ftrace: Add multi direct register/unregister interface

Adding interface to register multiple direct functions
within single call. Adding following functions:

  register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
  unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)

The register_ftrace_direct_multi registers direct function (addr)
with all functions in ops filter. The ops filter can be updated
before with ftrace_set_filter_ip calls.

All requested functions must not have direct function currently
registered, otherwise register_ftrace_direct_multi will fail.

The unregister_ftrace_direct_multi unregisters ops related direct
functions.

Link: https://lkml.kernel.org/r/20211008091336.33616-7-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 16a7baa..0158261 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -324,7 +324,10 @@ int ftrace_modify_direct_caller(struct ftrace_func_entry *entry,
                                unsigned long old_addr,
                                unsigned long new_addr);
 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);
 #else
+struct ftrace_ops;
 # define ftrace_direct_func_count 0
 static inline int register_ftrace_direct(unsigned long ip, unsigned long addr)
 {
@@ -354,6 +357,14 @@ static inline unsigned long ftrace_find_rec_direct(unsigned long ip)
 {
        return 0;
 }
+static inline int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+       return -ENODEV;
+}
+static inline int unregister_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 ccbd837..a05b25f 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5401,6 +5401,148 @@ int modify_ftrace_direct(unsigned long ip,
        return ret;
 }
 EXPORT_SYMBOL_GPL(modify_ftrace_direct);
+
+#define MULTI_FLAGS (FTRACE_OPS_FL_IPMODIFY | FTRACE_OPS_FL_DIRECT | \
+                    FTRACE_OPS_FL_SAVE_REGS)
+
+static int check_direct_multi(struct ftrace_ops *ops)
+{
+       if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED))
+               return -EINVAL;
+       if ((ops->flags & MULTI_FLAGS) != MULTI_FLAGS)
+               return -EINVAL;
+       return 0;
+}
+
+static void remove_direct_functions_hash(struct ftrace_hash *hash, unsigned long addr)
+{
+       struct ftrace_func_entry *entry, *del;
+       int size, i;
+
+       size = 1 << hash->size_bits;
+       for (i = 0; i < size; i++) {
+               hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
+                       del = __ftrace_lookup_ip(direct_functions, entry->ip);
+                       if (del && del->direct == addr) {
+                               remove_hash_entry(direct_functions, del);
+                               kfree(del);
+                       }
+               }
+       }
+}
+
+/**
+ * register_ftrace_direct_multi - Call a custom trampoline directly
+ * for multiple functions registered in @ops
+ * @ops: The address of the struct ftrace_ops object
+ * @addr: The address of the trampoline to call at @ops functions
+ *
+ * This is used to connect a direct calls to @addr from the nop locations
+ * of the functions registered in @ops (with by ftrace_set_filter_ip
+ * function).
+ *
+ * The location that it calls (@addr) must be able to handle a direct call,
+ * and save the parameters of the function being traced, and restore them
+ * (or inject new ones if needed), before returning.
+ *
+ * Returns:
+ *  0 on success
+ *  -EINVAL  - The @ops object was already registered with this call or
+ *             when there are no functions in @ops object.
+ *  -EBUSY   - Another direct function is already attached (there can be only one)
+ *  -ENODEV  - @ip does not point to a ftrace nop location (or not supported)
+ *  -ENOMEM  - There was an allocation failure.
+ */
+int register_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+       struct ftrace_hash *hash, *free_hash = NULL;
+       struct ftrace_func_entry *entry, *new;
+       int err = -EBUSY, size, i;
+
+       if (ops->func || ops->trampoline)
+               return -EINVAL;
+       if (!(ops->flags & FTRACE_OPS_FL_INITIALIZED))
+               return -EINVAL;
+       if (ops->flags & FTRACE_OPS_FL_ENABLED)
+               return -EINVAL;
+
+       hash = ops->func_hash->filter_hash;
+       if (ftrace_hash_empty(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_find_rec_direct(entry->ip))
+                               goto out_unlock;
+               }
+       }
+
+       /* ... and insert them to direct_functions hash. */
+       err = -ENOMEM;
+       for (i = 0; i < size; i++) {
+               hlist_for_each_entry(entry, &hash->buckets[i], hlist) {
+                       new = ftrace_add_rec_direct(entry->ip, addr, &free_hash);
+                       if (!new)
+                               goto out_remove;
+                       entry->direct = addr;
+               }
+       }
+
+       ops->func = call_direct_funcs;
+       ops->flags = MULTI_FLAGS;
+       ops->trampoline = FTRACE_REGS_ADDR;
+
+       err = register_ftrace_function(ops);
+
+ out_remove:
+       if (err)
+               remove_direct_functions_hash(hash, addr);
+
+ out_unlock:
+       mutex_unlock(&direct_mutex);
+
+       if (free_hash) {
+               synchronize_rcu_tasks();
+               free_ftrace_hash(free_hash);
+       }
+       return err;
+}
+EXPORT_SYMBOL_GPL(register_ftrace_direct_multi);
+
+/**
+ * unregister_ftrace_direct_multi - Remove calls to custom trampoline
+ * previously registered by register_ftrace_direct_multi for @ops object.
+ * @ops: The address of the struct ftrace_ops object
+ *
+ * This is used to remove a direct calls to @addr from the nop locations
+ * of the functions registered in @ops (with by ftrace_set_filter_ip
+ * function).
+ *
+ * Returns:
+ *  0 on success
+ *  -EINVAL - The @ops object was not properly registered.
+ */
+int unregister_ftrace_direct_multi(struct ftrace_ops *ops, unsigned long addr)
+{
+       struct ftrace_hash *hash = ops->func_hash->filter_hash;
+       int err;
+
+       if (check_direct_multi(ops))
+               return -EINVAL;
+       if (!(ops->flags & FTRACE_OPS_FL_ENABLED))
+               return -EINVAL;
+
+       mutex_lock(&direct_mutex);
+       err = unregister_ftrace_function(ops);
+       remove_direct_functions_hash(hash, addr);
+       mutex_unlock(&direct_mutex);
+       return err;
+}
+EXPORT_SYMBOL_GPL(unregister_ftrace_direct_multi);
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
 /**