image_scan.c

QNX ADS BSP code for i.MX27 chips

/*
 * $QNXLicenseC: 
 * Copyright 2007, QNX Software Systems.  
 *  
 * Licensed under the Apache License, Version 2.0 (the "License"). You  
 * may not reproduce, modify or distribute this software except in  
 * compliance with the License. You may obtain a copy of the License  
 * at: http://www.apache.org/licenses/LICENSE-2.0  
 *  
 * Unless required by applicable law or agreed to in writing, software  
 * distributed under the License is distributed on an "AS IS" basis,  
 * WITHOUT WARRANTIES OF ANY KIND, either express or implied. 
 * 
 * This file may contain contributions from others, either as  
 * contributors under the License or as licensors under other terms.   
 * Please review this entire file for other proprietary rights or license  
 * notices, as well as the QNX Development Suite License Guide at  
 * http://licensing.qnx.com/license-guide/ for other information. 
 * $ 
 */


/*
 *	image_scan: Scan through memory looking for an image 
*/

#include "ipl.h"

char					scratch [512];
struct startup_header	startup_hdr;

int zero_ok (struct startup_header *shdr) {
	return(shdr->zero[0] == 0 &&
           shdr->zero[1] == 0 &&
           shdr->zero[2] == 0 && 
           shdr->zero[3] == 0);
}

//
// This calculates the sum of an array of 4byte numbers
//

int small_checksum(int *iray, long len) {
	int sum;
	sum = 0;
	while (len > 0) {
		sum += *iray++;
		len -= 4;
	}
	return(sum);
}

//
// Return the total sum of bytes in memory, len/4 = integer
//

int checksum (unsigned long addr, long len) {
	int sum = 0;

	while (len >= sizeof scratch) {
		copy ((unsigned long) scratch, addr, sizeof(scratch));
		sum += small_checksum ((int *)scratch, sizeof(scratch));
		len -= sizeof(scratch);
		addr += sizeof(scratch);
	}
	if (len) {
		copy ((unsigned long)scratch, addr, len);
		sum += small_checksum ((int *)scratch, len);
	}
	
	return(sum);
}

//
//     Scan 1k boundaries for the image identifier byte and
//     then does a checksum on the image.
//

unsigned long image_scan (unsigned long start, unsigned long end) {
	unsigned long 	lastaddr = -1;
	unsigned short 	lastver = 0;
	 
	//
	// We assume that the images will all start on a 4 byte boundary
	//

	for (; start < end; start += 4) {
	
		copy ((unsigned long)(&startup_hdr), start, sizeof(startup_hdr));

		//
		//	No endian issues here since stored "naturally"
		//

		if (startup_hdr.signature != STARTUP_HDR_SIGNATURE)
			continue;

		//
		// There are two checksums, one for the startup hdr
		// and one for the image.  Check both of them.
		//

		if (checksum (start, startup_hdr.startup_size) != 0){
			continue;
		}

		if (checksum (start+startup_hdr.startup_size, 
					  startup_hdr.stored_size-startup_hdr.startup_size) != 0)
			continue;
		

		//
		// Stash the version and address and continue looking
		// for something newer than we are (jump ahead by
		// startup_hdr.stored_size)
		//

		if (startup_hdr.version > lastver) {
			lastver = startup_hdr.version;
			lastaddr = start;
		}
		
		start += startup_hdr.stored_size - 4;
	}
	return(lastaddr);
}