From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Tue, 16 Mar 2021 03:13:54 +0000 (-0400)
Subject: Refactoring: struct lttng_stack_ctx
X-Git-Tag: v2.13.0-rc1~283
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=2a9d9339386426860c1df91d0b8010c87809c84b;p=lttng-ust.git

Refactoring: struct lttng_stack_ctx

- Namespace this structure with lttng_ust_ prefix,
- Use struct_size extensibility scheme.
- Remove padding.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ieb0679f78a18553c6d60a70d78e0f7f99181d646
---

diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 13ecb6d7..624af8bb 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -566,12 +566,23 @@ struct lttng_channel {
 	int tstate:1;			/* Transient enable state */
 };
 
-#define LTTNG_UST_STACK_CTX_PADDING	32
-struct lttng_stack_ctx {
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ *
+ * The field @struct_size should be used to determine the size of the
+ * structure. It should be queried before using additional fields added
+ * at the end of the structure.
+ */
+struct lttng_ust_stack_ctx {
+	uint32_t struct_size;			/* Size of this structure */
+
 	struct lttng_ust_event_recorder *event_recorder;
 	struct lttng_ctx *chan_ctx;	/* RCU dereferenced. */
 	struct lttng_ctx *event_ctx;	/* RCU dereferenced. */
-	char padding[LTTNG_UST_STACK_CTX_PADDING];
+
+	/* End of base ABI. Fields below should be used after checking struct_size. */
 };
 
 struct lttng_ust_session_private;
diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index 428ff0b1..c4e4f1ed 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -846,12 +846,13 @@ void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))	      \
 		struct lttng_ust_event_recorder *__event_recorder = (struct lttng_ust_event_recorder *) __event->child; \
 		struct lttng_channel *__chan = __event_recorder->chan;	      \
 		struct lttng_ust_lib_ring_buffer_ctx __ctx;		      \
-		struct lttng_stack_ctx __lttng_ctx;			      \
+		struct lttng_ust_stack_ctx __lttng_ctx;			      \
 									      \
 		__event_len = __event_get_size__##_provider##___##_name(__stackvar.__dynamic_len, \
 			 _TP_ARGS_DATA_VAR(_args));			      \
 		__event_align = __event_get_align__##_provider##___##_name(_TP_ARGS_VAR(_args)); \
 		memset(&__lttng_ctx, 0, sizeof(__lttng_ctx));		      \
+		__lttng_ctx.struct_size = sizeof(struct lttng_ust_stack_ctx);     \
 		__lttng_ctx.event_recorder = __event_recorder;		      \
 		__lttng_ctx.chan_ctx = tp_rcu_dereference(__chan->ctx);	      \
 		__lttng_ctx.event_ctx = tp_rcu_dereference(__event_recorder->ctx); \
diff --git a/liblttng-ust/lttng-ring-buffer-client.h b/liblttng-ust/lttng-ring-buffer-client.h
index c3b77182..ad336737 100644
--- a/liblttng-ust/lttng-ring-buffer-client.h
+++ b/liblttng-ust/lttng-ring-buffer-client.h
@@ -172,7 +172,7 @@ size_t record_header_size(const struct lttng_ust_lib_ring_buffer_config *config,
 				 struct lttng_client_ctx *client_ctx)
 {
 	struct lttng_channel *lttng_chan = channel_get_private(chan);
-	struct lttng_stack_ctx *lttng_ctx = ctx->priv;
+	struct lttng_ust_stack_ctx *lttng_ctx = ctx->priv;
 	size_t orig_offset = offset;
 	size_t padding;
 
@@ -242,7 +242,7 @@ void lttng_write_event_header(const struct lttng_ust_lib_ring_buffer_config *con
 			    uint32_t event_id)
 {
 	struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
-	struct lttng_stack_ctx *lttng_ctx = ctx->priv;
+	struct lttng_ust_stack_ctx *lttng_ctx = ctx->priv;
 
 	if (caa_unlikely(ctx->rflags))
 		goto slow_path;
@@ -293,7 +293,7 @@ void lttng_write_event_header_slow(const struct lttng_ust_lib_ring_buffer_config
 				 uint32_t event_id)
 {
 	struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
-	struct lttng_stack_ctx *lttng_ctx = ctx->priv;
+	struct lttng_ust_stack_ctx *lttng_ctx = ctx->priv;
 
 	switch (lttng_chan->header_type) {
 	case 1:	/* compact */
@@ -680,7 +680,7 @@ int lttng_event_reserve(struct lttng_ust_lib_ring_buffer_ctx *ctx,
 		      uint32_t event_id)
 {
 	struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
-	struct lttng_stack_ctx *lttng_ctx = ctx->priv;
+	struct lttng_ust_stack_ctx *lttng_ctx = ctx->priv;
 	struct lttng_client_ctx client_ctx;
 	int ret, cpu;