From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/fs/seq_file.c | 144 ++++++++++++++++++++++++-----------------------
1 files changed, 74 insertions(+), 70 deletions(-)
diff --git a/kernel/fs/seq_file.c b/kernel/fs/seq_file.c
index e11f62b..4727147 100644
--- a/kernel/fs/seq_file.c
+++ b/kernel/fs/seq_file.c
@@ -6,6 +6,8 @@
* initial implementation -- AV, Oct 2001.
*/
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
#include <linux/cache.h>
#include <linux/fs.h>
#include <linux/export.h>
@@ -16,6 +18,7 @@
#include <linux/mm.h>
#include <linux/printk.h>
#include <linux/string_helpers.h>
+#include <linux/uio.h>
#include <linux/uaccess.h>
#include <asm/page.h>
@@ -71,13 +74,6 @@
p->file = file;
/*
- * 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() and pread(). They do not implement
* write() at all, but we clear FMODE_PWRITE here for historical
* reasons.
@@ -97,7 +93,6 @@
int error = 0;
void *p;
- m->version = 0;
m->index = 0;
m->count = m->from = 0;
if (!offset)
@@ -155,50 +150,58 @@
*/
ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
- struct seq_file *m = file->private_data;
+ struct iovec iov = { .iov_base = buf, .iov_len = size};
+ struct kiocb kiocb;
+ struct iov_iter iter;
+ ssize_t ret;
+
+ init_sync_kiocb(&kiocb, file);
+ iov_iter_init(&iter, READ, &iov, 1, size);
+
+ kiocb.ki_pos = *ppos;
+ ret = seq_read_iter(&kiocb, &iter);
+ *ppos = kiocb.ki_pos;
+ return ret;
+}
+EXPORT_SYMBOL(seq_read);
+
+/*
+ * Ready-made ->f_op->read_iter()
+ */
+ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+ struct seq_file *m = iocb->ki_filp->private_data;
size_t copied = 0;
size_t n;
void *p;
int err = 0;
- mutex_lock(&m->lock);
+ if (!iov_iter_count(iter))
+ return 0;
- /*
- * 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;
+ mutex_lock(&m->lock);
/*
* if request is to read from zero offset, reset iterator to first
* record as it might have been already advanced by previous requests
*/
- if (*ppos == 0) {
+ if (iocb->ki_pos == 0) {
m->index = 0;
- m->version = 0;
m->count = 0;
}
- /* Don't assume *ppos is where we left it */
- if (unlikely(*ppos != m->read_pos)) {
- while ((err = traverse(m, *ppos)) == -EAGAIN)
+ /* Don't assume ki_pos is where we left it */
+ if (unlikely(iocb->ki_pos != m->read_pos)) {
+ while ((err = traverse(m, iocb->ki_pos)) == -EAGAIN)
;
if (err) {
/* With prejudice... */
m->read_pos = 0;
- m->version = 0;
m->index = 0;
m->count = 0;
goto Done;
} else {
- m->read_pos = *ppos;
+ m->read_pos = iocb->ki_pos;
}
}
@@ -208,99 +211,91 @@
if (!m->buf)
goto Enomem;
}
- /* if not empty - flush it first */
+ // something left in the buffer - copy it out first
if (m->count) {
- n = min(m->count, size);
- err = copy_to_user(buf, m->buf + m->from, n);
- if (err)
- goto Efault;
+ n = copy_to_iter(m->buf + m->from, m->count, iter);
m->count -= n;
m->from += n;
- size -= n;
- buf += n;
copied += n;
- if (!size)
+ if (m->count) // hadn't managed to copy everything
goto Done;
}
- /* we need at least one record in buffer */
+ // get a non-empty record in the buffer
m->from = 0;
p = m->op->start(m, &m->index);
while (1) {
err = PTR_ERR(p);
- if (!p || IS_ERR(p))
+ if (!p || IS_ERR(p)) // EOF or an error
break;
err = m->op->show(m, p);
- if (err < 0)
+ if (err < 0) // hard error
break;
- if (unlikely(err))
+ if (unlikely(err)) // ->show() says "skip it"
m->count = 0;
- if (unlikely(!m->count)) {
+ if (unlikely(!m->count)) { // empty record
p = m->op->next(m, p, &m->index);
continue;
}
- if (m->count < m->size)
+ if (!seq_has_overflowed(m)) // got it
goto Fill;
+ // need a bigger buffer
m->op->stop(m, p);
kvfree(m->buf);
m->count = 0;
m->buf = seq_buf_alloc(m->size <<= 1);
if (!m->buf)
goto Enomem;
- m->version = 0;
p = m->op->start(m, &m->index);
}
+ // EOF or an error
m->op->stop(m, p);
m->count = 0;
goto Done;
Fill:
- /* they want more? let's try to get some more */
+ // one non-empty record is in the buffer; if they want more,
+ // try to fit more in, but in any case we need to advance
+ // the iterator once for every record shown.
while (1) {
size_t offs = m->count;
loff_t pos = m->index;
p = m->op->next(m, p, &m->index);
- if (pos == m->index)
- /* Buggy ->next function */
+ if (pos == m->index) {
+ pr_info_ratelimited("buggy .next function %ps did not update position index\n",
+ m->op->next);
m->index++;
- if (!p || IS_ERR(p)) {
- err = PTR_ERR(p);
- break;
}
- if (m->count >= size)
+ if (!p || IS_ERR(p)) // no next record for us
+ break;
+ if (m->count >= iov_iter_count(iter))
break;
err = m->op->show(m, p);
- if (seq_has_overflowed(m) || err) {
+ if (err > 0) { // ->show() says "skip it"
m->count = offs;
- if (likely(err <= 0))
- break;
+ } else if (err || seq_has_overflowed(m)) {
+ m->count = offs;
+ break;
}
}
m->op->stop(m, p);
- n = min(m->count, size);
- err = copy_to_user(buf, m->buf, n);
- if (err)
- goto Efault;
+ n = copy_to_iter(m->buf, m->count, iter);
copied += n;
m->count -= n;
m->from = n;
Done:
- if (!copied)
- copied = err;
- else {
- *ppos += copied;
+ if (unlikely(!copied)) {
+ copied = m->count ? -EFAULT : err;
+ } else {
+ iocb->ki_pos += copied;
m->read_pos += copied;
}
- file->f_version = m->version;
mutex_unlock(&m->lock);
return copied;
Enomem:
err = -ENOMEM;
goto Done;
-Efault:
- err = -EFAULT;
- goto Done;
}
-EXPORT_SYMBOL(seq_read);
+EXPORT_SYMBOL(seq_read_iter);
/**
* seq_lseek - ->llseek() method for sequential files.
@@ -316,10 +311,10 @@
loff_t retval = -EINVAL;
mutex_lock(&m->lock);
- m->version = file->f_version;
switch (whence) {
case SEEK_CUR:
offset += file->f_pos;
+ fallthrough;
case SEEK_SET:
if (offset < 0)
break;
@@ -331,7 +326,6 @@
/* with extreme prejudice... */
file->f_pos = 0;
m->read_pos = 0;
- m->version = 0;
m->index = 0;
m->count = 0;
} else {
@@ -342,7 +336,6 @@
file->f_pos = offset;
}
}
- file->f_version = m->version;
mutex_unlock(&m->lock);
return retval;
}
@@ -386,6 +379,17 @@
}
EXPORT_SYMBOL(seq_escape);
+void seq_escape_mem_ascii(struct seq_file *m, const char *src, size_t isz)
+{
+ char *buf;
+ size_t size = seq_get_buf(m, &buf);
+ int ret;
+
+ ret = string_escape_mem_ascii(src, isz, buf, size);
+ seq_commit(m, ret < size ? ret : -1);
+}
+EXPORT_SYMBOL(seq_escape_mem_ascii);
+
void seq_vprintf(struct seq_file *m, const char *f, va_list args)
{
int len;
--
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