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[ctf.git] / common-trace-format-specification.txt
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87502777 1Common Trace Format (CTF) Specification (v1.8.1)
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2
3Mathieu Desnoyers, EfficiOS Inc.
4
339a7dde 5The goal of the present document is to specify a trace format that suits the
cc089c3a 6needs of the embedded, telecom, high-performance and kernel communities. It is
5ba9f198 7based on the Common Trace Format Requirements (v1.4) document. It is designed to
cc089c3a 8allow traces to be natively generated by the Linux kernel, Linux user-space
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9applications written in C/C++, and hardware components. One major element of
10CTF is the Trace Stream Description Language (TSDL) which flexibility
11enables description of various binary trace stream layouts.
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12
13The latest version of this document can be found at:
14
15 git tree: git://git.efficios.com/ctf.git
16 gitweb: http://git.efficios.com/?p=ctf.git
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17
18A reference implementation of a library to read and write this trace format is
19being implemented within the BabelTrace project, a converter between trace
20formats. The development tree is available at:
21
22 git tree: git://git.efficios.com/babeltrace.git
23 gitweb: http://git.efficios.com/?p=babeltrace.git
24
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25The CE Workgroup of the Linux Foundation, Ericsson, and EfficiOS have
26sponsored this work.
27
5ba9f198 28
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29Table of Contents
30
311. Preliminary definitions
322. High-level representation of a trace
333. Event stream
344. Types
35 4.1 Basic types
36 4.1.1 Type inheritance
37 4.1.2 Alignment
38 4.1.3 Byte order
39 4.1.4 Size
40 4.1.5 Integers
41 4.1.6 GNU/C bitfields
42 4.1.7 Floating point
43 4.1.8 Enumerations
444.2 Compound types
45 4.2.1 Structures
46 4.2.2 Variants (Discriminated/Tagged Unions)
47 4.2.3 Arrays
48 4.2.4 Sequences
49 4.2.5 Strings
505. Event Packet Header
51 5.1 Event Packet Header Description
52 5.2 Event Packet Context Description
536. Event Structure
54 6.1 Event Header
55 6.1.1 Type 1 - Few event IDs
56 6.1.2 Type 2 - Many event IDs
57 6.2 Event Context
58 6.3 Event Payload
59 6.3.1 Padding
60 6.3.2 Alignment
617. Trace Stream Description Language (TSDL)
62 7.1 Meta-data
63 7.2 Declaration vs Definition
64 7.3 TSDL Scopes
65 7.3.1 Lexical Scope
37ab95c3 66 7.3.2 Static and Dynamic Scopes
beabf088 67 7.4 TSDL Examples
2fa70eba 688. Clocks
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69
70
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711. Preliminary definitions
72
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73 - Event Trace: An ordered sequence of events.
74 - Event Stream: An ordered sequence of events, containing a subset of the
75 trace event types.
76 - Event Packet: A sequence of physically contiguous events within an event
77 stream.
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78 - Event: This is the basic entry in a trace. (aka: a trace record).
79 - An event identifier (ID) relates to the class (a type) of event within
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80 an event stream.
81 e.g. event: irq_entry.
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82 - An event (or event record) relates to a specific instance of an event
83 class.
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84 e.g. event: irq_entry, at time X, on CPU Y
85 - Source Architecture: Architecture writing the trace.
86 - Reader Architecture: Architecture reading the trace.
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87
88
892. High-level representation of a trace
90
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91A trace is divided into multiple event streams. Each event stream contains a
92subset of the trace event types.
5ba9f198 93
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94The final output of the trace, after its generation and optional transport over
95the network, is expected to be either on permanent or temporary storage in a
96virtual file system. Because each event stream is appended to while a trace is
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97being recorded, each is associated with a distinct set of files for
98output. Therefore, a stored trace can be represented as a directory
99containing zero, one or more files per stream.
5ba9f198 100
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101Meta-data description associated with the trace contains information on
102trace event types expressed in the Trace Stream Description Language
103(TSDL). This language describes:
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104
105- Trace version.
106- Types available.
6672e9e1 107- Per-trace event header description.
3bf79539 108- Per-stream event header description.
6672e9e1 109- Per-stream event context description.
5ba9f198 110- Per-event
3bf79539 111 - Event type to stream mapping.
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112 - Event type to name mapping.
113 - Event type to ID mapping.
6672e9e1 114 - Event context description.
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115 - Event fields description.
116
117
3bf79539 1183. Event stream
5ba9f198 119
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120An event stream can be divided into contiguous event packets of variable
121size. These subdivisions have a variable size. An event packet can
122contain a certain amount of padding at the end. The stream header is
123repeated at the beginning of each event packet. The rationale for the
124event stream design choices is explained in Appendix B. Stream Header
125Rationale.
5ba9f198 126
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127The event stream header will therefore be referred to as the "event packet
128header" throughout the rest of this document.
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129
130
1314. Types
132
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133Types are organized as type classes. Each type class belong to either of two
134kind of types: basic types or compound types.
135
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1364.1 Basic types
137
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138A basic type is a scalar type, as described in this section. It includes
139integers, GNU/C bitfields, enumerations, and floating point values.
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140
1414.1.1 Type inheritance
142
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143Type specifications can be inherited to allow deriving types from a
144type class. For example, see the uint32_t named type derived from the "integer"
145type class below ("Integers" section). Types have a precise binary
146representation in the trace. A type class has methods to read and write these
147types, but must be derived into a type to be usable in an event field.
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148
1494.1.2 Alignment
150
151We define "byte-packed" types as aligned on the byte size, namely 8-bit.
152We define "bit-packed" types as following on the next bit, as defined by the
370eae99 153"Integers" section.
5ba9f198 154
6672e9e1 155Each basic type must specify its alignment, in bits. Examples of
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156possible alignments are: bit-packed (align = 1), byte-packed (align =
1578), or word-aligned (e.g. align = 32 or align = 64). The choice depends
158on the architecture preference and compactness vs performance trade-offs
159of the implementation. Architectures providing fast unaligned write
160byte-packed basic types to save space, aligning each type on byte
161boundaries (8-bit). Architectures with slow unaligned writes align types
162on specific alignment values. If no specific alignment is declared for a
163type, it is assumed to be bit-packed for integers with size not multiple
164of 8 bits and for gcc bitfields. All other basic types are byte-packed
165by default. It is however recommended to always specify the alignment
166explicitly. Alignment values must be power of two. Compound types are
167aligned as specified in their individual specification.
5ba9f198 168
6672e9e1 169TSDL meta-data attribute representation of a specific alignment:
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170
171 align = value; /* value in bits */
172
1734.1.3 Byte order
174
9f296be4 175By default, the native endianness of the source architecture is used.
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176Byte order can be overridden for a basic type by specifying a "byte_order"
177attribute. Typical use-case is to specify the network byte order (big endian:
178"be") to save data captured from the network into the trace without conversion.
179If not specified, the byte order is native.
5ba9f198 180
6672e9e1 181TSDL meta-data representation:
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182
183 byte_order = native OR network OR be OR le; /* network and be are aliases */
184
1854.1.4 Size
186
187Type size, in bits, for integers and floats is that returned by "sizeof()" in C
188multiplied by CHAR_BIT.
189We require the size of "char" and "unsigned char" types (CHAR_BIT) to be fixed
190to 8 bits for cross-endianness compatibility.
191
6672e9e1 192TSDL meta-data representation:
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193
194 size = value; (value is in bits)
195
1964.1.5 Integers
197
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198Signed integers are represented in two-complement. Integer alignment,
199size, signedness and byte ordering are defined in the TSDL meta-data.
200Integers aligned on byte size (8-bit) and with length multiple of byte
201size (8-bit) correspond to the C99 standard integers. In addition,
202integers with alignment and/or size that are _not_ a multiple of the
203byte size are permitted; these correspond to the C99 standard bitfields,
204with the added specification that the CTF integer bitfields have a fixed
205binary representation. A MIT-licensed reference implementation of the
206CTF portable bitfields is available at:
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207
208 http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h
209
210Binary representation of integers:
211
212- On little and big endian:
213 - Within a byte, high bits correspond to an integer high bits, and low bits
214 correspond to low bits.
215- On little endian:
216 - Integer across multiple bytes are placed from the less significant to the
217 most significant.
218 - Consecutive integers are placed from lower bits to higher bits (even within
219 a byte).
220- On big endian:
221 - Integer across multiple bytes are placed from the most significant to the
222 less significant.
223 - Consecutive integers are placed from higher bits to lower bits (even within
224 a byte).
225
226This binary representation is derived from the bitfield implementation in GCC
227for little and big endian. However, contrary to what GCC does, integers can
6672e9e1 228cross units boundaries (no padding is required). Padding can be explicitly
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229added (see 4.1.6 GNU/C bitfields) to follow the GCC layout if needed.
230
6672e9e1 231TSDL meta-data representation:
5ba9f198 232
80fd2569 233 integer {
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234 signed = true OR false; /* default false */
235 byte_order = native OR network OR be OR le; /* default native */
236 size = value; /* value in bits, no default */
237 align = value; /* value in bits */
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238 /* based used for pretty-printing output, default: decimal. */
239 base = decimal OR dec OR OR d OR i OR u OR 10 OR hexadecimal OR hex OR x OR X OR p OR 16
240 OR octal OR oct OR o OR 8 OR binary OR b OR 2;
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241 /* character encoding, default: none */
242 encoding = none or UTF8 or ASCII;
2152348f 243 }
5ba9f198 244
80fd2569 245Example of type inheritance (creation of a uint32_t named type):
5ba9f198 246
359894ac 247typealias integer {
9e4e34e9 248 size = 32;
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249 signed = false;
250 align = 32;
38b8da21 251} := uint32_t;
5ba9f198 252
80fd2569 253Definition of a named 5-bit signed bitfield:
5ba9f198 254
359894ac 255typealias integer {
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256 size = 5;
257 signed = true;
258 align = 1;
38b8da21 259} := int5_t;
5ba9f198 260
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261The character encoding field can be used to specify that the integer
262must be printed as a text character when read. e.g.:
263
264typealias integer {
265 size = 8;
266 align = 8;
267 signed = false;
268 encoding = UTF8;
269} := utf_char;
270
271
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2724.1.6 GNU/C bitfields
273
274The GNU/C bitfields follow closely the integer representation, with a
275particularity on alignment: if a bitfield cannot fit in the current unit, the
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276unit is padded and the bitfield starts at the following unit. The unit size is
277defined by the size of the type "unit_type".
5ba9f198 278
6672e9e1 279TSDL meta-data representation:
80fd2569 280
d674f4b8 281 unit_type name:size;
80fd2569 282
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283As an example, the following structure declared in C compiled by GCC:
284
285struct example {
286 short a:12;
287 short b:5;
288};
289
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290The example structure is aligned on the largest element (short). The second
291bitfield would be aligned on the next unit boundary, because it would not fit in
292the current unit.
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293
2944.1.7 Floating point
295
6672e9e1 296The floating point values byte ordering is defined in the TSDL meta-data.
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297
298Floating point values follow the IEEE 754-2008 standard interchange formats.
299Description of the floating point values include the exponent and mantissa size
300in bits. Some requirements are imposed on the floating point values:
301
302- FLT_RADIX must be 2.
303- mant_dig is the number of digits represented in the mantissa. It is specified
304 by the ISO C99 standard, section 5.2.4, as FLT_MANT_DIG, DBL_MANT_DIG and
305 LDBL_MANT_DIG as defined by <float.h>.
306- exp_dig is the number of digits represented in the exponent. Given that
307 mant_dig is one bit more than its actual size in bits (leading 1 is not
308 needed) and also given that the sign bit always takes one bit, exp_dig can be
309 specified as:
310
311 - sizeof(float) * CHAR_BIT - FLT_MANT_DIG
312 - sizeof(double) * CHAR_BIT - DBL_MANT_DIG
313 - sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG
314
6672e9e1 315TSDL meta-data representation:
5ba9f198 316
80fd2569 317floating_point {
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318 exp_dig = value;
319 mant_dig = value;
320 byte_order = native OR network OR be OR le;
321 align = value;
2152348f 322}
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323
324Example of type inheritance:
325
359894ac 326typealias floating_point {
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327 exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */
328 mant_dig = 24; /* FLT_MANT_DIG */
329 byte_order = native;
ec4404a7 330 align = 32;
38b8da21 331} := float;
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332
333TODO: define NaN, +inf, -inf behavior.
334
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335Bit-packed, byte-packed or larger alignments can be used for floating
336point values, similarly to integers.
337
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3384.1.8 Enumerations
339
340Enumerations are a mapping between an integer type and a table of strings. The
341numerical representation of the enumeration follows the integer type specified
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342by the meta-data. The enumeration mapping table is detailed in the enumeration
343description within the meta-data. The mapping table maps inclusive value
344ranges (or single values) to strings. Instead of being limited to simple
3bf79539 345"value -> string" mappings, these enumerations map
80fd2569 346"[ start_value ... end_value ] -> string", which map inclusive ranges of
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347values to strings. An enumeration from the C language can be represented in
348this format by having the same start_value and end_value for each element, which
349is in fact a range of size 1. This single-value range is supported without
4767a9e7 350repeating the start and end values with the value = string declaration.
80fd2569 351
a9b83695 352enum name : integer_type {
359894ac 353 somestring = start_value1 ... end_value1,
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354 "other string" = start_value2 ... end_value2,
355 yet_another_string, /* will be assigned to end_value2 + 1 */
356 "some other string" = value,
357 ...
358};
359
360If the values are omitted, the enumeration starts at 0 and increment of 1 for
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361each entry. An entry with omitted value that follows a range entry takes
362as value the end_value of the previous range + 1:
80fd2569 363
a9b83695 364enum name : unsigned int {
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365 ZERO,
366 ONE,
367 TWO,
368 TEN = 10,
369 ELEVEN,
3bf79539 370};
5ba9f198 371
80fd2569 372Overlapping ranges within a single enumeration are implementation defined.
5ba9f198 373
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374A nameless enumeration can be declared as a field type or as part of a typedef:
375
a9b83695 376enum : integer_type {
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377 ...
378}
379
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380Enumerations omitting the container type ": integer_type" use the "int"
381type (for compatibility with C99). The "int" type must be previously
382declared. E.g.:
383
384typealias integer { size = 32; align = 32; signed = true } := int;
385
386enum {
387 ...
388}
389
1fad7a85 390
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3914.2 Compound types
392
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393Compound are aggregation of type declarations. Compound types include
394structures, variant, arrays, sequences, and strings.
395
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3964.2.1 Structures
397
398Structures are aligned on the largest alignment required by basic types
399contained within the structure. (This follows the ISO/C standard for structures)
400
6672e9e1 401TSDL meta-data representation of a named structure:
5ba9f198 402
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403struct name {
404 field_type field_name;
405 field_type field_name;
406 ...
407};
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408
409Example:
410
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411struct example {
412 integer { /* Nameless type */
413 size = 16;
414 signed = true;
415 align = 16;
416 } first_field_name;
6672e9e1 417 uint64_t second_field_name; /* Named type declared in the meta-data */
3bf79539 418};
5ba9f198 419
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420The fields are placed in a sequence next to each other. They each
421possess a field name, which is a unique identifier within the structure.
422The identifier is not allowed to use any reserved keyword
423(see Section C.1.2). Replacing reserved keywords with
70375f92 424underscore-prefixed field names is recommended. Fields starting with an
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425underscore should have their leading underscore removed by the CTF trace
426readers.
5ba9f198 427
2152348f 428A nameless structure can be declared as a field type or as part of a typedef:
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429
430struct {
431 ...
2152348f 432}
80fd2569 433
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434Alignment for a structure compound type can be forced to a minimum value
435by adding an "align" specifier after the declaration of a structure
436body. This attribute is read as: align(value). The value is specified in
437bits. The structure will be aligned on the maximum value between this
438attribute and the alignment required by the basic types contained within
439the structure. e.g.
440
441struct {
442 ...
443} align(32)
444
77a98c82 4454.2.2 Variants (Discriminated/Tagged Unions)
fcba70d4 446
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447A CTF variant is a selection between different types. A CTF variant must
448always be defined within the scope of a structure or within fields
449contained within a structure (defined recursively). A "tag" enumeration
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450field must appear in either the same static scope, prior to the variant
451field (in field declaration order), in an upper static scope , or in an
452upper dynamic scope (see Section 7.3.2). The type selection is indicated
453by the mapping from the enumeration value to the string used as variant
454type selector. The field to use as tag is specified by the "tag_field",
455specified between "< >" after the "variant" keyword for unnamed
456variants, and after "variant name" for named variants.
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457
458The alignment of the variant is the alignment of the type as selected by the tag
459value for the specific instance of the variant. The alignment of the type
460containing the variant is independent of the variant alignment. The size of the
461variant is the size as selected by the tag value for the specific instance of
462the variant.
463
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464Each variant type selector possess a field name, which is a unique
465identifier within the variant. The identifier is not allowed to use any
466reserved keyword (see Section C.1.2). Replacing reserved keywords with
70375f92 467underscore-prefixed field names is recommended. Fields starting with an
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468underscore should have their leading underscore removed by the CTF trace
469readers.
70375f92 470
4cac83ee 471
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472A named variant declaration followed by its definition within a structure
473declaration:
474
475variant name {
476 field_type sel1;
477 field_type sel2;
478 field_type sel3;
479 ...
480};
481
482struct {
a9b83695 483 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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484 ...
485 variant name <tag_field> v;
486}
487
488An unnamed variant definition within a structure is expressed by the following
6672e9e1 489TSDL meta-data:
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490
491struct {
a9b83695 492 enum : integer_type { sel1, sel2, sel3, ... } tag_field;
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493 ...
494 variant <tag_field> {
495 field_type sel1;
496 field_type sel2;
497 field_type sel3;
498 ...
499 } v;
500}
501
502Example of a named variant within a sequence that refers to a single tag field:
503
504variant example {
505 uint32_t a;
506 uint64_t b;
507 short c;
508};
509
510struct {
a9b83695 511 enum : uint2_t { a, b, c } choice;
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512 unsigned int seqlen;
513 variant example <choice> v[seqlen];
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514}
515
516Example of an unnamed variant:
517
518struct {
a9b83695 519 enum : uint2_t { a, b, c, d } choice;
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520 /* Unrelated fields can be added between the variant and its tag */
521 int32_t somevalue;
522 variant <choice> {
523 uint32_t a;
524 uint64_t b;
525 short c;
526 struct {
527 unsigned int field1;
528 uint64_t field2;
529 } d;
530 } s;
531}
532
533Example of an unnamed variant within an array:
534
535struct {
a9b83695 536 enum : uint2_t { a, b, c } choice;
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537 variant <choice> {
538 uint32_t a;
539 uint64_t b;
540 short c;
15850440 541 } v[10];
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542}
543
544Example of a variant type definition within a structure, where the defined type
545is then declared within an array of structures. This variant refers to a tag
37ab95c3 546located in an upper static scope. This example clearly shows that a variant
fcba70d4 547type definition referring to the tag "x" uses the closest preceding field from
37ab95c3 548the static scope of the type definition.
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549
550struct {
a9b83695 551 enum : uint2_t { a, b, c, d } x;
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552
553 typedef variant <x> { /*
554 * "x" refers to the preceding "x" enumeration in the
37ab95c3 555 * static scope of the type definition.
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556 */
557 uint32_t a;
558 uint64_t b;
559 short c;
560 } example_variant;
561
562 struct {
a9b83695 563 enum : int { x, y, z } x; /* This enumeration is not used by "v". */
fcba70d4 564 example_variant v; /*
a9b83695 565 * "v" uses the "enum : uint2_t { a, b, c, d }"
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566 * tag.
567 */
568 } a[10];
569}
570
5714.2.3 Arrays
5ba9f198 572
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573Arrays are fixed-length. Their length is declared in the type
574declaration within the meta-data. They contain an array of "inner type"
575elements, which can refer to any type not containing the type of the
576array being declared (no circular dependency). The length is the number
577of elements in an array.
5ba9f198 578
6672e9e1 579TSDL meta-data representation of a named array:
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580
581typedef elem_type name[length];
5ba9f198 582
2152348f 583A nameless array can be declared as a field type within a structure, e.g.:
5ba9f198 584
2152348f 585 uint8_t field_name[10];
80fd2569 586
ec4404a7 587Arrays are always aligned on their element alignment requirement.
5ba9f198 588
fcba70d4 5894.2.4 Sequences
5ba9f198 590
1ab22b2a 591Sequences are dynamically-sized arrays. They refer to a a "length"
37ab95c3 592unsigned integer field, which must appear in either the same static scope,
1ab22b2a 593prior to the sequence field (in field declaration order), in an upper
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594static scope, or in an upper dynamic scope (see Section 7.3.2). This
595length field represents the number of elements in the sequence. The
596sequence per se is an array of "inner type" elements.
5ba9f198 597
1ab22b2a 598TSDL meta-data representation for a sequence type definition:
80fd2569 599
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600struct {
601 unsigned int length_field;
602 typedef elem_type typename[length_field];
603 typename seq_field_name;
604}
605
606A sequence can also be declared as a field type, e.g.:
80fd2569 607
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608struct {
609 unsigned int length_field;
610 long seq_field_name[length_field];
611}
80fd2569 612
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613Multiple sequences can refer to the same length field, and these length
614fields can be in a different upper dynamic scope:
615
616e.g., assuming the stream.event.header defines:
617
618stream {
619 ...
620 id = 1;
621 event.header := struct {
622 uint16_t seq_len;
623 };
624};
625
626event {
627 ...
628 stream_id = 1;
629 fields := struct {
630 long seq_a[stream.event.header.seq_len];
631 char seq_b[stream.event.header.seq_len];
632 };
633};
80fd2569 634
1ab22b2a 635The sequence elements follow the "array" specifications.
5ba9f198 636
fcba70d4 6374.2.5 Strings
5ba9f198
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638
639Strings are an array of bytes of variable size and are terminated by a '\0'
6672e9e1
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640"NULL" character. Their encoding is described in the TSDL meta-data. In
641absence of encoding attribute information, the default encoding is
642UTF-8.
5ba9f198 643
6672e9e1 644TSDL meta-data representation of a named string type:
80fd2569 645
359894ac 646typealias string {
5ba9f198 647 encoding = UTF8 OR ASCII;
38b8da21 648} := name;
5ba9f198 649
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650A nameless string type can be declared as a field type:
651
652string field_name; /* Use default UTF8 encoding */
5ba9f198 653
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654Strings are always aligned on byte size.
655
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6565. Event Packet Header
657
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658The event packet header consists of two parts: the "event packet header"
659is the same for all streams of a trace. The second part, the "event
660packet context", is described on a per-stream basis. Both are described
661in the TSDL meta-data. The packets are aligned on architecture-page-sized
662addresses.
3bf79539 663
6672e9e1 664Event packet header (all fields are optional, specified by TSDL meta-data):
3bf79539 665
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666- Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a
667 CTF packet. This magic number is optional, but when present, it should
668 come at the very beginning of the packet.
669- Trace UUID, used to ensure the event packet match the meta-data used.
670 (note: we cannot use a meta-data checksum in every cases instead of a
671 UUID because meta-data can be appended to while tracing is active)
672 This field is optional.
673- Stream ID, used as reference to stream description in meta-data.
674 This field is optional if there is only one stream description in the
675 meta-data, but becomes required if there are more than one stream in
676 the TSDL meta-data description.
3bf79539 677
6672e9e1 678Event packet context (all fields are optional, specified by TSDL meta-data):
3bf79539 679
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680- Event packet content size (in bits).
681- Event packet size (in bits, includes padding).
cda89682 682- Event packet content checksum. Checksum excludes the event packet
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683 header.
684- Per-stream event packet sequence count (to deal with UDP packet loss). The
685 number of significant sequence counter bits should also be present, so
b11853af 686 wrap-arounds are dealt with correctly.
6672e9e1 687- Time-stamp at the beginning and time-stamp at the end of the event packet.
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688 Both timestamps are written in the packet header, but sampled respectively
689 while (or before) writing the first event and while (or after) writing the
690 last event in the packet. The inclusive range between these timestamps should
691 include all event timestamps assigned to events contained within the packet.
5ba9f198 692- Events discarded count
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693 - Snapshot of a per-stream free-running counter, counting the number of
694 events discarded that were supposed to be written in the stream prior to
695 the first event in the event packet.
5ba9f198 696 * Note: producer-consumer buffer full condition should fill the current
3bf79539 697 event packet with padding so we know exactly where events have been
5ba9f198 698 discarded.
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699- Lossless compression scheme used for the event packet content. Applied
700 directly to raw data. New types of compression can be added in following
701 versions of the format.
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702 0: no compression scheme
703 1: bzip2
704 2: gzip
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705 3: xz
706- Cypher used for the event packet content. Applied after compression.
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707 0: no encryption
708 1: AES
3bf79539 709- Checksum scheme used for the event packet content. Applied after encryption.
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710 0: no checksum
711 1: md5
712 2: sha1
713 3: crc32
714
6672e9e1 7155.1 Event Packet Header Description
3bf79539 716
fc5425db 717The event packet header layout is indicated by the trace packet.header
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718field. Here is a recommended structure type for the packet header with
719the fields typically expected (although these fields are each optional):
fc5425db 720
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721struct event_packet_header {
722 uint32_t magic;
3fde5da1 723 uint8_t uuid[16];
3bf79539 724 uint32_t stream_id;
80fd2569 725};
5ba9f198 726
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727trace {
728 ...
729 packet.header := struct event_packet_header;
730};
731
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732If the magic number is not present, tools such as "file" will have no
733mean to discover the file type.
734
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735If the uuid is not present, no validation that the meta-data actually
736corresponds to the stream is performed.
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737
738If the stream_id packet header field is missing, the trace can only
739contain a single stream. Its "id" field can be left out, and its events
740don't need to declare a "stream_id" field.
741
742
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7435.2 Event Packet Context Description
744
745Event packet context example. These are declared within the stream declaration
6672e9e1 746in the meta-data. All these fields are optional. If the packet size field is
6a7c61df 747missing, the whole stream only contains a single packet. If the content
f6b81726
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748size field is missing, the packet is filled (no padding). The content
749and packet sizes include all headers.
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750
751An example event packet context type:
752
80fd2569 753struct event_packet_context {
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754 uint64_t timestamp_begin;
755 uint64_t timestamp_end;
756 uint32_t checksum;
757 uint32_t stream_packet_count;
758 uint32_t events_discarded;
759 uint32_t cpu_id;
760 uint32_t/uint16_t content_size;
761 uint32_t/uint16_t packet_size;
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762 uint8_t compression_scheme;
763 uint8_t encryption_scheme;
3b0f8e4d 764 uint8_t checksum_scheme;
3bf79539 765};
5ba9f198 766
fcba70d4 767
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7686. Event Structure
769
770The overall structure of an event is:
771
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7721 - Stream Packet Context (as specified by the stream meta-data)
773 2 - Event Header (as specified by the stream meta-data)
774 3 - Stream Event Context (as specified by the stream meta-data)
775 4 - Event Context (as specified by the event meta-data)
776 5 - Event Payload (as specified by the event meta-data)
5ba9f198 777
fdf2bb05 778This structure defines an implicit dynamic scoping, where variants
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779located in inner structures (those with a higher number in the listing
780above) can refer to the fields of outer structures (with lower number in
6c7226e9 781the listing above). See Section 7.3 TSDL Scopes for more detail.
5ba9f198 782
fdf2bb05 7836.1 Event Header
fcba70d4 784
6672e9e1 785Event headers can be described within the meta-data. We hereby propose, as an
fcba70d4
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786example, two types of events headers. Type 1 accommodates streams with less than
78731 event IDs. Type 2 accommodates streams with 31 or more event IDs.
5ba9f198 788
3bf79539
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789One major factor can vary between streams: the number of event IDs assigned to
790a stream. Luckily, this information tends to stay relatively constant (modulo
5ba9f198 791event registration while trace is being recorded), so we can specify different
3bf79539 792representations for streams containing few event IDs and streams containing
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MD
793many event IDs, so we end up representing the event ID and time-stamp as
794densely as possible in each case.
5ba9f198 795
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796The header is extended in the rare occasions where the information cannot be
797represented in the ranges available in the standard event header. They are also
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798used in the rare occasions where the data required for a field could not be
799collected: the flag corresponding to the missing field within the missing_fields
800array is then set to 1.
5ba9f198 801
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MD
802Types uintX_t represent an X-bit unsigned integer, as declared with
803either:
5ba9f198 804
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805 typealias integer { size = X; align = X; signed = false } := uintX_t;
806
807 or
808
809 typealias integer { size = X; align = 1; signed = false } := uintX_t;
5ba9f198 810
fdf2bb05 8116.1.1 Type 1 - Few event IDs
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812
813 - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture
814 preference).
5ba9f198 815 - Native architecture byte ordering.
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816 - For "compact" selection
817 - Fixed size: 32 bits.
818 - For "extended" selection
819 - Size depends on the architecture and variant alignment.
5ba9f198 820
80fd2569 821struct event_header_1 {
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MD
822 /*
823 * id: range: 0 - 30.
824 * id 31 is reserved to indicate an extended header.
825 */
a9b83695 826 enum : uint5_t { compact = 0 ... 30, extended = 31 } id;
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MD
827 variant <id> {
828 struct {
829 uint27_t timestamp;
830 } compact;
831 struct {
832 uint32_t id; /* 32-bit event IDs */
833 uint64_t timestamp; /* 64-bit timestamps */
834 } extended;
835 } v;
cb108fea 836} align(32); /* or align(8) */
5ba9f198 837
5ba9f198 838
fdf2bb05 8396.1.2 Type 2 - Many event IDs
5ba9f198 840
fcba70d4 841 - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture
5ba9f198 842 preference).
5ba9f198 843 - Native architecture byte ordering.
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MD
844 - For "compact" selection
845 - Size depends on the architecture and variant alignment.
846 - For "extended" selection
847 - Size depends on the architecture and variant alignment.
5ba9f198 848
80fd2569 849struct event_header_2 {
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MD
850 /*
851 * id: range: 0 - 65534.
852 * id 65535 is reserved to indicate an extended header.
853 */
a9b83695 854 enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;
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855 variant <id> {
856 struct {
857 uint32_t timestamp;
858 } compact;
859 struct {
860 uint32_t id; /* 32-bit event IDs */
861 uint64_t timestamp; /* 64-bit timestamps */
862 } extended;
863 } v;
cb108fea 864} align(16); /* or align(8) */
5ba9f198 865
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MD
866
8676.2 Event Context
868
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MD
869The event context contains information relative to the current event.
870The choice and meaning of this information is specified by the TSDL
871stream and event meta-data descriptions. The stream context is applied
872to all events within the stream. The stream context structure follows
873the event header. The event context is applied to specific events. Its
874structure follows the stream context structure.
5ba9f198 875
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MD
876An example of stream-level event context is to save the event payload size with
877each event, or to save the current PID with each event. These are declared
6672e9e1 878within the stream declaration within the meta-data:
5ba9f198 879
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MD
880 stream {
881 ...
6672e9e1 882 event.context := struct {
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MD
883 uint pid;
884 uint16_t payload_size;
6672e9e1 885 };
fcba70d4
MD
886 };
887
888An example of event-specific event context is to declare a bitmap of missing
889fields, only appended after the stream event context if the extended event
890header is selected. NR_FIELDS is the number of fields within the event (a
891numeric value).
5ba9f198 892
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MD
893 event {
894 context = struct {
895 variant <id> {
896 struct { } compact;
897 struct {
898 uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */
899 } extended;
900 } v;
901 };
902 ...
903 }
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MD
904
9056.3 Event Payload
906
907An event payload contains fields specific to a given event type. The fields
6672e9e1 908belonging to an event type are described in the event-specific meta-data
5ba9f198
MD
909within a structure type.
910
9116.3.1 Padding
912
913No padding at the end of the event payload. This differs from the ISO/C standard
914for structures, but follows the CTF standard for structures. In a trace, even
915though it makes sense to align the beginning of a structure, it really makes no
916sense to add padding at the end of the structure, because structures are usually
917not followed by a structure of the same type.
918
919This trick can be done by adding a zero-length "end" field at the end of the C
920structures, and by using the offset of this field rather than using sizeof()
3bf79539 921when calculating the size of a structure (see Appendix "A. Helper macros").
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MD
922
9236.3.2 Alignment
924
925The event payload is aligned on the largest alignment required by types
926contained within the payload. (This follows the ISO/C standard for structures)
927
928
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MD
9297. Trace Stream Description Language (TSDL)
930
931The Trace Stream Description Language (TSDL) allows expression of the
932binary trace streams layout in a C99-like Domain Specific Language
933(DSL).
934
935
6672e9e1 9367.1 Meta-data
6c7226e9
MD
937
938The trace stream layout description is located in the trace meta-data.
939The meta-data is itself located in a stream identified by its name:
940"metadata".
5ba9f198 941
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MD
942The meta-data description can be expressed in two different formats:
943text-only and packet-based. The text-only description facilitates
944generation of meta-data and provides a convenient way to enter the
945meta-data information by hand. The packet-based meta-data provides the
946CTF stream packet facilities (checksumming, compression, encryption,
947network-readiness) for meta-data stream generated and transported by a
948tracer.
949
1b4d35eb
MD
950The text-only meta-data file is a plain-text TSDL description. This file
951must begin with the following characters to identify the file as a CTF
9486a18c 952TSDL text-based metadata file (without the double-quotes) :
1b4d35eb 953
ec2b4db8 954"/* CTF"
1b4d35eb 955
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MD
956It must be followed by a space, and the version of the specification
957followed by the CTF trace, e.g.:
958
959" 1.8"
960
961These characters allow automated discovery of file type and CTF
962specification version. They are interpreted as a the beginning of a
963comment by the TSDL metadata parser. The comment can be continued to
964contain extra commented characters before it is closed.
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MD
965
966The packet-based meta-data is made of "meta-data packets", which each
967start with a meta-data packet header. The packet-based meta-data
968description is detected by reading the magic number "0x75D11D57" at the
969beginning of the file. This magic number is also used to detect the
970endianness of the architecture by trying to read the CTF magic number
971and its counterpart in reversed endianness. The events within the
972meta-data stream have no event header nor event context. Each event only
5ae2352d 973contains a "sequence" payload, which is a sequence of bits using the
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MD
974"trace.packet.header.content_size" field as a placeholder for its length
975(the packet header size should be substracted). The formatting of this
976sequence of bits is a plain-text representation of the TSDL description.
977Each meta-data packet start with a special packet header, specific to
978the meta-data stream, which contains, exactly:
6672e9e1
MD
979
980struct metadata_packet_header {
2daeaa3a 981 uint32_t magic; /* 0x75D11D57 */
3fde5da1 982 uint8_t uuid[16]; /* Unique Universal Identifier */
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983 uint32_t checksum; /* 0 if unused */
984 uint32_t content_size; /* in bits */
985 uint32_t packet_size; /* in bits */
986 uint8_t compression_scheme; /* 0 if unused */
987 uint8_t encryption_scheme; /* 0 if unused */
988 uint8_t checksum_scheme; /* 0 if unused */
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MD
989 uint8_t major; /* CTF spec version major number */
990 uint8_t minor; /* CTF spec version minor number */
6672e9e1
MD
991};
992
993The packet-based meta-data can be converted to a text-only meta-data by
994concatenating all the strings in contains.
4fafe1ad 995
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MD
996In the textual representation of the meta-data, the text contained
997within "/*" and "*/", as well as within "//" and end of line, are
998treated as comments. Boolean values can be represented as true, TRUE,
999or 1 for true, and false, FALSE, or 0 for false. Within the string-based
1000meta-data description, the trace UUID is represented as a string of
1001hexadecimal digits and dashes "-". In the event packet header, the trace
1002UUID is represented as an array of bytes.
fcba70d4 1003
fdf2bb05 1004
6c7226e9 10057.2 Declaration vs Definition
fdf2bb05
MD
1006
1007A declaration associates a layout to a type, without specifying where
1008this type is located in the event structure hierarchy (see Section 6).
1009This therefore includes typedef, typealias, as well as all type
1010specifiers. In certain circumstances (typedef, structure field and
1011variant field), a declaration is followed by a declarator, which specify
1012the newly defined type name (for typedef), or the field name (for
1013declarations located within structure and variants). Array and sequence,
1014declared with square brackets ("[" "]"), are part of the declarator,
a9b83695 1015similarly to C99. The enumeration base type is specified by
6c7226e9 1016": enum_base", which is part of the type specifier. The variant tag
a9b83695 1017name, specified between "<" ">", is also part of the type specifier.
fdf2bb05
MD
1018
1019A definition associates a type to a location in the event structure
b9606a77
MD
1020hierarchy (see Section 6). This association is denoted by ":=", as shown
1021in Section 7.3.
fdf2bb05
MD
1022
1023
6c7226e9 10247.3 TSDL Scopes
fdf2bb05 1025
37ab95c3
MD
1026TSDL uses three different types of scoping: a lexical scope is used for
1027declarations and type definitions, and static and dynamic scopes are
1028used for variants references to tag fields (with relative and absolute
1029path lookups) and for sequence references to length fields.
fdf2bb05 1030
6c7226e9 10317.3.1 Lexical Scope
fdf2bb05 1032
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MD
1033Each of "trace", "env", "stream", "event", "struct" and "variant" have
1034their own nestable declaration scope, within which types can be declared
1035using "typedef" and "typealias". A root declaration scope also contains
1036all declarations located outside of any of the aforementioned
1037declarations. An inner declaration scope can refer to type declared
1038within its container lexical scope prior to the inner declaration scope.
1039Redefinition of a typedef or typealias is not valid, although hiding an
1040upper scope typedef or typealias is allowed within a sub-scope.
fdf2bb05 1041
37ab95c3 10427.3.2 Static and Dynamic Scopes
fdf2bb05 1043
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MD
1044A local static scope consists in the scope generated by the declaration
1045of fields within a compound type. A static scope is a local static scope
1046augmented with the nested sub-static-scopes it contains.
1047
1048A dynamic scope consists in the static scope augmented with the
7d9d7e92 1049implicit event structure definition hierarchy presented at Section 6.
fdf2bb05 1050
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MD
1051Multiple declarations of the same field name within a local static scope
1052is not valid. It is however valid to re-use the same field name in
1053different local scopes.
1054
1055Nested static and dynamic scopes form lookup paths. These are used for
1056variant tag and sequence length references. They are used at the variant
1057and sequence definition site to look up the location of the tag field
1058associated with a variant, and to lookup up the location of the length
1059field associated with a sequence.
1060
1061Variants and sequences can refer to a tag field either using a relative
4cac83ee
MD
1062path or an absolute path. The relative path is relative to the scope in
1063which the variant or sequence performing the lookup is located.
37ab95c3
MD
1064Relative paths are only allowed to lookup within the same static scope,
1065which includes its nested static scopes. Lookups targeting parent static
1066scopes need to be performed with an absolute path.
1067
1068Absolute path lookups use the full path including the dynamic scope
1069followed by a "." and then the static scope. Therefore, variants (or
1070sequences) in lower levels in the dynamic scope (e.g. event context) can
1071refer to a tag (or length) field located in upper levels (e.g. in the
1072event header) by specifying, in this case, the associated tag with
1073<stream.event.header.field_name>. This allows, for instance, the event
1074context to define a variant referring to the "id" field of the event
1075header as selector.
1076
284724ae 1077The dynamic scope prefixes are thus:
fdf2bb05 1078
570ecabe 1079 - Trace Environment: <env. >,
e0d9e2c7 1080 - Trace Packet Header: <trace.packet.header. >,
7d9d7e92
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1081 - Stream Packet Context: <stream.packet.context. >,
1082 - Event Header: <stream.event.header. >,
1083 - Stream Event Context: <stream.event.context. >,
1084 - Event Context: <event.context. >,
1085 - Event Payload: <event.fields. >.
fdf2bb05 1086
37ab95c3
MD
1087
1088The target dynamic scope must be specified explicitly when referring to
4cac83ee
MD
1089a field outside of the static scope (absolute scope reference). No
1090conflict can occur between relative and dynamic paths, because the
1091keywords "trace", "stream", and "event" are reserved, and thus
1092not permitted as field names. It is recommended that field names
1093clashing with CTF and C99 reserved keywords use an underscore prefix to
1094eliminate the risk of generating a description containing an invalid
70375f92 1095field name. Consequently, fields starting with an underscore should have
92250c71 1096their leading underscore removed by the CTF trace readers.
70375f92 1097
fdf2bb05 1098
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MD
1099The information available in the dynamic scopes can be thought of as the
1100current tracing context. At trace production, information about the
1101current context is saved into the specified scope field levels. At trace
1102consumption, for each event, the current trace context is therefore
1103readable by accessing the upper dynamic scopes.
1104
fdf2bb05 1105
6c7226e9 11067.4 TSDL Examples
d285084f 1107
6672e9e1 1108The grammar representing the TSDL meta-data is presented in Appendix C.
7df6b93a 1109TSDL Grammar. This section presents a rather lighter reading that
6672e9e1 1110consists in examples of TSDL meta-data, with template values.
969f30c0 1111
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MD
1112The stream "id" can be left out if there is only one stream in the
1113trace. The event "id" field can be left out if there is only one event
1114in a stream.
1115
5ba9f198 1116trace {
1e9de2d1
MD
1117 major = value; /* CTF spec version major number */
1118 minor = value; /* CTF spec version minor number */
fdf2bb05 1119 uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */
58997e9e 1120 byte_order = be OR le; /* Endianness (required) */
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MD
1121 packet.header := struct {
1122 uint32_t magic;
3fde5da1 1123 uint8_t uuid[16];
fc5425db
MD
1124 uint32_t stream_id;
1125 };
3bf79539 1126};
5ba9f198 1127
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MD
1128/*
1129 * The "env" (environment) scope contains assignment expressions. The
1130 * field names and content are implementation-defined.
1131 */
1132env {
1133 pid = value; /* example */
1134 proc_name = "name"; /* example */
1135 ...
1136};
1137
3bf79539
MD
1138stream {
1139 id = stream_id;
fdf2bb05 1140 /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */
4fa992a5
MD
1141 event.header := event_header_1 OR event_header_2;
1142 event.context := struct {
77a98c82 1143 ...
3bf79539 1144 };
4fa992a5 1145 packet.context := struct {
77a98c82 1146 ...
3bf79539
MD
1147 };
1148};
5ba9f198
MD
1149
1150event {
980015f9 1151 name = "event_name";
3bf79539 1152 id = value; /* Numeric identifier within the stream */
67f02e24 1153 stream_id = stream_id;
dc56f167 1154 loglevel = value;
4fa992a5 1155 context := struct {
fcba70d4
MD
1156 ...
1157 };
4fa992a5 1158 fields := struct {
80fd2569
MD
1159 ...
1160 };
3bf79539 1161};
5ba9f198
MD
1162
1163/* More detail on types in section 4. Types */
1164
3d13ef1a
MD
1165/*
1166 * Named types:
1167 *
4fa992a5 1168 * Type declarations behave similarly to the C standard.
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1169 */
1170
80af8ac6 1171typedef aliased_type_specifiers new_type_declarators;
2152348f 1172
3d13ef1a 1173/* e.g.: typedef struct example new_type_name[10]; */
80fd2569 1174
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1175/*
1176 * typealias
1177 *
1178 * The "typealias" declaration can be used to give a name (including
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MD
1179 * pointer declarator specifier) to a type. It should also be used to
1180 * map basic C types (float, int, unsigned long, ...) to a CTF type.
1181 * Typealias is a superset of "typedef": it also allows assignment of a
38b8da21 1182 * simple variable identifier to a type.
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1183 */
1184
1185typealias type_class {
80fd2569 1186 ...
38b8da21 1187} := type_specifiers type_declarator;
2152348f 1188
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1189/*
1190 * e.g.:
4fa992a5 1191 * typealias integer {
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1192 * size = 32;
1193 * align = 32;
1194 * signed = false;
38b8da21 1195 * } := struct page *;
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1196 *
1197 * typealias integer {
1198 * size = 32;
1199 * align = 32;
1200 * signed = true;
38b8da21 1201 * } := int;
3d13ef1a 1202 */
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1203
1204struct name {
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1205 ...
1206};
5ba9f198 1207
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1208variant name {
1209 ...
1210};
1211
a9b83695 1212enum name : integer_type {
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1213 ...
1214};
1215
2152348f 1216
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1217/*
1218 * Unnamed types, contained within compound type fields, typedef or typealias.
1219 */
2152348f 1220
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1221struct {
1222 ...
2152348f 1223}
5ba9f198 1224
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1225struct {
1226 ...
1227} align(value)
1228
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1229variant {
1230 ...
1231}
1232
a9b83695 1233enum : integer_type {
80fd2569 1234 ...
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1235}
1236
1237typedef type new_type[length];
3bf79539 1238
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1239struct {
1240 type field_name[length];
1241}
1242
1243typedef type new_type[length_type];
1244
1245struct {
1246 type field_name[length_type];
1247}
1248
1249integer {
80fd2569 1250 ...
2152348f 1251}
3bf79539 1252
2152348f 1253floating_point {
80fd2569 1254 ...
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1255}
1256
1257struct {
1258 integer_type field_name:size; /* GNU/C bitfield */
1259}
1260
1261struct {
1262 string field_name;
1263}
3bf79539 1264
fcba70d4 1265
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12668. Clocks
1267
1268Clock metadata allows to describe the clock topology of the system, as
1269well as to detail each clock parameter. In absence of clock description,
1270it is assumed that all fields named "timestamp" use the same clock
aed18b5e 1271source, which increments once per nanosecond.
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1272
1273Describing a clock and how it is used by streams is threefold: first,
1274the clock and clock topology should be described in a "clock"
1275description block, e.g.:
1276
d803bfcb 1277clock {
58262d97 1278 name = cycle_counter_sync;
2fa70eba 1279 uuid = "62189bee-96dc-11e0-91a8-cfa3d89f3923";
58262d97 1280 description = "Cycle counter synchronized across CPUs";
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1281 freq = 1000000000; /* frequency, in Hz */
1282 /* precision in seconds is: 1000 * (1/freq) */
1283 precision = 1000;
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1284 /*
1285 * clock value offset from Epoch is:
1286 * offset_s + (offset * (1/freq))
1287 */
1288 offset_s = 1326476837;
1289 offset = 897235420;
ce0fadbd 1290 absolute = FALSE;
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1291};
1292
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1293The mandatory "name" field specifies the name of the clock identifier,
1294which can later be used as a reference. The optional field "uuid" is the
1295unique identifier of the clock. It can be used to correlate different
1296traces that use the same clock. An optional textual description string
1297can be added with the "description" field. The "freq" field is the
1298initial frequency of the clock, in Hz. If the "freq" field is not
1299present, the frequency is assumed to be 1000000000 (providing clock
1300increment of 1 ns). The optional "precision" field details the
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1301uncertainty on the clock measurements, in (1/freq) units. The "offset_s"
1302and "offset" fields indicate the offset from POSIX.1 Epoch, 1970-01-01
130300:00:00 +0000 (UTC), to the zero of value of the clock. The "offset_s"
1304field is in seconds. The "offset" field is in (1/freq) units. If any of
1305the "offset_s" or "offset" field is not present, it is assigned the 0
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1306value. The field "absolute" is TRUE if the clock is a global reference
1307across different clock uuid (e.g. NTP time). Otherwise, "absolute" is
1308FALSE, and the clock can be considered as synchronized only with other
1309clocks that have the same uuid.
1310
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1311
1312Secondly, a reference to this clock should be added within an integer
1313type:
1314
1315typealias integer {
1316 size = 64; align = 1; signed = false;
58262d97 1317 map = clock.cycle_counter_sync.value;
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1318} := uint64_ccnt_t;
1319
1320Thirdly, stream declarations can reference the clock they use as a
1321time-stamp source:
1322
1323struct packet_context {
1324 uint64_ccnt_t ccnt_begin;
1325 uint64_ccnt_t ccnt_end;
1326 /* ... */
1327};
1328
1329stream {
1330 /* ... */
1331 event.header := struct {
1332 uint64_ccnt_t timestamp;
1333 /* ... */
1334 }
1335 packet.context := struct packet_context;
1336};
1337
1338For a N-bit integer type referring to a clock, if the integer overflows
1339compared to the N low order bits of the clock prior value, then it is
1340assumed that one, and only one, overflow occurred. It is therefore
1341important that events encoding time on a small number of bits happen
1342frequently enough to detect when more than one N-bit overflow occurs.
1343
1344In a packet context, clock field names ending with "_begin" and "_end"
1345have a special meaning: this refers to the time-stamps at, respectively,
1346the beginning and the end of each packet.
1347
1348
3bf79539 1349A. Helper macros
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1350
1351The two following macros keep track of the size of a GNU/C structure without
1352padding at the end by placing HEADER_END as the last field. A one byte end field
1353is used for C90 compatibility (C99 flexible arrays could be used here). Note
1354that this does not affect the effective structure size, which should always be
1355calculated with the header_sizeof() helper.
1356
1357#define HEADER_END char end_field
1358#define header_sizeof(type) offsetof(typeof(type), end_field)
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1359
1360
1361B. Stream Header Rationale
1362
1363An event stream is divided in contiguous event packets of variable size. These
1364subdivisions allow the trace analyzer to perform a fast binary search by time
1365within the stream (typically requiring to index only the event packet headers)
1366without reading the whole stream. These subdivisions have a variable size to
1367eliminate the need to transfer the event packet padding when partially filled
1368event packets must be sent when streaming a trace for live viewing/analysis.
1369An event packet can contain a certain amount of padding at the end. Dividing
1370streams into event packets is also useful for network streaming over UDP and
1371flight recorder mode tracing (a whole event packet can be swapped out of the
1372buffer atomically for reading).
1373
1374The stream header is repeated at the beginning of each event packet to allow
1375flexibility in terms of:
1376
1377 - streaming support,
1378 - allowing arbitrary buffers to be discarded without making the trace
1379 unreadable,
1380 - allow UDP packet loss handling by either dealing with missing event packet
1381 or asking for re-transmission.
1382 - transparently support flight recorder mode,
1383 - transparently support crash dump.
1384
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1385
1386C. TSDL Grammar
fcba70d4 1387
4fa992a5 1388/*
6c7226e9 1389 * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar.
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1390 *
1391 * Inspired from the C99 grammar:
1392 * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A)
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1393 * and c++1x grammar (draft)
1394 * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A)
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1395 *
1396 * Specialized for CTF needs by including only constant and declarations from
1397 * C99 (excluding function declarations), and by adding support for variants,
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1398 * sequences and CTF-specific specifiers. Enumeration container types
1399 * semantic is inspired from c++1x enum-base.
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1400 */
1401
14021) Lexical grammar
1403
14041.1) Lexical elements
1405
1406token:
1407 keyword
1408 identifier
1409 constant
1410 string-literal
1411 punctuator
1412
14131.2) Keywords
1414
1415keyword: is one of
1416
ec4404a7 1417align
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1418const
1419char
2fa70eba 1420clock
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1421double
1422enum
570ecabe 1423env
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1424event
1425floating_point
1426float
1427integer
1428int
1429long
1430short
1431signed
1432stream
1433string
1434struct
1435trace
3e1e1a78 1436typealias
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1437typedef
1438unsigned
1439variant
1440void
1441_Bool
1442_Complex
1443_Imaginary
1444
1445
14461.3) Identifiers
1447
1448identifier:
1449 identifier-nondigit
1450 identifier identifier-nondigit
1451 identifier digit
1452
1453identifier-nondigit:
1454 nondigit
1455 universal-character-name
1456 any other implementation-defined characters
1457
1458nondigit:
1459 _
1460 [a-zA-Z] /* regular expression */
1461
1462digit:
1463 [0-9] /* regular expression */
1464
14651.4) Universal character names
1466
1467universal-character-name:
1468 \u hex-quad
1469 \U hex-quad hex-quad
1470
1471hex-quad:
1472 hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit
1473
14741.5) Constants
1475
1476constant:
1477 integer-constant
1478 enumeration-constant
1479 character-constant
1480
1481integer-constant:
1482 decimal-constant integer-suffix-opt
1483 octal-constant integer-suffix-opt
1484 hexadecimal-constant integer-suffix-opt
1485
1486decimal-constant:
1487 nonzero-digit
1488 decimal-constant digit
1489
1490octal-constant:
1491 0
1492 octal-constant octal-digit
1493
1494hexadecimal-constant:
1495 hexadecimal-prefix hexadecimal-digit
1496 hexadecimal-constant hexadecimal-digit
1497
1498hexadecimal-prefix:
1499 0x
1500 0X
1501
1502nonzero-digit:
1503 [1-9]
1504
1505integer-suffix:
1506 unsigned-suffix long-suffix-opt
1507 unsigned-suffix long-long-suffix
1508 long-suffix unsigned-suffix-opt
1509 long-long-suffix unsigned-suffix-opt
1510
1511unsigned-suffix:
1512 u
1513 U
1514
1515long-suffix:
1516 l
1517 L
1518
1519long-long-suffix:
1520 ll
1521 LL
1522
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1523enumeration-constant:
1524 identifier
1525 string-literal
1526
1527character-constant:
1528 ' c-char-sequence '
1529 L' c-char-sequence '
1530
1531c-char-sequence:
1532 c-char
1533 c-char-sequence c-char
1534
1535c-char:
1536 any member of source charset except single-quote ('), backslash
1537 (\), or new-line character.
1538 escape-sequence
1539
1540escape-sequence:
1541 simple-escape-sequence
1542 octal-escape-sequence
1543 hexadecimal-escape-sequence
1544 universal-character-name
1545
1546simple-escape-sequence: one of
1547 \' \" \? \\ \a \b \f \n \r \t \v
1548
1549octal-escape-sequence:
1550 \ octal-digit
1551 \ octal-digit octal-digit
1552 \ octal-digit octal-digit octal-digit
1553
1554hexadecimal-escape-sequence:
1555 \x hexadecimal-digit
1556 hexadecimal-escape-sequence hexadecimal-digit
1557
15581.6) String literals
1559
1560string-literal:
1561 " s-char-sequence-opt "
1562 L" s-char-sequence-opt "
1563
1564s-char-sequence:
1565 s-char
1566 s-char-sequence s-char
1567
1568s-char:
1569 any member of source charset except double-quote ("), backslash
1570 (\), or new-line character.
1571 escape-sequence
1572
15731.7) Punctuators
1574
1575punctuator: one of
1576 [ ] ( ) { } . -> * + - < > : ; ... = ,
1577
1578
15792) Phrase structure grammar
1580
1581primary-expression:
1582 identifier
1583 constant
1584 string-literal
1585 ( unary-expression )
1586
1587postfix-expression:
1588 primary-expression
1589 postfix-expression [ unary-expression ]
1590 postfix-expression . identifier
1591 postfix-expressoin -> identifier
1592
1593unary-expression:
1594 postfix-expression
1595 unary-operator postfix-expression
1596
1597unary-operator: one of
1598 + -
1599
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1600assignment-operator:
1601 =
1602
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1603type-assignment-operator:
1604 :=
1605
4fa992a5 1606constant-expression-range:
73d61ac3 1607 unary-expression ... unary-expression
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1608
16092.2) Declarations:
1610
1611declaration:
689e04b4 1612 declaration-specifiers declarator-list-opt ;
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1613 ctf-specifier ;
1614
1615declaration-specifiers:
689e04b4 1616 storage-class-specifier declaration-specifiers-opt
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1617 type-specifier declaration-specifiers-opt
1618 type-qualifier declaration-specifiers-opt
1619
1620declarator-list:
1621 declarator
1622 declarator-list , declarator
1623
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1624abstract-declarator-list:
1625 abstract-declarator
1626 abstract-declarator-list , abstract-declarator
1627
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1628storage-class-specifier:
1629 typedef
1630
1631type-specifier:
1632 void
1633 char
1634 short
1635 int
1636 long
1637 float
1638 double
1639 signed
1640 unsigned
1641 _Bool
1642 _Complex
cfdd51ec 1643 _Imaginary
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1644 struct-specifier
1645 variant-specifier
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1646 enum-specifier
1647 typedef-name
1648 ctf-type-specifier
1649
ec4404a7 1650align-attribute:
73d61ac3 1651 align ( unary-expression )
ec4404a7 1652
4fa992a5 1653struct-specifier:
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MD
1654 struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt
1655 struct identifier align-attribute-opt
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MD
1656
1657struct-or-variant-declaration-list:
1658 struct-or-variant-declaration
1659 struct-or-variant-declaration-list struct-or-variant-declaration
1660
1661struct-or-variant-declaration:
1662 specifier-qualifier-list struct-or-variant-declarator-list ;
eacb16d1 1663 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ;
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1664 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ;
1665 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ;
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1666
1667specifier-qualifier-list:
1668 type-specifier specifier-qualifier-list-opt
1669 type-qualifier specifier-qualifier-list-opt
1670
1671struct-or-variant-declarator-list:
1672 struct-or-variant-declarator
1673 struct-or-variant-declarator-list , struct-or-variant-declarator
1674
1675struct-or-variant-declarator:
1676 declarator
73d61ac3 1677 declarator-opt : unary-expression
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1678
1679variant-specifier:
1680 variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list }
1681 variant identifier variant-tag
1682
1683variant-tag:
37ab95c3 1684 < unary-expression >
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1685
1686enum-specifier:
1687 enum identifier-opt { enumerator-list }
1688 enum identifier-opt { enumerator-list , }
1689 enum identifier
a9b83695
MD
1690 enum identifier-opt : declaration-specifiers { enumerator-list }
1691 enum identifier-opt : declaration-specifiers { enumerator-list , }
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MD
1692
1693enumerator-list:
1694 enumerator
1695 enumerator-list , enumerator
1696
1697enumerator:
1698 enumeration-constant
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1699 enumeration-constant assignment-operator unary-expression
1700 enumeration-constant assignment-operator constant-expression-range
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1701
1702type-qualifier:
1703 const
1704
1705declarator:
1706 pointer-opt direct-declarator
1707
1708direct-declarator:
1709 identifier
1710 ( declarator )
1ab22b2a 1711 direct-declarator [ unary-expression ]
4fa992a5 1712
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1713abstract-declarator:
1714 pointer-opt direct-abstract-declarator
1715
1716direct-abstract-declarator:
1717 identifier-opt
1718 ( abstract-declarator )
1ab22b2a 1719 direct-abstract-declarator [ unary-expression ]
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1720 direct-abstract-declarator [ ]
1721
4fa992a5 1722pointer:
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1723 * type-qualifier-list-opt
1724 * type-qualifier-list-opt pointer
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MD
1725
1726type-qualifier-list:
1727 type-qualifier
1728 type-qualifier-list type-qualifier
1729
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1730typedef-name:
1731 identifier
1732
17332.3) CTF-specific declarations
1734
1735ctf-specifier:
662baf84 1736 clock { ctf-assignment-expression-list-opt }
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1737 event { ctf-assignment-expression-list-opt }
1738 stream { ctf-assignment-expression-list-opt }
570ecabe 1739 env { ctf-assignment-expression-list-opt }
4fa992a5 1740 trace { ctf-assignment-expression-list-opt }
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1741 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1742 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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1743
1744ctf-type-specifier:
1745 floating_point { ctf-assignment-expression-list-opt }
1746 integer { ctf-assignment-expression-list-opt }
1747 string { ctf-assignment-expression-list-opt }
7609d3c7 1748 string
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1749
1750ctf-assignment-expression-list:
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1751 ctf-assignment-expression ;
1752 ctf-assignment-expression-list ctf-assignment-expression ;
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1753
1754ctf-assignment-expression:
1755 unary-expression assignment-operator unary-expression
1756 unary-expression type-assignment-operator type-specifier
eacb16d1 1757 declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list
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1758 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list
1759 typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list
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