Background Checksum integrity monitor implementation. More...

#include "icarus/icarus.h"
#include <string.h>

Data Structures
struct	cs_entry_t
	Per-region entry in the monitor table. More...

Macros
#define	CS_SELFTEST_EXPECTED 0x29B1u
	Known CRC16-CCITT test vector.

Functions
static bool	cs_selftest (void)
	Run the CRC engine self-test against a known vector.

void	__cs_init (void)
	Privileged implementation of cs_init().

void	__cs_set_callback (cs_mismatch_fn fn)
	Privileged implementation of cs_set_callback().

bool	__cs_add_region (uint8_t idx, const uint8_t *addr, uint32_t size)
	Privileged implementation of cs_add_region().

bool	__cs_enable (uint8_t idx, bool enabled)
	Privileged implementation of cs_enable().

bool	__cs_rebaseline (uint8_t idx)
	Privileged implementation of cs_rebaseline().

uint8_t	__cs_check_all (void)
	Privileged implementation of cs_check_all().

bool	__cs_get_region (uint8_t idx, cs_region_t *out)
	Privileged implementation of cs_get_region().

uint8_t	__cs_region_count (void)
	Privileged implementation of cs_region_count().

Variables
static cs_entry_t	regions [8]
	Region table — privileged DTCM, zero wait-state.

static cs_mismatch_fn	mismatch_cb
	User-supplied mismatch callback.

static bool	cs_hw_ok
	CRC engine self-test result.

Detailed Description

Background Checksum integrity monitor implementation.

Version: 0.1.0

Maintains a table of up to CS_MAX_REGIONS memory regions, each with a baseline CRC16-CCITT. cs_check_all() recomputes the CRC over each enabled region and invokes the mismatch callback on any discrepancy.

CRC computation uses crc16_ccitt() from icarus/crc.h, which runs on the STM32H7 hardware CRC peripheral on target and falls back to a software loop under HOST_TEST.

cs_init() performs a self-test of the CRC engine against a known test vector ("123456789" → 0x29B1 for CRC16-CCITT). If the self-test fails (e.g. HW CRC peripheral damaged by radiation), the cs_hw_ok flag is cleared and cs_check_all() reports region index 0xFF via the mismatch callback to signal a CRC engine failure.

Memory placement:

Region table + state: DTCM_DATA_PRIV
All functions: ITCM_FUNC

Author: Souham Biswas

Date: 2026

Copyright: Copyright 2025-2026 Souham Biswas https://github.com/ironhide23586/icarus-os-core Licensed under the Apache License, Version 2.0

Definition in file cs.c.

Macro Definition Documentation

◆ CS_SELFTEST_EXPECTED

#define CS_SELFTEST_EXPECTED 0x29B1u

Known CRC16-CCITT test vector.

"123456789" (9 bytes) → CRC = 0x29B1 per ITU-T V.41.

Definition at line 65 of file cs.c.

Function Documentation

◆ __cs_add_region()

bool __cs_add_region	(	uint8_t	idx,
		const uint8_t *	addr,
		uint32_t	size
	)

Privileged implementation of cs_add_region().

Parameters

[in]	idx	Region index.
[in]	addr	Start address.
[in]	size	Size in bytes.

Return values

true	Region registered and baseline CRC computed.
false	Invalid parameters.

Computes the baseline CRC immediately from the current memory contents using crc16_ccitt() (HW-accelerated on target, software fallback under HOST_TEST).

Definition at line 118 of file cs.c.

References cs_entry_t::addr, cs_entry_t::baseline, crc16_ccitt(), CS_MAX_REGIONS, cs_entry_t::enabled, regions, cs_entry_t::registered, and cs_entry_t::size.

Referenced by cs_add_region(), and SVC_Handler_C().

◆ __cs_check_all()

uint8_t __cs_check_all ( void )

Privileged implementation of cs_check_all().

Returns: Number of regions that failed the CRC check.

First checks cs_hw_ok; if the CRC engine itself is suspect, invokes the callback with region_idx = 0xFF (sentinel) and returns 1 without scanning any regions.

Otherwise iterates all enabled regions, recomputes CRC, and invokes the callback for each mismatch.

Definition at line 172 of file cs.c.

References crc16_ccitt(), cs_hw_ok, CS_MAX_REGIONS, cs_entry_t::enabled, mismatch_cb, and regions.

Referenced by cs_check_all(), and SVC_Handler_C().