GNU linker marking section with no initialized data for LOAD - Raw binary huge

Question

I'm writing a bare metal ARM boot loader and am trying to use some internal SRAM as a scratch pad to communicate to the application code. For my needs I don't need to initialise or zero the memory. Using this script I can place my desired variables in the memory just fine.

/**
 * Linker script for secondary bootloader.
 *
 * Allocatest the first 1Mb of DRAM for its use.
 * Scratchpad in internal SRAM.
 */

MEMORY
{
    SRAM : o = 0x402F0400, l = 0x0000FC00  /* 63kB available internal SRAM */
    DDR0 : o = 0x80000000, l = 1M          /* 1Mb external DDR Bank 0 */
}

OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
OUTPUT_ARCH(arm)

SECTIONS
{
    .startcode :
    {
        __AppBase = .;
        . = ALIGN(4);
        *init.o      (.text)
    } >DDR0

    .text :
    {
        . = ALIGN(4);
        *(.text*)
        *(.rodata*)
    } >DDR0

    .data :
    {
        . = ALIGN(4);
        *(.data*)
    } >DDR0

    .bss :
    {
        . = ALIGN(4);
        _bss_start = .;
        *(.bss*)
        *(COMMON)
        _bss_end = .;
    } >DDR0

    .stack :
    {
        . = ALIGN(4);
        __StackLimit = . ;
        *(.stack*)
        . = __AppBase + 1M;
        __StackTop = .;
    } >DDR0
    _stack = __StackTop;

    .internal_ram :
    {
        . = ALIGN(4);
        *(.internal_ram*)
    } >SRAM
}

When using objcopy to create the raw binary, I'm getting huge files. I'm assuming this is because the first bytes of the raw binary are actually the internal memory with megabytes of padding up to the start of the .text section. Objdump -h shows that the internal_ram section being marked with the CONTENTS, LOAD, and DATA flags even though the variables placed there are not initialised.

I can clean this up in objcopy using --remove-section=.internal_ram but it seems there should be a way to get the linker to recognise that the data is not initialised.

Is there a way to mark the section appropriately?

Answer 1

The correct section declaration is:

.internal_ram (NOLOAD) :
{
    . = ALIGN(4);
    *(.internal_ram*)
} >SRAM

The NOLOAD section attribute is documented but speaks in terms of program loaders handling the section at load time. At first this doesn't seem to apply to bare metal images but, for that purpose, objcopy acts like a program loader and honors the flag settings in the object file, omitting the section from the raw image.