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273 lines
7.3 KiB
273 lines
7.3 KiB
=====================================
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CodeView Symbol Records
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=====================================
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.. contents::
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:local:
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.. _symbols_intro:
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Introduction
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============
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This document describes the usage and serialization format of the various
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CodeView symbol records that LLVM understands. Like
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:doc:`CodeView Type Records <CodeViewTypes>`, we describe only the important
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types which are generated by modern C++ toolchains.
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Record Categories
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=================
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Symbol records share one major similarity with :doc:`type records <CodeViewTypes>`:
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They start with the same :ref:`record prefix <leaf_types>`, which we will not describe
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again (refer to the previous link for a description). As a result of this, a sequence
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of symbol records can be processed with largely the same code as that which processes
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type records. There are several important differences between symbol and type records:
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* Symbol records only appear in the :doc:`PublicStream`, :doc:`GlobalStream`, and
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:doc:`Module Info Streams <ModiStream>`.
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* Type records only appear in the :doc:`TPI & IPI streams <TpiStream>`.
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* While types are referenced from other CodeView records via :ref:`type indices <type_indices>`,
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symbol records are referenced by the byte offset of the record in the stream that it appears
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in.
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* Types can reference types (via type indices), and symbols can reference both types (via type
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indices) and symbols (via offsets), but types can never reference symbols.
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* There is no notion of :ref:`Leaf Records <leaf_types>` and :ref:`Member Records <member_types>`
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as there are with types. Every symbol record describes is own length.
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* Certain special symbol records begin a "scope". For these records, all following records
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up until the next ``S_END`` record are "children" of this symbol record. For example,
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given a symbol record which describes a certain function, all local variables of this
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function would appear following the function up until the corresponding ``S_END`` record.
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Finally, there are three general categories of symbol record, grouped by where they are legal
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to appear in a PDB file. Public Symbols (which appear only in the
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:doc:`publics stream <PublicStream>`), Global Symbols (which appear only in the
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:doc:`globals stream <GlobalStream>`) and module symbols (which appear in the
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:doc:`module info stream <ModiStream>`).
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.. _public_symbols:
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Public Symbols
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--------------
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Public symbols are the CodeView equivalent of DWARF ``.debug_pubnames``. There
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is one public symbol record for every function or variable in the program that
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has a mangled name. The :doc:`Publics Stream <PublicStream>`, which contains these
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records, additionally contains a hash table that allows one to quickly locate a
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record by mangled name.
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S_PUB32 (0x110e)
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^^^^^^^^^^^^^^^^
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There is only type of public symbol, an ``S_PUB32`` which describes a mangled
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name, a flag indicating what kind of symbol it is (e.g. function, variable), and
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the symbol's address. The :ref:`dbi_section_map_substream` of the
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:doc:`DBI Stream <DbiStream>` can be consulted to determine what module this address
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corresponds to, and from there that module's :doc:`module debug stream <ModiStream>`
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can be consulted to locate full information for the symbol with the given address.
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.. _global_symbols:
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Global Symbols
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--------------
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While there is one :ref:`public symbol <public_symbols>` for every symbol in the
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program with `external` linkage, there is one global symbol for every symbol in the
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program with linkage (including internal linkage). As a result, global symbols do
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not describe a mangled name *or* an address, since symbols with internal linkage
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need not have any mangling at all, and also may not have an address. Thus, all
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global symbols simply refer directly to the full symbol record via a module/offset
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combination.
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Similarly to :ref:`public symbols <public_symbols>`, all global symbols are contained
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in a single :doc:`Globals Stream <GlobalStream>`, which contains a hash table mapping
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fully qualified name to the corresponding record in the globals stream (which as
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mentioned, then contains information allowing one to locate the full record in the
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corresponding module symbol stream).
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Note that a consequence and limitation of this design is that program-wide lookup
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by anything other than an exact textually matching fully-qualified name of whatever
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the compiler decided to emit is impractical. This differs from DWARF, where even
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though we don't necessarily have O(1) lookup by basename within a given scope (including
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O(1) scope, we at least have O(n) access within a given scope).
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.. important::
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Program-wide lookup of names by anything other than an exact textually matching fully
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qualified name is not possible.
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S_GDATA32
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^^^^^^^^^^
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S_GTHREAD32 (0x1113)
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^^^^^^^^^^^^^^^^^^^^
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S_PROCREF (0x1125)
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^^^^^^^^^^^^^^^^^^
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S_LPROCREF (0x1127)
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^^^^^^^^^^^^^^^^^^^
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S_GMANDATA (0x111d)
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^^^^^^^^^^^^^^^^^^^
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.. _module_symbols:
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Module Symbols
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--------------
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S_END (0x0006)
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^^^^^^^^^^^^^^
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S_FRAMEPROC (0x1012)
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^^^^^^^^^^^^^^^^^^^^
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S_OBJNAME (0x1101)
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^^^^^^^^^^^^^^^^^^
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S_THUNK32 (0x1102)
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^^^^^^^^^^^^^^^^^^
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S_BLOCK32 (0x1103)
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^^^^^^^^^^^^^^^^^^
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S_LABEL32 (0x1105)
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^^^^^^^^^^^^^^^^^^
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S_REGISTER (0x1106)
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^^^^^^^^^^^^^^^^^^^
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S_BPREL32 (0x110b)
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^^^^^^^^^^^^^^^^^^
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S_LPROC32 (0x110f)
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^^^^^^^^^^^^^^^^^^
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S_GPROC32 (0x1110)
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^^^^^^^^^^^^^^^^^^
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S_REGREL32 (0x1111)
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^^^^^^^^^^^^^^^^^^^
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S_COMPILE2 (0x1116)
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^^^^^^^^^^^^^^^^^^^
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S_UNAMESPACE (0x1124)
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^^^^^^^^^^^^^^^^^^^^^
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S_TRAMPOLINE (0x112c)
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^^^^^^^^^^^^^^^^^^^^^
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S_SECTION (0x1136)
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^^^^^^^^^^^^^^^^^^
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S_COFFGROUP (0x1137)
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^^^^^^^^^^^^^^^^^^^^
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S_EXPORT (0x1138)
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^^^^^^^^^^^^^^^^^
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S_CALLSITEINFO (0x1139)
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^^^^^^^^^^^^^^^^^^^^^^^
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S_FRAMECOOKIE (0x113a)
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^^^^^^^^^^^^^^^^^^^^^^
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S_COMPILE3 (0x113c)
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^^^^^^^^^^^^^^^^^^^
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S_ENVBLOCK (0x113d)
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^^^^^^^^^^^^^^^^^^^
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S_LOCAL (0x113e)
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^^^^^^^^^^^^^^^^
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S_DEFRANGE (0x113f)
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^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_SUBFIELD (0x1140)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_REGISTER (0x1141)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_FRAMEPOINTER_REL (0x1142)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_SUBFIELD_REGISTER (0x1143)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_FRAMEPOINTER_REL_FULL_SCOPE (0x1144)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_DEFRANGE_REGISTER_REL (0x1145)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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S_LPROC32_ID (0x1146)
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^^^^^^^^^^^^^^^^^^^^^
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S_GPROC32_ID (0x1147)
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^^^^^^^^^^^^^^^^^^^^^
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S_BUILDINFO (0x114c)
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^^^^^^^^^^^^^^^^^^^^
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S_INLINESITE (0x114d)
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^^^^^^^^^^^^^^^^^^^^^
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S_INLINESITE_END (0x114e)
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^^^^^^^^^^^^^^^^^^^^^^^^^
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S_PROC_ID_END (0x114f)
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^^^^^^^^^^^^^^^^^^^^^^
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S_FILESTATIC (0x1153)
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^^^^^^^^^^^^^^^^^^^^^
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S_LPROC32_DPC (0x1155)
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^^^^^^^^^^^^^^^^^^^^^^
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S_LPROC32_DPC_ID (0x1156)
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^^^^^^^^^^^^^^^^^^^^^^^^^
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S_CALLEES (0x115a)
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^^^^^^^^^^^^^^^^^^
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S_CALLERS (0x115b)
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^^^^^^^^^^^^^^^^^^
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S_HEAPALLOCSITE (0x115e)
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^^^^^^^^^^^^^^^^^^^^^^^^
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S_FASTLINK (0x1167)
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^^^^^^^^^^^^^^^^^^^
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S_INLINEES (0x1168)
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^^^^^^^^^^^^^^^^^^^
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.. _module_and_global_symbols:
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Symbols which can go in either/both of the module info stream & global stream
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-----------------------------------------------------------------------------
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S_CONSTANT (0x1107)
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^^^^^^^^^^^^^^^^^^^
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S_UDT (0x1108)
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^^^^^^^^^^^^^^
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S_LDATA32 (0x110c)
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^^^^^^^^^^^^^^^^^^
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S_LTHREAD32 (0x1112)
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^^^^^^^^^^^^^^^^^^^^
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S_LMANDATA (0x111c)
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^^^^^^^^^^^^^^^^^^^
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S_MANCONSTANT (0x112d)
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^^^^^^^^^^^^^^^^^^^^^^
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