main.c File Reference

CPU0 (M85) Secure fallback entry for the TZ ping-pong demo. More...

#include <stdint.h>
#include "ra8_boot_entry.h"

Include dependency graph for main.c:

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Functions
void	main (void)
	CPU0 S-side fallback entry point.

Variables
volatile uint32_t	g_cpu1_pingpong_s_fallback_count = 0U
	Bench diagnostic: bumps when the S-side fallback main runs.

Detailed Description

CPU0 (M85) Secure fallback entry for the TZ ping-pong demo.

Tag

[Ring 1 / app] {World: S}

On the happy path this function is never reached. SystemInit calls ra8_trustzone_init, which programmes the SAU, writes IPCSAR=0x00050000, releases CPU1 via ra8_cpu1_release (still in S), then BLXNS-es into the NS image at 0x02080000 (ns_reset_handler in ns_main.c). BLXNS does not return on hardware, so the Reset_Handler step that calls main() is unreachable.

If the BLXNS path fails – the NS vector table is blank, the SAU could not be programmed, or the IPCSAR write was rejected – the secure-boot library returns and main becomes the fallback. We stamp a diagnostic counter so the bench memprobe can distinguish "BLXNS succeeded -> main never ran" (counter stays 0) from "BLXNS failed -> main ran" (counter advances). The fallback then parks the CPU in a NOP loop so it cannot accidentally touch the NS-attributed IPC channels (which would BusFault in S state).

Copyright

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

Since

0.1.0

Definition in file main.c.

Function Documentation

main()

void main

(

void

)

CPU0 S-side fallback entry point.

The application entry point Reset_Handler hands control to.

See file header.

Precondition

Boot init has completed.

The secure-boot library's BLXNS into NS image either failed or was skipped (the call site in ra8_trustzone_init is a no-op on host builds).

Postcondition

Diagnostic counter latched, CPU parked in a halt loop.

Function never returns.

Note

Single-threaded entry.

Since

0.1.0

Definition at line 67 of file main.c.

References g_cpu1_pingpong_s_fallback_count.

Variable Documentation

g_cpu1_pingpong_s_fallback_count

volatile uint32_t g_cpu1_pingpong_s_fallback_count = 0U

Bench diagnostic: bumps when the S-side fallback main runs.

Stays 0 on the happy path because BLXNS in ra8_trustzone_init never returns. Any non-zero value means the secure-boot library bailed out before transferring control to the NS image – bench scripts should treat that as a regression in the TZ scaffolding, not in the NS ping-pong logic.

Note

Read externally by J-Link only; firmware never reads back.

Since

0.1.0

Definition at line 49 of file main.c.

Referenced by main().