From: Francis Deslauriers <francis.deslauriers@efficios.com>
Date: Mon, 27 Apr 2020 19:11:38 +0000 (-0400)
Subject: Add `interpreter_funcs` to `lttng_bytecode_runtime`
X-Git-Tag: v2.13.0-rc1~438
X-Git-Url: http://git.lttng.org/?p=lttng-ust.git;a=commitdiff_plain;h=c42416df21bb28b9b19ca509f7242f660c5469b2

Add `interpreter_funcs` to `lttng_bytecode_runtime`

Background
==========
The current filter interpreter function signature looks like this:

  uint64_t lttng_bytecode_filter_interpret(void *filter_data,
                  const char *filter_stack_data);

The upcoming capture interpreter function will need an output parameter
to extract the top of stack register. It will look like this:

  uint64_t lttng_bytecode_capture_interpret(void *capture_data,
                  const char *capture_stack_data,
                  struct output_register *output);

Problems
========
We can't reuse the same function pointer field in `struct
lttng_bytecode_runtime` as the two interpreter functions will have
different signatures.

We can't change the signature of this existing filter function because
it's used in the tracepoint probes.

Solution
========
Add a union of callbacks to hold both interpreter functions. This also
doesn't change the layout of the `struct lttng_bytecode_runtime`
objects.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I9fcd6def9ce7783087b9648ddbf5ec71fb7b997a
---

diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index ae5ce5f6..41164ac3 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -443,8 +443,10 @@ enum lttng_bytecode_interpreter_ret {
 struct lttng_bytecode_runtime {
 	/* Associated bytecode */
 	struct lttng_ust_bytecode_node *bc;
-	uint64_t (*filter)(void *interpreter_data,
-			const char *interpreter_stack_data);
+	union {
+		uint64_t (*filter)(void *interpreter_data,
+				const char *interpreter_stack_data);
+	} interpreter_funcs;
 	int link_failed;
 	struct cds_list_head node;	/* list of bytecode runtime in event */
 	/*
diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index 00e931a8..1f8be1a9 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -878,7 +878,7 @@ void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))	      \
 		__event_prepare_filter_stack__##_provider##___##_name(__stackvar.__filter_stack_data, \
 			_TP_ARGS_DATA_VAR(_args));			      \
 		tp_list_for_each_entry_rcu(__filter_bc_runtime, &__event->filter_bytecode_runtime_head, node) { \
-			if (caa_unlikely(__filter_bc_runtime->filter(__filter_bc_runtime,	      \
+			if (caa_unlikely(__filter_bc_runtime->interpreter_funcs.filter(__filter_bc_runtime,     \
 					__stackvar.__filter_stack_data) & LTTNG_INTERPRETER_RECORD_FLAG)) { \
 				__filter_record = 1;			      \
 				break;					      \
@@ -960,7 +960,7 @@ void __event_notifier_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))
 		__event_prepare_filter_stack__##_provider##___##_name(__stackvar.__filter_stack_data, \
 			_TP_ARGS_DATA_VAR(_args));			      \
 		tp_list_for_each_entry_rcu(__filter_bc_runtime, &__event_notifier->filter_bytecode_runtime_head, node) { \
-			if (caa_unlikely(__filter_bc_runtime->filter(__filter_bc_runtime,	     \
+			if (caa_unlikely(__filter_bc_runtime->interpreter_funcs.filter(__filter_bc_runtime,	  \
 					__stackvar.__filter_stack_data) & LTTNG_INTERPRETER_RECORD_FLAG)) \
 				__filter_record = 1;			      \
 		}							      \
diff --git a/liblttng-ust/lttng-bytecode.c b/liblttng-ust/lttng-bytecode.c
index 47efdeca..bbf8e7e7 100644
--- a/liblttng-ust/lttng-bytecode.c
+++ b/liblttng-ust/lttng-bytecode.c
@@ -478,14 +478,29 @@ int _lttng_filter_link_bytecode(const struct lttng_event_desc *event_desc,
 	if (ret) {
 		goto link_error;
 	}
-	runtime->p.filter = lttng_bytecode_filter_interpret;
+
+	switch (bytecode->type) {
+	case LTTNG_UST_BYTECODE_NODE_TYPE_FILTER:
+		runtime->p.interpreter_funcs.filter = lttng_bytecode_filter_interpret;
+		break;
+	default:
+		abort();
+	}
+
 	runtime->p.link_failed = 0;
 	cds_list_add_rcu(&runtime->p.node, insert_loc);
 	dbg_printf("Linking successful.\n");
 	return 0;
 
 link_error:
-	runtime->p.filter = lttng_bytecode_filter_interpret_false;
+	switch (bytecode->type) {
+	case LTTNG_UST_BYTECODE_NODE_TYPE_FILTER:
+		runtime->p.interpreter_funcs.filter = lttng_bytecode_filter_interpret_false;
+		break;
+	default:
+		abort();
+	}
+
 	runtime->p.link_failed = 1;
 	cds_list_add_rcu(&runtime->p.node, insert_loc);
 alloc_error:
@@ -498,9 +513,9 @@ void lttng_bytecode_filter_sync_state(struct lttng_bytecode_runtime *runtime)
 	struct lttng_ust_bytecode_node *bc = runtime->bc;
 
 	if (!bc->enabler->enabled || runtime->link_failed)
-		runtime->filter = lttng_bytecode_filter_interpret_false;
+		runtime->interpreter_funcs.filter = lttng_bytecode_filter_interpret_false;
 	else
-		runtime->filter = lttng_bytecode_filter_interpret;
+		runtime->interpreter_funcs.filter = lttng_bytecode_filter_interpret;
 }
 
 /*