SLAA534A June   2013  – June 2020

 

  1. 1 Introduction
    1. 1.1  ABIs for the MSP430
    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  MSP430 Architecture Overview
    9. 1.9  MSP430 Memory Models
    10. 1.10 Reference Documents
    11. 1.11 Code Fragment Notation
  2. 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
  3. 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 Register Singles
      2. 3.3.2 Register Pairs
      3. 3.3.3 Split Pairs
      4. 3.3.4 Quads (Four-Register Arguments)
      5. 3.3.5 Special Convention for Compiler Helper Functions
      6. 3.3.6 C++ Argument Passing
      7. 3.3.7 Passing Structs and Unions
      8. 3.3.8 Stack Layout of Arguments Not Passed in Registers
      9. 3.3.9 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 Scratch Registers for Functions Already Seen
    8. 3.8 _ _mspabi_func_epilog Helper Functions
    9. 3.9 Interrupt Functions
  4. 4 Data Allocation and Addressing
    1. 4.1 Data Sections and Segments
    2. 4.2 Addressing Modes
    3. 4.3 Allocation and Addressing of Static Data
      1. 4.3.1 Addressing Methods for Static Data
        1. 4.3.1.1 Absolute Addressing
        2. 4.3.1.2 Symbolic Addressing
        3. 4.3.1.3 Immediate Addressing
      2. 4.3.2 Placement Conventions for Static Data
        1. 4.3.2.1 Abstract Conventions for Placement
        2. 4.3.2.2 Abstract Conventions for Addressing
      3. 4.3.3 Initialization of Static Data
    4. 4.4 Automatic Variables
    5. 4.5 Frame Layout
      1. 4.5.1 Stack Alignment
      2. 4.5.2 Register Save Order
    6. 4.6 Heap-Allocated Objects
  5. 5 Code Allocation and Addressing
    1. 5.1 Computing the Address of a Code Label
      1. 5.1.1 Absolute Addressing for Code
      2. 5.1.2 Symbolic Addressing
      3. 5.1.3 Immediate Addressing
    2. 5.2 Branching
    3. 5.3 Calls
      1. 5.3.1 Direct Call
      2. 5.3.2 Far Call Trampoline
      3. 5.3.3 Indirect Calls
  6. 6 Helper Function API
    1. 6.1 Floating-Point Behavior
    2. 6.2 C Helper Function API
    3. 6.3 Special Register Conventions for Helper Functions
    4. 6.4 Floating-Point Helper Functions for C99
  7. 7 Standard C Library API
    1. 7.1  Reserved Symbols
    2. 7.2  <assert.h> Implementation
    3. 7.3  <complex.h> Implementation
    4. 7.4  <ctype.h> Implementation
    5. 7.5  <errno.h> Implementation
    6. 7.6  <float.h> Implementation
    7. 7.7  <inttypes.h> Implementation
    8. 7.8  <iso646.h> Implementation
    9. 7.9  <limits.h> Implementation
    10. 7.10 <locale.h> Implementation
    11. 7.11 <math.h> Implementation
    12. 7.12 <setjmp.h> Implementation
    13. 7.13 <signal.h> Implementation
    14. 7.14 <stdarg.h> Implementation
    15. 7.15 <stdbool.h> Implementation
    16. 7.16 <stddef.h> Implementation
    17. 7.17 <stdint.h> Implementation
    18. 7.18 <stdio.h> Implementation
    19. 7.19 <stdlib.h> Implementation
    20. 7.20 <string.h> Implementation
    21. 7.21 <tgmath.h> Implementation
    22. 7.22 <time.h> Implementation
    23. 7.23 <wchar.h> Implementation
    24. 7.24 <wctype.h> Implementation
  8. 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)
  9. 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
  10. 10DWARF
    1. 10.1 DWARF Register Names
    2. 10.2 Call Frame Information
    3. 10.3 Vendor Names
    4. 10.4 Vendor Extensions
  11. 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 MSP430 Instructions
        5. 11.5.1.5 Relocations for MSP430X Instructions
        6. 11.5.1.6 Other Relocation Types
      2. 11.5.2 Relocation Operations
      3. 11.5.3 Relocation of Unresolved Weak References
  12. 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
  13. 13Build Attributes
    1. 13.1 MSP430 ABI Build Attribute Subsection
    2. 13.2 MSP430 Build Attribute Tags
  14. 14Copy Tables and Variable Initialization
    1. 14.1 Copy Table Format
    2. 14.2 Compressed Data Formats
      1. 14.2.1 RLE
      2. 14.2.2 LZSS Format
    3. 14.3 Variable Initialization
  15. 15Revision History

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 MSP430 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 MSP430 Special Sections
PrefixTypeAttributes
Code Sections
.textSHT_PROGBITSSHF_ALLOC + SHF_EXECINSTR
Data Sections
.dataSHT_PROGBITSSHF_ALLOC + SHF_WRITE
.bssSHT_NOBITSSHF_ALLOC + SHF_WRITE
.TI.noinitSHT_NOBITSSHF_MSP_NOINIT
.TI.persistentSHT_PROGBITSSHF_MSP_NOINIT
.constSHT_PROGBITSSHF_ALLOC
Exception Handling Data Sections
.MSP430.exidxSHT_MSP430_UNWINDSHF_ALLOC + SHF_LINK_ORDER
.MSP430.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
.MSP430.attributesSHT_MSP430_ATTRIBUTESNone
Symbolic Debug Sections
.debug (1)SHT_PROGBITSNone
TI Toolchain-Specific Sections
.stackSHT_NOBITSSHF_ALLOC + SHF_WRITE
.sysmemSHT_NOBITSSHF_ALLOC + SHF_WRITE
.cioSHT_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 MSP430 EABI (2)
.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.
(2) These section names are unused for MSP430, which does not support the features related to these sections. However, this section name is reserved and should not be used.

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 MSP430 EABI" sections in the previous table are specified by the System V ABI, but are not used or defined under the MSP430 ABI. Other sections are used by TI for other devices; these names are reserved.

In addition, .common is a section name used by the linker. This is an abstract section, not an actual section in the object files. The name is a convention in the linker command file for placing variables. This section should not be used for other purposes.