SPRAC71B February   2019  – October 2023

 

  1.   1
  2. 1 Introduction
    1. 1.1  ABIs for the C28x
    2. 1.2  Scope
    3. 1.3  ABI Variants
    4. 1.4  Toolchains and Interoperability
    5. 1.5  Libraries
    6. 1.6  Types of Object Files
    7. 1.7  Segments
    8. 1.8  C28x Architecture Overview
    9. 1.9  C28x Memory Models
    10. 1.10 Reference Documents
    11. 1.11 Code Fragment Notation
  3. 2 Data Representation
    1. 2.1 Basic Types
    2. 2.2 Data in Registers
    3. 2.3 Data in Memory
    4. 2.4 Pointer Types
    5. 2.5 Complex Types
    6. 2.6 Structures and Unions
    7. 2.7 Arrays
    8. 2.8 Bit Fields
      1. 2.8.1 Volatile Bit Fields
    9. 2.9 Enumeration Types
  4. 3 Calling Conventions
    1. 3.1 Call and Return
      1. 3.1.1 Call Instructions
        1. 3.1.1.1 Indirect Calls
        2. 3.1.1.2 Direct Calls
      2. 3.1.2 Return Instruction
      3. 3.1.3 Pipeline Conventions
      4. 3.1.4 Weak Functions
    2. 3.2 Register Conventions
      1. 3.2.1 Argument Registers
      2. 3.2.2 Callee-Saved Registers
    3. 3.3 Argument Passing
      1. 3.3.1 Passing 16-Bit Arguments
      2. 3.3.2 Passing Longer Arguments
      3. 3.3.3 C++ Argument Passing
      4. 3.3.4 Passing Structs and Unions
      5. 3.3.5 Stack Layout of Arguments Not Passed in Registers
      6. 3.3.6 Frame Pointer
    4. 3.4 Return Values
    5. 3.5 Structures and Unions Passed and Returned by Reference
    6. 3.6 Conventions for Compiler Helper Functions
    7. 3.7 Prolog and Epilog Helper Functions
    8. 3.8 Scratch Registers for Functions Already Seen
    9. 3.9 Interrupt Functions
  5. 4 Data Allocation and Addressing
    1. 4.1 Data Sections and Segments
    2. 4.2 Data Blocking
    3. 4.3 Addressing Modes
    4. 4.4 Allocation and Addressing of Static Data
      1. 4.4.1 Addressing Methods for Static Data
      2. 4.4.2 Placement Conventions for Static Data
        1. 4.4.2.1 Abstract Conventions for Addressing
      3. 4.4.3 Initialization of Static Data
    5. 4.5 Automatic Variables
    6. 4.6 Frame Layout
      1. 4.6.1 Stack Alignment
      2. 4.6.2 Register Save Order
    7. 4.7 Heap-Allocated Objects
  6. 5 Code Allocation and Addressing
    1. 5.1 Computing the Address of a Code Label
    2. 5.2 Calls
      1. 5.2.1 Direct Call
      2. 5.2.2 Far Call Trampoline
      3. 5.2.3 Indirect Calls
  7. 6 Helper Function API
    1. 6.1 Floating-Point Behavior
    2. 6.2 C Helper Function API
    3. 6.3 Floating-Point Helper Functions for C99
  8. 7 Standard C Library API
    1. 7.1  About Standard C Libraries
    2. 7.2  Reserved Symbols
    3. 7.3  <assert.h> Implementation
    4. 7.4  <complex.h> Implementation
    5. 7.5  <ctype.h> Implementation
    6. 7.6  <errno.h> Implementation
    7. 7.7  <float.h> Implementation
    8. 7.8  <inttypes.h> Implementation
    9. 7.9  <iso646.h> Implementation
    10. 7.10 <limits.h> Implementation
    11. 7.11 <locale.h> Implementation
    12. 7.12 <math.h> Implementation
    13. 7.13 <setjmp.h> Implementation
    14. 7.14 <signal.h> Implementation
    15. 7.15 <stdarg.h> Implementation
    16. 7.16 <stdbool.h> Implementation
    17. 7.17 <stddef.h> Implementation
    18. 7.18 <stdint.h> Implementation
    19. 7.19 <stdio.h> Implementation
    20. 7.20 <stdlib.h> Implementation
    21. 7.21 <string.h> Implementation
    22. 7.22 <tgmath.h> Implementation
    23. 7.23 <time.h> Implementation
    24. 7.24 <wchar.h> Implementation
    25. 7.25 <wctype.h> Implementation
  9. 8 C++ ABI
    1. 8.1  Limits (GC++ABI 1.2)
    2. 8.2  Export Template (GC++ABI 1.4.2)
    3. 8.3  Data Layout (GC++ABI Chapter 2)
    4. 8.4  Initialization Guard Variables (GC++ABI 2.8)
    5. 8.5  Constructor Return Value (GC++ABI 3.1.5)
    6. 8.6  One-Time Construction API (GC++ABI 3.3.2)
    7. 8.7  Controlling Object Construction Order (GC++ ABI 3.3.4)
    8. 8.8  Demangler API (GC++ABI 3.4)
    9. 8.9  Static Data (GC++ ABI 5.2.2)
    10. 8.10 Virtual Tables and the Key function (GC++ABI 5.2.3)
    11. 8.11 Unwind Table Location (GC++ABI 5.3)
  10. 9 Exception Handling
    1. 9.1  Overview
    2. 9.2  PREL31 Encoding
    3. 9.3  The Exception Index Table (EXIDX)
      1. 9.3.1 Pointer to Out-of-Line EXTAB Entry
      2. 9.3.2 EXIDX_CANTUNWIND
      3. 9.3.3 Inlined EXTAB Entry
    4. 9.4  The Exception Handling Instruction Table (EXTAB)
      1. 9.4.1 EXTAB Generic Model
      2. 9.4.2 EXTAB Compact Model
      3. 9.4.3 Personality Routines
    5. 9.5  Unwinding Instructions
      1. 9.5.1 Common Sequence
      2. 9.5.2 Byte-Encoded Unwinding Instructions
    6. 9.6  Descriptors
      1. 9.6.1 Encoding of Type Identifiers
      2. 9.6.2 Scope
      3. 9.6.3 Cleanup Descriptor
      4. 9.6.4 Catch Descriptor
      5. 9.6.5 Function Exception Specification (FESPEC) Descriptor
    7. 9.7  Special Sections
    8. 9.8  Interaction With Non-C++ Code
      1. 9.8.1 Automatic EXIDX Entry Generation
      2. 9.8.2 Hand-Coded Assembly Functions
    9. 9.9  Interaction With System Features
      1. 9.9.1 Shared Libraries
      2. 9.9.2 Overlays
      3. 9.9.3 Interrupts
    10. 9.10 Assembly Language Operators in the TI Toolchain
  11. 10DWARF
    1. 10.1 DWARF Register Names
    2. 10.2 Call Frame Information
    3. 10.3 Vendor Names
    4. 10.4 Vendor Extensions
  12. 11ELF Object Files (Processor Supplement)
    1. 11.1 Registered Vendor Names
    2. 11.2 ELF Header
    3. 11.3 Sections
      1. 11.3.1 Section Indexes
      2. 11.3.2 Section Types
      3. 11.3.3 Extended Section Header Attributes
      4. 11.3.4 Subsections
      5. 11.3.5 Special Sections
      6. 11.3.6 Section Alignment
    4. 11.4 Symbol Table
      1. 11.4.1 Symbol Types
      2. 11.4.2 Common Block Symbols
      3. 11.4.3 Symbol Names
      4. 11.4.4 Reserved Symbol Names
      5. 11.4.5 Mapping Symbols
    5. 11.5 Relocation
      1. 11.5.1 Relocation Types
        1. 11.5.1.1 Absolute Relocations
        2. 11.5.1.2 PC-Relative Relocations
        3. 11.5.1.3 Relocations in Data Sections
        4. 11.5.1.4 Relocations for C28x Instructions
        5. 11.5.1.5 Other Relocation Types
      2. 11.5.2 Relocation Operations
      3. 11.5.3 Relocation of Unresolved Weak References
  13. 12ELF Program Loading and Linking (Processor Supplement)
    1. 12.1 Program Header
      1. 12.1.1 Base Address
      2. 12.1.2 Segment Contents
      3. 12.1.3 Thread-Local Storage
    2. 12.2 Program Loading
  14. 13Build Attributes
    1. 13.1 About Build Attributes
    2. 13.2 C28x ABI Build Attribute Subsection
    3. 13.3 Build Attribute Tags
  15. 14Copy Tables and Variable Initialization
    1. 14.1 About Copy Tables
    2. 14.2 Copy Table Format
    3. 14.3 Compressed Data Formats
      1. 14.3.1 RLE
      2. 14.3.2 LZSS Format
    4. 14.4 Variable Initialization
  16. 15Revision History
    1.     188

11.3.5 Special Sections

The System V ABI, along with other base documents and other sections of this ABI, defines several sections with dedicated purposes. Table 11-4 consolidates dedicated sections used by the C28x and groups them by functionality.

Section names are not mandated by the ABI. Special sections should be identified by type, not by name. However, interoperability among toolchains can be improved by following these conventions. For example, using these names may decrease the likelihood of having to write custom linker commands to link relocatable files built by different compilers.

The ABI does mandate that a section whose name does match an entry in the table must be used for the specified purpose. For example, the compiler is not required to generate code into a section called .text, but it is not allowed to generate a section called .text containing anything other than code.

All of the section names listed in the table that follows are prefixes. The type and attributes apply to all sections with names that begin with these strings.

Table 11-4 C28x Special Sections
PrefixTypeAttributes
Code Sections
.textSHT_PROGBITSSHF_ALLOC + SHF_EXECINSTR
Data Sections
.dataSHT_PROGBITSSHF_ALLOC + SHF_WRITE
.bssSHT_NOBITSSHF_ALLOC + SHF_WRITE
.TI.noinitSHT_NOBITSTI_SHF_NOINIT
.TI.persistentSHT_PROGBITSTI_SHF_NOINIT
.constSHT_PROGBITSSHF_ALLOC
Exception Handling Data Sections
.C28x.exidxSHT_C28x_UNWINDSHF_ALLOC + SHF_LINK_ORDER
.C28x.extabSHT_PROGBITSSHF_ALLOC
Initialization and Termination Sections
.init_arraySHT_INIT_ARRAYSHF_ALLOC + SHF_WRITE
ELF Structures
.relSHT_RELNone
.relaSHT_RELANone
.symtabSHT_SYMTABNone
.symtab_shndxSHT_SYMTAB_SHNDXNone
.strtabSHT_STRTABSHF_STRINGS
.shstrtabSHT_STRTABSHF_STRINGS
.noteSHT_NOTENone
Build Attributes
.C28x.attributesSHT_C28x_ATTRIBUTESNone
Symbolic Debug Sections
.debug (1)SHT_PROGBITSNone
TI Toolchain-Specific Sections
.stackSHT_NOBITSSHF_ALLOC + SHF_WRITE
.sysmemSHT_NOBITSSHF_ALLOC + SHF_WRITE
.switchSHT_PROGBITSSHF_ALLOC
.binitSHT_PROGBITSSHF_ALLOC
.cinitSHT_TI_INITINFOSHF_ALLOC
.const:handler_tableSHT_PROGBITSSHF_ALLOC
.ovlySHT_PROGBITSSHF_ALLOC
.ppdataSHT_NOBITSSHF_ALLOC + SHF_WRITE
.ppinfoSHT_NOBITSSHF_ALLOC + SHF_WRITE
.TI.crctabSHT_PROGBITSSHF_ALLOC
.TI.icodeSHT_TI_ICODENone
.TI.xrefSHT_TI_XREFNone
.TI.section.flagsSHT_TI_SH_FLAGSNone
.TI.symbol.aliasSHT_TI_SYMALIASNone
.TI.section.pageSHT_TI_SH_PAGENone
Sections in the System V ABI but Unused by the C28x EABI
.comment
.data1
.dsbt
.dynamic
.dynstr
.dynsym
.far
.fardata
.fardata:const
.fini
.fini_array
.gnu.version
.gnu.version_d
.gnu.version_r
.got
.hash
.init
.interp
.line
.neardata
.plt
.preinit_array
.rodata
.rodata1
.tbss
.tdata
.tdata1
.TI.tls_init
(1) Additional sections with names like .debug_info and .debug_line are also used. The .debug section name is a prefix, as are other section names. The type and attributes apply to all sections with names that begin with .debug.

The "TI Toolchain-Specific Sections" sections in the previous table are used by the TI toolchain in various toolchain-specific ways. The ABI does not mandate the use of these sections (although interoperability encourages their use), but it does reserve these names.

The "Sections in the System V ABI but Unused by the C28x EABI" sections in the previous table are specified by the System V ABI, but are not used or defined under the C28x ABI. Other sections are used by TI for other devices; these names are reserved.