For those interested: here is how I managed to partially solve the problem:
- Dearchive the *,a library (in my case it is libSTM32Cryptographic_CM7.a) into a separate directory using 7-zip. It will create a collection of *.o files; there is also a 1.txt file listing the functions defined in each module.
- dir /b >file_list.txt to create a list of all *.o files; open it in editor
- cut the list of names of all *.o files only and paste them in the new section definition. In my case, it will look as follows
.itcm_text :
{
. = ALIGN(4);
itcm_text_start = .;
*(.itcm_text) /* Fast-executing code */
*(.itcm_text*) /* Fast-executing code */
cmox_aesfast_decrypt.c.o
cmox_aesfast_encrypt.c.o
cmox_aessmall_decrypt.c.o
cmox_aessmall_encrypt.c.o
cmox_aes_common.c.o
cmox_bn.c.o
....
. = ALIGN(4);
itcm_text_end = .;
} >ITCMRAM /* AT >FLASH*/
The AT>FLASH will be needed only if the program is designed for flash storage.
This is a brute force method, but the linker will only pick the modules which are called from the user program, and eliminates the unused modules.
Interestingly, the trick moved not only the code, but also the constant tables for the cryptographic functions into ITCM. It might be good to place them in the DTCM for faster access, but I did not yet learn how to do it.
One more hint: the sections are defined as following; that allows to aggregate and remap them:
