Using binutils 2.43.1 for riscv32, RaspberryPi RP2350.

To support loading a program into flash, I need to insert 5 magic constants (so that the boot rom recognises the binary as a valid program image) “within the first 4 kB of a flash image”.

To do a similar job for an Espressif ESP32-H2’s ‘direct boot’ feature, where two magic constants are needed at the start of the binary, this worked:

    .header :
    {
        _rom_start = .;
        LONG(0xaedb041d)
        LONG(0xaedb041d)
    } >flash

    .text.entry ORIGIN(flash) + 8 :
    {
        KEEP(*(.program_entry))
    } >flash

but this doesn’t work for the RP2350 (the entry point is at the start of flash, rather than +8 for the ESP32-H2):

    .text.entry ORIGIN(flash):
    {
        KEEP(*(.program_entry));
        . = ALIGN(4);
        LONG(0xffffded3)
        LONG(0x11010142)
        LONG(0x000001ff)
        LONG(0x00000000)
        LONG(0xab123579)
    } >flash

The 5 constants are ignored, and all that appears in the binary is the *(.program_entry) code.

Must I provide this data in a C file?