[lttng-dev] [RFC-patch] Add support of variant (raw) metadata

[Geneviève Bastien]

Add macros to allow to specify some raw metadata for a tracepoint event
field.
Add macros to copy dynamic length data without the length field with it,
for instance for variant event types.

Signed-off-by: Geneviève Bastien <gbastien+lttng at versatic.net>
---
 lttng-events.c              |  7 +++++++
 lttng-events.h              |  4 ++++
 probes/lttng-events-reset.h |  6 ++++++
 probes/lttng-events.h       | 45 +++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 62 insertions(+)

diff --git a/lttng-events.c b/lttng-events.c
index 4f30904..8ceecf5 100644
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -654,6 +654,13 @@ int _lttng_field_statedump(struct lttng_session *session,
 				" { encoding = ASCII; }" : "",
 			field->name);
 		break;
+	case atype_raw:
+		/* field contains raw metadata!  No guarantee it is valid */
+		ret = lttng_metadata_printf(session,
+			"		%s _%s;\n",
+			field->type.u.raw.raw_data,
+			field->name);
+		break;
 	default:
 		WARN_ON_ONCE(1);
 		return -EINVAL;
diff --git a/lttng-events.h b/lttng-events.h
index 09d5618..968e2a4 100644
--- a/lttng-events.h
+++ b/lttng-events.h
@@ -48,6 +48,7 @@ enum abstract_types {
 	atype_array,
 	atype_sequence,
 	atype_string,
+	atype_raw,
 	NR_ABSTRACT_TYPES,
 };
 
@@ -116,6 +117,9 @@ struct lttng_type {
 			struct lttng_basic_type length_type;
 			struct lttng_basic_type elem_type;
 		} sequence;
+		struct {
+			char *raw_data;
+		} raw;
 	} u;
 };
 
diff --git a/probes/lttng-events-reset.h b/probes/lttng-events-reset.h
index 7355e18..8c9cf4d 100644
--- a/probes/lttng-events-reset.h
+++ b/probes/lttng-events-reset.h
@@ -35,6 +35,9 @@
 #undef __string
 #define __string(_item, _src)
 
+#undef __variant_raw
+#define __variant_raw(_item, _raw_metadata, _length)
+
 #undef tp_assign
 #define tp_assign(dest, src)
 
@@ -44,6 +47,9 @@
 #undef tp_memcpy_dyn
 #define tp_memcpy_dyn(dest, src, len)
 
+#undef tp_memcpy_var
+#define tp_memcpy_var(dest, src, len)
+
 #undef tp_strcpy
 #define tp_strcpy(dest, src)
 
diff --git a/probes/lttng-events.h b/probes/lttng-events.h
index 33cabcf..ce5b647 100644
--- a/probes/lttng-events.h
+++ b/probes/lttng-events.h
@@ -205,6 +205,21 @@ void trace_##_name(void *__data);
 #define __string_from_user(_item, _src)				\
 	__string(_item, _src)
 
+#undef __variant_raw
+#define __variant_raw(_item, _raw_metadata, _length)			\
+	{							\
+	  .name = #_item,					\
+	  .type =						\
+		{						\
+		  .atype = atype_raw,			\
+		  .u.raw.raw_data = #_raw_metadata,	\
+		},						\
+	},
+
+#undef __variant_raw_from_user
+#define __variant_raw_from_user(_item, _raw_metadata, _length)	\
+	__variant_raw(_item, _raw_metadata, _length)
+
 #undef TP_STRUCT__entry
 #define TP_STRUCT__entry(args...) args	/* Only one used in this phase */
 
@@ -353,6 +368,11 @@ static __used struct lttng_probe_desc TP_ID(__probe_desc___, TRACE_SYSTEM) = {
 #define __string(_item, _src)						       \
 	__event_len += __dynamic_len[__dynamic_len_idx++] = strlen(_src) + 1;
 
+#undef __variant_raw
+#define __variant_raw(_item, _raw_metadata, _length)			\
+	__event_len += __dynamic_len[__dynamic_len_idx++] = (_length);
+
+
 /*
  * strlen_user includes \0. If returns 0, it faulted, so we set size to
  * 1 (\0 only).
@@ -459,6 +479,10 @@ static inline size_t __event_get_align__##_name(_proto)			      \
 #define __string_from_user(_item, _src)		\
 	__string(_item, _src)
 
+#undef __variant_raw
+#define __variant_raw(_item, _raw_metadata, _length)	\
+	char	*_item;
+
 #undef TP_STRUCT__entry
 #define TP_STRUCT__entry(args...) args
 
@@ -510,6 +534,11 @@ __end_field_##_item:
 #define __string_from_user(_item, _src)					\
 	__string(_item, _src)
 
+#undef __variant_raw
+#define __variant_raw(_item, _raw_metadata, _length)		\
+	goto __assign_##_item;		\
+__end_field_##_item:
+
 /*
  * Macros mapping tp_assign() to "=", tp_memcpy() to memcpy() and tp_strcpy() to
  * strcpy().
@@ -566,6 +595,22 @@ __assign_##dest##_2:							\
 #define tp_memcpy_dyn_from_user(dest, src)				\
 	tp_memcpy_dyn_gen(event_write_from_user, dest, src)
 
+/* variable length sequence copy, with no size in metadata */
+#undef tp_memcpy_var_gen
+#define tp_memcpy_var_gen(write_ops, dest, src)			\
+__assign_##dest:						\
+	lib_ring_buffer_align_ctx(&__ctx, 8);	\
+	__chan->ops->write_ops(&__ctx, src, __get_dynamic_array_len(dest));	\
+	goto __end_field_##dest;
+
+#undef tp_memcpy_var
+#define tp_memcpy_var(dest, src)					\
+	tp_memcpy_var_gen(event_write, dest, src)
+
+#undef tp_memcpy_var_from_user
+#define tp_memcpy_var_from_user(dest, src)				\
+	tp_memcpy_var_gen(event_write_from_user, dest, src)
+
 /*
  * The string length including the final \0.
  */
-- 
1.8.2