[PATCH v3 11/27] ftrace: Allow subops filtering to be modified

Steven Rostedt
2024-06-03T19:07:12Z

From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The subops filters use a "manager" ops to enable and disable its filters.
The manager ops can handle more than one subops, and its filter is what
controls what functions get set. Add a ftrace_hash_move_and_update_subops()
function that will update the manager ops when the subops filters change.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/linux/ftrace.h | 3 +
kernel/trace/ftrace.c | 141 +++++++++++++++++++++++++++++++++--------
2 files changed, 116 insertions(+), 28 deletions(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 978a1d3b270a..63238a9a9270 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -227,6 +227,7 @@ ftrace_func_t ftrace_ops_get_func(struct ftrace_ops *ops);
* ftrace_enabled.
* DIRECT - Used by the direct ftrace_ops helper for direct functions
* (internal ftrace only, should not be used by others)
+ * SUBOP - Is controlled by another op in field managed.
*/
enum {
FTRACE_OPS_FL_ENABLED = BIT(0),
@@ -247,6 +248,7 @@ enum {
FTRACE_OPS_FL_TRACE_ARRAY = BIT(15),
FTRACE_OPS_FL_PERMANENT = BIT(16),
FTRACE_OPS_FL_DIRECT = BIT(17),
+ FTRACE_OPS_FL_SUBOP = BIT(18),
};

#ifndef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
@@ -336,6 +338,7 @@ struct ftrace_ops {
struct list_head list;
struct list_head subop_list;
ftrace_ops_func_t ops_func;
+ struct ftrace_ops *managed;
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
unsigned long direct_call;
#endif
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 63b8d1fe1dd8..cbb91b0afcc8 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3343,10 +3343,28 @@ static bool ops_equal(struct ftrace_hash *A, struct ftrace_hash *B)
return true;
}

-static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
- struct ftrace_hash **orig_hash,
- struct ftrace_hash *hash,
- int enable);
+static void ftrace_ops_update_code(struct ftrace_ops *ops,
+ struct ftrace_ops_hash *old_hash);
+
+static int __ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
+ struct ftrace_hash **orig_hash,
+ struct ftrace_hash *hash,
+ int enable)
+{
+ struct ftrace_ops_hash old_hash_ops;
+ struct ftrace_hash *old_hash;
+ int ret;
+
+ old_hash = *orig_hash;
+ old_hash_ops.filter_hash = ops->func_hash->filter_hash;
+ old_hash_ops.notrace_hash = ops->func_hash->notrace_hash;
+ ret = ftrace_hash_move(ops, enable, orig_hash, hash);
+ if (!ret) {
+ ftrace_ops_update_code(ops, &old_hash_ops);
+ free_ftrace_hash_rcu(old_hash);
+ }
+ return ret;
+}

static int ftrace_update_ops(struct ftrace_ops *ops, struct ftrace_hash *filter_hash,
struct ftrace_hash *notrace_hash)
@@ -3354,15 +3372,15 @@ static int ftrace_update_ops(struct ftrace_ops *ops, struct ftrace_hash *filter_
int ret;

if (!ops_equal(filter_hash, ops->func_hash->filter_hash)) {
- ret = ftrace_hash_move_and_update_ops(ops, &ops->func_hash->filter_hash,
- filter_hash, 1);
+ ret = __ftrace_hash_move_and_update_ops(ops, &ops->func_hash->filter_hash,
+ filter_hash, 1);
if (ret < 0)
return ret;
}

if (!ops_equal(notrace_hash, ops->func_hash->notrace_hash)) {
- ret = ftrace_hash_move_and_update_ops(ops, &ops->func_hash->notrace_hash,
- notrace_hash, 0);
+ ret = __ftrace_hash_move_and_update_ops(ops, &ops->func_hash->notrace_hash,
+ notrace_hash, 0);
if (ret < 0)
return ret;
}
@@ -3435,7 +3453,8 @@ int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int
} else {
free_ftrace_hash(save_filter_hash);
free_ftrace_hash(save_notrace_hash);
- subops->flags |= FTRACE_OPS_FL_ENABLED;
+ subops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP;
+ subops->managed = ops;
}
return ret;
}
@@ -3489,11 +3508,12 @@ int ftrace_startup_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, int
ret = ftrace_update_ops(ops, filter_hash, notrace_hash);
free_ftrace_hash(filter_hash);
free_ftrace_hash(notrace_hash);
- if (ret < 0)
+ if (ret < 0) {
list_del(&subops->list);
- else
- subops->flags |= FTRACE_OPS_FL_ENABLED;
-
+ } else {
+ subops->flags |= FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP;
+ subops->managed = ops;
+ }
return ret;
}

@@ -3538,6 +3558,8 @@ int ftrace_shutdown_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, in
free_ftrace_hash(ops->func_hash->notrace_hash);
ops->func_hash->filter_hash = EMPTY_HASH;
ops->func_hash->notrace_hash = EMPTY_HASH;
+ subops->flags &= ~(FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP);
+ subops->managed = NULL;

return 0;
}
@@ -3553,16 +3575,65 @@ int ftrace_shutdown_subops(struct ftrace_ops *ops, struct ftrace_ops *subops, in
}

ret = ftrace_update_ops(ops, filter_hash, notrace_hash);
- if (ret < 0)
+ if (ret < 0) {
list_add(&subops->list, &ops->subop_list);
- else
- subops->flags &= ~FTRACE_OPS_FL_ENABLED;
-
+ } else {
+ subops->flags &= ~(FTRACE_OPS_FL_ENABLED | FTRACE_OPS_FL_SUBOP);
+ subops->managed = NULL;
+ }
free_ftrace_hash(filter_hash);
free_ftrace_hash(notrace_hash);
return ret;
}

+static int ftrace_hash_move_and_update_subops(struct ftrace_ops *subops,
+ struct ftrace_hash **orig_subhash,
+ struct ftrace_hash *hash,
+ int enable)
+{
+ struct ftrace_ops *ops = subops->managed;
+ struct ftrace_hash **orig_hash;
+ struct ftrace_hash *save_hash;
+ struct ftrace_hash *new_hash;
+ int ret;
+
+ /* Manager ops can not be subops (yet) */
+ if (WARN_ON_ONCE(!ops || ops->flags & FTRACE_OPS_FL_SUBOP))
+ return -EINVAL;
+
+ /* Move the new hash over to the subops hash */
+ save_hash = *orig_subhash;
+ *orig_subhash = __ftrace_hash_move(hash);
+ if (!*orig_subhash) {
+ *orig_subhash = save_hash;
+ return -ENOMEM;
+ }
+
+ /* Create a new_hash to hold the ops new functions */
+ if (enable) {
+ orig_hash = &ops->func_hash->filter_hash;
+ new_hash = append_hashes(ops);
+ } else {
+ orig_hash = &ops->func_hash->notrace_hash;
+ new_hash = intersect_hashes(ops);
+ }
+
+ /* Move the hash over to the new hash */
+ ret = __ftrace_hash_move_and_update_ops(ops, orig_hash, new_hash, enable);
+
+ free_ftrace_hash(new_hash);
+
+ if (ret) {
+ /* Put back the original hash */
+ free_ftrace_hash_rcu(*orig_subhash);
+ *orig_subhash = save_hash;
+ } else {
+ free_ftrace_hash_rcu(save_hash);
+ }
+ return ret;
+}
+
+
static u64 ftrace_update_time;
unsigned long ftrace_update_tot_cnt;
unsigned long ftrace_number_of_pages;
@@ -4779,19 +4850,33 @@ static int ftrace_hash_move_and_update_ops(struct ftrace_ops *ops,
struct ftrace_hash *hash,
int enable)
{
- struct ftrace_ops_hash old_hash_ops;
- struct ftrace_hash *old_hash;
- int ret;
+ if (ops->flags & FTRACE_OPS_FL_SUBOP)
+ return ftrace_hash_move_and_update_subops(ops, orig_hash, hash, enable);

- old_hash = *orig_hash;
- old_hash_ops.filter_hash = ops->func_hash->filter_hash;
- old_hash_ops.notrace_hash = ops->func_hash->notrace_hash;
- ret = ftrace_hash_move(ops, enable, orig_hash, hash);
- if (!ret) {
- ftrace_ops_update_code(ops, &old_hash_ops);
- free_ftrace_hash_rcu(old_hash);
+ /*
+ * If this ops is not enabled, it could be sharing its filters
+ * with a subop. If that's the case, update the subop instead of
+ * this ops. Shared filters are only allowed to have one ops set
+ * at a time, and if we update the ops that is not enabled,
+ * it will not affect subops that share it.
+ */
+ if (!(ops->flags & FTRACE_OPS_FL_ENABLED)) {
+ struct ftrace_ops *op;
+
+ /* Check if any other manager subops maps to this hash */
+ do_for_each_ftrace_op(op, ftrace_ops_list) {
+ struct ftrace_ops *subops;
+
+ list_for_each_entry(subops, &op->subop_list, list) {
+ if ((subops->flags & FTRACE_OPS_FL_ENABLED) &&
+ subops->func_hash == ops->func_hash) {
+ return ftrace_hash_move_and_update_subops(subops, orig_hash, hash, enable);
+ }
+ }
+ } while_for_each_ftrace_op(op);
}
- return ret;
+
+ return __ftrace_hash_move_and_update_ops(ops, orig_hash, hash, enable);
}

static bool module_exists(const char *module)
--
2.43.0