From: Mathieu Desnoyers Date: Fri, 29 Apr 2011 05:04:06 +0000 (-0400) Subject: Introduce TSDL (Trace Stream Description Language) X-Git-Tag: v1.8~62 X-Git-Url: http://git.efficios.com/?p=ctf.git;a=commitdiff_plain;h=6c7226e9d56e54d2387748a40d9198c333511442 Introduce TSDL (Trace Stream Description Language) Signed-off-by: Mathieu Desnoyers --- diff --git a/common-trace-format-proposal.txt b/common-trace-format-proposal.txt index d61b58c..91a9504 100644 --- a/common-trace-format-proposal.txt +++ b/common-trace-format-proposal.txt @@ -7,7 +7,9 @@ The goal of the present document is to propose a trace format that suits the needs of the embedded, telecom, high-performance and kernel communities. It is based on the Common Trace Format Requirements (v1.4) document. It is designed to allow traces to be natively generated by the Linux kernel, Linux user-space -applications written in C/C++, and hardware components. +applications written in C/C++, and hardware components. One major element of +CTF is the Trace Stream Description Language (TSDL) which flexibility +enables description of various binary trace stream layouts. The latest version of this document can be found at: @@ -51,7 +53,8 @@ virtual file system. Because each event stream is appended to while a trace is being recorded, each is associated with a separate file for output. Therefore, a stored trace can be represented as a directory containing one file per stream. -A metadata event stream contains information on trace event types. It describes: +A metadata event stream contains information on trace event types +expressed in the Trace Stream Description Language (TSDL). It describes: - Trace version. - Types available. @@ -354,7 +357,7 @@ 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). +Section 7.3.1), or in an uppermost dynamic scope (see Section 7.3.2). The type selection is indicated by the mapping from the enumeration value to the string used as variant type selector. The field to use as tag is specified by the "tag_field", specified between "< >" after the @@ -622,7 +625,7 @@ The overall structure of an event is: This structure defines an implicit dynamic scoping, where variants located in inner structures (those with a higher number in the listing above) can refer to the fields of outer structures (with lower number in -the listing above). See Section 7.2 Metadata Scopes for more detail. +the listing above). See Section 7.3 TSDL Scopes for more detail. 6.1 Event Header @@ -767,28 +770,38 @@ The event payload is aligned on the largest alignment required by types contained within the payload. (This follows the ISO/C standard for structures) -7. Metadata +7. Trace Stream Description Language (TSDL) + +The Trace Stream Description Language (TSDL) allows expression of the +binary trace streams layout in a C99-like Domain Specific Language +(DSL). + + +7.1 Metadata + +The trace stream layout description is located in the trace meta-data. +The meta-data is itself located in a stream identified by its name: +"metadata". -The meta-data is located in a stream identified by its name: "metadata". It is made of "event packets", which each start with an event packet header. The event type within the metadata stream have no event header -nor event context. Each event only contains a null-terminated "string" -payload, which is a metadata description entry. The events are packed -one next to another. Each event packet start with an event packet -header, which contains, amongst other fields, the magic number and trace -UUID. In the event packet header, the trace UUID is represented as an -array of bytes. Within the string-based metadata description, the trace -UUID is represented as a string of hexadecimal digits and dashes "-". +nor event context. Each event only contains a "string" payload without +any null-character. The events are packed one next to another. Each +event packet start with an event packet header, which contains, amongst +other fields, the magic number, trace UUID and packet length. In the +event packet header, the trace UUID is represented as an array of bytes. +Within the string-based metadata description, the trace UUID is +represented as a string of hexadecimal digits and dashes "-". -The metadata can be parsed by reading through the metadata strings, -skipping null-characters. Type names are made of a single identifier, -and can be surrounded by prefix/postfix. Text contained within "/*" and -"*/", as well as within "//" and end of line, are treated as comments. -Boolean values can be represented as true, TRUE, or 1 for true, and -false, FALSE, or 0 for false. +The metadata can be parsed by reading characters within the metadata +stream, for each packet starting after the packet header, for the length +of the packet payload specified in the header. Text contained within +"/*" and "*/", as well as within "//" and end of line, are treated as +comments. Boolean values can be represented as true, TRUE, or 1 for +true, and false, FALSE, or 0 for false. -7.1 Declaration vs Definition +7.2 Declaration vs Definition A declaration associates a layout to a type, without specifying where this type is located in the event structure hierarchy (see Section 6). @@ -799,7 +812,7 @@ 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 +": enum_base", which is part of the type specifier. The variant tag name, specified between "<" ">", is also part of the type specifier. A definition associates a type to a location in the event structure @@ -807,13 +820,13 @@ hierarchy (see Section 6). This association is denoted by ":=", as shown in Section 7.3. -7.2 Metadata Scopes +7.3 TSDL Scopes -CTF metadata uses two different types of scoping: a lexical scope is -used for declarations and type definitions, and a dynamic scope is used -for variants references to tag fields. +TSDL uses two different types of scoping: a lexical scope is used for +declarations and type definitions, and a dynamic scope is used for +variants references to tag fields. -7.2.1 Lexical Scope +7.3.1 Lexical Scope Each of "trace", "stream", "event", "struct" and "variant" have their own nestable declaration scope, within which types can be declared using "typedef" @@ -824,7 +837,7 @@ 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 +7.3.2 Dynamic Scope A dynamic scope consists in the lexical scope augmented with the implicit event structure definition hierarchy presented at Section 6. @@ -862,11 +875,11 @@ consumption, for each event, the current trace context is therefore readable by accessing the upper dynamic scopes. -7.3 Metadata Examples +7.4 TSDL Examples -The grammar representing the CTF metadata is presented in -Appendix C. CTF Metadata Grammar. This section presents a rather ligher -reading that consists in examples of CTF metadata, with template values: +The grammar representing the TSDL metadata is presented in Appendix C. +TSDL Grammar. This section presents a rather ligher reading that +consists in examples of TSDL metadata, with template values: trace { major = value; /* Trace format version */ @@ -1037,17 +1050,21 @@ flexibility in terms of: The event stream header will therefore be referred to as the "event packet header" throughout the rest of this document. -C. CTF Metadata Grammar + +C. TSDL Grammar /* - * Common Trace Format (CTF) Metadata Grammar. + * Common Trace Format (CTF) Trace Stream Description Language (TSDL) Grammar. * * Inspired from the C99 grammar: * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1124.pdf (Annex A) + * and c++1x grammar (draft) + * http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3291.pdf (Annex A) * * Specialized for CTF needs by including only constant and declarations from * C99 (excluding function declarations), and by adding support for variants, - * sequences and CTF-specific specifiers. + * sequences and CTF-specific specifiers. Enumeration container types + * semantic is inspired from c++1x enum-base. */ 1) Lexical grammar