How to place a variable or function at specific location in IAR compiler?

Question

I am using IAR Embedded Workbench for Renesas Syenrgy (ARM cortex M4) 7.40.5.9722

Code flash size : 1MB

Consider following example:

void function (void)
{
     unsigned char a;
     a = a+1;
}

I want to put this function at a specific location in flash. What is method for defining a user defined section for this code.

I have been gone through IAR compiler user guide and implemented a method mentioned as below:

#pragma default_function_attribute = @ "MY_FUNC"
void function (void)
{
     unsigned char a;
     a = a + 1;
}
#pragma default_function_attribute =

And in .icf file, i have added the section as follows :

define symbol region_VECT_start    = 0x00000000;
define symbol region_VECT_end      = 0x000003FF;
define symbol region_ROMREG_start  = 0x00000400;
define symbol region_ROMREG_end    = 0x000004FF;
define symbol region_FLASH_start   = 0x00000500;
define symbol region_FLASH_end     = 0x000BFFFF;  // Fklsh end address is modified from 0x000FFFFF to 0x000BFFFF
define symbol region_MY_FUNC_start = 0x000C0000;  // This statement is added
define symbol region_MY_FUNC_end   = 0x000FFFFF;  // This statement is added
define symbol region_RAM_start     = 0x20000000;
define symbol region_RAM_end       = 0x2002FFFF;
define symbol region_DF_start      = 0x40100000;
define symbol region_DF_end        = 0x40103FFF;
define symbol region_QSPI_start    = 0x60000000;
define symbol region_QSPI_end      = 0x63FFFFFF;

/* Stack and heap sizes are defined in bsp_cfg.h */

define memory mem with size     = 4G;
define region VECT_region       = mem:[from region_VECT_start   to region_VECT_end];
define region ROMREG_region     = mem:[from region_ROMREG_start to region_ROMREG_end];
define region FLASH_region      = mem:[from region_FLASH_start  to region_FLASH_end];
define region RAM_region        = mem:[from region_RAM_start    to region_RAM_end];
define region DF_region         = mem:[from region_DF_start     to region_DF_end];
define region QSPI_region       = mem:[from region_QSPI_start   to region_QSPI_end];
define region MY_FUNC           = mem:[from region_MY_FUNC_start to region_MY_FUNC_end];  // New section is added

With these changes, the code is compiling properly. But, "function" is not placed at required location 0x000C0000

Why is it so?

Answer 1

You can place _Pragma("location=\"__your_section__\"") in front of the function.

And then in the linker file (for example):

define block __your_section_block__ size = 0x100 { section __your_section__ };

And make sure you add the line to the linker:

place in MY_FUNC   { block __your_section_block__ };

Answer 2

You should change the definition of "MY_FUNC" to "MY_FUNC_region" in the .icf file to avoid confusions:

define region MY_FUNC_region     = mem:[from region_MY_FUNC_start to region_MY_FUNC_end];

And then add the following line to place the "MY_FUNC" code inside the "MY_FUNC_region":

place in MY_FUNC_region   { readonly section MY_FUNC };  

(Not entirely sure if "readonly" keyword is absolutely needed but works for me)

Or, alternatively:

place at address mem:region_MY_FUNC_start { readonly section MY_FUNC};