Extensible struct side_event_state

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/include/side/trace.h b/include/side/trace.h
index 811a283e8f67f34e1c976ec5758457412390e63e..15d74f2b1ffd146aa2b85005e549c377495763a8 100644 (file)
--- a/include/side/trace.h
+++ b/include/side/trace.h
@@ -88,8 +88,9 @@
  *   receiving the side_call arguments.
  *
  * * Event descriptions can be extended by adding fields at the end of
- *   the structure. The "struct side_event_description" is therefore a
- *   structure with flexible size and must not be used within arrays.
+ *   the structure. The "struct side_event_description" and "struct
+ *   side_event_state" are therefore structures with flexible size and
+ *   must not be used within arrays.
  */
 
 #define SIDE_ABI_VERSION       0
@@ -739,9 +740,12 @@ struct side_event_description {
  * fields.
  */
 struct side_event_state {
-       uintptr_t enabled;
-       const struct side_callback *callbacks;
-       struct side_event_description *desc;
+       uint32_t struct_size;   /* Size of this structure. */
+       uint32_t enabled;
+       side_ptr_t(const struct side_callback) callbacks;
+       side_ptr_t(struct side_event_description) desc;
+
+       char end[];     /* End with a flexible array to account for extensibility. */
 };
 
 /* Event and type attributes */
@@ -1878,9 +1882,10 @@ struct side_event_state {
                        _identifier; \
        _linkage struct side_event_state __attribute__((section("side_event_state"))) \
                        side_event_state__##_identifier = { \
+               .struct_size = offsetof(struct side_event_state, end), \
                .enabled = 0, \
-               .callbacks = &side_empty_callback, \
-               .desc = &(_identifier), \
+               .callbacks = SIDE_PTR_INIT(&side_empty_callback), \
+               .desc = SIDE_PTR_INIT(&(_identifier)), \
        }; \
        _linkage struct side_event_description __attribute__((section("side_event_description"))) \
                        _identifier = { \

diff --git a/src/side.c b/src/side.c
index 84f5b32de0cb0ea6f0129ef2f2ce8f316ca6638a..d02a34f135b6ada078ed5821cdd5245c8cdad7a4 100644 (file)
--- a/src/side.c
+++ b/src/side.c
@@ -73,14 +73,14 @@ void side_call(const struct side_event_state *event_state, const struct side_arg
                return;
        if (side_unlikely(!initialized))
                side_init();
-       assert(!(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC));
+       assert(!(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC));
        enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
        if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
                // TODO: call kernel write.
        }
        side_rcu_read_begin(&rcu_gp, &rcu_read_state);
-       for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call != NULL; side_cb++)
-               side_cb->u.call(event_state->desc, side_arg_vec, side_cb->priv);
+       for (side_cb = side_rcu_dereference(side_ptr_get(event_state->callbacks)); side_cb->u.call != NULL; side_cb++)
+               side_cb->u.call(side_ptr_get(event_state->desc), side_arg_vec, side_cb->priv);
        side_rcu_read_end(&rcu_gp, &rcu_read_state);
 }
 
@@ -96,14 +96,14 @@ void side_call_variadic(const struct side_event_state *event_state,
                return;
        if (side_unlikely(!initialized))
                side_init();
-       assert(event_state->desc->flags & SIDE_EVENT_FLAG_VARIADIC);
+       assert(side_ptr_get(event_state->desc)->flags & SIDE_EVENT_FLAG_VARIADIC);
        enabled = __atomic_load_n(&event_state->enabled, __ATOMIC_RELAXED);
        if (side_unlikely(enabled & SIDE_EVENT_ENABLED_KERNEL_USER_EVENT_MASK)) {
                // TODO: call kernel write.
        }
        side_rcu_read_begin(&rcu_gp, &rcu_read_state);
-       for (side_cb = side_rcu_dereference(event_state->callbacks); side_cb->u.call_variadic != NULL; side_cb++)
-               side_cb->u.call_variadic(event_state->desc, side_arg_vec, var_struct, side_cb->priv);
+       for (side_cb = side_rcu_dereference(side_ptr_get(event_state->callbacks)); side_cb->u.call_variadic != NULL; side_cb++)
+               side_cb->u.call_variadic(side_ptr_get(event_state->desc), side_arg_vec, var_struct, side_cb->priv);
        side_rcu_read_end(&rcu_gp, &rcu_read_state);
 }
 
@@ -115,7 +115,7 @@ const struct side_callback *side_tracer_callback_lookup(
        struct side_event_state *event_state = side_ptr_get(desc->state);
        const struct side_callback *cb;
 
-       for (cb = event_state->callbacks; cb->u.call != NULL; cb++) {
+       for (cb = side_ptr_get(event_state->callbacks); cb->u.call != NULL; cb++) {
                if ((void *) cb->u.call == call && cb->priv == priv)
                        return cb;
        }
@@ -149,7 +149,7 @@ int _side_tracer_callback_register(struct side_event_description *desc,
                ret = SIDE_ERROR_EXIST;
                goto unlock;
        }
-       old_cb = (struct side_callback *) event_state->callbacks;
+       old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
        /* old_nr_cb + 1 (new cb) + 1 (NULL) */
        new_cb = (struct side_callback *) calloc(old_nr_cb + 2, sizeof(struct side_callback));
        if (!new_cb) {
@@ -164,7 +164,8 @@ int _side_tracer_callback_register(struct side_event_description *desc,
                new_cb[old_nr_cb].u.call =
                        (side_tracer_callback_func) call;
        new_cb[old_nr_cb].priv = priv;
-       side_rcu_assign_pointer(event_state->callbacks, new_cb);
+       /* High order bits are already zeroed. */
+       side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), new_cb);
        side_rcu_wait_grace_period(&rcu_gp);
        if (old_nr_cb)
                free(old_cb);
@@ -219,11 +220,11 @@ static int _side_tracer_callback_unregister(struct side_event_description *desc,
                goto unlock;
        }
        old_nr_cb = desc->nr_callbacks;
-       old_cb = (struct side_callback *) event_state->callbacks;
+       old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
        if (old_nr_cb == 1) {
                new_cb = (struct side_callback *) &side_empty_callback;
        } else {
-               pos_idx = cb_pos - event_state->callbacks;
+               pos_idx = cb_pos - side_ptr_get(event_state->callbacks);
                /* Remove entry at pos_idx. */
                /* old_nr_cb - 1 (removed cb) + 1 (NULL) */
                new_cb = (struct side_callback *) calloc(old_nr_cb, sizeof(struct side_callback));
@@ -234,7 +235,8 @@ static int _side_tracer_callback_unregister(struct side_event_description *desc,
                memcpy(new_cb, old_cb, pos_idx);
                memcpy(&new_cb[pos_idx], &old_cb[pos_idx + 1], old_nr_cb - pos_idx - 1);
        }
-       side_rcu_assign_pointer(event_state->callbacks, new_cb);
+       /* High order bits are already zeroed. */
+       side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), new_cb);
        side_rcu_wait_grace_period(&rcu_gp);
        free(old_cb);
        desc->nr_callbacks--;
@@ -300,7 +302,7 @@ void side_event_remove_callbacks(struct side_event_description *desc)
 
        if (!nr_cb)
                return;
-       old_cb = (struct side_callback *) event_state->callbacks;
+       old_cb = (struct side_callback *) side_ptr_get(event_state->callbacks);
        (void) __atomic_add_fetch(&event_state->enabled, -1, __ATOMIC_RELAXED);
        /*
         * Setting the state back to 0 cb and empty callbacks out of
@@ -308,7 +310,7 @@ void side_event_remove_callbacks(struct side_event_description *desc)
         * unreachable.
         */
        desc->nr_callbacks = 0;
-       side_rcu_assign_pointer(event_state->callbacks, &side_empty_callback);
+       side_rcu_assign_pointer(side_ptr_get(event_state->callbacks), &side_empty_callback);
        /*
         * No need to wait for grace period because instrumentation is
         * unreachable.