Introduction to Linker Map Files
Generating and using linker map files in IAR Linker is essential for gaining insight into memory utilization, analyzing symbol addresses, and debugging complex issues in embedded systems. A linker map provides a detailed view of the memory layout and can be pivotal for optimizing and debugging firmware. This document explains how to generate and utilize linker map files effectively.
Generating Linker Map Files
To generate a linker map file in IAR Embedded Workbench, follow these configurations:
- Open your project in IAR Embedded Workbench.
- Navigate to Project > Options.
- In the Options dialog, select the Linker category.
- Under the Output tab, ensure that the Generate linker map file option is checked.
Upon building your project, the linker will produce a map file, typically with a .map extension, in your project’s output directory.
Understanding the Linker Map File Structure
The map file provides comprehensive information about the linking process, organized into several sections:
Summary of Sections and Mapping: Displays how different sections from the input files are mapped into memory sections. This part is crucial for understanding where each part of your code resides in memory.
Symbol Definitions: Lists all the symbols used in the program along with their addresses. This helps in identifying the location of functions and global variables.
Cross-reference Listings: This is useful for understanding which modules and files contribute specific symbols or memory sections.
- Memory Utilization Summary: Provides a succinct overview of how much memory is used and available, split between ROM, RAM, etc.
Using Linker Map Files for Debugging
Analyzing Memory Usage: A map file allows you to inspect stack and heap sizes, determine which variables or code sections consume the most memory, and identify memory bloat. This is useful for optimizing memory-constrained applications.
Tracing Symbol Addresses: When debugging, you might need to determine the address of a specific function or variable. Use the symbol definitions section to map symbolic names to addresses.
Detecting Linker Errors: If there are linker errors, the map file can help track down incorrect memory allocations and overlapping sections which can be indicators of the root cause.
Example of Analyzing a Linker Map File Entry
Consider the following snippet from a typical link map file:
0x20000000 0x20000 DATA
*(.bss)
.bss 0x20000000 0x20000 main.o
0x20000000 myGlobalArray
- Memory Section (.bss): The start address is
0x20000000, and it occupies a size of 0x20000 bytes.
- Symbol Location: The symbol
myGlobalArray is located at address 0x20000000.
Optimization and Fixes
Enhance your debugging efforts by:
Reorganizing Sections: Use the map file to reorganize memory sections, potentially reducing gaps and improving efficiency.
Reducing Code Size: Identify large sections of code or data, then refactor or use compiler/linker options to reduce size.
Resolving Conflict: Use the map to identify and resolve overlapping sections or symbols, which can cause mysterious breakage.
The insights gained from a linker map file guide decisions around code structure, memory allocation, and usage optimization, an invaluable part of embedded system development. Understanding how to leverage these files aids in producing efficient and reliable firmware.
