X-Git-Url: http://git.efficios.com/?p=ctf.git;a=blobdiff_plain;f=common-trace-format-proposal.txt;h=d61b58c0fd73cc0856562db4b7c211e2ae338070;hp=fd7731f1bdd23ea435bb522bd04cd887a5fe35ce;hb=c2742c56519734d85410b6d65aa7603772413bdf;hpb=359894ac70b4a9b936c328751ba10b3a2f2f0e67 diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt index fd7731f..d61b58c 100644 --- a/common-trace-format-proposal.txt +++ b/common-trace-format-proposal.txt @@ -68,14 +68,10 @@ A metadata event stream contains information on trace event types. It describes: 3. Event stream An event stream is divided in contiguous event packets of variable size. These -subdivisions have a variable size. An event packet can contain a certain amount -of padding at the end. The rationale for the event stream design choices is -explained in Appendix B. Stream Header Rationale. - -An event stream is divided in contiguous event packets of variable size. These -subdivisions have a variable size. An event packet can contain a certain amount -of padding at the end. The stream header is repeated at the beginning of each -event packet. +subdivisions have a variable size. An event packet can contain a certain +amount of padding at the end. The stream header is repeated at the +beginning of each event packet. The rationale for the event stream +design choices is explained in Appendix B. Stream Header Rationale. The event stream header will therefore be referred to as the "event packet header" throughout the rest of this document. @@ -83,9 +79,13 @@ header" throughout the rest of this document. 4. Types +Types are organized as type classes. Each type class belong to either of two +kind of types: basic types or compound types. + 4.1 Basic types -A basic type is a scalar type, as described in this section. +A basic type is a scalar type, as described in this section. It includes +integers, GNU/C bitfields, enumerations, and floating point values. 4.1.1 Type inheritance @@ -99,15 +99,16 @@ types, but must be derived into a type to be usable in an event field. We define "byte-packed" types as aligned on the byte size, namely 8-bit. We define "bit-packed" types as following on the next bit, as defined by the -"bitfields" section. +"Integers" section. All basic types, except bitfields, are either aligned on an architecture-defined specific alignment or byte-packed, depending on the architecture preference. Architectures providing fast unaligned write byte-packed basic types to save space, aligning each type on byte boundaries (8-bit). Architectures with slow unaligned writes align types on specific alignment values. If no specific -alignment is declared for a type nor its parents, it is assumed to be bit-packed -for bitfields and byte-packed for other types. +alignment is declared for a type, it is assumed to be bit-packed for +integers with size not multiple of 8 bits and for gcc bitfields. All +other types are byte-packed. Metadata attribute representation of a specific alignment: @@ -185,7 +186,7 @@ typealias integer { size = 32; signed = false; align = 32; -} : uint32_t; +} := uint32_t; Definition of a named 5-bit signed bitfield: @@ -193,7 +194,7 @@ typealias integer { size = 5; signed = true; align = 1; -} : int5_t; +} := int5_t; 4.1.6 GNU/C bitfields @@ -252,7 +253,7 @@ typealias floating_point { exp_dig = 8; /* sizeof(float) * CHAR_BIT - FLT_MANT_DIG */ mant_dig = 24; /* FLT_MANT_DIG */ byte_order = native; -} : float; +} := float; TODO: define NaN, +inf, -inf behavior. @@ -270,10 +271,7 @@ this format by having the same start_value and end_value for each element, which is in fact a range of size 1. This single-value range is supported without repeating the start and end values with the value = string declaration. -If a numeric value is encountered between < >, it represents the integer type -size used to hold the enumeration, in bits. - -enum name { +enum name : integer_type { somestring = start_value1 ... end_value1, "other string" = start_value2 ... end_value2, yet_another_string, /* will be assigned to end_value2 + 1 */ @@ -284,7 +282,7 @@ enum name { If the values are omitted, the enumeration starts at 0 and increment of 1 for each entry: -enum name <32> { +enum name : unsigned int { ZERO, ONE, TWO, @@ -296,12 +294,26 @@ Overlapping ranges within a single enumeration are implementation defined. A nameless enumeration can be declared as a field type or as part of a typedef: -enum { +enum : integer_type { + ... +} + +Enumerations omitting the container type ": integer_type" use the "int" +type (for compatibility with C99). The "int" type must be previously +declared. E.g.: + +typealias integer { size = 32; align = 32; signed = true } := int; + +enum { ... } + 4.2 Compound types +Compound are aggregation of type declarations. Compound types include +structures, variant, arrays, sequences, and strings. + 4.2.1 Structures Structures are aligned on the largest alignment required by basic types @@ -337,15 +349,17 @@ struct { 4.2.2 Variants (Discriminated/Tagged Unions) -A CTF variant is a selection between different types. A CTF variant must always -be defined within the scope of a structure or within fields contained within a -structure (defined recursively). A "tag" enumeration field must appear in either -the same lexical scope or an uppermost scope, prior to the variant field (in -field declaration order). The type selection is indicated by the mapping from -the enumeration value to the string used as variant type selector. The field to -use as tag is specified by the "tag_field", specified between "< >" after the -"variant" keyword for unnamed variants, and after "variant name" for named -variants. +A CTF variant is a selection between different types. A CTF variant must +always be defined within the scope of a structure or within fields +contained within a structure (defined recursively). A "tag" enumeration +field must appear in either the same lexical scope, prior to the variant +field (in field declaration order), in an uppermost lexical scope (see +Section 7.2.1), or in an uppermost dynamic scope (see Section 7.2.2). +The type selection is indicated by the mapping from the enumeration +value to the string used as variant type selector. The field to use as +tag is specified by the "tag_field", specified between "< >" after the +"variant" keyword for unnamed variants, and after "variant name" for +named variants. The alignment of the variant is the alignment of the type as selected by the tag value for the specific instance of the variant. The alignment of the type @@ -364,7 +378,7 @@ variant name { }; struct { - enum { sel1, sel2, sel3, ... } tag_field; + enum : integer_type { sel1, sel2, sel3, ... } tag_field; ... variant name v; } @@ -373,7 +387,7 @@ An unnamed variant definition within a structure is expressed by the following metadata: struct { - enum { sel1, sel2, sel3, ... } tag_field; + enum : integer_type { sel1, sel2, sel3, ... } tag_field; ... variant { field_type sel1; @@ -392,14 +406,14 @@ variant example { }; struct { - enum { a, b, c } choice; + enum : uint2_t { a, b, c } choice; variant example v[unsigned int]; } Example of an unnamed variant: struct { - enum { a, b, c, d } choice; + enum : uint2_t { a, b, c, d } choice; /* Unrelated fields can be added between the variant and its tag */ int32_t somevalue; variant { @@ -416,7 +430,7 @@ struct { Example of an unnamed variant within an array: struct { - enum { a, b, c } choice; + enum : uint2_t { a, b, c } choice; variant { uint32_t a; uint64_t b; @@ -431,7 +445,7 @@ type definition referring to the tag "x" uses the closest preceding field from the lexical scope of the type definition. struct { - enum { a, b, c, d } x; + enum : uint2_t { a, b, c, d } x; typedef variant { /* * "x" refers to the preceding "x" enumeration in the @@ -443,9 +457,9 @@ struct { } example_variant; struct { - enum { x, y, z } x; /* This enumeration is not used by "v". */ + enum : int { x, y, z } x; /* This enumeration is not used by "v". */ example_variant v; /* - * "v" uses the "enum { a, b, c, d }" + * "v" uses the "enum : uint2_t { a, b, c, d }" * tag. */ } a[10]; @@ -494,7 +508,7 @@ Metadata representation of a named string type: typealias string { encoding = UTF8 OR ASCII; -} : name; +} := name; A nameless string type can be declared as a field type: @@ -600,23 +614,17 @@ struct event_packet_context { The overall structure of an event is: 1 - Stream Packet Context (as specified by the stream metadata) -2 - Event Header (as specifed by the stream metadata) -3 - Stream Event Context (as specified by the stream metadata) -4 - Event Context (as specified by the event metadata) -5 - Event Payload (as specified by the event metadata) - -6.1 Lexical Scope + 2 - Event Header (as specified by the stream metadata) + 3 - Stream Event Context (as specified by the stream metadata) + 4 - Event Context (as specified by the event metadata) + 5 - Event Payload (as specified by the event metadata) -For variant tag definition only, the lexical scope of each structure (stream -packet context, header, stream event context, event context and payload) is -extended in the following way: lower levels (e.g. 3) can refer to fields defined -in prior levels (e.g. 2 and 1). The field in the closest level has priority in -case of field name conflict. +This structure defines an implicit dynamic scoping, where variants +located in inner structures (those with a higher number in the listing +above) can refer to the fields of outer structures (with lower number in +the listing above). See Section 7.2 Metadata Scopes for more detail. -This allows, for instance, the event context to define a variant refering to the -"id" field of the event header as selector. - -6.2 Event Header +6.1 Event Header Event headers can be described within the metadata. We hereby propose, as an example, two types of events headers. Type 1 accommodates streams with less than @@ -638,7 +646,7 @@ array is then set to 1. Types uintX_t represent an X-bit unsigned integer. -6.2.1 Type 1 - Few event IDs +6.1.1 Type 1 - Few event IDs - Aligned on 32-bit (or 8-bit if byte-packed, depending on the architecture preference). @@ -653,7 +661,7 @@ struct event_header_1 { * id: range: 0 - 30. * id 31 is reserved to indicate an extended header. */ - enum { compact = 0 ... 30, extended = 31 } id; + enum : uint5_t { compact = 0 ... 30, extended = 31 } id; variant { struct { uint27_t timestamp; @@ -666,7 +674,7 @@ struct event_header_1 { }; -6.2.2 Type 2 - Many event IDs +6.1.2 Type 2 - Many event IDs - Aligned on 16-bit (or 8-bit if byte-packed, depending on the architecture preference). @@ -681,7 +689,7 @@ struct event_header_2 { * id: range: 0 - 65534. * id 65535 is reserved to indicate an extended header. */ - enum { compact = 0 ... 65534, extended = 65535 } id; + enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id; variant { struct { uint32_t timestamp; @@ -761,40 +769,115 @@ contained within the payload. (This follows the ISO/C standard for structures) 7. Metadata -The meta-data is located in a stream named "metadata". It is made of "event -packets", which each start with an event packet header. The event type within -the metadata stream have no event header nor event context. Each event only -contains a null-terminated "string" payload, which is a metadata description -entry. The events are packed one next to another. Each event packet start with -an event packet header, which contains, amongst other fields, the magic number -and trace UUID. +The meta-data is located in a stream identified by its name: "metadata". +It is made of "event packets", which each start with an event packet +header. The event type within the metadata stream have no event header +nor event context. Each event only contains a null-terminated "string" +payload, which is a metadata description entry. The events are packed +one next to another. Each event packet start with an event packet +header, which contains, amongst other fields, the magic number and trace +UUID. In the event packet header, the trace UUID is represented as an +array of bytes. Within the string-based metadata description, the trace +UUID is represented as a string of hexadecimal digits and dashes "-". + +The metadata can be parsed by reading through the metadata strings, +skipping null-characters. Type names are made of a single identifier, +and can be surrounded by prefix/postfix. Text contained within "/*" and +"*/", as well as within "//" and end of line, are treated as comments. +Boolean values can be represented as true, TRUE, or 1 for true, and +false, FALSE, or 0 for false. + + +7.1 Declaration vs Definition + +A declaration associates a layout to a type, without specifying where +this type is located in the event structure hierarchy (see Section 6). +This therefore includes typedef, typealias, as well as all type +specifiers. In certain circumstances (typedef, structure field and +variant field), a declaration is followed by a declarator, which specify +the newly defined type name (for typedef), or the field name (for +declarations located within structure and variants). Array and sequence, +declared with square brackets ("[" "]"), are part of the declarator, +similarly to C99. The enumeration base type is specified by +": base_type", which is part of the type specifier. The variant tag +name, specified between "<" ">", is also part of the type specifier. + +A definition associates a type to a location in the event structure +hierarchy (see Section 6). This association is denoted by ":=", as shown +in Section 7.3. -The metadata can be parsed by reading through the metadata strings, skipping -newlines and null-characters. Type names are made of a single identifier, and -can be surrounded by prefix/postfix. Text contained within "/*" and "*/", as -well as within "//" and end of line, are treated as comments. Boolean values can -be represented as true, TRUE, or 1 for true, and false, FALSE, or 0 for false. + +7.2 Metadata Scopes + +CTF metadata uses two different types of scoping: a lexical scope is +used for declarations and type definitions, and a dynamic scope is used +for variants references to tag fields. + +7.2.1 Lexical Scope Each of "trace", "stream", "event", "struct" and "variant" have their own nestable declaration scope, within which types can be declared using "typedef" -and "typealias". An innermost declaration scope can refer to type declared -within its container lexical scope prior to the innermost declaration scope. -Redefinition of a typedef or typealias, or hiding an uppermost definition, is -not valid. +and "typealias". A root declaration scope also contains all declarations +located outside of any of the aforementioned declarations. An inner +declaration scope can refer to type declared within its container +lexical scope prior to the inner declaration scope. Redefinition of a +typedef or typealias is not valid, although hiding an upper scope +typedef or typealias is allowed within a sub-scope. + +7.2.2 Dynamic Scope + +A dynamic scope consists in the lexical scope augmented with the +implicit event structure definition hierarchy presented at Section 6. +The dynamic scope is only used for variant tag definitions. It is used +at definition time to look up the location of the tag field associated +with a variant. + +Therefore, variants in lower levels in the dynamic scope (e.g. event +context) can refer to a tag field located in upper levels (e.g. in the +event header) by specifying, in this case, the associated tag with +. This allows, for instance, the event context to +define a variant referring to the "id" field of the event header as +selector. + +The target dynamic scope must be specified explicitly when referring to +a field outside of the local static scope. The dynamic scope prefixes +are thus: + + - Stream Packet Context: , + - Event Header: , + - Stream Event Context: , + - Event Context: , + - Event Payload: . + +Multiple declarations of the same field name within a single scope is +not valid. It is however valid to re-use the same field name in +different scopes. There is no possible conflict, because the dynamic +scope must be specified when a variant refers to a tag field located in +a different dynamic scope. + +The information available in the dynamic scopes can be thought of as the +current tracing context. At trace production, information about the +current context is saved into the specified scope field levels. At trace +consumption, for each event, the current trace context is therefore +readable by accessing the upper dynamic scopes. + + +7.3 Metadata Examples The grammar representing the CTF metadata is presented in -Appendix C. CTF Metadata Grammar. +Appendix C. CTF Metadata Grammar. This section presents a rather ligher +reading that consists in examples of CTF metadata, with template values: trace { - major = value; /* Trace format version */ + major = value; /* Trace format version */ minor = value; - uuid = value; /* Trace UUID */ + uuid = "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa"; /* Trace UUID */ word_size = value; }; stream { id = stream_id; - /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.2. */ + /* Type 1 - Few event IDs; Type 2 - Many event IDs. See section 6.1. */ event.header := event_header_1 OR event_header_2; event.context := struct { ... @@ -824,7 +907,7 @@ event { * Type declarations behave similarly to the C standard. */ -typedef aliased_type_prefix aliased_type new_type aliased_type_postfix; +typedef aliased_type_specifiers new_type_declarators; /* e.g.: typedef struct example new_type_name[10]; */ @@ -832,15 +915,15 @@ typedef aliased_type_prefix aliased_type new_type aliased_type_postfix; * typealias * * The "typealias" declaration can be used to give a name (including - * prefix/postfix) to a type. It should also be used to map basic C types - * (float, int, unsigned long, ...) to a CTF type. Typealias is a superset of - * "typedef": it also allows assignment of a simple variable identifier to a - * type. + * pointer declarator specifier) to a type. It should also be used to + * map basic C types (float, int, unsigned long, ...) to a CTF type. + * Typealias is a superset of "typedef": it also allows assignment of a + * simple variable identifier to a type. */ typealias type_class { ... -} : new_type_prefix new_type new_type_postfix; +} := type_specifiers type_declarator; /* * e.g.: @@ -848,13 +931,13 @@ typealias type_class { * size = 32; * align = 32; * signed = false; - * } : struct page *; + * } := struct page *; * * typealias integer { * size = 32; * align = 32; * signed = true; - * } : int; + * } := int; */ struct name { @@ -865,7 +948,7 @@ variant name { ... }; -enum name { +enum name : integer_type { ... }; @@ -882,7 +965,7 @@ variant { ... } -enum { +enum : integer_type { ... } @@ -1173,6 +1256,9 @@ unary-operator: one of assignment-operator: = +type-assignment-operator: + := + constant-expression: unary-expression @@ -1182,11 +1268,11 @@ constant-expression-range: 2.2) Declarations: declaration: - declaration-specifiers ; - declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ; + declaration-specifiers declarator-list-opt ; ctf-specifier ; declaration-specifiers: + storage-class-specifier declaration-specifiers-opt type-specifier declaration-specifiers-opt type-qualifier declaration-specifiers-opt @@ -1213,6 +1299,7 @@ type-specifier: unsigned _Bool _Complex + _Imaginary struct-specifier variant-specifier enum-specifier @@ -1230,8 +1317,8 @@ struct-or-variant-declaration-list: struct-or-variant-declaration: specifier-qualifier-list struct-or-variant-declarator-list ; declaration-specifiers storage-class-specifier declaration-specifiers declarator-list ; - typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list ; - typealias declaration-specifiers abstract-declarator-list : declarator-list ; + typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list ; + typealias declaration-specifiers abstract-declarator-list := declarator-list ; specifier-qualifier-list: type-specifier specifier-qualifier-list-opt @@ -1256,12 +1343,8 @@ enum-specifier: enum identifier-opt { enumerator-list } enum identifier-opt { enumerator-list , } enum identifier - enum identifier-opt < declaration-specifiers > { enumerator-list } - enum identifier-opt < declaration-specifiers > { enumerator-list , } - enum identifier < declaration-specifiers > - enum identifier-opt < integer-constant > { enumerator-list } - enum identifier-opt < integer-constant > { enumerator-list , } - enum identifier < integer-constant > + enum identifier-opt : declaration-specifiers { enumerator-list } + enum identifier-opt : declaration-specifiers { enumerator-list , } enumerator-list: enumerator @@ -1311,8 +1394,8 @@ ctf-specifier: event { ctf-assignment-expression-list-opt } stream { ctf-assignment-expression-list-opt } trace { ctf-assignment-expression-list-opt } - typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list ; - typealias declaration-specifiers abstract-declarator-list : declarator-list ; + typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list ; + typealias declaration-specifiers abstract-declarator-list := declarator-list ; ctf-type-specifier: floating_point { ctf-assignment-expression-list-opt } @@ -1327,5 +1410,5 @@ ctf-assignment-expression: unary-expression assignment-operator unary-expression unary-expression type-assignment-operator type-specifier declaration-specifiers storage-class-specifier declaration-specifiers declarator-list - typealias declaration-specifiers abstract-declarator-list : declaration-specifiers abstract-declarator-list - typealias declaration-specifiers abstract-declarator-list : declarator-list + typealias declaration-specifiers abstract-declarator-list := declaration-specifiers abstract-declarator-list + typealias declaration-specifiers abstract-declarator-list := declarator-list