Problem adding section to linker script

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This topic contains 15 replies, has 2 voices, and was last updated by  engicoder 5 years, 10 months ago.

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  • #10224

    engicoder
    Participant

    I am trying to add a section to flash memory to store user settings that would be updated by using the FLASH erase/program functions. I copied the default flash linker script for the device I am using (STM32F030R8), modified it, and updated the project settings to use the modified script.

    Here is the modified section of the linker script:

    I added a variable to my code and used the __attribute__(__section__()) attribute to assign it to the new .settings section.

    The code builds fine but when I try to program the device using GDB I get an error on the load indicating that the size of my new section does match the “loaded file”.

    Am I missing something?

    • This topic was modified 5 years, 10 months ago by  engicoder.
    • This topic was modified 5 years, 10 months ago by  engicoder.
    • This topic was modified 5 years, 10 months ago by  engicoder.
    • This topic was modified 5 years, 10 months ago by  engicoder.
    #10232

    engicoder
    Participant

    Note: There is a mismatch in the info above. The array dimension is 512, but should be 64. The error dump is when the array length was 64, hence the section size of 128. I tried both array sizes.

    #10235

    support
    Keymaster

    Hi,

    Please check the contents of the OpenOCD window for more specific error messages. This should explain why FLASH programming fails.

    #10238

    engicoder
    Participant

    Where do I find the OpenOCD window? If you mean the test OpenOCD settings, the runs successfully. The errors I am seeing are coming from GDB after OpenOCD connects successfully.

    • This reply was modified 5 years, 10 months ago by  engicoder.
    #10240

    support
    Keymaster

    Hi,

    The testing only checks the JTAG connectivity and does not try to load the FLASH. In order to see FLASH-related errors, please select Debug->Windows->GDBServer Console.

    #10246

    engicoder
    Participant

    I don’t see a GDBServer Console under Debug->Windows

    The problem I am seeing occur when I select Debug->Program and Start without Debugging

    First I see this popup:

    When I click on View GDB log I see this popup

    If I select the GDB Server log tab I see this:

     

    If I remove any references to the array declared

    __attribute__((__section__(".settings"))) const uint16_t settings[64];

    It programs without problem.

    • This reply was modified 5 years, 10 months ago by  engicoder.
    #10248

    engicoder
    Participant

    I created a project using the Standard Peripheral template and replace LEDBlink.cpp with main.c

    Here is the source for main.c

    #10249

    support
    Keymaster

    Hi,

    The “GDBServer Console” command will only be available during debugging, so you can view it after pressing F5.

    Based on the other details you provided, it looks like OpenOCD may have troubles programming sections that are not properly aligned. Please try modifying your linker script to place the new section inside the .text section:

     

    #10267

    engicoder
    Participant

    Thanks for the quick replies!
    I tried what you suggested. Flash is 64K so should extend to 0x08010000. Subtracting 1K gives us 0x0800C00 as the address for the .settings section.
    Using the following linker script:

    I get a linker error:

    I got the same result if I try to create a separate section declaration as follows:

    • This reply was modified 5 years, 10 months ago by  engicoder.
    #10269

    support
    Keymaster

    Hi,

    Please try using the section-relative address, i.e.

    • This reply was modified 5 years, 10 months ago by  support.
    • This reply was modified 5 years, 10 months ago by  support.
    #10274

    engicoder
    Participant

    Thank you, that worked. I did have to compensate for the standard .isr_vector section that comes before text. In the default linker scrip there are also some sections that follow .text such as .ARM.extab, .init_array, .fini_array, etc. These seemed to be have sizes of zero, but I assume that is not always the case. Using your suggest as a hint, I was able to write a section definition that I placed after all other FLASH sections and calculate the current offset.

    Oddly two other seemingly equivalent offset expressions generated a linker overflow error:
    . = 0x0800FC00;
    . = . + 0x0800FC00 - .;
    I assume this has to do with how the linker evaluates the expressions.

    For future readers, following is the FLASH section of the default linker script with the above addition.

    I would still like to understand why I could not create a separate MEMORY entry and associate a section with it.

    • This reply was modified 5 years, 10 months ago by  engicoder.
    #10279

    support
    Keymaster

    Hi,

    Most likely something went wrong with the alignment and one of the sections ended up not being aligned properly. Running “arm-eabi-objdump -h <ELF file>” and checking the section addresses and sizes could explain what could be wrong.

    #10288

    engicoder
    Participant

    How do I generate an elf file with an MSBuild based project, like the ones created by the template?

    #10290

    engicoder
    Participant

    Ah, my mistake, it is generated, it just doesn’t have a .elf extension. The elf file has no extension.

    #10293

    support
    Keymaster

    No problem. Let us know if you need advice on interpreting the section offsets/sizes.

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