repair.c

系统迁移的源代码： http://www.diku.dk/hjemmesider/ansatte/jacobg/

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <string.h>


#define PAGE_SIZE 4096
#define O_DIRECT      040000

extern void sha1_digest(unsigned char* out, unsigned char* data, size_t len);

unsigned char page_digests[0x1000][20];

void hex(char* out, unsigned char* in)
{
	int i;
	char* o = out;
	char digits[] = "0123456789abcdef";
	for(i=0; i<20; i++)
	{
		char c = *in++;
		*o++= digits[(c & 0xf0)>>4];
		*o++= digits[ c & 0xf];
	}
	*o = '\0';
}

int main(int argc, char** argv)
{
	int i;
	int o,f;
	size_t loader_size;
	char* loader = mmap(0, 8*PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0,0);
	unsigned long offset = 0;
	unsigned long loader_pages;

	unsigned char final_digest[20];
	char dout[41];

	if(argc!=3)
	{
		puts("usage: repair disk checkpoint-no");
		exit(-1);
	}


	o = open("/tmp/chk.img",O_WRONLY|O_CREAT);
	if(o<0)
	{
		puts("could not open /tmp/chk.img for write!");
		exit(-1);
	}

	printf("input from %s\n",argv[1]);
	f = open(argv[1], O_RDONLY|O_DIRECT);
	if(f<0)
	{
		printf("could not open %s for read!\n",argv[2]);
		exit(-1);
	}

	printf("offset %d\n",atoi(argv[2]));
	offset = atoi(argv[2]) * 4200 * PAGE_SIZE;

	for(i=0; i<(0x1000+3); i++)
	{
		if(lseek(f, offset + i*PAGE_SIZE, SEEK_SET)<0)
		{
			puts("seek err\n");
			exit(-1);
		}

		if(read(f,loader,PAGE_SIZE) < 0)
		{
			puts("read err\n");
			exit(-1);
		}

		if(i>=2 && i<0x1002)
		{
			
			sha1_digest(page_digests[i-2],(unsigned char*)loader,PAGE_SIZE);
		}

		lseek(o, i*PAGE_SIZE, SEEK_SET);
		if(write(o,loader,PAGE_SIZE) < 0)
		{
			puts("write err\n");
			exit(-1);
		}
	}
	close(f);




	f = open("/bin/loader", O_RDONLY);
	if(f<0) f = open("loader", O_RDONLY);

	memset(loader,0,8*PAGE_SIZE);

	/* to work with O_DIRECT, we need to correctly align the loader. 512 bytes should be
	 * enough, but let's do PAGE_SIZE for now
	 */

	if(f>=0)
	{
		size_t* a;
		loader_size = read(f,loader+4, 8*PAGE_SIZE);
		close(f);
		loader_pages = (loader_size + 3*sizeof(size_t) + (PAGE_SIZE-1)) / PAGE_SIZE;
		printf("loader pages %d\n", (int)loader_pages);
		a = (size_t*) loader;

		/* first long has length of loader minus arguments */
		*a = loader_pages*PAGE_SIZE - 12;

		a = (size_t*) ( loader+loader_pages * PAGE_SIZE - 8);
		*a++ = sizeof(size_t);  /* four bytes of args */
		*a++ = 0x1000;          /* argument: number of pages in checkpoint */

		/* so loader and arguments ended up page-aligned after all */

	}
	else
	{
		puts("no file: 'loader'");
		exit(-1);
	}
	/* write the loader and its args */
	lseek(o, 0, SEEK_SET);
	write(o, loader, loader_pages * PAGE_SIZE);




	close(f);
	close(o);

	sha1_digest(final_digest,page_digests[0],sizeof(page_digests));
	hex(dout,final_digest);

	printf("checkpoint chksum is %s\n",dout);

	return 0;
}