mem.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 734 行 · 第 1/2 页

	if (verify_area(VERIFY_READ,buf,count))
		return -EFAULT;
	while (count-- > 0 && i < 65536) {
		char c;
		if (__get_user(c, tmp)) 
			return -EFAULT; 
		outb(c,i);
		i++;
		tmp++;
	}
	*ppos = i;
	return tmp-buf;
}
#endif

static ssize_t read_null(struct file * file, char __user * buf,
			 size_t count, loff_t *ppos)
{
	return 0;
}

static ssize_t write_null(struct file * file, const char __user * buf,
			  size_t count, loff_t *ppos)
{
	return count;
}

#ifdef CONFIG_MMU
/*
 * For fun, we are using the MMU for this.
 */
static inline size_t read_zero_pagealigned(char __user * buf, size_t size)
{
	struct mm_struct *mm;
	struct vm_area_struct * vma;
	unsigned long addr=(unsigned long)buf;

	mm = current->mm;
	/* Oops, this was forgotten before. -ben */
	down_read(&mm->mmap_sem);

	/* For private mappings, just map in zero pages. */
	for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
		unsigned long count;

		if (vma->vm_start > addr || (vma->vm_flags & VM_WRITE) == 0)
			goto out_up;
		if (vma->vm_flags & (VM_SHARED | VM_HUGETLB))
			break;
		count = vma->vm_end - addr;
		if (count > size)
			count = size;

		zap_page_range(vma, addr, count, NULL);
        	zeromap_page_range(vma, addr, count, PAGE_COPY);

		size -= count;
		buf += count;
		addr += count;
		if (size == 0)
			goto out_up;
	}

	up_read(&mm->mmap_sem);
	
	/* The shared case is hard. Let's do the conventional zeroing. */ 
	do {
		unsigned long unwritten = clear_user(buf, PAGE_SIZE);
		if (unwritten)
			return size + unwritten - PAGE_SIZE;
		cond_resched();
		buf += PAGE_SIZE;
		size -= PAGE_SIZE;
	} while (size);

	return size;
out_up:
	up_read(&mm->mmap_sem);
	return size;
}

static ssize_t read_zero(struct file * file, char __user * buf, 
			 size_t count, loff_t *ppos)
{
	unsigned long left, unwritten, written = 0;

	if (!count)
		return 0;

	if (!access_ok(VERIFY_WRITE, buf, count))
		return -EFAULT;

	left = count;

	/* do we want to be clever? Arbitrary cut-off */
	if (count >= PAGE_SIZE*4) {
		unsigned long partial;

		/* How much left of the page? */
		partial = (PAGE_SIZE-1) & -(unsigned long) buf;
		unwritten = clear_user(buf, partial);
		written = partial - unwritten;
		if (unwritten)
			goto out;
		left -= partial;
		buf += partial;
		unwritten = read_zero_pagealigned(buf, left & PAGE_MASK);
		written += (left & PAGE_MASK) - unwritten;
		if (unwritten)
			goto out;
		buf += left & PAGE_MASK;
		left &= ~PAGE_MASK;
	}
	unwritten = clear_user(buf, left);
	written += left - unwritten;
out:
	return written ? written : -EFAULT;
}

static int mmap_zero(struct file * file, struct vm_area_struct * vma)
{
	if (vma->vm_flags & VM_SHARED)
		return shmem_zero_setup(vma);
	if (zeromap_page_range(vma, vma->vm_start, vma->vm_end - vma->vm_start, vma->vm_page_prot))
		return -EAGAIN;
	return 0;
}
#else /* CONFIG_MMU */
static ssize_t read_zero(struct file * file, char * buf, 
			 size_t count, loff_t *ppos)
{
	size_t todo = count;

	while (todo) {
		size_t chunk = todo;

		if (chunk > 4096)
			chunk = 4096;	/* Just for latency reasons */
		if (clear_user(buf, chunk))
			return -EFAULT;
		buf += chunk;
		todo -= chunk;
		cond_resched();
	}
	return count;
}

static int mmap_zero(struct file * file, struct vm_area_struct * vma)
{
	return -ENOSYS;
}
#endif /* CONFIG_MMU */

static ssize_t write_full(struct file * file, const char __user * buf,
			  size_t count, loff_t *ppos)
{
	return -ENOSPC;
}

/*
 * Special lseek() function for /dev/null and /dev/zero.  Most notably, you
 * can fopen() both devices with "a" now.  This was previously impossible.
 * -- SRB.
 */

static loff_t null_lseek(struct file * file, loff_t offset, int orig)
{
	return file->f_pos = 0;
}

/*
 * The memory devices use the full 32/64 bits of the offset, and so we cannot
 * check against negative addresses: they are ok. The return value is weird,
 * though, in that case (0).
 *
 * also note that seeking relative to the "end of file" isn't supported:
 * it has no meaning, so it returns -EINVAL.
 */
static loff_t memory_lseek(struct file * file, loff_t offset, int orig)
{
	loff_t ret;

	down(&file->f_dentry->d_inode->i_sem);
	switch (orig) {
		case 0:
			file->f_pos = offset;
			ret = file->f_pos;
			force_successful_syscall_return();
			break;
		case 1:
			file->f_pos += offset;
			ret = file->f_pos;
			force_successful_syscall_return();
			break;
		default:
			ret = -EINVAL;
	}
	up(&file->f_dentry->d_inode->i_sem);
	return ret;
}

static int open_port(struct inode * inode, struct file * filp)
{
	return capable(CAP_SYS_RAWIO) ? 0 : -EPERM;
}

#define mmap_kmem	mmap_mem
#define zero_lseek	null_lseek
#define full_lseek      null_lseek
#define write_zero	write_null
#define read_full       read_zero
#define open_mem	open_port
#define open_kmem	open_mem

static struct file_operations mem_fops = {
	.llseek		= memory_lseek,
	.read		= read_mem,
	.write		= write_mem,
	.mmap		= mmap_mem,
	.open		= open_mem,
};

static struct file_operations kmem_fops = {
	.llseek		= memory_lseek,
	.read		= read_kmem,
	.write		= write_kmem,
	.mmap		= mmap_kmem,
	.open		= open_kmem,
};

static struct file_operations null_fops = {
	.llseek		= null_lseek,
	.read		= read_null,
	.write		= write_null,
};

#if defined(CONFIG_ISA) || !defined(__mc68000__)
static struct file_operations port_fops = {
	.llseek		= memory_lseek,
	.read		= read_port,
	.write		= write_port,
	.open		= open_port,
};
#endif

static struct file_operations zero_fops = {
	.llseek		= zero_lseek,
	.read		= read_zero,
	.write		= write_zero,
	.mmap		= mmap_zero,
};

static struct file_operations full_fops = {
	.llseek		= full_lseek,
	.read		= read_full,
	.write		= write_full,
};

static ssize_t kmsg_write(struct file * file, const char __user * buf,
			  size_t count, loff_t *ppos)
{
	char *tmp;
	int ret;

	tmp = kmalloc(count + 1, GFP_KERNEL);
	if (tmp == NULL)
		return -ENOMEM;
	ret = -EFAULT;
	if (!copy_from_user(tmp, buf, count)) {
		tmp[count] = 0;
		ret = printk("%s", tmp);
	}
	kfree(tmp);
	return ret;
}

static struct file_operations kmsg_fops = {
	.write =	kmsg_write,
};

static int memory_open(struct inode * inode, struct file * filp)
{
	switch (iminor(inode)) {
		case 1:
			filp->f_op = &mem_fops;
			break;
		case 2:
			filp->f_op = &kmem_fops;
			break;
		case 3:
			filp->f_op = &null_fops;
			break;
#if defined(CONFIG_ISA) || !defined(__mc68000__)
		case 4:
			filp->f_op = &port_fops;
			break;
#endif
		case 5:
			filp->f_op = &zero_fops;
			break;
		case 7:
			filp->f_op = &full_fops;
			break;
		case 8:
			filp->f_op = &random_fops;
			break;
		case 9:
			filp->f_op = &urandom_fops;
			break;
		case 11:
			filp->f_op = &kmsg_fops;
			break;
		default:
			return -ENXIO;
	}
	if (filp->f_op && filp->f_op->open)
		return filp->f_op->open(inode,filp);
	return 0;
}

static struct file_operations memory_fops = {
	.open		= memory_open,	/* just a selector for the real open */
};

static const struct {
	unsigned int		minor;
	char			*name;
	umode_t			mode;
	struct file_operations	*fops;
} devlist[] = { /* list of minor devices */
	{1, "mem",     S_IRUSR | S_IWUSR | S_IRGRP, &mem_fops},
	{2, "kmem",    S_IRUSR | S_IWUSR | S_IRGRP, &kmem_fops},
	{3, "null",    S_IRUGO | S_IWUGO,           &null_fops},
#if defined(CONFIG_ISA) || !defined(__mc68000__)
	{4, "port",    S_IRUSR | S_IWUSR | S_IRGRP, &port_fops},
#endif
	{5, "zero",    S_IRUGO | S_IWUGO,           &zero_fops},
	{7, "full",    S_IRUGO | S_IWUGO,           &full_fops},
	{8, "random",  S_IRUGO | S_IWUSR,           &random_fops},
	{9, "urandom", S_IRUGO | S_IWUSR,           &urandom_fops},
	{11,"kmsg",    S_IRUGO | S_IWUSR,           &kmsg_fops},
};

static struct class_simple *mem_class;

static int __init chr_dev_init(void)
{
	int i;

	if (register_chrdev(MEM_MAJOR,"mem",&memory_fops))
		printk("unable to get major %d for memory devs\n", MEM_MAJOR);

	mem_class = class_simple_create(THIS_MODULE, "mem");
	for (i = 0; i < ARRAY_SIZE(devlist); i++) {
		class_simple_device_add(mem_class,
					MKDEV(MEM_MAJOR, devlist[i].minor),
					NULL, devlist[i].name);
		devfs_mk_cdev(MKDEV(MEM_MAJOR, devlist[i].minor),
				S_IFCHR | devlist[i].mode, devlist[i].name);
	}
	
	return 0;
}

fs_initcall(chr_dev_init);