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

10.2 Call Frame Information

Debuggers need to be able to view and modify the local variables of any function as its execution progresses.

DWARF3 does this by having the compiler keep track of where (in registers or on the stack) a function stores its data. The compiler encodes this information in a byte-coded language specified in Section 6.4 of the DWARF3 standard. This allows the debugger to progressively recreate a previous state by interpreting the byte-coded language. Each function activation is represented by a base address, called the Canonical Frame address (CFA), and a set of values corresponding to the contents of the machine's registers during that activation. Given the point to which the activation's execution has progressed, the debugger can figure out where all of the function's data is, and can unwind the stack to a previous state, including a previous function activation.

The DWARF3 standard suggests a very large unwinding table, with one row for each code address and one column for each register, virtual or not, including the CFA. Each cell contains unwinding instructions for that register at that point in time (code address).

Both the definition of the CFA and the set of registers comprising the state are architecture-specific.

The set of registers includes all the registers listed in Table 10-1, indexed by their DWARF register numbers from the first column.

For the CFA, the MSP430 ABI follows the convention suggested in the DWARF3 standard, defining it as the value of SP (R1) at the call site in the previous frame (that of the calling procedure).

The unwinding table may include registers that are not present on all MSP430 ISAs. Therefore a situation may arise in which the ISA executing the program has registers that are not mentioned in the call frame information. In this situation, the interpreter should behave as follows:

  • Callee-saved registers should be initialized to the same-value rule.
  • All other registers should be initialized to the undefined rule.