mapfile.c

开放源码的Boot

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <linux/fs.h>

extern void *xmalloc (size_t size);
extern void *xrealloc (void *ptr, size_t size);
extern char *boot_dev;
extern int verbose;

static dev_t boot_dev_nr = -1;

dev_t get_dev (const char *path)
{
	struct stat statbuf;

	if (stat (path, &statbuf) < 0)
	{
		perror ("stat");
		return -1;
	}

	if (S_ISBLK(statbuf.st_mode))
		return statbuf.st_rdev;
	else
		return statbuf.st_dev;
}

dev_t get_boot_dev (void)
{
	if (boot_dev_nr == (dev_t)-1)
		boot_dev_nr = get_dev (boot_dev);
	return boot_dev_nr;
}

/*
 * get the block map for a file, checking that it is on the root partition
 */
int map_file(const char *path, unsigned long **bmap)
{
	int fild;
	struct stat statbuf;
	unsigned long *buffer, blksize, fblocks;
	unsigned int blw, curblkindex, blk;

	if (get_boot_dev() == (dev_t)-1)
		return -1;

	if (boot_dev_nr != get_dev (path)) {
		fprintf(stderr, "Kernel '%s' is not on the boot device '%s' "
			"- ignored\n", path, boot_dev);
		return -1;
	}

	fild = open(path, O_RDONLY, 0);
	if (fild < 0) {
		perror("open");
		return -1;
	}
	if (ioctl(fild, FIGETBSZ, &blksize) < 0) {
		perror("ioctl FIGETBSZ");
		close(fild);
		return -1;
	}
	if (fstat(fild, &statbuf) < 0) {
		perror("fstat");
		close(fild);
		return -1;
	}

	fblocks = (statbuf.st_size + blksize - 1) / blksize;

	if (verbose)
		printf("map_file(%s, %ld blocks): ", path, fblocks);

	curblkindex = 0;
	blw = 64;
	blk = 0;
	buffer = xmalloc (blw * 4);
	buffer[0] = 0xC53A4B2D;
	buffer[1] = blksize;

	for (blk = 0; blk < fblocks; blk++) {
		volatile unsigned long fibmap_blk;

		fibmap_blk = blk;
		if (ioctl(fild, FIBMAP, &fibmap_blk) < 0) {
			perror("ioctl FIBMAP");
			close(fild);
			return -1;
		}

		if (verbose)
			printf("[%05lX] ", fibmap_blk);

		if (fibmap_blk == 0) {
			fprintf(stderr, "Unable to map file '%s' (has holes).\n", path);
			close(fild);
			return -1;
		}

		if (curblkindex >= 2 && buffer[curblkindex] + buffer[curblkindex + 1] == fibmap_blk)
			buffer[curblkindex + 1] += 1;
		else {
			curblkindex += 2;
			if (curblkindex >= blw)
				buffer = xrealloc (buffer, (blw *= 2) * 4);

			buffer[curblkindex] = fibmap_blk;
			buffer[curblkindex + 1] = 1;
		}
	}
	curblkindex += 2;
	buffer[curblkindex] = 0;
	buffer[curblkindex+1] = 0;
	curblkindex += 2;

	if (verbose)
		printf("\n");

	if (buffer[0] != 0)
		*bmap = buffer;
	return curblkindex * sizeof (unsigned long);
}