size_bits;
> + for (i = 0; i < size; i++) {
If you want, you can remove the i declaration and use for(int i = 0; ... here.
> + hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
> + if (__ftrace_lookup_ip(direct_functions, entry->ip))
> + goto out_unlock;
> + }
> + }
> +
> + old_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(old_filter_hash) == 0;
> + if (reg) {
> + if (ops->func || ops->trampoline)
> + goto out_unlock;
> + if (ops->flags & FTRACE_OPS_FL_ENABLED)
> + goto out_unlock;
> + }
> +
> + err = -ENOMEM;
> + new_filter_hash = hash_add(old_filter_hash, hash);
> + if (!new_filter_hash)
> + goto out_unlock;
> +
> + new_direct_functions = hash_add(direct_functions, hash);
> + if (!new_direct_functions)
> + goto out_unlock;
> +
> + old_direct_functions = direct_functions;
> + rcu_assign_pointer(direct_functions, new_direct_functions);
> +
> + if (reg) {
> + ops->func = call_direct_funcs;
> + ops->flags |= MULTI_FLAGS;
> + ops->trampoline = FTRACE_REGS_ADDR;
> + ops->local_hash.filter_hash = new_filter_hash;
> +
> + err = register_ftrace_function_nolock(ops);
> + if (err) {
> + /* restore old filter on error */
> + ops->local_hash.filter_hash = old_filter_hash;
> +
> + /* cleanup for possible another register call */
> + ops->func = NULL;
> + ops->trampoline = 0;
> + } else {
> + new_filter_hash = old_filter_hash;
> + }
> + } else {
> + err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
> + /*
> + * new_filter_hash is dup-ed, so we need to release it anyway,
> + * old_filter_hash either stays on error or is already released
> + */
> + }
> +
> + if (err) {
> + /* reset direct_functions and free the new one */
> + rcu_assign_pointer(direct_functions, old_direct_functions);
> + old_direct_functions = new_direct_functions;
> + }
> +
> + out_unlock:
> + mutex_unlock(&direct_mutex);
> +
> + if (old_direct_functions && old_direct_functions != EMPTY_HASH)
> + call_rcu_tasks(&old_direct_functions->rcu, register_ftrace_direct_cb);
> + if (new_filter_hash)
free_ftrace_hash() checks for NULL, so you don't need the above if statement.
> + free_ftrace_hash(new_filter_hash);
> +
> + return err;
-- Steve
> +}
> +
> #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
>
> /**
On Wed, Dec 17, 2025 at 08:39:09PM -0500, Steven Rostedt wrote:
> On Mon, 15 Dec 2025 22:13:57 +0100
> Jiri Olsa <jolsa@kernel.org> wrote:
>
>
> > +/**
> > + * 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;
>
> You can just return NULL here, as add is NULL.
ok
>
> > +
> > + 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;
>
> Could remove the error and have:
>
> if (add_hash_entry_direct(add, entry->ip, entry->direct) == NULL) {
> free_ftrace_hash(add);
> return NULL;
> }
ok
>
>
> > + }
> > + }
> > + return add;
> > +
> > + error:
> > + free_ftrace_hash(add);
> > + return NULL;
> > +}
> > +
>
> Non static functions require a kerneldoc header.
ah right, will add
>
> > +int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash)
> > +{
> > + struct ftrace_hash *old_direct_functions = NULL, *new_direct_functions;
> > + struct ftrace_hash *old_filter_hash, *new_filter_hash = NULL;
>
> BTW, I prefer to not double up on variables. That is to have each on
> their own lines. Makes it easier to read for me.
>
> > + struct ftrace_func_entry *entry;
> > + int i, size, err = -EINVAL;
>
> Even here.
ok, will split
>
> > + bool reg;
> > +
> > + if (!hash_count(hash))
> > + return -EINVAL;
> > +
> > + mutex_lock(&direct_mutex);
> > +
> > + /* Make sure requested entries are not already registered. */
> > + size = 1 << hash->size_bits;
> > + for (i = 0; i < size; i++) {
>
> If you want, you can remove the i declaration and use for(int i = 0; ... here.
ok
SNIP
> > + }
> > +
> > + if (err) {
> > + /* reset direct_functions and free the new one */
> > + rcu_assign_pointer(direct_functions, old_direct_functions);
> > + old_direct_functions = new_direct_functions;
> > + }
> > +
> > + out_unlock:
> > + mutex_unlock(&direct_mutex);
> > +
> > + if (old_direct_functions && old_direct_functions != EMPTY_HASH)
> > + call_rcu_tasks(&old_direct_functions->rcu, register_ftrace_direct_cb);
> > + if (new_filter_hash)
>
> free_ftrace_hash() checks for NULL, so you don't need the above if statement.
ok
thanks,
jirka
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