Minimal copy-to-run payload – one image that runs from the SRAM run base. More...

#include <stdint.h>

Include dependency graph for payload.c:

Enumerations
enum	payload_probe_t : uintptr_t { k_payload_probe_sentinel = 0x22010000U , k_payload_probe_counter = 0x22010004U }
	Fixed SRAM probe words the bootloader leaves untouched. More...
enum	payload_sentinel_t : uint32_t { k_payload_sentinel_value = 0x9710C0DEU }
	Sentinel value ("#97 1 code"): this payload ran via copy-to-run. More...

Functions
void	payload_reset (void)
	Payload reset entry: set the sentinel, then advance a heartbeat forever.

Variables
uint32_t	g_ra8_ls_stack_top
	Initial-MSP symbol, defined by payload.ld at the top of the run region.
static const uintptr_t	s_vectors [2]
	2-entry vector table: initial MSP + reset, at the image base.

Detailed Description

Minimal copy-to-run payload – one image that runs from the SRAM run base.

Tag: [Ring 6 / APP] {World: S}

A tiny, self-contained application linked ONCE at the dfu_bootloader's SRAM run base (k_ra8_dfu_run_base = 0x22020000, see payload.ld). A copy-to-run launcher (ra8_dfu_launch) copies this image to that base and branches here, so the IDENTICAL .bin is bootable from Slot A or Slot B – the proof that copy-to-run removes the per-slot build (issue #97). It backs both the dfu_copy_to_run HIL demo (which embeds and launches it) and the bench staging of ../dfu_bootloader (which stages it into a real slot).

On entry it writes a distinctive sentinel and then advances a heartbeat counter forever, both at a fixed probe word that sits between the bootloader's low .bss and the run base (so neither the bootloader nor this image's copy touches it). A J-Link probe of those two words – plus a PC inside the SRAM run window – confirms the image ran via copy-to-run. Interrupts stay masked (the launcher masked them before the hand-off and this payload never re-enables them), so the 2-entry vector table is sufficient.

Build with examples/ek_ra8d2/hw_validated/hil/dfu_copy_to_run/scripts/ build_payload.sh (also emits payload_image.h for the demo).

Author: Brighton Sikarskie

Date: 2026-06-16

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file payload.c.

Enumeration Type Documentation

◆ payload_probe_t

enum payload_probe_t : uintptr_t

Fixed SRAM probe words the bootloader leaves untouched.

0x22010000 lies above the bootloader's low-SRAM footprint and below the run base, so it is owned by neither the bootloader nor this image.

Enumerator
k_payload_probe_sentinel	Sentinel word (proof-of-run).
k_payload_probe_counter	Heartbeat counter (liveness).

Definition at line 43 of file payload.c.

◆ payload_sentinel_t

enum payload_sentinel_t : uint32_t

Sentinel value ("#97 1 code"): this payload ran via copy-to-run.

Enumerator
k_payload_sentinel_value	Distinctive proof-of-run value.

Definition at line 49 of file payload.c.

Function Documentation

◆ payload_reset()

void payload_reset ( void )

Payload reset entry: set the sentinel, then advance a heartbeat forever.

Returns: Does not return.

Precondition: A copy-to-run launcher copied this image to k_ra8_dfu_run_base and set MSP.; Interrupts are masked (the launcher masked them before the hand-off).

Postcondition: The sentinel word holds k_payload_sentinel_value.; The heartbeat counter advances continuously.

Note: Bare entry: no C runtime, no .data/.bss (writes go to fixed addresses).; Non-static so the linker ENTRY(payload_reset) resolves (the launcher actually branches via the vector table, not the ELF entry).

Since: 0.1.0

Definition at line 70 of file payload.c.

References k_payload_probe_counter, k_payload_probe_sentinel, and k_payload_sentinel_value.

Variable Documentation

◆ g_ra8_ls_stack_top

uint32_t g_ra8_ls_stack_top

extern

Initial-MSP symbol, defined by payload.ld at the top of the run region.

◆ s_vectors

const uintptr_t s_vectors[2]

static

Initial value:

                                  = {
  (uintptr_t)&g_ra8_ls_stack_top, 
  (uintptr_t)&payload_reset,      
}

2-entry vector table: initial MSP + reset, at the image base.

The launcher reads [0] as the initial MSP and branches to [1]; the reset entry keeps its Thumb bit because it is a function address.

Since: 0.1.0

Definition at line 89 of file payload.c.

Enumerations

Functions

Variables