Define a section to consistently place rtt

Question

NCS 2.7 with sysbuild + mcuboot 
 NRF52840 (custom boards) 
 In my previous projects with NRF5 SDK I found it was very helpful to define a section in the linker so the rtt control block is always placed in the same place. This way when updating between different versions of the application or when running through the bootloader (if rtt output is enabled) the debugger always find the rtt control block. 
 How would I define this in zephyr? It seems like I need to add a linker ld script. 
 I tried adding it to my pm_static.yml but it doesn't appear to interface all the way to the linker. 
 rtt: address: 0x2003F800 end_address: 0x2003FC00 region: sram_primary size: 0x400

Anthony Ambuehl · Accepted Answer

I think I have this working. In my board dts file I added: 
 
 / { 
 
 sram @ 2003FB00 { 
 compatible = "zephyr,memory-region" ; 
 reg = < 0x2003FB00 0x500 >; 
 zephyr,memory-region = "rtt" ; 
 status = "okay" ; 
 }; 
 }; 
 
 In my application CMakeLists.txt I added:

zephyr_compile_definitions(SEGGER_RTT_SECTION= "rtt" ) 
 
 When I run a single image build I see this in my zephyr/zephyr_pre0.map 
 
 rtt 0x000000002003fb00 0x4b8
 0x000000002003fb00 __rtt_start = .
 *(SORT_BY_ALIGNMENT(rtt))
 rtt 0x000000002003fb00 0x4b8 modules/segger/libmodules__segger.a(SEGGER_RTT.c.obj)
 0x000000002003ff10 _SEGGER_RTT
 *(SORT_BY_ALIGNMENT(rtt.*))
 0x000000002003ffb8 __rtt_end = .
 0x00000000000004b8 __rtt_size = (__rtt_end - __rtt_start)
 0x000000002003fb00 __rtt_load_start = LOADADDR (rtt)

Define a section to consistently place rtt

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