i want to make a checksum of linux kernel ,with the CRC arigorithm.but i didn't work. i 'm confused .
The code is following:
////////////////////////////////////////////////////////////////////////
// the kernel is no matter, i use the kernel at the url:
//ftp://ftp.arca.com.cn/pub/Arca-Products/5Software/2os/linux/v2.4.18/binary/vm-draco
#include <stdio.h>
#include <stdlib.h>
#define KERNEL_SIZE 14911305 //bytes£¬here is the true size of kernel£®
int main(int argc,char *argv[])
{
unsigned char *crc_input=malloc(sizeof(char)*KERNEL_SIZE£«£±);
unsigned long crc_output;
FILE *fp;
int i;
if (!crc_input){
printf("out of memory. \n");
exit(1);
}
//vm-draco is a kernel where is in the url:
//ftp://ftp.arca.com.cn/pub/Arca-Products/5Software/2os/linux/v2.4.18/binary/vm-draco
if((fp=fopen("vm-draco","rb"))==NULL){
printf("Cannot open file. \n");
exit(1);
}
fseek(fp,0,SEEK_SET);
fread(crc_input,sizeof(char),KERNEL_SIZE,fp);
crc_input[KERNEL_SIZE]=0;
fclose(fp);
//crc_input="polynomial";
crc_output=crc32(crc_input,KERNEL_SIZE); // the CRC32 function is in Linux /// source code , not listed here.
printf("the crc_input is : 0x%x \n",crc_input);
printf("the length of crc_input is: %d \n",strlen(crc_input));
printf("the crc_output is :0x%x\n",crc_output);

free(crc_input);
return 0;
}
///////////////////////////////////////////////
but the result is:
the crc_input is : 0x40029008
the length of crc_input is: 7
the crc_output is : 0xa4ae400c

why?
1.why the length of crc_input is 7?
2.i have test the checksum of the kernel in Windows with some checksum tools ,but the CRC checksum is 0x7adfb959.
If my program is wrong ,how can i get the CRC checksum of kernel ???

Thanks a lot .


best regards..

yours alphasophie.

What the hell is stuff like «£± supposed to be? Please use code tags when posting code.

sorry,i don't understand your words completely.
my english is a bit poor.
but i just want to make a checksum of kernel,
perhaps i didn't descripte it clearly.
any advice? your help is needed.

presumeably the eighth byte of your kernel image is 0; thus strlen() sees a string of seven bytes.

I don't know what library you found the crc32() function in so I can't tell if you're using it correctly.

thanks a lot for your reply,
first,the kernel image indeed contain some ugly chars not shown as ASCII code,perhaps
as you said ,the eighth byte is 0,i am to check it.but how to solve it? The CRC tool can get correct checksum,it should use some correct method to solve the problem,what is it?
second ,the crc32() function is in linux/addon/cipe/crc32.c, i think it is in correct use.
as following:
///////////////////////////////////////////////
// COPYRIGHT (C) 1986 Gary S. Brown.
static unsigned long crc32_tab[] = {
0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
...........
}
/* Return a 32-bit CRC of the contents of the buffer. */

unsigned long crc32(unsigned char *s, unsigned int len)
{
unsigned int i;
unsigned long crc32val;

crc32val = 0;
for (i = 0; i < len; i ++)
{
crc32val =
crc32_tab[(crc32val ^ s[i]) & 0xff] ^
(crc32val >> 8);
}
return crc32val;
}
/////////////////////////////////////////////

best regards and your help is needed.

any advise?

the only error I see left is that crcinput should be KERNEL_SIZE+1 bytes long, not just KERNEL_SIZE. (I'm assuming the garbled characters in the malloc call aren't a +1..) I don't think this is what's causing your problem though. not sure what is.

thanks a lot ,aluser.
let me try again