I also made some BLE DFU OTA code for gcc just today and I made this changes to nrf6310\device_firmware_updates\bootloader project:

1. Linker scripts:

1.1. gcc_nrf51_common.ld

Add sections:

    SECTIONS
    {
        .bootloader_settings_block 0x0003FC00 :
        {
            KEEP(*(.bootloader_settings_sect))
        } > bootloader_settings

        .NRF_UICR_BOOT_START_BLOCK 0x10001014 :
        {
            KEEP(*(.NRF_UICR_BOOT_START_SECT))
        } > NRF_UICR_BOOT_START
    ...
    }

1.2. gcc_nrf51_s110_xxaa.ld

    MEMORY
    {
      FLASH (rx) : ORIGIN = 0x3C000, LENGTH = 0x3C00 /* bootloader */
      bootloader_settings (rwx) : ORIGIN = 0x3FC00, LENGTH = 0x400 /* bootloader specific settings */
      NRF_UICR_BOOT_START (rwx) : ORIGIN = 0x10001014, LENGTH = 0x4 /* bootloader start address in UICR register */
      RAM (rwx) : ORIGIN = 0x20002000, LENGTH = 0x2000 /* 8 kB, 8 kB is taken by S110. */
    }

2. bootloader_util_arm.c

        uint8_t __attribute__((section (".bootloader_settings_sect"))) m_boot_settings[CODE_PAGE_SIZE] __attribute__((used));
        uint32_t __attribute__((section (".NRF_UICR_BOOT_START_SECT"))) m_uicr_bootloader_start_address = BOOTLOADER_REGION_START;


        inline void StartApplication(uint32_t start_addr)
        {
            asm volatile("LDR   R2, [R0]               \n\t" // Get App MSP.
                         "MSR   MSP, R2                \n\t" //Set the main stack pointer to the applications MSP.
                         "LDR   R3, [R0, #0x00000004]  \n\t" //Get application reset vector address.
                         "BX    R3                     \n\t" //No return - stack code is now activated only through SVC and plain interrupts.
                         ".ALIGN"
                        );
        }

3. dfu_types.h

        #define BOOTLOADER_REGION_START         0x0003C000

4. pstorage_platform.h
I had error from some check in pstorage, so I had to change PSTORAGE_MIN_BLOCK_SIZE value from 0x0010 to 0x000C:

        #define PSTORAGE_MIN_BLOCK_SIZE     0x000C

UPD:
But I think additional padding word for bootloader_settings_t is better solution for PSTORAGE_MIN_BLOCK_SIZE problem.
UPD2:
And with -Os optimization I have:


    'Invoking: Cross ARM GNU Print Size'
    arm-none-eabi-size  --format=berkeley "nRF51822_BLE_DFU.elf"
       text	   data	    bss	    dec	    hex	filename
      13988	   2128	   2096	  18212	   4724	nRF51822_BLE_DFU.elf
    'Finished building: nRF51822_BLE_DFU.siz'
    ' '

Compiled with gcc version 4.8.3 20131129 (release) [ARM/embedded-4_8-branch revision 205641] (GNU Tools for ARM Embedded Processors).

UPD3:
I forgot that I deleted DFU start from button push and replaced it with NRF_POWER->GPREGRET check so code size was a bit smaller.
With button usage:


    'Invoking: Cross ARM GNU Print Size'
    arm-none-eabi-size  --format=berkeley "nRF51822_BLE_DFU.elf"
       text	   data	    bss	    dec	    hex	filename
      14128	   2136	   2096	  18360	   47b8	nRF51822_BLE_DFU.elf
    'Finished building: nRF51822_BLE_DFU.siz'
    ' '

UPD4:
I attached eclipse project for bootloader.

UPD 2014.06.26:

I attached updated eclipse project for bootloader:

[C:\fakepath\Eclipse_workspace_2.rar](/attachment/50d398306ed418fa1a9fc86385457b3f)

Changes:

 - Added the function of simultaneous flashing bootloader and application via J-Link from this question:
https://devzone.nordicsemi.com/question/12800/flashing-bootloader-and-application-via-j-link/

 - Added additional optimization as Joe Merten suggested:
--specs=nano.specs
-flto
For -flto optimization you need to change your SDK files and add __attribute__ ((used, section(".Vectors"))) to the IRQ handlers (GPIOTE_IRQHandler, RTC1_IRQHandler, SWI0_IRQHandler, SWI2_IRQHandler) like this:

        void __attribute__ ((used, section(".Vectors"))) GPIOTE_IRQHandler(void)
        {
        ...
        }

in files:

    app_common/app_gpiote.c
    app_timer/app_gpiote.c
    sd_common/softdevice_handler.c

To tim,
I don't use makefile, but you can find autogenerated by Eclipse makefile in attached Eclipse_workspace_2.rar in this folder:

nRF51822_BLE_DFU_flashing_with_app\Debug

But if you want to use pure Makefile project then I would suggest you use the Joe Merten's project.