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