Understand Memory Region Errors
Memory region errors in the ARM Linker typically occur when the linker script or configuration specifies memory regions incorrectly, or when allocated memory exceeds available regions. These problems often arise during embedded development due to the limited and specific nature of target system resources.
Examine the Linker Script
The linker script controls how memory is allocated. Check for syntax errors, incorrect memory region addresses, sizes, or if a memory region is missing.
Commonly, the linker script file will have a .ld extension. Open and modify this file to ensure all sections and regions are correctly defined. Example:
```ld
MEMORY
{
FLASH (rx) : ORIGIN = 0x08000000, LENGTH = 512K
RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 128K
}
SECTIONS
{
.text : {
(.text)
(.rodata)
} > FLASH
.data : {
_sdata = .;
(.data)
_edata = .;
} > RAM AT > FLASH
.bss : {
_sbss = .;
(.bss)
*(COMMON)
_ebss = .;
} > RAM
}
```
Check Symbol Definitions
Ensure that symbols like _sdata, _edata, _sbss, and _ebss are defined and correctly referenced in your startup code. Incorrect symbols could lead to improperly initialized memory.
Example in initial startup code:
```c
extern uint32_t _sdata, _edata, _sbss, _ebss;
void data_init(uint32_t _src, uint32_t _dest, uint32_t *end) {
while (dest < end) {
_dest++ = _src++;
}
}
void bss_init(uint32_t _start, uint32_t _end) {
while (start < end) {
*start++ = 0;
}
}
```
Review and Adjust Code Sections
Ensure that sections such as .text, .data, and .bss are properly assigned based on your embedded application's needs. Review allocations in the following way:
.text section should be placed in flash memory.
.data should be initialized in RAM, with its initial value stored in flash.
.bss should be in RAM and be initialized with zeros at startup.
Optimize for Size
- Consider optimizing your application to fit the available memory if you frequently face memory region overflow errors. Utilize compiler optimization flags for size and strip unused sections. Example flags:
```bash
arm-none-eabi-gcc -Os -ffunction-sections -fdata-sections
arm-none-eabi-ld --gc-sections
```
Consult ARM Linker Documentation
Utilize official ARM documentation to fully understand linker file syntax and advanced configurations. ARM's extensive documentation can provide additional guidance on managing more complex memory arrangements and linker features.
Particularly, check for specific directives like KEEP to manage sections that might otherwise be discarded:
```ld
KEEP(_(.important_section_))
```
Use Linker Diagnostics
- Enable diagnostic details to help you pinpoint the exact cause of the errors. Compiler and linker options can provide verbose output:
```bash
arm-none-eabi-gcc -Wall -Wextra
arm-none-eabi-ld -Map=output.map
```
By following these steps, you should be equipped to understand, diagnose, and resolve memory region errors in ARM Linker for embedded applications, thereby improving the reliability and efficiency of your firmware development process.
