From f60d81217ef391d12654f4b35eb9af852bf1c3c5 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 23 Nov 2023 17:06:06 -0500 Subject: [PATCH] Extensible struct side_event_state Signed-off-by: Mathieu Desnoyers --- include/side/trace.h | 19 ++++++++++++------- src/side.c | 30 ++++++++++++++++-------------- 2 files changed, 28 insertions(+), 21 deletions(-) diff --git a/include/side/trace.h b/include/side/trace.h index 811a283..15d74f2 100644 --- 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 84f5b32..d02a34f 100644 --- 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. -- 2.34.1