needs of the embedded, telecom, high-performance and kernel communities. It is
based on the Common Trace Format Requirements (v1.4) document. It is designed to
allow traces to be natively generated by the Linux kernel, Linux user-space
-applications written in C/C++, and hardware components.
+applications written in C/C++, and hardware components. One major element of
+CTF is the Trace Stream Description Language (TSDL) which flexibility
+enables description of various binary trace stream layouts.
The latest version of this document can be found at:
being recorded, each is associated with a separate file for output. Therefore,
a stored trace can be represented as a directory containing one file per stream.
-A metadata event stream contains information on trace event types. It describes:
+A metadata event stream contains information on trace event types
+expressed in the Trace Stream Description Language (TSDL). It describes:
- Trace version.
- Types available.
size = 32;
signed = false;
align = 32;
-} typename uint32_t;
+} := uint32_t;
Definition of a named 5-bit signed bitfield:
size = 5;
signed = true;
align = 1;
-} typename int5_t;
+} := int5_t;
4.1.6 GNU/C bitfields
exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
mant_dig = 24; /* FLT_MANT_DIG */
byte_order = native;
-} typename float;
+} := float;
TODO: define NaN, +inf, -inf behavior.
is in fact a range of size 1. This single-value range is supported without
repeating the start and end values with the value = string declaration.
-enum name <integer_type> {
+enum name : integer_type {
somestring = start_value1 ... end_value1,
"other string" = start_value2 ... end_value2,
yet_another_string, /* will be assigned to end_value2 + 1 */
If the values are omitted, the enumeration starts at 0 and increment of 1 for
each entry:
-enum name <unsigned int> {
+enum name : unsigned int {
ZERO,
ONE,
TWO,
A nameless enumeration can be declared as a field type or as part of a typedef:
-enum <integer_type> {
+enum : integer_type {
+ ...
+}
+
+Enumerations omitting the container type ": integer_type" use the "int"
+type (for compatibility with C99). The "int" type must be previously
+declared. E.g.:
+
+typealias integer { size = 32; align = 32; signed = true } := int;
+
+enum {
...
}
contained within a structure (defined recursively). A "tag" enumeration
field must appear in either the same lexical scope, prior to the variant
field (in field declaration order), in an uppermost lexical scope (see
-Section 7.2.1), or in an uppermost dynamic scope (see Section 7.2.2).
+Section 7.3.1), or in an uppermost dynamic scope (see Section 7.3.2).
The type selection is indicated by the mapping from the enumeration
value to the string used as variant type selector. The field to use as
tag is specified by the "tag_field", specified between "< >" after the
};
struct {
- enum <integer_type> { sel1, sel2, sel3, ... } tag_field;
+ enum : integer_type { sel1, sel2, sel3, ... } tag_field;
...
variant name <tag_field> v;
}
metadata:
struct {
- enum <integer_type> { sel1, sel2, sel3, ... } tag_field;
+ enum : integer_type { sel1, sel2, sel3, ... } tag_field;
...
variant <tag_field> {
field_type sel1;
};
struct {
- enum <uint2_t> { a, b, c } choice;
+ enum : uint2_t { a, b, c } choice;
variant example <choice> v[unsigned int];
}
Example of an unnamed variant:
struct {
- enum <uint2_t> { a, b, c, d } choice;
+ enum : uint2_t { a, b, c, d } choice;
/* Unrelated fields can be added between the variant and its tag */
int32_t somevalue;
variant <choice> {
Example of an unnamed variant within an array:
struct {
- enum <uint2_t> { a, b, c } choice;
+ enum : uint2_t { a, b, c } choice;
variant <choice> {
uint32_t a;
uint64_t b;
the lexical scope of the type definition.
struct {
- enum <uint2_t> { a, b, c, d } x;
+ enum : uint2_t { a, b, c, d } x;
typedef variant <x> { /*
* "x" refers to the preceding "x" enumeration in the
} example_variant;
struct {
- enum <int> { x, y, z } x; /* This enumeration is not used by "v". */
+ enum : int { x, y, z } x; /* This enumeration is not used by "v". */
example_variant v; /*
- * "v" uses the "enum <uint2_t> { a, b, c, d }"
+ * "v" uses the "enum : uint2_t { a, b, c, d }"
* tag.
*/
} a[10];
typealias string {
encoding = UTF8 OR ASCII;
-} typename name;
+} := name;
A nameless string type can be declared as a field type:
5.1 Event Packet Header Fixed Layout Description
+The event packet header layout is indicated by the trace packet.header
+field. Here is an example structure type for the packet header with the
+fields typically expected:
+
struct event_packet_header {
uint32_t magic;
uint8_t trace_uuid[16];
uint32_t stream_id;
};
+trace {
+ ...
+ packet.header := struct event_packet_header;
+};
+
+If a packet header lacks the "magic" number field, the trace endianness
+needs to be specified in the trace "endian" metadata attribute.
+
+If the trace_uuid is not present, no validation that the metadata
+actually corresponds to the stream is performed.
+
+If the stream_id packet header field is missing, the trace can only
+contain a single stream. Its "id" field can be left out, and its events
+don't need to declare a "stream_id" field.
+
+
5.2 Event Packet Context Description
Event packet context example. These are declared within the stream declaration
This structure defines an implicit dynamic scoping, where variants
located in inner structures (those with a higher number in the listing
above) can refer to the fields of outer structures (with lower number in
-the listing above). See Section 7.2 Metadata Scopes for more detail.
+the listing above). See Section 7.3 TSDL Scopes for more detail.
6.1 Event Header
* id: range: 0 - 30.
* id 31 is reserved to indicate an extended header.
*/
- enum <uint5_t> { compact = 0 ... 30, extended = 31 } id;
+ enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
variant <id> {
struct {
uint27_t timestamp;
* id: range: 0 - 65534.
* id 65535 is reserved to indicate an extended header.
*/
- enum <uint16_t> { compact = 0 ... 65534, extended = 65535 } id;
+ enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
variant <id> {
struct {
uint32_t timestamp;
contained within the payload. (This follows the ISO/C standard for structures)
-7. Metadata
+7. Trace Stream Description Language (TSDL)
+
+The Trace Stream Description Language (TSDL) allows expression of the
+binary trace streams layout in a C99-like Domain Specific Language
+(DSL).
+
+
+7.1 Metadata
+
+The trace stream layout description is located in the trace meta-data.
+The meta-data is itself located in a stream identified by its name:
+"metadata".
-The meta-data is located in a stream identified by its name: "metadata".
It is made of "event packets", which each start with an event packet
header. The event type within the metadata stream have no event header
-nor event context. Each event only contains a null-terminated "string"
-payload, which is a metadata description entry. The events are packed
-one next to another. Each event packet start with an event packet
-header, which contains, amongst other fields, the magic number and trace
-UUID. In the event packet header, the trace UUID is represented as an
-array of bytes. Within the string-based metadata description, the trace
-UUID is represented as a string of hexadecimal digits and dashes "-".
+nor event context. Each event only contains a "string" payload without
+any null-character. The events are packed one next to another. Each
+event packet start with an event packet header, which contains, amongst
+other fields, the magic number, trace UUID and packet length. In the
+event packet header, the trace UUID is represented as an array of bytes.
+Within the string-based metadata description, the trace UUID is
+represented as a string of hexadecimal digits and dashes "-".
-The metadata can be parsed by reading through the metadata strings,
-skipping null-characters. Type names are made of a single identifier,
-and can be surrounded by prefix/postfix. Text contained within "/*" and
-"*/", as well as within "//" and end of line, are treated as comments.
-Boolean values can be represented as true, TRUE, or 1 for true, and
-false, FALSE, or 0 for false.
+The metadata can be parsed by reading characters within the metadata
+stream, for each packet starting after the packet header, for the length
+of the packet payload specified in the header. Text contained within
+"/*" and "*/", as well as within "//" and end of line, are treated as
+comments. Boolean values can be represented as true, TRUE, or 1 for
+true, and false, FALSE, or 0 for false.
-7.1 Declaration vs Definition
+7.2 Declaration vs Definition
A declaration associates a layout to a type, without specifying where
this type is located in the event structure hierarchy (see Section 6).
the newly defined type name (for typedef), or the field name (for
declarations located within structure and variants). Array and sequence,
declared with square brackets ("[" "]"), are part of the declarator,
-similarly to C99. The enumeration type specifier and variant tag name
-(both specified with "<" ">") are part of the type specifier.
+similarly to C99. The enumeration base type is specified by
+": enum_base", which is part of the type specifier. The variant tag
+name, specified between "<" ">", is also part of the type specifier.
A definition associates a type to a location in the event structure
hierarchy (see Section 6). This association is denoted by ":=", as shown
in Section 7.3.
-7.2 Metadata Scopes
+7.3 TSDL Scopes
-CTF metadata uses two different types of scoping: a lexical scope is
-used for declarations and type definitions, and a dynamic scope is used
-for variants references to tag fields.
+TSDL uses two different types of scoping: a lexical scope is used for
+declarations and type definitions, and a dynamic scope is used for
+variants references to tag fields.
-7.2.1 Lexical Scope
+7.3.1 Lexical Scope
Each of "trace", "stream", "event", "struct" and "variant" have their own
nestable declaration scope, within which types can be declared using "typedef"
typedef or typealias is not valid, although hiding an upper scope
typedef or typealias is allowed within a sub-scope.
-7.2.2 Dynamic Scope
+7.3.2 Dynamic Scope
A dynamic scope consists in the lexical scope augmented with the
implicit event structure definition hierarchy presented at Section 6.
a field outside of the local static scope. The dynamic scope prefixes
are thus:
+ - Trace Packet Header: <trace.packet.header. >,
- Stream Packet Context: <stream.packet.context. >,
- Event Header: <stream.event.header. >,
- Stream Event Context: <stream.event.context. >,
readable by accessing the upper dynamic scopes.
-7.3 Metadata Examples
+7.4 TSDL Examples
+
+The grammar representing the TSDL metadata is presented in Appendix C.
+TSDL Grammar. This section presents a rather ligher reading that
+consists in examples of TSDL metadata, with template values.
+
+Note that the trace endianness is usually extracted from the packet
+header magic number. The "endian" field is only needed when the magic
+number packet header field is not present.
-The grammar representing the CTF metadata is presented in
-Appendix C. CTF Metadata Grammar. This section presents a rather ligher
-reading that consists in examples of CTF metadata, with template values:
+The stream "id" can be left out if there is only one stream in the
+trace. The event "id" field can be left out if there is only one event
+in a stream.
trace {
major = value; /* Trace format version */
minor = value;
uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
- word_size = value;
+ endian = big OR little; /* Endianness (optional) */
+ packet.header := struct {
+ uint32_t magic;
+ uint8_t trace_uuid[16];
+ uint32_t stream_id;
+ };
};
stream {
* pointer declarator specifier) to a type. It should also be used to
* map basic C types (float, int, unsigned long, ...) to a CTF type.
* Typealias is a superset of "typedef": it also allows assignment of a
- * simple variable identifier to a type. The keyword "typename" is
- * reserved to separate the aliased type from the newly declared alias
- * name.
+ * simple variable identifier to a type.
*/
typealias type_class {
...
-} typename type_specifiers type_declarator;
+} := type_specifiers type_declarator;
/*
* e.g.:
* size = 32;
* align = 32;
* signed = false;
- * } typename struct page *;
+ * } := struct page *;
*
* typealias integer {
* size = 32;
* align = 32;
* signed = true;
- * } typename int;
+ * } := int;
*/
struct name {
...
};
-enum name <integer_type> {
+enum name : integer_type {
...
};
...
}
-enum <integer_type> {
+enum : integer_type {
...
}
The event stream header will therefore be referred to as the "event packet
header" throughout the rest of this document.
-C. CTF Metadata Grammar
+
+C. TSDL Grammar
/*
- * Common Trace Format (CTF) Metadata Grammar.
+ * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
*
* Inspired from the C99 grammar:
* http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
+ * and c++1x grammar (draft)
+ * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
*
* Specialized for CTF needs by including only constant and declarations from
* C99 (excluding function declarations), and by adding support for variants,
- * sequences and CTF-specific specifiers.
+ * sequences and CTF-specific specifiers. Enumeration container types
+ * semantic is inspired from c++1x enum-base.
*/
1) Lexical grammar
trace
typealias
typedef
-typename
unsigned
variant
void
struct-or-variant-declaration:
specifier-qualifier-list struct-or-variant-declarator-list ;
declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ;
- typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list ;
- typealias declaration-specifiers abstract-declarator-list typename declarator-list ;
+ typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list ;
+ typealias declaration-specifiers abstract-declarator-list := declarator-list ;
specifier-qualifier-list:
type-specifier specifier-qualifier-list-opt
enum identifier-opt { enumerator-list }
enum identifier-opt { enumerator-list , }
enum identifier
- enum identifier-opt < declaration-specifiers > { enumerator-list }
- enum identifier-opt < declaration-specifiers > { enumerator-list , }
- enum identifier < declaration-specifiers >
+ enum identifier-opt : declaration-specifiers { enumerator-list }
+ enum identifier-opt : declaration-specifiers { enumerator-list , }
enumerator-list:
enumerator
event { ctf-assignment-expression-list-opt }
stream { ctf-assignment-expression-list-opt }
trace { ctf-assignment-expression-list-opt }
- typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list ;
- typealias declaration-specifiers abstract-declarator-list typename declarator-list ;
+ typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list ;
+ typealias declaration-specifiers abstract-declarator-list := declarator-list ;
ctf-type-specifier:
floating_point { ctf-assignment-expression-list-opt }
unary-expression assignment-operator unary-expression
unary-expression type-assignment-operator type-specifier
declaration-specifiers storage-class-specifier declaration-specifiers declarator-list
- typealias declaration-specifiers abstract-declarator-list typename declaration-specifiers abstract-declarator-list
- typealias declaration-specifiers abstract-declarator-list typename declarator-list
+ typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list
+ typealias declaration-specifiers abstract-declarator-list := declarator-list
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