rd.c

arm平台上的uclinux系统全部源代码

/*
 * ramdisk.c - Multiple ramdisk driver - gzip-loading version - v. 0.8 beta.
 * 
 * (C) Chad Page, Theodore Ts'o, et. al, 1995. 
 *
 * This ramdisk is designed to have filesystems created on it and mounted
 * just like a regular floppy disk.  
 *  
 * It also does something suggested by Linus: use the buffer cache as the
 * ramdisk data.  This makes it possible to dynamically allocate the ramdisk
 * buffer - with some consequences I have to deal with as I write this. 
 * 
 * This code is based on the original ramdisk.c, written mostly by
 * Theodore Ts'o (TYT) in 1991.  The code was largely rewritten by
 * Chad Page to use the buffer cache to store the ramdisk data in
 * 1995; Theodore then took over the driver again, and cleaned it up
 * for inclusion in the mainline kernel.
 *
 * The original CRAMDISK code was written by Richard Lyons, and
 * adapted by Chad Page to use the new ramdisk interface.  Theodore
 * Ts'o rewrote it so that both the compressed ramdisk loader and the
 * kernel decompressor uses the same inflate.c codebase.  The ramdisk
 * loader now also loads into a dynamic (buffer cache based) ramdisk,
 * not the old static ramdisk.  Support for the old static ramdisk has
 * been completely removed.
 *
 * Loadable module support added by Tom Dyas.
 *
 * Further cleanups by Chad Page ([e-mail]):
 *	Cosmetic changes in #ifdef MODULE, code movement, etc...
 * 	When the ramdisk is rmmod'ed, free the protected buffers
 * 	Default ramdisk size changed to 2.88MB
 *
 *  Added initrd: Werner Almesberger & Hans Lermen, Feb '96
 *
 * 4/25/96 : Made ramdisk size a parameter (default is now 4MB) 
 *		- Chad Page
 */

#include <linux/config.h>
#include <linux/sched.h>
#include <linux/minix_fs.h>
#include <linux/ext2_fs.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/malloc.h>
#include <linux/ioctl.h>
#include <linux/fd.h>
#include <linux/module.h>

#include <asm/system.h>
#include <asm/segment.h>

extern void wait_for_keypress(void);

/*
 * 35 has been officially registered as the RAMDISK major number, but
 * so is the original MAJOR number of 1.  We're using 1 in
 * include/linux/major.h for now
 */
#define MAJOR_NR RAMDISK_MAJOR
#include <linux/blk.h>

/* The ramdisk size is now a parameter */
#define NUM_RAMDISKS 16		/* This cannot be overridden (yet) */ 

#ifndef MODULE
/* We don't have to load ramdisks or gunzip them in a module... */
#define RD_LOADER
#define BUILD_CRAMDISK

void rd_load(void);
static int crd_load(struct file *fp, struct file *outfp);

#ifdef CONFIG_BLK_DEV_INITRD
static int initrd_users = 0;
#endif
#endif

/* Various static variables go here... mostly used within the ramdisk code only. */

static int rd_length[NUM_RAMDISKS];
static int rd_blocksizes[NUM_RAMDISKS];

/*
 * Parameters for the boot-loading of the ramdisk.  These are set by
 * init/main.c (from arguments to the kernel command line) or from the
 * architecture-specific setup routine (from the stored bootsector
 * information). 
 */
int rd_size = 4096;		/* Size of the ramdisks */

#ifndef MODULE
int rd_doload = 0;		/* 1 = load ramdisk, 0 = don't load */
int rd_prompt = 1;		/* 1 = prompt for ramdisk, 0 = don't prompt */
int rd_image_start = 0;		/* starting block # of image */
#ifdef CONFIG_BLK_DEV_INITRD
unsigned long initrd_start,initrd_end;
int mount_initrd = 1;		/* zero if initrd should not be mounted */
#endif
#endif

/*
 *  Basically, my strategy here is to set up a buffer-head which can't be
 *  deleted, and make that my Ramdisk.  If the request is outside of the
 *  allocated size, we must get rid of it...
 *
 */
static void rd_request(void)
{
	unsigned int minor;
	int offset, len;

repeat:
	INIT_REQUEST;
	
	minor = MINOR(CURRENT->rq_dev);

	if (minor >= NUM_RAMDISKS) {
		end_request(0);
		goto repeat;
	}
	
	offset = CURRENT->sector << 9;
	len = CURRENT->current_nr_sectors << 9;

	if ((offset + len) > rd_length[minor]) {
		end_request(0);
		goto repeat;
	}

	/*
	 * If we're reading, fill the buffer with 0's.  This is okay since
         * we're using protected buffers which should never get freed...
	 *
	 * If we're writing, we protect the buffer.
  	 */

	if (CURRENT->cmd == READ) 
		memset(CURRENT->buffer, 0, len); 
	else	
		set_bit(BH_Protected, &CURRENT->bh->b_state);

	end_request(1);
	goto repeat;
} 

static int rd_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
	int err;
	
	if (!inode || !inode->i_rdev) 	
		return -EINVAL;

	switch (cmd) {
		case BLKFLSBUF:
			if (!suser()) return -EACCES;
			invalidate_buffers(inode->i_rdev);
			break;
         	case BLKGETSIZE:   /* Return device size */
			if (!arg)  return -EINVAL;
			err = verify_area(VERIFY_WRITE, (long *) arg,
					  sizeof(long));
			if (err)
				return err;
			put_user(rd_length[MINOR(inode->i_rdev)] / 512, 
				 (long *) arg);
			return 0;
			
		default:
			break;
	};

	return 0;
}


#ifdef CONFIG_BLK_DEV_INITRD

static int initrd_read(struct inode *inode,struct file *file,char *buf,
    int count)
{
	int left;

	left = initrd_end-initrd_start-file->f_pos;
	if (count > left) count = left;
	if (count <= 0) return 0;
	memcpy_tofs(buf,(char *) initrd_start+file->f_pos,count);
	file->f_pos += count;
	return count;
}


static void initrd_release(struct inode *inode,struct file *file)
{
	unsigned long i;

	if (--initrd_users) return;
	for (i = initrd_start; i < initrd_end; i += PAGE_SIZE)
		free_page(i);
	initrd_start = 0;
}


static struct file_operations initrd_fops = {
	NULL,		/* lseek */
	initrd_read,	/* read */
	NULL,		/* write */
	NULL,		/* readdir */
	NULL,		/* select */
	NULL, 		/* ioctl */
	NULL,		/* mmap */
	NULL,		/* open */
	initrd_release,	/* release */
	NULL		/* fsync */ 
};

#endif


static int rd_open(struct inode * inode, struct file * filp)
{
#ifdef CONFIG_BLK_DEV_INITRD
	if (DEVICE_NR(inode->i_rdev) == INITRD_MINOR) {
		if (!initrd_start) return -ENODEV;
		initrd_users++;
		filp->f_op = &initrd_fops;
		return 0;
	}
#endif

	if (DEVICE_NR(inode->i_rdev) >= NUM_RAMDISKS)
		return -ENXIO;

	MOD_INC_USE_COUNT;

	return 0;
}

#ifdef MODULE
static void rd_release(struct inode * inode, struct file * filp)
{
	MOD_DEC_USE_COUNT;
}
#endif

static struct file_operations fd_fops = {
	NULL,		/* lseek - default */
	block_read,	/* read - block dev read */
	block_write,	/* write - block dev write */
	NULL,		/* readdir - not here! */
	NULL,		/* select */
	rd_ioctl, 	/* ioctl */
	NULL,		/* mmap */
	rd_open,	/* open */
#ifndef MODULE
	NULL,		/* no special release code... */
#else
	rd_release,	/* module needs to decrement use count */
#endif
	block_fsync		/* fsync */ 
};

/* This is the registration and initialization section of the ramdisk driver */
int rd_init(void)
{
	int		i;

	if (register_blkdev(MAJOR_NR, "ramdisk", &fd_fops)) {
		printk("RAMDISK: Could not get major %d", MAJOR_NR);
		return -EIO;
	}

	blk_dev[MAJOR_NR].request_fn = &rd_request;

	for (i = 0; i < NUM_RAMDISKS; i++) {
		rd_length[i] = (rd_size * 1024);
		rd_blocksizes[i] = 1024;
	}

	blksize_size[MAJOR_NR] = rd_blocksizes;

	printk("Ramdisk driver initialized : %d ramdisks of %dK size\n",
							NUM_RAMDISKS, rd_size);

	return 0;
}

/* loadable module support */

#ifdef MODULE

int init_module(void)
{
	int error = rd_init();
	if (!error)
		printk(KERN_INFO "RAMDISK: Loaded as module.\n");
	return error;
}

/* Before freeing the module, invalidate all of the protected buffers! */
void cleanup_module(void)
{
	int i;

	for (i = 0 ; i < NUM_RAMDISKS; i++)
		invalidate_buffers(MKDEV(MAJOR_NR, i));

	unregister_blkdev( MAJOR_NR, "ramdisk" );
	blk_dev[MAJOR_NR].request_fn = 0;
}

#endif  /* MODULE */

/* End of non-loading portions of the ramdisk driver */

#ifdef RD_LOADER 
/*
 * This routine tries to a ramdisk image to load, and returns the
 * number of blocks to read for a non-compressed image, 0 if the image
 * is a compressed image, and -1 if an image with the right magic
 * numbers could not be found.
 *
 * We currently check for the following magic numbers:
 * 	minix
 * 	ext2
 * 	gzip
 */
int
identify_ramdisk_image(kdev_t device, struct file *fp, int start_block)
{
	const int size = 512;
	struct minix_super_block *minixsb;
	struct ext2_super_block *ext2sb;
	int nblocks = -1;
	int max_blocks;
	unsigned char *buf;

	buf = kmalloc(size, GFP_KERNEL);
	if (buf == 0)
		return -1;

	minixsb = (struct minix_super_block *) buf;
	ext2sb = (struct ext2_super_block *) buf;
	memset(buf, 0xe5, size);

	/*
	 * Read block 0 to test for gzipped kernel
	 */
	if (fp->f_op->lseek)
		fp->f_op->lseek(fp->f_inode, fp, start_block * BLOCK_SIZE, 0);
	fp->f_pos = start_block * BLOCK_SIZE;