SMT32CubeIDE - How to store a const struct at a specific flash memory address?

[ERODR.1]

I'm trying to store a const struct at a specific flash memory location using the STM32CubeIDE. I tried appending the __attribute__((at(address))) to the struct initialization, but the compiler ignores it: "warning: 'at' attribute directive ignored [-Wattributes]"

const runtimeParams params __attribute__((at(0x0801F800))) = {
 // ... initialization values
};

What would be the correct way to accomplish this?

[TDK]

There's not an easy way to do this in GCC. You either need to create a separate section in the linker to place the code, or use a pointer to store it somewhere directly while ensuring nothing else lives in that space.

[ERODR.1]

Thanks for your input. I created a new section in the linker as suggested.

[ERODR.1]

For anybody else wondering how to do it. I edited the STM32F072CBTX_FLASH.ld to add a new section as below:

 /* Runtime parameters section in FLASH */
 _params_start_address = 0x0801F800;
 
 .params _params_start_address :
 {
 . = ALIGN(4);
 KEEP (*(.params))
 } >FLASH

And then specified the section attribute in the const initialization as follows:

const runtimeParams __attribute__((section (".params"))) params = {
 // ... Initialization values
};

[rohittheozzy]

This creates an overlap with the .rodata for stm32f030, how do you get around this?

 

 

MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 8K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 64K
}

 

[gbm]

MEMORY
{
 RAM (xrw) : ORIGIN = 0x20000000, LENGTH = 8K
 FLASH (rx) : ORIGIN = 0x8000000, LENGTH = 64K
 PARAMFLASH (rx) : ORIGIN = 0x801F800, LENGTH = 2K
}

.params _params_start_address :
 {
 . = ALIGN(4);
 KEEP (*(.params))
 } >PARAMFLASH

This should be one step closer to what you want to achieve.

I assume however, that you want to keep the config data when flashing a new program. If this is the case, don't declare the structure as const, just make sure that the address is unused (outside of MEMORY ranges), then do this:

#define cfg_in_Flash (*(const struct cfgdata_ *)(CFG_ADDRESS))