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/*
* linux/fs/seq_file.c
*
* helper functions for making synthetic files from sequences of records.
* initial implementation -- AV, Oct 2001.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/page.h>
/**
* seq_open - initialize sequential file
* @file: file we initialize
* @op: method table describing the sequence
*
* seq_open() sets @file, associating it with a sequence described
* by @op. @op->start() sets the iterator up and returns the first
* element of sequence. @op->stop() shuts it down. @op->next()
* returns the next element of sequence. @op->show() prints element
* into the buffer. In case of error ->start() and ->next() return
* ERR_PTR(error). In the end of sequence they return %NULL. ->show()
* returns 0 in case of success and negative number in case of error.
*/
int seq_open(struct file *file, struct seq_operations *op)
{
struct seq_file *p = kmalloc(sizeof(*p), GFP_KERNEL);
if (!p)
return -ENOMEM;
memset(p, 0, sizeof(*p));
sema_init(&p->sem, 1);
p->op = op;
file->private_data = p;
/*
* Wrappers around seq_open(e.g. swaps_open) need to be
* aware of this. If they set f_version themselves, they
* should call seq_open first and then set f_version.
*/
file->f_version = 0;
/* SEQ files support lseek, but not pread/pwrite */
file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
return 0;
}
EXPORT_SYMBOL(seq_open);
/**
* seq_read - ->read() method for sequential files.
* @file: the file to read from
* @buf: the buffer to read to
* @size: the maximum number of bytes to read
* @ppos: the current position in the file
*
* Ready-made ->f_op->read()
*/
ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
struct seq_file *m = (struct seq_file *)file->private_data;
size_t copied = 0;
loff_t pos;
size_t n;
void *p;
int err = 0;
down(&m->sem);
/*
* seq_file->op->..m_start/m_stop/m_next may do special actions
* or optimisations based on the file->f_version, so we want to
* pass the file->f_version to those methods.
*
* seq_file->version is just copy of f_version, and seq_file
* methods can treat it simply as file version.
* It is copied in first and copied out after all operations.
* It is convenient to have it as part of structure to avoid the
* need of passing another argument to all the seq_file methods.
*/
m->version = file->f_version;
/* grab buffer if we didn't have one */
if (!m->buf) {
m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
if (!m->buf)
goto Enomem;
}
/* if not empty - flush it first */
if (m->count) {
n = min(m->count, size);
err = copy_to_user(buf, m->buf + m->from, n);
if (err)
goto Efault;
m->count -= n;
m->from += n;
size -= n;
buf += n;
copied += n;
if (!m->count)
m->index++;
if (!size)
goto Done;
}
/* we need at least one record in buffer */
while (1) {
pos = m->index;
p = m->op->start(m, &pos);
err = PTR_ERR(p);
if (!p || IS_ERR(p))
break;
err = m->op->show(m, p);
if (err)
break;
if (m->count < m->size)
goto Fill;
m->op->stop(m, p);
kfree(m->buf);
m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
if (!m->buf)
goto Enomem;
m->count = 0;
m->version = 0;
}
m->op->stop(m, p);
m->count = 0;
goto Done;
Fill:
/* they want more? let's try to get some more */
while (m->count < size) {
size_t offs = m->count;
loff_t next = pos;
p = m->op->next(m, p, &next);
if (!p || IS_ERR(p)) {
err = PTR_ERR(p);
break;
}
err = m->op->show(m, p);
if (err || m->count == m->size) {
m->count = offs;
break;
}
pos = next;
}
m->op->stop(m, p);
n = min(m->count, size);
err = copy_to_user(buf, m->buf, n);
if (err)
goto Efault;
copied += n;
m->count -= n;
if (m->count)
m->from = n;
else
pos++;
m->index = pos;
Done:
if (!copied)
copied = err;
else
*ppos += copied;
file->f_version = m->version;
up(&m->sem);
return copied;
Enomem:
err = -ENOMEM;
goto Done;
Efault:
err = -EFAULT;
goto Done;
}
EXPORT_SYMBOL(seq_read);
static int traverse(struct seq_file *m, loff_t offset)
{
loff_t pos = 0;
int error = 0;
void *p;
m->version = 0;
m->index = 0;
m->count = m->from = 0;
if (!offset)
return 0;
if (!m->buf) {
m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
if (!m->buf)
return -ENOMEM;
}
p = m->op->start(m, &m->index);
while (p) {
error = PTR_ERR(p);
if (IS_ERR(p))
break;
error = m->op->show(m, p);
if (error)
break;
if (m->count == m->size)
goto Eoverflow;
if (pos + m->count > offset) {
m->from = offset - pos;
m->count -= m->from;
break;
}
pos += m->count;
m->count = 0;
if (pos == offset) {
m->index++;
break;
}
p = m->op->next(m, p, &m->index);
}
m->op->stop(m, p);
return error;
Eoverflow:
m->op->stop(m, p);
kfree(m->buf);
m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
return !m->buf ? -ENOMEM : -EAGAIN;
}
/**
* seq_lseek - ->llseek() method for sequential files.
* @file: the file in question
* @offset: new position
* @origin: 0 for absolute, 1 for relative position
*
* Ready-made ->f_op->llseek()
*/
loff_t seq_lseek(struct file *file, loff_t offset, int origin)
{
struct seq_file *m = (struct seq_file *)file->private_data;
long long retval = -EINVAL;
down(&m->sem);
m->version = file->f_version;
switch (origin) {
case 1:
offset += file->f_pos;
case 0:
if (offset < 0)
break;
retval = offset;
if (offset !=
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