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5ba9f198 | 1 | |
4767a9e7 | 2 | RFC: Common Trace Format (CTF) Proposal (pre-v1.7) |
5ba9f198 MD |
3 | |
4 | Mathieu Desnoyers, EfficiOS Inc. | |
5 | ||
6 | The goal of the present document is to propose a trace format that suits the | |
cc089c3a | 7 | needs of the embedded, telecom, high-performance and kernel communities. It is |
5ba9f198 | 8 | based on the Common Trace Format Requirements (v1.4) document. It is designed to |
cc089c3a | 9 | allow traces to be natively generated by the Linux kernel, Linux user-space |
6c7226e9 MD |
10 | applications written in C/C++, and hardware components. One major element of |
11 | CTF is the Trace Stream Description Language (TSDL) which flexibility | |
12 | enables description of various binary trace stream layouts. | |
cc089c3a MD |
13 | |
14 | The latest version of this document can be found at: | |
15 | ||
16 | git tree: git://git.efficios.com/ctf.git | |
17 | gitweb: http://git.efficios.com/?p=ctf.git | |
5ba9f198 MD |
18 | |
19 | A reference implementation of a library to read and write this trace format is | |
20 | being implemented within the BabelTrace project, a converter between trace | |
21 | formats. The development tree is available at: | |
22 | ||
23 | git tree: git://git.efficios.com/babeltrace.git | |
24 | gitweb: http://git.efficios.com/?p=babeltrace.git | |
25 | ||
26 | ||
beabf088 MD |
27 | Table of Contents |
28 | ||
29 | 1. Preliminary definitions | |
30 | 2. High-level representation of a trace | |
31 | 3. Event stream | |
32 | 4. Types | |
33 | 4.1 Basic types | |
34 | 4.1.1 Type inheritance | |
35 | 4.1.2 Alignment | |
36 | 4.1.3 Byte order | |
37 | 4.1.4 Size | |
38 | 4.1.5 Integers | |
39 | 4.1.6 GNU/C bitfields | |
40 | 4.1.7 Floating point | |
41 | 4.1.8 Enumerations | |
42 | 4.2 Compound types | |
43 | 4.2.1 Structures | |
44 | 4.2.2 Variants (Discriminated/Tagged Unions) | |
45 | 4.2.3 Arrays | |
46 | 4.2.4 Sequences | |
47 | 4.2.5 Strings | |
48 | 5. Event Packet Header | |
49 | 5.1 Event Packet Header Description | |
50 | 5.2 Event Packet Context Description | |
51 | 6. Event Structure | |
52 | 6.1 Event Header | |
53 | 6.1.1 Type 1 - Few event IDs | |
54 | 6.1.2 Type 2 - Many event IDs | |
55 | 6.2 Event Context | |
56 | 6.3 Event Payload | |
57 | 6.3.1 Padding | |
58 | 6.3.2 Alignment | |
59 | 7. Trace Stream Description Language (TSDL) | |
60 | 7.1 Meta-data | |
61 | 7.2 Declaration vs Definition | |
62 | 7.3 TSDL Scopes | |
63 | 7.3.1 Lexical Scope | |
64 | 7.3.2 Dynamic Scope | |
65 | 7.4 TSDL Examples | |
66 | ||
67 | ||
5ba9f198 MD |
68 | 1. Preliminary definitions |
69 | ||
3bf79539 MD |
70 | - Event Trace: An ordered sequence of events. |
71 | - Event Stream: An ordered sequence of events, containing a subset of the | |
72 | trace event types. | |
73 | - Event Packet: A sequence of physically contiguous events within an event | |
74 | stream. | |
5ba9f198 MD |
75 | - Event: This is the basic entry in a trace. (aka: a trace record). |
76 | - An event identifier (ID) relates to the class (a type) of event within | |
3bf79539 MD |
77 | an event stream. |
78 | e.g. event: irq_entry. | |
5ba9f198 MD |
79 | - An event (or event record) relates to a specific instance of an event |
80 | class. | |
3bf79539 MD |
81 | e.g. event: irq_entry, at time X, on CPU Y |
82 | - Source Architecture: Architecture writing the trace. | |
83 | - Reader Architecture: Architecture reading the trace. | |
5ba9f198 MD |
84 | |
85 | ||
86 | 2. High-level representation of a trace | |
87 | ||
3bf79539 MD |
88 | A trace is divided into multiple event streams. Each event stream contains a |
89 | subset of the trace event types. | |
5ba9f198 | 90 | |
3bf79539 MD |
91 | The final output of the trace, after its generation and optional transport over |
92 | the network, is expected to be either on permanent or temporary storage in a | |
93 | virtual file system. Because each event stream is appended to while a trace is | |
94 | being recorded, each is associated with a separate file for output. Therefore, | |
95 | a stored trace can be represented as a directory containing one file per stream. | |
5ba9f198 | 96 | |
6672e9e1 MD |
97 | Meta-data description associated with the trace contains information on |
98 | trace event types expressed in the Trace Stream Description Language | |
99 | (TSDL). This language describes: | |
5ba9f198 MD |
100 | |
101 | - Trace version. | |
102 | - Types available. | |
6672e9e1 | 103 | - Per-trace event header description. |
3bf79539 | 104 | - Per-stream event header description. |
6672e9e1 | 105 | - Per-stream event context description. |
5ba9f198 | 106 | - Per-event |
3bf79539 | 107 | - Event type to stream mapping. |
5ba9f198 MD |
108 | - Event type to name mapping. |
109 | - Event type to ID mapping. | |
6672e9e1 | 110 | - Event context description. |
5ba9f198 MD |
111 | - Event fields description. |
112 | ||
113 | ||
3bf79539 | 114 | 3. Event stream |
5ba9f198 | 115 | |
6672e9e1 MD |
116 | An event stream can be divided into contiguous event packets of variable |
117 | size. These subdivisions have a variable size. An event packet can | |
118 | contain a certain amount of padding at the end. The stream header is | |
119 | repeated at the beginning of each event packet. The rationale for the | |
120 | event stream design choices is explained in Appendix B. Stream Header | |
121 | Rationale. | |
5ba9f198 | 122 | |
3bf79539 MD |
123 | The event stream header will therefore be referred to as the "event packet |
124 | header" throughout the rest of this document. | |
5ba9f198 MD |
125 | |
126 | ||
127 | 4. Types | |
128 | ||
1fad7a85 MD |
129 | Types are organized as type classes. Each type class belong to either of two |
130 | kind of types: basic types or compound types. | |
131 | ||
5ba9f198 MD |
132 | 4.1 Basic types |
133 | ||
1fad7a85 MD |
134 | A basic type is a scalar type, as described in this section. It includes |
135 | integers, GNU/C bitfields, enumerations, and floating point values. | |
5ba9f198 MD |
136 | |
137 | 4.1.1 Type inheritance | |
138 | ||
80fd2569 MD |
139 | Type specifications can be inherited to allow deriving types from a |
140 | type class. For example, see the uint32_t named type derived from the "integer" | |
141 | type class below ("Integers" section). Types have a precise binary | |
142 | representation in the trace. A type class has methods to read and write these | |
143 | types, but must be derived into a type to be usable in an event field. | |
5ba9f198 MD |
144 | |
145 | 4.1.2 Alignment | |
146 | ||
147 | We define "byte-packed" types as aligned on the byte size, namely 8-bit. | |
148 | We define "bit-packed" types as following on the next bit, as defined by the | |
370eae99 | 149 | "Integers" section. |
5ba9f198 | 150 | |
6672e9e1 | 151 | Each basic type must specify its alignment, in bits. Examples of |
ec4404a7 MD |
152 | possible alignments are: bit-packed (align = 1), byte-packed (align = |
153 | 8), or word-aligned (e.g. align = 32 or align = 64). The choice depends | |
154 | on the architecture preference and compactness vs performance trade-offs | |
155 | of the implementation. Architectures providing fast unaligned write | |
156 | byte-packed basic types to save space, aligning each type on byte | |
157 | boundaries (8-bit). Architectures with slow unaligned writes align types | |
158 | on specific alignment values. If no specific alignment is declared for a | |
159 | type, it is assumed to be bit-packed for integers with size not multiple | |
160 | of 8 bits and for gcc bitfields. All other basic types are byte-packed | |
161 | by default. It is however recommended to always specify the alignment | |
162 | explicitly. Alignment values must be power of two. Compound types are | |
163 | aligned as specified in their individual specification. | |
5ba9f198 | 164 | |
6672e9e1 | 165 | TSDL meta-data attribute representation of a specific alignment: |
5ba9f198 MD |
166 | |
167 | align = value; /* value in bits */ | |
168 | ||
169 | 4.1.3 Byte order | |
170 | ||
3bf79539 MD |
171 | By default, the native endianness of the source architecture the trace is used. |
172 | Byte order can be overridden for a basic type by specifying a "byte_order" | |
173 | attribute. Typical use-case is to specify the network byte order (big endian: | |
174 | "be") to save data captured from the network into the trace without conversion. | |
175 | If not specified, the byte order is native. | |
5ba9f198 | 176 | |
6672e9e1 | 177 | TSDL meta-data representation: |
5ba9f198 MD |
178 | |
179 | byte_order = native OR network OR be OR le; /* network and be are aliases */ | |
180 | ||
181 | 4.1.4 Size | |
182 | ||
183 | Type size, in bits, for integers and floats is that returned by "sizeof()" in C | |
184 | multiplied by CHAR_BIT. | |
185 | We require the size of "char" and "unsigned char" types (CHAR_BIT) to be fixed | |
186 | to 8 bits for cross-endianness compatibility. | |
187 | ||
6672e9e1 | 188 | TSDL meta-data representation: |
5ba9f198 MD |
189 | |
190 | size = value; (value is in bits) | |
191 | ||
192 | 4.1.5 Integers | |
193 | ||
6672e9e1 MD |
194 | Signed integers are represented in two-complement. Integer alignment, |
195 | size, signedness and byte ordering are defined in the TSDL meta-data. | |
196 | Integers aligned on byte size (8-bit) and with length multiple of byte | |
197 | size (8-bit) correspond to the C99 standard integers. In addition, | |
198 | integers with alignment and/or size that are _not_ a multiple of the | |
199 | byte size are permitted; these correspond to the C99 standard bitfields, | |
200 | with the added specification that the CTF integer bitfields have a fixed | |
201 | binary representation. A MIT-licensed reference implementation of the | |
202 | CTF portable bitfields is available at: | |
5ba9f198 MD |
203 | |
204 | http://git.efficios.com/?p=babeltrace.git;a=blob;f=include/babeltrace/bitfield.h | |
205 | ||
206 | Binary representation of integers: | |
207 | ||
208 | - On little and big endian: | |
209 | - Within a byte, high bits correspond to an integer high bits, and low bits | |
210 | correspond to low bits. | |
211 | - On little endian: | |
212 | - Integer across multiple bytes are placed from the less significant to the | |
213 | most significant. | |
214 | - Consecutive integers are placed from lower bits to higher bits (even within | |
215 | a byte). | |
216 | - On big endian: | |
217 | - Integer across multiple bytes are placed from the most significant to the | |
218 | less significant. | |
219 | - Consecutive integers are placed from higher bits to lower bits (even within | |
220 | a byte). | |
221 | ||
222 | This binary representation is derived from the bitfield implementation in GCC | |
223 | for little and big endian. However, contrary to what GCC does, integers can | |
6672e9e1 | 224 | cross units boundaries (no padding is required). Padding can be explicitly |
5ba9f198 MD |
225 | added (see 4.1.6 GNU/C bitfields) to follow the GCC layout if needed. |
226 | ||
6672e9e1 | 227 | TSDL meta-data representation: |
5ba9f198 | 228 | |
80fd2569 | 229 | integer { |
5ba9f198 MD |
230 | signed = true OR false; /* default false */ |
231 | byte_order = native OR network OR be OR le; /* default native */ | |
232 | size = value; /* value in bits, no default */ | |
233 | align = value; /* value in bits */ | |
56b77c06 MD |
234 | /* based used for pretty-printing output, default: decimal. */ |
235 | 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 | |
236 | OR octal OR oct OR o OR 8 OR binary OR b OR 2; | |
13441bf5 MD |
237 | /* character encoding, default: none */ |
238 | encoding = none or UTF8 or ASCII; | |
2152348f | 239 | } |
5ba9f198 | 240 | |
80fd2569 | 241 | Example of type inheritance (creation of a uint32_t named type): |
5ba9f198 | 242 | |
359894ac | 243 | typealias integer { |
9e4e34e9 | 244 | size = 32; |
5ba9f198 MD |
245 | signed = false; |
246 | align = 32; | |
38b8da21 | 247 | } := uint32_t; |
5ba9f198 | 248 | |
80fd2569 | 249 | Definition of a named 5-bit signed bitfield: |
5ba9f198 | 250 | |
359894ac | 251 | typealias integer { |
5ba9f198 MD |
252 | size = 5; |
253 | signed = true; | |
254 | align = 1; | |
38b8da21 | 255 | } := int5_t; |
5ba9f198 | 256 | |
13441bf5 MD |
257 | The character encoding field can be used to specify that the integer |
258 | must be printed as a text character when read. e.g.: | |
259 | ||
260 | typealias integer { | |
261 | size = 8; | |
262 | align = 8; | |
263 | signed = false; | |
264 | encoding = UTF8; | |
265 | } := utf_char; | |
266 | ||
267 | ||
5ba9f198 MD |
268 | 4.1.6 GNU/C bitfields |
269 | ||
270 | The GNU/C bitfields follow closely the integer representation, with a | |
271 | particularity on alignment: if a bitfield cannot fit in the current unit, the | |
80fd2569 MD |
272 | unit is padded and the bitfield starts at the following unit. The unit size is |
273 | defined by the size of the type "unit_type". | |
5ba9f198 | 274 | |
6672e9e1 | 275 | TSDL meta-data representation: |
80fd2569 | 276 | |
d674f4b8 | 277 | unit_type name:size; |
80fd2569 | 278 | |
5ba9f198 MD |
279 | As an example, the following structure declared in C compiled by GCC: |
280 | ||
281 | struct example { | |
282 | short a:12; | |
283 | short b:5; | |
284 | }; | |
285 | ||
2152348f MD |
286 | The example structure is aligned on the largest element (short). The second |
287 | bitfield would be aligned on the next unit boundary, because it would not fit in | |
288 | the current unit. | |
5ba9f198 MD |
289 | |
290 | 4.1.7 Floating point | |
291 | ||
6672e9e1 | 292 | The floating point values byte ordering is defined in the TSDL meta-data. |
5ba9f198 MD |
293 | |
294 | Floating point values follow the IEEE 754-2008 standard interchange formats. | |
295 | Description of the floating point values include the exponent and mantissa size | |
296 | in bits. Some requirements are imposed on the floating point values: | |
297 | ||
298 | - FLT_RADIX must be 2. | |
299 | - mant_dig is the number of digits represented in the mantissa. It is specified | |
300 | by the ISO C99 standard, section 5.2.4, as FLT_MANT_DIG, DBL_MANT_DIG and | |
301 | LDBL_MANT_DIG as defined by <float.h>. | |
302 | - exp_dig is the number of digits represented in the exponent. Given that | |
303 | mant_dig is one bit more than its actual size in bits (leading 1 is not | |
304 | needed) and also given that the sign bit always takes one bit, exp_dig can be | |
305 | specified as: | |
306 | ||
307 | - sizeof(float) * CHAR_BIT - FLT_MANT_DIG | |
308 | - sizeof(double) * CHAR_BIT - DBL_MANT_DIG | |
309 | - sizeof(long double) * CHAR_BIT - LDBL_MANT_DIG | |
310 | ||
6672e9e1 | 311 | TSDL meta-data representation: |
5ba9f198 | 312 | |
80fd2569 | 313 | floating_point { |
ec4404a7 MD |
314 | exp_dig = value; |
315 | mant_dig = value; | |
316 | byte_order = native OR network OR be OR le; | |
317 | align = value; | |
2152348f | 318 | } |
5ba9f198 MD |
319 | |
320 | Example of type inheritance: | |
321 | ||
359894ac | 322 | typealias floating_point { |
5ba9f198 MD |
323 | exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */ |
324 | mant_dig = 24; /* FLT_MANT_DIG */ | |
325 | byte_order = native; | |
ec4404a7 | 326 | align = 32; |
38b8da21 | 327 | } := float; |
5ba9f198 MD |
328 | |
329 | TODO: define NaN, +inf, -inf behavior. | |
330 | ||
ec4404a7 MD |
331 | Bit-packed, byte-packed or larger alignments can be used for floating |
332 | point values, similarly to integers. | |
333 | ||
5ba9f198 MD |
334 | 4.1.8 Enumerations |
335 | ||
336 | Enumerations are a mapping between an integer type and a table of strings. The | |
337 | numerical representation of the enumeration follows the integer type specified | |
6672e9e1 MD |
338 | by the meta-data. The enumeration mapping table is detailed in the enumeration |
339 | description within the meta-data. The mapping table maps inclusive value | |
340 | ranges (or single values) to strings. Instead of being limited to simple | |
3bf79539 | 341 | "value -> string" mappings, these enumerations map |
80fd2569 | 342 | "[ start_value ... end_value ] -> string", which map inclusive ranges of |
3bf79539 MD |
343 | values to strings. An enumeration from the C language can be represented in |
344 | this format by having the same start_value and end_value for each element, which | |
345 | is in fact a range of size 1. This single-value range is supported without | |
4767a9e7 | 346 | repeating the start and end values with the value = string declaration. |
80fd2569 | 347 | |
a9b83695 | 348 | enum name : integer_type { |
359894ac | 349 | somestring = start_value1 ... end_value1, |
80fd2569 MD |
350 | "other string" = start_value2 ... end_value2, |
351 | yet_another_string, /* will be assigned to end_value2 + 1 */ | |
352 | "some other string" = value, | |
353 | ... | |
354 | }; | |
355 | ||
356 | If the values are omitted, the enumeration starts at 0 and increment of 1 for | |
357 | each entry: | |
358 | ||
a9b83695 | 359 | enum name : unsigned int { |
80fd2569 MD |
360 | ZERO, |
361 | ONE, | |
362 | TWO, | |
363 | TEN = 10, | |
364 | ELEVEN, | |
3bf79539 | 365 | }; |
5ba9f198 | 366 | |
80fd2569 | 367 | Overlapping ranges within a single enumeration are implementation defined. |
5ba9f198 | 368 | |
2152348f MD |
369 | A nameless enumeration can be declared as a field type or as part of a typedef: |
370 | ||
a9b83695 | 371 | enum : integer_type { |
2152348f MD |
372 | ... |
373 | } | |
374 | ||
c2742c56 MD |
375 | Enumerations omitting the container type ": integer_type" use the "int" |
376 | type (for compatibility with C99). The "int" type must be previously | |
377 | declared. E.g.: | |
378 | ||
379 | typealias integer { size = 32; align = 32; signed = true } := int; | |
380 | ||
381 | enum { | |
382 | ... | |
383 | } | |
384 | ||
1fad7a85 | 385 | |
5ba9f198 MD |
386 | 4.2 Compound types |
387 | ||
1fad7a85 MD |
388 | Compound are aggregation of type declarations. Compound types include |
389 | structures, variant, arrays, sequences, and strings. | |
390 | ||
5ba9f198 MD |
391 | 4.2.1 Structures |
392 | ||
393 | Structures are aligned on the largest alignment required by basic types | |
394 | contained within the structure. (This follows the ISO/C standard for structures) | |
395 | ||
6672e9e1 | 396 | TSDL meta-data representation of a named structure: |
5ba9f198 | 397 | |
80fd2569 MD |
398 | struct name { |
399 | field_type field_name; | |
400 | field_type field_name; | |
401 | ... | |
402 | }; | |
5ba9f198 MD |
403 | |
404 | Example: | |
405 | ||
80fd2569 MD |
406 | struct example { |
407 | integer { /* Nameless type */ | |
408 | size = 16; | |
409 | signed = true; | |
410 | align = 16; | |
411 | } first_field_name; | |
6672e9e1 | 412 | uint64_t second_field_name; /* Named type declared in the meta-data */ |
3bf79539 | 413 | }; |
5ba9f198 MD |
414 | |
415 | The fields are placed in a sequence next to each other. They each possess a | |
416 | field name, which is a unique identifier within the structure. | |
417 | ||
2152348f | 418 | A nameless structure can be declared as a field type or as part of a typedef: |
80fd2569 MD |
419 | |
420 | struct { | |
421 | ... | |
2152348f | 422 | } |
80fd2569 | 423 | |
ec4404a7 MD |
424 | Alignment for a structure compound type can be forced to a minimum value |
425 | by adding an "align" specifier after the declaration of a structure | |
426 | body. This attribute is read as: align(value). The value is specified in | |
427 | bits. The structure will be aligned on the maximum value between this | |
428 | attribute and the alignment required by the basic types contained within | |
429 | the structure. e.g. | |
430 | ||
431 | struct { | |
432 | ... | |
433 | } align(32) | |
434 | ||
77a98c82 | 435 | 4.2.2 Variants (Discriminated/Tagged Unions) |
fcba70d4 | 436 | |
fdf2bb05 MD |
437 | A CTF variant is a selection between different types. A CTF variant must |
438 | always be defined within the scope of a structure or within fields | |
439 | contained within a structure (defined recursively). A "tag" enumeration | |
440 | field must appear in either the same lexical scope, prior to the variant | |
1ab22b2a MD |
441 | field (in field declaration order), in an upper lexical scope (see |
442 | Section 7.3.1), or in an upper dynamic scope (see Section 7.3.2). The | |
443 | type selection is indicated by the mapping from the enumeration value to | |
444 | the string used as variant type selector. The field to use as tag is | |
445 | specified by the "tag_field", specified between "< >" after the | |
fdf2bb05 MD |
446 | "variant" keyword for unnamed variants, and after "variant name" for |
447 | named variants. | |
fcba70d4 MD |
448 | |
449 | The alignment of the variant is the alignment of the type as selected by the tag | |
450 | value for the specific instance of the variant. The alignment of the type | |
451 | containing the variant is independent of the variant alignment. The size of the | |
452 | variant is the size as selected by the tag value for the specific instance of | |
453 | the variant. | |
454 | ||
455 | A named variant declaration followed by its definition within a structure | |
456 | declaration: | |
457 | ||
458 | variant name { | |
459 | field_type sel1; | |
460 | field_type sel2; | |
461 | field_type sel3; | |
462 | ... | |
463 | }; | |
464 | ||
465 | struct { | |
a9b83695 | 466 | enum : integer_type { sel1, sel2, sel3, ... } tag_field; |
fcba70d4 MD |
467 | ... |
468 | variant name <tag_field> v; | |
469 | } | |
470 | ||
471 | An unnamed variant definition within a structure is expressed by the following | |
6672e9e1 | 472 | TSDL meta-data: |
fcba70d4 MD |
473 | |
474 | struct { | |
a9b83695 | 475 | enum : integer_type { sel1, sel2, sel3, ... } tag_field; |
fcba70d4 MD |
476 | ... |
477 | variant <tag_field> { | |
478 | field_type sel1; | |
479 | field_type sel2; | |
480 | field_type sel3; | |
481 | ... | |
482 | } v; | |
483 | } | |
484 | ||
485 | Example of a named variant within a sequence that refers to a single tag field: | |
486 | ||
487 | variant example { | |
488 | uint32_t a; | |
489 | uint64_t b; | |
490 | short c; | |
491 | }; | |
492 | ||
493 | struct { | |
a9b83695 | 494 | enum : uint2_t { a, b, c } choice; |
1ab22b2a MD |
495 | unsigned int seqlen; |
496 | variant example <choice> v[seqlen]; | |
fcba70d4 MD |
497 | } |
498 | ||
499 | Example of an unnamed variant: | |
500 | ||
501 | struct { | |
a9b83695 | 502 | enum : uint2_t { a, b, c, d } choice; |
fcba70d4 MD |
503 | /* Unrelated fields can be added between the variant and its tag */ |
504 | int32_t somevalue; | |
505 | variant <choice> { | |
506 | uint32_t a; | |
507 | uint64_t b; | |
508 | short c; | |
509 | struct { | |
510 | unsigned int field1; | |
511 | uint64_t field2; | |
512 | } d; | |
513 | } s; | |
514 | } | |
515 | ||
516 | Example of an unnamed variant within an array: | |
517 | ||
518 | struct { | |
a9b83695 | 519 | enum : uint2_t { a, b, c } choice; |
fcba70d4 MD |
520 | variant <choice> { |
521 | uint32_t a; | |
522 | uint64_t b; | |
523 | short c; | |
15850440 | 524 | } v[10]; |
fcba70d4 MD |
525 | } |
526 | ||
527 | Example of a variant type definition within a structure, where the defined type | |
528 | is then declared within an array of structures. This variant refers to a tag | |
529 | located in an upper lexical scope. This example clearly shows that a variant | |
530 | type definition referring to the tag "x" uses the closest preceding field from | |
531 | the lexical scope of the type definition. | |
532 | ||
533 | struct { | |
a9b83695 | 534 | enum : uint2_t { a, b, c, d } x; |
fcba70d4 MD |
535 | |
536 | typedef variant <x> { /* | |
537 | * "x" refers to the preceding "x" enumeration in the | |
538 | * lexical scope of the type definition. | |
539 | */ | |
540 | uint32_t a; | |
541 | uint64_t b; | |
542 | short c; | |
543 | } example_variant; | |
544 | ||
545 | struct { | |
a9b83695 | 546 | enum : int { x, y, z } x; /* This enumeration is not used by "v". */ |
fcba70d4 | 547 | example_variant v; /* |
a9b83695 | 548 | * "v" uses the "enum : uint2_t { a, b, c, d }" |
fcba70d4 MD |
549 | * tag. |
550 | */ | |
551 | } a[10]; | |
552 | } | |
553 | ||
554 | 4.2.3 Arrays | |
5ba9f198 | 555 | |
6672e9e1 MD |
556 | Arrays are fixed-length. Their length is declared in the type |
557 | declaration within the meta-data. They contain an array of "inner type" | |
558 | elements, which can refer to any type not containing the type of the | |
559 | array being declared (no circular dependency). The length is the number | |
560 | of elements in an array. | |
5ba9f198 | 561 | |
6672e9e1 | 562 | TSDL meta-data representation of a named array: |
80fd2569 MD |
563 | |
564 | typedef elem_type name[length]; | |
5ba9f198 | 565 | |
2152348f | 566 | A nameless array can be declared as a field type within a structure, e.g.: |
5ba9f198 | 567 | |
2152348f | 568 | uint8_t field_name[10]; |
80fd2569 | 569 | |
ec4404a7 | 570 | Arrays are always aligned on their element alignment requirement. |
5ba9f198 | 571 | |
fcba70d4 | 572 | 4.2.4 Sequences |
5ba9f198 | 573 | |
1ab22b2a MD |
574 | Sequences are dynamically-sized arrays. They refer to a a "length" |
575 | unsigned integer field, which must appear in either the same lexical scope, | |
576 | prior to the sequence field (in field declaration order), in an upper | |
577 | lexical scope (see Section 7.3.1), or in an upper dynamic scope (see | |
578 | Section 7.3.2). This length field represents the number of elements in | |
579 | the sequence. The sequence per se is an array of "inner type" elements. | |
5ba9f198 | 580 | |
1ab22b2a | 581 | TSDL meta-data representation for a sequence type definition: |
80fd2569 | 582 | |
1ab22b2a MD |
583 | struct { |
584 | unsigned int length_field; | |
585 | typedef elem_type typename[length_field]; | |
586 | typename seq_field_name; | |
587 | } | |
588 | ||
589 | A sequence can also be declared as a field type, e.g.: | |
80fd2569 | 590 | |
1ab22b2a MD |
591 | struct { |
592 | unsigned int length_field; | |
593 | long seq_field_name[length_field]; | |
594 | } | |
80fd2569 | 595 | |
1ab22b2a MD |
596 | Multiple sequences can refer to the same length field, and these length |
597 | fields can be in a different upper dynamic scope: | |
598 | ||
599 | e.g., assuming the stream.event.header defines: | |
600 | ||
601 | stream { | |
602 | ... | |
603 | id = 1; | |
604 | event.header := struct { | |
605 | uint16_t seq_len; | |
606 | }; | |
607 | }; | |
608 | ||
609 | event { | |
610 | ... | |
611 | stream_id = 1; | |
612 | fields := struct { | |
613 | long seq_a[stream.event.header.seq_len]; | |
614 | char seq_b[stream.event.header.seq_len]; | |
615 | }; | |
616 | }; | |
80fd2569 | 617 | |
1ab22b2a | 618 | The sequence elements follow the "array" specifications. |
5ba9f198 | 619 | |
fcba70d4 | 620 | 4.2.5 Strings |
5ba9f198 MD |
621 | |
622 | Strings are an array of bytes of variable size and are terminated by a '\0' | |
6672e9e1 MD |
623 | "NULL" character. Their encoding is described in the TSDL meta-data. In |
624 | absence of encoding attribute information, the default encoding is | |
625 | UTF-8. | |
5ba9f198 | 626 | |
6672e9e1 | 627 | TSDL meta-data representation of a named string type: |
80fd2569 | 628 | |
359894ac | 629 | typealias string { |
5ba9f198 | 630 | encoding = UTF8 OR ASCII; |
38b8da21 | 631 | } := name; |
5ba9f198 | 632 | |
80fd2569 MD |
633 | A nameless string type can be declared as a field type: |
634 | ||
635 | string field_name; /* Use default UTF8 encoding */ | |
5ba9f198 | 636 | |
ec4404a7 MD |
637 | Strings are always aligned on byte size. |
638 | ||
3bf79539 MD |
639 | 5. Event Packet Header |
640 | ||
6672e9e1 MD |
641 | The event packet header consists of two parts: the "event packet header" |
642 | is the same for all streams of a trace. The second part, the "event | |
643 | packet context", is described on a per-stream basis. Both are described | |
644 | in the TSDL meta-data. The packets are aligned on architecture-page-sized | |
645 | addresses. | |
3bf79539 | 646 | |
6672e9e1 | 647 | Event packet header (all fields are optional, specified by TSDL meta-data): |
3bf79539 | 648 | |
6672e9e1 MD |
649 | - Magic number (CTF magic number: 0xC1FC1FC1) specifies that this is a |
650 | CTF packet. This magic number is optional, but when present, it should | |
651 | come at the very beginning of the packet. | |
652 | - Trace UUID, used to ensure the event packet match the meta-data used. | |
653 | (note: we cannot use a meta-data checksum in every cases instead of a | |
654 | UUID because meta-data can be appended to while tracing is active) | |
655 | This field is optional. | |
656 | - Stream ID, used as reference to stream description in meta-data. | |
657 | This field is optional if there is only one stream description in the | |
658 | meta-data, but becomes required if there are more than one stream in | |
659 | the TSDL meta-data description. | |
3bf79539 | 660 | |
6672e9e1 | 661 | Event packet context (all fields are optional, specified by TSDL meta-data): |
3bf79539 MD |
662 | |
663 | - Event packet content size (in bytes). | |
664 | - Event packet size (in bytes, includes padding). | |
665 | - Event packet content checksum (optional). Checksum excludes the event packet | |
666 | header. | |
667 | - Per-stream event packet sequence count (to deal with UDP packet loss). The | |
668 | number of significant sequence counter bits should also be present, so | |
b11853af | 669 | wrap-arounds are dealt with correctly. |
6672e9e1 | 670 | - Time-stamp at the beginning and time-stamp at the end of the event packet. |
3bf79539 MD |
671 | Both timestamps are written in the packet header, but sampled respectively |
672 | while (or before) writing the first event and while (or after) writing the | |
673 | last event in the packet. The inclusive range between these timestamps should | |
674 | include all event timestamps assigned to events contained within the packet. | |
5ba9f198 | 675 | - Events discarded count |
3bf79539 MD |
676 | - Snapshot of a per-stream free-running counter, counting the number of |
677 | events discarded that were supposed to be written in the stream prior to | |
678 | the first event in the event packet. | |
5ba9f198 | 679 | * Note: producer-consumer buffer full condition should fill the current |
3bf79539 | 680 | event packet with padding so we know exactly where events have been |
5ba9f198 | 681 | discarded. |
3bf79539 MD |
682 | - Lossless compression scheme used for the event packet content. Applied |
683 | directly to raw data. New types of compression can be added in following | |
684 | versions of the format. | |
5ba9f198 MD |
685 | 0: no compression scheme |
686 | 1: bzip2 | |
687 | 2: gzip | |
3bf79539 MD |
688 | 3: xz |
689 | - Cypher used for the event packet content. Applied after compression. | |
5ba9f198 MD |
690 | 0: no encryption |
691 | 1: AES | |
3bf79539 | 692 | - Checksum scheme used for the event packet content. Applied after encryption. |
5ba9f198 MD |
693 | 0: no checksum |
694 | 1: md5 | |
695 | 2: sha1 | |
696 | 3: crc32 | |
697 | ||
6672e9e1 | 698 | 5.1 Event Packet Header Description |
3bf79539 | 699 | |
fc5425db | 700 | The event packet header layout is indicated by the trace packet.header |
6672e9e1 MD |
701 | field. Here is a recommended structure type for the packet header with |
702 | the fields typically expected (although these fields are each optional): | |
fc5425db | 703 | |
80fd2569 MD |
704 | struct event_packet_header { |
705 | uint32_t magic; | |
3fde5da1 | 706 | uint8_t uuid[16]; |
3bf79539 | 707 | uint32_t stream_id; |
80fd2569 | 708 | }; |
5ba9f198 | 709 | |
fc5425db MD |
710 | trace { |
711 | ... | |
712 | packet.header := struct event_packet_header; | |
713 | }; | |
714 | ||
6672e9e1 MD |
715 | If the magic number is not present, tools such as "file" will have no |
716 | mean to discover the file type. | |
717 | ||
3fde5da1 MD |
718 | If the uuid is not present, no validation that the meta-data actually |
719 | corresponds to the stream is performed. | |
37b39e47 MD |
720 | |
721 | If the stream_id packet header field is missing, the trace can only | |
722 | contain a single stream. Its "id" field can be left out, and its events | |
723 | don't need to declare a "stream_id" field. | |
724 | ||
725 | ||
3bf79539 MD |
726 | 5.2 Event Packet Context Description |
727 | ||
728 | Event packet context example. These are declared within the stream declaration | |
6672e9e1 | 729 | in the meta-data. All these fields are optional. If the packet size field is |
6a7c61df | 730 | missing, the whole stream only contains a single packet. If the content |
f6b81726 MD |
731 | size field is missing, the packet is filled (no padding). The content |
732 | and packet sizes include all headers. | |
3bf79539 MD |
733 | |
734 | An example event packet context type: | |
735 | ||
80fd2569 | 736 | struct event_packet_context { |
3bf79539 MD |
737 | uint64_t timestamp_begin; |
738 | uint64_t timestamp_end; | |
739 | uint32_t checksum; | |
740 | uint32_t stream_packet_count; | |
741 | uint32_t events_discarded; | |
742 | uint32_t cpu_id; | |
743 | uint32_t/uint16_t content_size; | |
744 | uint32_t/uint16_t packet_size; | |
745 | uint8_t stream_packet_count_bits; /* Significant counter bits */ | |
746 | uint8_t compression_scheme; | |
747 | uint8_t encryption_scheme; | |
3b0f8e4d | 748 | uint8_t checksum_scheme; |
3bf79539 | 749 | }; |
5ba9f198 | 750 | |
fcba70d4 | 751 | |
5ba9f198 MD |
752 | 6. Event Structure |
753 | ||
754 | The overall structure of an event is: | |
755 | ||
6672e9e1 MD |
756 | 1 - Stream Packet Context (as specified by the stream meta-data) |
757 | 2 - Event Header (as specified by the stream meta-data) | |
758 | 3 - Stream Event Context (as specified by the stream meta-data) | |
759 | 4 - Event Context (as specified by the event meta-data) | |
760 | 5 - Event Payload (as specified by the event meta-data) | |
5ba9f198 | 761 | |
fdf2bb05 | 762 | This structure defines an implicit dynamic scoping, where variants |
7d9d7e92 MD |
763 | located in inner structures (those with a higher number in the listing |
764 | above) can refer to the fields of outer structures (with lower number in | |
6c7226e9 | 765 | the listing above). See Section 7.3 TSDL Scopes for more detail. |
5ba9f198 | 766 | |
fdf2bb05 | 767 | 6.1 Event Header |
fcba70d4 | 768 | |
6672e9e1 | 769 | Event headers can be described within the meta-data. We hereby propose, as an |
fcba70d4 MD |
770 | example, two types of events headers. Type 1 accommodates streams with less than |
771 | 31 event IDs. Type 2 accommodates streams with 31 or more event IDs. | |
5ba9f198 | 772 | |
3bf79539 MD |
773 | One major factor can vary between streams: the number of event IDs assigned to |
774 | a stream. Luckily, this information tends to stay relatively constant (modulo | |
5ba9f198 | 775 | event registration while trace is being recorded), so we can specify different |
3bf79539 | 776 | representations for streams containing few event IDs and streams containing |
6672e9e1 MD |
777 | many event IDs, so we end up representing the event ID and time-stamp as |
778 | densely as possible in each case. | |
5ba9f198 | 779 | |
fcba70d4 MD |
780 | The header is extended in the rare occasions where the information cannot be |
781 | represented in the ranges available in the standard event header. They are also | |
3bf79539 MD |
782 | used in the rare occasions where the data required for a field could not be |
783 | collected: the flag corresponding to the missing field within the missing_fields | |
784 | array is then set to 1. | |
5ba9f198 | 785 | |
6672e9e1 MD |
786 | Types uintX_t represent an X-bit unsigned integer, as declared with |
787 | either: | |
5ba9f198 | 788 | |
6672e9e1 MD |
789 | typealias integer { size = X; align = X; signed = false } := uintX_t; |
790 | ||
791 | or | |
792 | ||
793 | typealias integer { size = X; align = 1; signed = false } := uintX_t; | |
5ba9f198 | 794 | |
fdf2bb05 | 795 | 6.1.1 Type 1 - Few event IDs |
5ba9f198 MD |
796 | |
797 | - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture | |
798 | preference). | |
5ba9f198 | 799 | - Native architecture byte ordering. |
fcba70d4 MD |
800 | - For "compact" selection |
801 | - Fixed size: 32 bits. | |
802 | - For "extended" selection | |
803 | - Size depends on the architecture and variant alignment. | |
5ba9f198 | 804 | |
80fd2569 | 805 | struct event_header_1 { |
fcba70d4 MD |
806 | /* |
807 | * id: range: 0 - 30. | |
808 | * id 31 is reserved to indicate an extended header. | |
809 | */ | |
a9b83695 | 810 | enum : uint5_t { compact = 0 ... 30, extended = 31 } id; |
fcba70d4 MD |
811 | variant <id> { |
812 | struct { | |
813 | uint27_t timestamp; | |
814 | } compact; | |
815 | struct { | |
816 | uint32_t id; /* 32-bit event IDs */ | |
817 | uint64_t timestamp; /* 64-bit timestamps */ | |
818 | } extended; | |
819 | } v; | |
cb108fea | 820 | } align(32); /* or align(8) */ |
5ba9f198 | 821 | |
5ba9f198 | 822 | |
fdf2bb05 | 823 | 6.1.2 Type 2 - Many event IDs |
5ba9f198 | 824 | |
fcba70d4 | 825 | - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture |
5ba9f198 | 826 | preference). |
5ba9f198 | 827 | - Native architecture byte ordering. |
fcba70d4 MD |
828 | - For "compact" selection |
829 | - Size depends on the architecture and variant alignment. | |
830 | - For "extended" selection | |
831 | - Size depends on the architecture and variant alignment. | |
5ba9f198 | 832 | |
80fd2569 | 833 | struct event_header_2 { |
fcba70d4 MD |
834 | /* |
835 | * id: range: 0 - 65534. | |
836 | * id 65535 is reserved to indicate an extended header. | |
837 | */ | |
a9b83695 | 838 | enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id; |
fcba70d4 MD |
839 | variant <id> { |
840 | struct { | |
841 | uint32_t timestamp; | |
842 | } compact; | |
843 | struct { | |
844 | uint32_t id; /* 32-bit event IDs */ | |
845 | uint64_t timestamp; /* 64-bit timestamps */ | |
846 | } extended; | |
847 | } v; | |
cb108fea | 848 | } align(16); /* or align(8) */ |
5ba9f198 | 849 | |
5ba9f198 MD |
850 | |
851 | 6.2 Event Context | |
852 | ||
6672e9e1 MD |
853 | The event context contains information relative to the current event. |
854 | The choice and meaning of this information is specified by the TSDL | |
855 | stream and event meta-data descriptions. The stream context is applied | |
856 | to all events within the stream. The stream context structure follows | |
857 | the event header. The event context is applied to specific events. Its | |
858 | structure follows the stream context structure. | |
5ba9f198 | 859 | |
fcba70d4 MD |
860 | An example of stream-level event context is to save the event payload size with |
861 | each event, or to save the current PID with each event. These are declared | |
6672e9e1 | 862 | within the stream declaration within the meta-data: |
5ba9f198 | 863 | |
fcba70d4 MD |
864 | stream { |
865 | ... | |
6672e9e1 | 866 | event.context := struct { |
80fd2569 MD |
867 | uint pid; |
868 | uint16_t payload_size; | |
6672e9e1 | 869 | }; |
fcba70d4 MD |
870 | }; |
871 | ||
872 | An example of event-specific event context is to declare a bitmap of missing | |
873 | fields, only appended after the stream event context if the extended event | |
874 | header is selected. NR_FIELDS is the number of fields within the event (a | |
875 | numeric value). | |
5ba9f198 | 876 | |
fcba70d4 MD |
877 | event { |
878 | context = struct { | |
879 | variant <id> { | |
880 | struct { } compact; | |
881 | struct { | |
882 | uint1_t missing_fields[NR_FIELDS]; /* missing event fields bitmap */ | |
883 | } extended; | |
884 | } v; | |
885 | }; | |
886 | ... | |
887 | } | |
5ba9f198 MD |
888 | |
889 | 6.3 Event Payload | |
890 | ||
891 | An event payload contains fields specific to a given event type. The fields | |
6672e9e1 | 892 | belonging to an event type are described in the event-specific meta-data |
5ba9f198 MD |
893 | within a structure type. |
894 | ||
895 | 6.3.1 Padding | |
896 | ||
897 | No padding at the end of the event payload. This differs from the ISO/C standard | |
898 | for structures, but follows the CTF standard for structures. In a trace, even | |
899 | though it makes sense to align the beginning of a structure, it really makes no | |
900 | sense to add padding at the end of the structure, because structures are usually | |
901 | not followed by a structure of the same type. | |
902 | ||
903 | This trick can be done by adding a zero-length "end" field at the end of the C | |
904 | structures, and by using the offset of this field rather than using sizeof() | |
3bf79539 | 905 | when calculating the size of a structure (see Appendix "A. Helper macros"). |
5ba9f198 MD |
906 | |
907 | 6.3.2 Alignment | |
908 | ||
909 | The event payload is aligned on the largest alignment required by types | |
910 | contained within the payload. (This follows the ISO/C standard for structures) | |
911 | ||
912 | ||
6c7226e9 MD |
913 | 7. Trace Stream Description Language (TSDL) |
914 | ||
915 | The Trace Stream Description Language (TSDL) allows expression of the | |
916 | binary trace streams layout in a C99-like Domain Specific Language | |
917 | (DSL). | |
918 | ||
919 | ||
6672e9e1 | 920 | 7.1 Meta-data |
6c7226e9 MD |
921 | |
922 | The trace stream layout description is located in the trace meta-data. | |
923 | The meta-data is itself located in a stream identified by its name: | |
924 | "metadata". | |
5ba9f198 | 925 | |
6672e9e1 MD |
926 | The meta-data description can be expressed in two different formats: |
927 | text-only and packet-based. The text-only description facilitates | |
928 | generation of meta-data and provides a convenient way to enter the | |
929 | meta-data information by hand. The packet-based meta-data provides the | |
930 | CTF stream packet facilities (checksumming, compression, encryption, | |
931 | network-readiness) for meta-data stream generated and transported by a | |
932 | tracer. | |
933 | ||
934 | The text-only meta-data file is a plain text TSDL description. | |
935 | ||
936 | The packet-based meta-data is made of "meta-data packets", which each | |
937 | start with a meta-data packet header. The packet-based meta-data | |
938 | description is detected by reading the magic number "0x75D11D57" at the | |
939 | beginning of the file. This magic number is also used to detect the | |
940 | endianness of the architecture by trying to read the CTF magic number | |
941 | and its counterpart in reversed endianness. The events within the | |
942 | meta-data stream have no event header nor event context. Each event only | |
5ae2352d | 943 | contains a "sequence" payload, which is a sequence of bits using the |
ce2228da MD |
944 | "trace.packet.header.content_size" field as a placeholder for its length |
945 | (the packet header size should be substracted). The formatting of this | |
946 | sequence of bits is a plain-text representation of the TSDL description. | |
947 | Each meta-data packet start with a special packet header, specific to | |
948 | the meta-data stream, which contains, exactly: | |
6672e9e1 MD |
949 | |
950 | struct metadata_packet_header { | |
2daeaa3a | 951 | uint32_t magic; /* 0x75D11D57 */ |
3fde5da1 | 952 | uint8_t uuid[16]; /* Unique Universal Identifier */ |
6672e9e1 MD |
953 | uint32_t checksum; /* 0 if unused */ |
954 | uint32_t content_size; /* in bits */ | |
955 | uint32_t packet_size; /* in bits */ | |
956 | uint8_t compression_scheme; /* 0 if unused */ | |
957 | uint8_t encryption_scheme; /* 0 if unused */ | |
958 | uint8_t checksum_scheme; /* 0 if unused */ | |
959 | }; | |
960 | ||
961 | The packet-based meta-data can be converted to a text-only meta-data by | |
962 | concatenating all the strings in contains. | |
4fafe1ad | 963 | |
6672e9e1 MD |
964 | In the textual representation of the meta-data, the text contained |
965 | within "/*" and "*/", as well as within "//" and end of line, are | |
966 | treated as comments. Boolean values can be represented as true, TRUE, | |
967 | or 1 for true, and false, FALSE, or 0 for false. Within the string-based | |
968 | meta-data description, the trace UUID is represented as a string of | |
969 | hexadecimal digits and dashes "-". In the event packet header, the trace | |
970 | UUID is represented as an array of bytes. | |
fcba70d4 | 971 | |
fdf2bb05 | 972 | |
6c7226e9 | 973 | 7.2 Declaration vs Definition |
fdf2bb05 MD |
974 | |
975 | A declaration associates a layout to a type, without specifying where | |
976 | this type is located in the event structure hierarchy (see Section 6). | |
977 | This therefore includes typedef, typealias, as well as all type | |
978 | specifiers. In certain circumstances (typedef, structure field and | |
979 | variant field), a declaration is followed by a declarator, which specify | |
980 | the newly defined type name (for typedef), or the field name (for | |
981 | declarations located within structure and variants). Array and sequence, | |
982 | declared with square brackets ("[" "]"), are part of the declarator, | |
a9b83695 | 983 | similarly to C99. The enumeration base type is specified by |
6c7226e9 | 984 | ": enum_base", which is part of the type specifier. The variant tag |
a9b83695 | 985 | name, specified between "<" ">", is also part of the type specifier. |
fdf2bb05 MD |
986 | |
987 | A definition associates a type to a location in the event structure | |
b9606a77 MD |
988 | hierarchy (see Section 6). This association is denoted by ":=", as shown |
989 | in Section 7.3. | |
fdf2bb05 MD |
990 | |
991 | ||
6c7226e9 | 992 | 7.3 TSDL Scopes |
fdf2bb05 | 993 | |
6c7226e9 MD |
994 | TSDL uses two different types of scoping: a lexical scope is used for |
995 | declarations and type definitions, and a dynamic scope is used for | |
2e7d7fcb MD |
996 | variants references to tag fields and for sequence references to length |
997 | fields. | |
fdf2bb05 | 998 | |
6c7226e9 | 999 | 7.3.1 Lexical Scope |
fdf2bb05 | 1000 | |
d285084f MD |
1001 | Each of "trace", "stream", "event", "struct" and "variant" have their own |
1002 | nestable declaration scope, within which types can be declared using "typedef" | |
fdf2bb05 | 1003 | and "typealias". A root declaration scope also contains all declarations |
7d9d7e92 | 1004 | located outside of any of the aforementioned declarations. An inner |
fdf2bb05 | 1005 | declaration scope can refer to type declared within its container |
7d9d7e92 MD |
1006 | lexical scope prior to the inner declaration scope. Redefinition of a |
1007 | typedef or typealias is not valid, although hiding an upper scope | |
fdf2bb05 MD |
1008 | typedef or typealias is allowed within a sub-scope. |
1009 | ||
6c7226e9 | 1010 | 7.3.2 Dynamic Scope |
fdf2bb05 | 1011 | |
7d9d7e92 MD |
1012 | A dynamic scope consists in the lexical scope augmented with the |
1013 | implicit event structure definition hierarchy presented at Section 6. | |
2e7d7fcb MD |
1014 | The dynamic scope is used for variant tag and sequence length |
1015 | definitions. It is used at definition time to look up the location of | |
1016 | the tag field associated with a variant, and to lookup up the location | |
1017 | of the length field associated with a sequence. | |
1018 | ||
1019 | Therefore, variants (or sequences) in lower levels in the dynamic scope | |
1020 | (e.g. event context) can refer to a tag (or length) field located in | |
1021 | upper levels (e.g. in the event header) by specifying, in this case, the | |
1022 | associated tag with <header.field_name>. This allows, for instance, the | |
1023 | event context to define a variant referring to the "id" field of the | |
1024 | event header as selector. | |
fdf2bb05 MD |
1025 | |
1026 | The target dynamic scope must be specified explicitly when referring to | |
1027 | a field outside of the local static scope. The dynamic scope prefixes | |
1028 | are thus: | |
1029 | ||
e0d9e2c7 | 1030 | - Trace Packet Header: <trace.packet.header. >, |
7d9d7e92 MD |
1031 | - Stream Packet Context: <stream.packet.context. >, |
1032 | - Event Header: <stream.event.header. >, | |
1033 | - Stream Event Context: <stream.event.context. >, | |
1034 | - Event Context: <event.context. >, | |
1035 | - Event Payload: <event.fields. >. | |
fdf2bb05 MD |
1036 | |
1037 | Multiple declarations of the same field name within a single scope is | |
1038 | not valid. It is however valid to re-use the same field name in | |
1039 | different scopes. There is no possible conflict, because the dynamic | |
1040 | scope must be specified when a variant refers to a tag field located in | |
1041 | a different dynamic scope. | |
1042 | ||
457d8b0a MD |
1043 | The information available in the dynamic scopes can be thought of as the |
1044 | current tracing context. At trace production, information about the | |
1045 | current context is saved into the specified scope field levels. At trace | |
1046 | consumption, for each event, the current trace context is therefore | |
1047 | readable by accessing the upper dynamic scopes. | |
1048 | ||
fdf2bb05 | 1049 | |
6c7226e9 | 1050 | 7.4 TSDL Examples |
d285084f | 1051 | |
6672e9e1 | 1052 | The grammar representing the TSDL meta-data is presented in Appendix C. |
7df6b93a | 1053 | TSDL Grammar. This section presents a rather lighter reading that |
6672e9e1 | 1054 | consists in examples of TSDL meta-data, with template values. |
969f30c0 | 1055 | |
350bb633 MD |
1056 | The stream "id" can be left out if there is only one stream in the |
1057 | trace. The event "id" field can be left out if there is only one event | |
1058 | in a stream. | |
1059 | ||
5ba9f198 | 1060 | trace { |
fdf2bb05 | 1061 | major = value; /* Trace format version */ |
5ba9f198 | 1062 | minor = value; |
fdf2bb05 | 1063 | uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */ |
58997e9e | 1064 | byte_order = be OR le; /* Endianness (required) */ |
fc5425db MD |
1065 | packet.header := struct { |
1066 | uint32_t magic; | |
3fde5da1 | 1067 | uint8_t uuid[16]; |
fc5425db MD |
1068 | uint32_t stream_id; |
1069 | }; | |
3bf79539 | 1070 | }; |
5ba9f198 | 1071 | |
3bf79539 MD |
1072 | stream { |
1073 | id = stream_id; | |
fdf2bb05 | 1074 | /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */ |
4fa992a5 MD |
1075 | event.header := event_header_1 OR event_header_2; |
1076 | event.context := struct { | |
77a98c82 | 1077 | ... |
3bf79539 | 1078 | }; |
4fa992a5 | 1079 | packet.context := struct { |
77a98c82 | 1080 | ... |
3bf79539 MD |
1081 | }; |
1082 | }; | |
5ba9f198 MD |
1083 | |
1084 | event { | |
3d13ef1a | 1085 | name = event_name; |
3bf79539 | 1086 | id = value; /* Numeric identifier within the stream */ |
67f02e24 | 1087 | stream_id = stream_id; |
4fa992a5 | 1088 | context := struct { |
fcba70d4 MD |
1089 | ... |
1090 | }; | |
4fa992a5 | 1091 | fields := struct { |
80fd2569 MD |
1092 | ... |
1093 | }; | |
3bf79539 | 1094 | }; |
5ba9f198 MD |
1095 | |
1096 | /* More detail on types in section 4. Types */ | |
1097 | ||
3d13ef1a MD |
1098 | /* |
1099 | * Named types: | |
1100 | * | |
4fa992a5 | 1101 | * Type declarations behave similarly to the C standard. |
3d13ef1a MD |
1102 | */ |
1103 | ||
80af8ac6 | 1104 | typedef aliased_type_specifiers new_type_declarators; |
2152348f | 1105 | |
3d13ef1a | 1106 | /* e.g.: typedef struct example new_type_name[10]; */ |
80fd2569 | 1107 | |
4fa992a5 MD |
1108 | /* |
1109 | * typealias | |
1110 | * | |
1111 | * The "typealias" declaration can be used to give a name (including | |
80af8ac6 MD |
1112 | * pointer declarator specifier) to a type. It should also be used to |
1113 | * map basic C types (float, int, unsigned long, ...) to a CTF type. | |
1114 | * Typealias is a superset of "typedef": it also allows assignment of a | |
38b8da21 | 1115 | * simple variable identifier to a type. |
4fa992a5 MD |
1116 | */ |
1117 | ||
1118 | typealias type_class { | |
80fd2569 | 1119 | ... |
38b8da21 | 1120 | } := type_specifiers type_declarator; |
2152348f | 1121 | |
3d13ef1a MD |
1122 | /* |
1123 | * e.g.: | |
4fa992a5 | 1124 | * typealias integer { |
3d13ef1a MD |
1125 | * size = 32; |
1126 | * align = 32; | |
1127 | * signed = false; | |
38b8da21 | 1128 | * } := struct page *; |
359894ac MD |
1129 | * |
1130 | * typealias integer { | |
1131 | * size = 32; | |
1132 | * align = 32; | |
1133 | * signed = true; | |
38b8da21 | 1134 | * } := int; |
3d13ef1a | 1135 | */ |
80fd2569 MD |
1136 | |
1137 | struct name { | |
3bf79539 MD |
1138 | ... |
1139 | }; | |
5ba9f198 | 1140 | |
fcba70d4 MD |
1141 | variant name { |
1142 | ... | |
1143 | }; | |
1144 | ||
a9b83695 | 1145 | enum name : integer_type { |
3bf79539 MD |
1146 | ... |
1147 | }; | |
1148 | ||
2152348f | 1149 | |
4fa992a5 MD |
1150 | /* |
1151 | * Unnamed types, contained within compound type fields, typedef or typealias. | |
1152 | */ | |
2152348f | 1153 | |
80fd2569 MD |
1154 | struct { |
1155 | ... | |
2152348f | 1156 | } |
5ba9f198 | 1157 | |
ec4404a7 MD |
1158 | struct { |
1159 | ... | |
1160 | } align(value) | |
1161 | ||
fcba70d4 MD |
1162 | variant { |
1163 | ... | |
1164 | } | |
1165 | ||
a9b83695 | 1166 | enum : integer_type { |
80fd2569 | 1167 | ... |
2152348f MD |
1168 | } |
1169 | ||
1170 | typedef type new_type[length]; | |
3bf79539 | 1171 | |
2152348f MD |
1172 | struct { |
1173 | type field_name[length]; | |
1174 | } | |
1175 | ||
1176 | typedef type new_type[length_type]; | |
1177 | ||
1178 | struct { | |
1179 | type field_name[length_type]; | |
1180 | } | |
1181 | ||
1182 | integer { | |
80fd2569 | 1183 | ... |
2152348f | 1184 | } |
3bf79539 | 1185 | |
2152348f | 1186 | floating_point { |
80fd2569 | 1187 | ... |
2152348f MD |
1188 | } |
1189 | ||
1190 | struct { | |
1191 | integer_type field_name:size; /* GNU/C bitfield */ | |
1192 | } | |
1193 | ||
1194 | struct { | |
1195 | string field_name; | |
1196 | } | |
3bf79539 | 1197 | |
fcba70d4 | 1198 | |
3bf79539 | 1199 | A. Helper macros |
5ba9f198 MD |
1200 | |
1201 | The two following macros keep track of the size of a GNU/C structure without | |
1202 | padding at the end by placing HEADER_END as the last field. A one byte end field | |
1203 | is used for C90 compatibility (C99 flexible arrays could be used here). Note | |
1204 | that this does not affect the effective structure size, which should always be | |
1205 | calculated with the header_sizeof() helper. | |
1206 | ||
1207 | #define HEADER_END char end_field | |
1208 | #define header_sizeof(type) offsetof(typeof(type), end_field) | |
3bf79539 MD |
1209 | |
1210 | ||
1211 | B. Stream Header Rationale | |
1212 | ||
1213 | An event stream is divided in contiguous event packets of variable size. These | |
1214 | subdivisions allow the trace analyzer to perform a fast binary search by time | |
1215 | within the stream (typically requiring to index only the event packet headers) | |
1216 | without reading the whole stream. These subdivisions have a variable size to | |
1217 | eliminate the need to transfer the event packet padding when partially filled | |
1218 | event packets must be sent when streaming a trace for live viewing/analysis. | |
1219 | An event packet can contain a certain amount of padding at the end. Dividing | |
1220 | streams into event packets is also useful for network streaming over UDP and | |
1221 | flight recorder mode tracing (a whole event packet can be swapped out of the | |
1222 | buffer atomically for reading). | |
1223 | ||
1224 | The stream header is repeated at the beginning of each event packet to allow | |
1225 | flexibility in terms of: | |
1226 | ||
1227 | - streaming support, | |
1228 | - allowing arbitrary buffers to be discarded without making the trace | |
1229 | unreadable, | |
1230 | - allow UDP packet loss handling by either dealing with missing event packet | |
1231 | or asking for re-transmission. | |
1232 | - transparently support flight recorder mode, | |
1233 | - transparently support crash dump. | |
1234 | ||
6c7226e9 MD |
1235 | |
1236 | C. TSDL Grammar | |
fcba70d4 | 1237 | |
4fa992a5 | 1238 | /* |
6c7226e9 | 1239 | * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar. |
4fa992a5 MD |
1240 | * |
1241 | * Inspired from the C99 grammar: | |
1242 | * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A) | |
6c7226e9 MD |
1243 | * and c++1x grammar (draft) |
1244 | * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A) | |
4fa992a5 MD |
1245 | * |
1246 | * Specialized for CTF needs by including only constant and declarations from | |
1247 | * C99 (excluding function declarations), and by adding support for variants, | |
6c7226e9 MD |
1248 | * sequences and CTF-specific specifiers. Enumeration container types |
1249 | * semantic is inspired from c++1x enum-base. | |
4fa992a5 MD |
1250 | */ |
1251 | ||
1252 | 1) Lexical grammar | |
1253 | ||
1254 | 1.1) Lexical elements | |
1255 | ||
1256 | token: | |
1257 | keyword | |
1258 | identifier | |
1259 | constant | |
1260 | string-literal | |
1261 | punctuator | |
1262 | ||
1263 | 1.2) Keywords | |
1264 | ||
1265 | keyword: is one of | |
1266 | ||
ec4404a7 | 1267 | align |
4fa992a5 MD |
1268 | const |
1269 | char | |
1270 | double | |
1271 | enum | |
1272 | event | |
1273 | floating_point | |
1274 | float | |
1275 | integer | |
1276 | int | |
1277 | long | |
1278 | short | |
1279 | signed | |
1280 | stream | |
1281 | string | |
1282 | struct | |
1283 | trace | |
3e1e1a78 | 1284 | typealias |
4fa992a5 MD |
1285 | typedef |
1286 | unsigned | |
1287 | variant | |
1288 | void | |
1289 | _Bool | |
1290 | _Complex | |
1291 | _Imaginary | |
1292 | ||
1293 | ||
1294 | 1.3) Identifiers | |
1295 | ||
1296 | identifier: | |
1297 | identifier-nondigit | |
1298 | identifier identifier-nondigit | |
1299 | identifier digit | |
1300 | ||
1301 | identifier-nondigit: | |
1302 | nondigit | |
1303 | universal-character-name | |
1304 | any other implementation-defined characters | |
1305 | ||
1306 | nondigit: | |
1307 | _ | |
1308 | [a-zA-Z] /* regular expression */ | |
1309 | ||
1310 | digit: | |
1311 | [0-9] /* regular expression */ | |
1312 | ||
1313 | 1.4) Universal character names | |
1314 | ||
1315 | universal-character-name: | |
1316 | \u hex-quad | |
1317 | \U hex-quad hex-quad | |
1318 | ||
1319 | hex-quad: | |
1320 | hexadecimal-digit hexadecimal-digit hexadecimal-digit hexadecimal-digit | |
1321 | ||
1322 | 1.5) Constants | |
1323 | ||
1324 | constant: | |
1325 | integer-constant | |
1326 | enumeration-constant | |
1327 | character-constant | |
1328 | ||
1329 | integer-constant: | |
1330 | decimal-constant integer-suffix-opt | |
1331 | octal-constant integer-suffix-opt | |
1332 | hexadecimal-constant integer-suffix-opt | |
1333 | ||
1334 | decimal-constant: | |
1335 | nonzero-digit | |
1336 | decimal-constant digit | |
1337 | ||
1338 | octal-constant: | |
1339 | 0 | |
1340 | octal-constant octal-digit | |
1341 | ||
1342 | hexadecimal-constant: | |
1343 | hexadecimal-prefix hexadecimal-digit | |
1344 | hexadecimal-constant hexadecimal-digit | |
1345 | ||
1346 | hexadecimal-prefix: | |
1347 | 0x | |
1348 | 0X | |
1349 | ||
1350 | nonzero-digit: | |
1351 | [1-9] | |
1352 | ||
1353 | integer-suffix: | |
1354 | unsigned-suffix long-suffix-opt | |
1355 | unsigned-suffix long-long-suffix | |
1356 | long-suffix unsigned-suffix-opt | |
1357 | long-long-suffix unsigned-suffix-opt | |
1358 | ||
1359 | unsigned-suffix: | |
1360 | u | |
1361 | U | |
1362 | ||
1363 | long-suffix: | |
1364 | l | |
1365 | L | |
1366 | ||
1367 | long-long-suffix: | |
1368 | ll | |
1369 | LL | |
1370 | ||
4fa992a5 MD |
1371 | enumeration-constant: |
1372 | identifier | |
1373 | string-literal | |
1374 | ||
1375 | character-constant: | |
1376 | ' c-char-sequence ' | |
1377 | L' c-char-sequence ' | |
1378 | ||
1379 | c-char-sequence: | |
1380 | c-char | |
1381 | c-char-sequence c-char | |
1382 | ||
1383 | c-char: | |
1384 | any member of source charset except single-quote ('), backslash | |
1385 | (\), or new-line character. | |
1386 | escape-sequence | |
1387 | ||
1388 | escape-sequence: | |
1389 | simple-escape-sequence | |
1390 | octal-escape-sequence | |
1391 | hexadecimal-escape-sequence | |
1392 | universal-character-name | |
1393 | ||
1394 | simple-escape-sequence: one of | |
1395 | \' \" \? \\ \a \b \f \n \r \t \v | |
1396 | ||
1397 | octal-escape-sequence: | |
1398 | \ octal-digit | |
1399 | \ octal-digit octal-digit | |
1400 | \ octal-digit octal-digit octal-digit | |
1401 | ||
1402 | hexadecimal-escape-sequence: | |
1403 | \x hexadecimal-digit | |
1404 | hexadecimal-escape-sequence hexadecimal-digit | |
1405 | ||
1406 | 1.6) String literals | |
1407 | ||
1408 | string-literal: | |
1409 | " s-char-sequence-opt " | |
1410 | L" s-char-sequence-opt " | |
1411 | ||
1412 | s-char-sequence: | |
1413 | s-char | |
1414 | s-char-sequence s-char | |
1415 | ||
1416 | s-char: | |
1417 | any member of source charset except double-quote ("), backslash | |
1418 | (\), or new-line character. | |
1419 | escape-sequence | |
1420 | ||
1421 | 1.7) Punctuators | |
1422 | ||
1423 | punctuator: one of | |
1424 | [ ] ( ) { } . -> * + - < > : ; ... = , | |
1425 | ||
1426 | ||
1427 | 2) Phrase structure grammar | |
1428 | ||
1429 | primary-expression: | |
1430 | identifier | |
1431 | constant | |
1432 | string-literal | |
1433 | ( unary-expression ) | |
1434 | ||
1435 | postfix-expression: | |
1436 | primary-expression | |
1437 | postfix-expression [ unary-expression ] | |
1438 | postfix-expression . identifier | |
1439 | postfix-expressoin -> identifier | |
1440 | ||
1441 | unary-expression: | |
1442 | postfix-expression | |
1443 | unary-operator postfix-expression | |
1444 | ||
1445 | unary-operator: one of | |
1446 | + - | |
1447 | ||
4fa992a5 MD |
1448 | assignment-operator: |
1449 | = | |
1450 | ||
b9606a77 MD |
1451 | type-assignment-operator: |
1452 | := | |
1453 | ||
4fa992a5 | 1454 | constant-expression-range: |
73d61ac3 | 1455 | unary-expression ... unary-expression |
4fa992a5 MD |
1456 | |
1457 | 2.2) Declarations: | |
1458 | ||
1459 | declaration: | |
689e04b4 | 1460 | declaration-specifiers declarator-list-opt ; |
4fa992a5 MD |
1461 | ctf-specifier ; |
1462 | ||
1463 | declaration-specifiers: | |
689e04b4 | 1464 | storage-class-specifier declaration-specifiers-opt |
4fa992a5 MD |
1465 | type-specifier declaration-specifiers-opt |
1466 | type-qualifier declaration-specifiers-opt | |
1467 | ||
1468 | declarator-list: | |
1469 | declarator | |
1470 | declarator-list , declarator | |
1471 | ||
d285084f MD |
1472 | abstract-declarator-list: |
1473 | abstract-declarator | |
1474 | abstract-declarator-list , abstract-declarator | |
1475 | ||
4fa992a5 MD |
1476 | storage-class-specifier: |
1477 | typedef | |
1478 | ||
1479 | type-specifier: | |
1480 | void | |
1481 | char | |
1482 | short | |
1483 | int | |
1484 | long | |
1485 | float | |
1486 | double | |
1487 | signed | |
1488 | unsigned | |
1489 | _Bool | |
1490 | _Complex | |
cfdd51ec | 1491 | _Imaginary |
9dfcfc0f MD |
1492 | struct-specifier |
1493 | variant-specifier | |
4fa992a5 MD |
1494 | enum-specifier |
1495 | typedef-name | |
1496 | ctf-type-specifier | |
1497 | ||
ec4404a7 | 1498 | align-attribute: |
73d61ac3 | 1499 | align ( unary-expression ) |
ec4404a7 | 1500 | |
4fa992a5 | 1501 | struct-specifier: |
ec4404a7 MD |
1502 | struct identifier-opt { struct-or-variant-declaration-list-opt } align-attribute-opt |
1503 | struct identifier align-attribute-opt | |
4fa992a5 MD |
1504 | |
1505 | struct-or-variant-declaration-list: | |
1506 | struct-or-variant-declaration | |
1507 | struct-or-variant-declaration-list struct-or-variant-declaration | |
1508 | ||
1509 | struct-or-variant-declaration: | |
1510 | specifier-qualifier-list struct-or-variant-declarator-list ; | |
eacb16d1 | 1511 | declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list ; |
6143bab7 MD |
1512 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list ; |
1513 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list ; | |
4fa992a5 MD |
1514 | |
1515 | specifier-qualifier-list: | |
1516 | type-specifier specifier-qualifier-list-opt | |
1517 | type-qualifier specifier-qualifier-list-opt | |
1518 | ||
1519 | struct-or-variant-declarator-list: | |
1520 | struct-or-variant-declarator | |
1521 | struct-or-variant-declarator-list , struct-or-variant-declarator | |
1522 | ||
1523 | struct-or-variant-declarator: | |
1524 | declarator | |
73d61ac3 | 1525 | declarator-opt : unary-expression |
4fa992a5 MD |
1526 | |
1527 | variant-specifier: | |
1528 | variant identifier-opt variant-tag-opt { struct-or-variant-declaration-list } | |
1529 | variant identifier variant-tag | |
1530 | ||
1531 | variant-tag: | |
1532 | < identifier > | |
1533 | ||
1534 | enum-specifier: | |
1535 | enum identifier-opt { enumerator-list } | |
1536 | enum identifier-opt { enumerator-list , } | |
1537 | enum identifier | |
a9b83695 MD |
1538 | enum identifier-opt : declaration-specifiers { enumerator-list } |
1539 | enum identifier-opt : declaration-specifiers { enumerator-list , } | |
4fa992a5 MD |
1540 | |
1541 | enumerator-list: | |
1542 | enumerator | |
1543 | enumerator-list , enumerator | |
1544 | ||
1545 | enumerator: | |
1546 | enumeration-constant | |
8d2d41f7 MD |
1547 | enumeration-constant assignment-operator unary-expression |
1548 | enumeration-constant assignment-operator constant-expression-range | |
4fa992a5 MD |
1549 | |
1550 | type-qualifier: | |
1551 | const | |
1552 | ||
1553 | declarator: | |
1554 | pointer-opt direct-declarator | |
1555 | ||
1556 | direct-declarator: | |
1557 | identifier | |
1558 | ( declarator ) | |
1ab22b2a | 1559 | direct-declarator [ unary-expression ] |
4fa992a5 | 1560 | |
d285084f MD |
1561 | abstract-declarator: |
1562 | pointer-opt direct-abstract-declarator | |
1563 | ||
1564 | direct-abstract-declarator: | |
1565 | identifier-opt | |
1566 | ( abstract-declarator ) | |
1ab22b2a | 1567 | direct-abstract-declarator [ unary-expression ] |
d285084f MD |
1568 | direct-abstract-declarator [ ] |
1569 | ||
4fa992a5 | 1570 | pointer: |
3b0f8e4d MD |
1571 | * type-qualifier-list-opt |
1572 | * type-qualifier-list-opt pointer | |
4fa992a5 MD |
1573 | |
1574 | type-qualifier-list: | |
1575 | type-qualifier | |
1576 | type-qualifier-list type-qualifier | |
1577 | ||
4fa992a5 MD |
1578 | typedef-name: |
1579 | identifier | |
1580 | ||
1581 | 2.3) CTF-specific declarations | |
1582 | ||
1583 | ctf-specifier: | |
1584 | event { ctf-assignment-expression-list-opt } | |
1585 | stream { ctf-assignment-expression-list-opt } | |
1586 | trace { ctf-assignment-expression-list-opt } | |
b12919a5 MD |
1587 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list |
1588 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list | |
4fa992a5 MD |
1589 | |
1590 | ctf-type-specifier: | |
1591 | floating_point { ctf-assignment-expression-list-opt } | |
1592 | integer { ctf-assignment-expression-list-opt } | |
1593 | string { ctf-assignment-expression-list-opt } | |
7609d3c7 | 1594 | string |
4fa992a5 MD |
1595 | |
1596 | ctf-assignment-expression-list: | |
13441bf5 MD |
1597 | ctf-assignment-expression ; |
1598 | ctf-assignment-expression-list ctf-assignment-expression ; | |
4fa992a5 MD |
1599 | |
1600 | ctf-assignment-expression: | |
1601 | unary-expression assignment-operator unary-expression | |
1602 | unary-expression type-assignment-operator type-specifier | |
eacb16d1 | 1603 | declaration-specifiers-opt storage-class-specifier declaration-specifiers-opt declarator-list |
6143bab7 MD |
1604 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declaration-specifiers abstract-declarator-list |
1605 | typealias declaration-specifiers abstract-declarator-list type-assignment-operator declarator-list |