add webassembly binary format

executable/webassembly.ksy

@@ -0,0 +1,385 @@
+meta:
+  id: webassembly
+  title: Binary format for WebAssembly modules
+  file-extension: wasm
+  tags: 
+    - webassembly
+    - schema
+  license: MIT
+  ks-version: 0.9
+  imports:
+    - /common/vlq_base128_le
+  endian: le
+
+doc: |
+  This document describes the binary format of a WebAssembly module 
+  following the version 1.0 of the core WebAssembly standard.
+
+  Repository: https://github.com/henrythasler/wasm-kaitai-struct
+
+  * Naming of entities follows the official specification.
+  * All integers are encoded using the LEB128 variable-length integer encoding (see vlq_base128_le.ksy).
+  * The schema follows the KSY Style Guide
+  * Requires ks-version 0.9+ because of attribute value validation
+  * types appear in the order in which they are required
+
+doc-ref: |
+  * https://www.w3.org/TR/wasm-core-1/
+
+seq:
+  - id: magic
+    contents: [0x00, "asm"]
+    doc: Magic number identifying the file as a WebAssembly module
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-magic
+  - id: version
+    type: u4
+    doc: Version of the WebAssembly binary format
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-version
+  - id: sections
+    type: section
+    repeat: eos
+    doc: A WebAssembly module is a set of sections
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-module
+
+types:
+  section:
+    doc: A specific section as part of a module
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-section
+    seq:
+      - id: id
+        type: u1
+        enum: section_id
+        doc: Section identifier
+      - id: len_content
+        type: vlq_base128_le
+        doc: Length of the section content in bytes
+      - id: content
+        size: len_content.value
+        type: 
+          switch-on: id
+          cases:
+            'section_id::custom': custom_section
+            'section_id::type': type_section
+            'section_id::import': import_section
+            'section_id::function': function_section
+            'section_id::table': table_section
+            'section_id::memory': memory_section
+            'section_id::global': global_section
+            'section_id::export': export_section
+            'section_id::start': start_section
+            'section_id::element': element_section
+            'section_id::code': code_section
+            'section_id::data': data_section
+        doc: Section content
+
+  custom_section:
+    doc: (id 0) - Custom section whose content is application-specific and not defined by the WebAssembly specification.
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-customsec
+    seq:
+      - id: name
+        type: name
+      - id: data
+        size-eos: true
+        doc: Custom section data; out of scope for this schema
+
+  name:
+    doc: UTF-8 encoded character sequence
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-name
+    seq:
+      - id: length
+        type: vlq_base128_le
+      - id: value
+        size: length.value
+        type: str
+        encoding: UTF-8
+
+  type_section:
+    doc: (id 1) - A vector of function types
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-typesec
+    seq:
+      - id: num_functypes
+        type: vlq_base128_le
+      - id: functypes
+        type: functype
+        repeat: eos
+
+  functype:
+    doc: Byte `0x60` followed by a vector of parameters and results
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-functype
+    seq:
+      - id: functype
+        type: u1
+        enum: types
+        valid:
+          eq: types::function
+      - id: parameters
+        type: vec_valtype
+      - id: results
+        type: vec_valtype
+
+  vec_valtype:
+    seq:
+      - id: num_types
+        type: vlq_base128_le
+      - id: valtype
+        type: u1
+        enum: valtype
+        repeat: expr
+        repeat-expr: num_types.value
+        doc: Value Types
+        doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-valtype
+
+  import_section:
+    doc: (id 2) - Imported components
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-importsec
+    seq:
+      - id: num_imports
+        type: vlq_base128_le
+      - id: imports
+        type: import
+        repeat: eos
+
+  import:
+    doc: An element of the import section
+    seq:
+      - id: module
+        type: name
+      - id: name
+        type: name
+      - id: import_type
+        type: u1
+        enum: import_types
+      - id: importdesc
+        type: 
+          switch-on: import_type
+          cases:
+            'import_types::func': vlq_base128_le
+            'import_types::table': table
+            'import_types::mem': memory
+            'import_types::global': global
+
+  table:
+    seq:
+      - id: elemtype
+        type: u1
+        enum: types
+        valid:
+          eq: types::element
+      - id: limits
+        type: limits
+
+  limits:
+    seq:
+      - id: flags
+        type: u1
+        valid:
+          any-of: [0x00, 0x01]
+      - id: min
+        type: vlq_base128_le
+      - id: max
+        type: vlq_base128_le
+        if: flags == 0x01
+
+  memory:
+    seq:
+      - id: limits
+        type: limits
+
+  global:
+    seq:
+      - id: valtype
+        type: u1
+        enum: valtype
+      - id: is_mutable
+        type: u1
+        doc: the `is_` prefix avoids conflicts with the C++ keyword `mutable` in generated code
+
+  function_section:
+    doc: (id 3) - Vector of type indices (see `Type Section`) for all functions in the `Code Section`
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-funcsec
+    seq:
+      - id: num_typeidx
+        type: vlq_base128_le
+      - id: typeidx
+        type: vlq_base128_le
+        repeat: eos
+
+  table_section:
+    doc: (id 4) Vector of tables
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-tablesec
+    seq:
+      - id: num_tables
+        type: vlq_base128_le
+      - id: tables
+        type: table
+        repeat: eos
+
+  memory_section:
+    doc: (id 5) Vector of memories
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-memsec
+    seq:
+      - id: num_memories
+        type: vlq_base128_le
+      - id: memories
+        type: memory
+        repeat: eos
+
+  global_section:
+    doc: (id 6) Vector of globals
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-memsec
+    seq:
+      - id: num_globals
+        type: vlq_base128_le
+      - id: globals
+        type: global
+        repeat: eos
+
+  export_section:
+    doc: (id 7) - Exported entities
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-exportsec
+    seq:
+      - id: num_exports
+        type: vlq_base128_le
+      - id: exports
+        type: export
+        repeat: eos
+
+  export:
+    seq:
+      - id: name
+        type: name
+      - id: exportdesc
+        type: u1
+        enum: export_types
+      - id: idx
+        type: vlq_base128_le    
+
+  start_section:
+    doc: (id 8) - Start-function or -component of the module
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-startsec
+    seq:
+      - id: start
+        type: vlq_base128_le
+        doc: function index of the start-function
+
+  element_section:
+    doc: (id 9) - Vector of element sections
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-elemsec
+    seq:
+      - id: num_elements
+        type: vlq_base128_le
+      - id: elements
+        type: element
+        repeat: eos
+
+  element:
+    seq:
+      - id: tableidx
+        type: vlq_base128_le
+      - id: offset_expr
+        terminator: 0x0b
+        doc: The offset is given by a constant expression that DOES NOT include an end marker
+        doc-ref: https://www.w3.org/TR/wasm-core-1/#valid-constant
+      - id: num_init
+        type: vlq_base128_le
+      - id: init_vec
+        type: vlq_base128_le
+        repeat: expr
+        repeat-expr: num_init.value
+
+  code_section:
+    doc: (id 10) A vector of code entries
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-codesec
+    seq:
+      - id: num_entries
+        type: vlq_base128_le
+      - id: entries
+        type: code
+        repeat: eos
+
+  code:
+    seq:
+      - id: len_func
+        type: vlq_base128_le
+      - id: func
+        size: len_func.value
+        type: func
+
+  func:
+    seq:
+      - id: num_locals
+        type: vlq_base128_le
+      - id: locals
+        type: local
+        repeat: expr
+        repeat-expr: num_locals.value
+      - id: expr
+        size-eos: true
+
+  local:
+    seq:
+      - id: num_valtype
+        type: vlq_base128_le
+      - id: valtype
+        type: u1
+        enum: valtype
+
+  data_section:
+    doc: (11) - Vector of data segments
+    doc-ref: https://www.w3.org/TR/wasm-core-1/#binary-datasec
+    seq:
+      - id: num_data
+        type: vlq_base128_le
+      - id: data_segments
+        type: data_segment
+        repeat: eos
+
+  data_segment:
+    seq:
+      - id: data_memidx
+        type: vlq_base128_le
+      - id: offset_expr
+        terminator: 0x0b
+        doc: The offset is given by a constant expression that DOES NOT include an end marker
+        doc-ref: https://www.w3.org/TR/wasm-core-1/#valid-constant
+      - id: num_init
+        type: vlq_base128_le
+      - id: init_vec
+        size: num_init.value
+
+enums:
+  section_id:
+    0: custom
+    1: type
+    2: import
+    3: function
+    4: table
+    5: memory
+    6: global
+    7: export
+    8: start
+    9: element
+    10: code
+    11: data
+
+  valtype:
+    0x7f: i32
+    0x7E: i64
+    0x7D: f32
+    0x7C: f64
+
+  types:
+    0x60: function
+    0x70: element
+
+  export_types:
+    0x00: func
+    0x01: table
+    0x02: mem
+    0x03: global
+
+  import_types:
+    0x00: func
+    0x01: table
+    0x02: mem
+    0x03: global