Hey Rusty,
These updated patches in the series return -EFAULT on copy_xx_user
errors and also move the copy_from_user into fops_write() instead of it
being in send_buf. This enables send_buf to just read from kernel
buffers, making it simpler.
This also allows write()s to write more to the host in one go,
removingthe 4k limitation. I do limit the writes to 32k at once to not
put too much pressure on the GFP_KERNEL area.
Both of these were pointed out by Marcelo.
I'm including the relative diff between the version that's in linux-next
and the new version below.
Please apply,
Thanks.
Amit.
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index b923b5c..2c2de35 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -162,9 +162,6 @@ struct port {
*/
spinlock_t inbuf_lock;
- /* Buffer that's used to pass data from the guest to the host */
- struct port_buffer *outbuf;
-
/* The IO vqs for this port */
struct virtqueue *in_vq, *out_vq;
@@ -399,43 +396,23 @@ static ssize_t send_control_msg(struct port *port,
unsigned int event,
return 0;
}
-static ssize_t send_buf(struct port *port, const char *in_buf, size_t in_count,
- bool from_user)
+static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count)
{
struct scatterlist sg[1];
struct virtqueue *out_vq;
- struct port_buffer *buf;
ssize_t ret;
- unsigned int tmplen;
+ unsigned int len;
out_vq = port->out_vq;
- buf = port->outbuf;
- if (in_count > buf->size)
- in_count = buf->size;
-
- if (from_user) {
- ret = copy_from_user(buf->buf, in_buf, in_count);
- } else {
- /*
- * Since we're not sure when the host will actually
- * consume the data and tell us about it, we have to
- * copy the data here in case the caller frees the
- * in_buf.
- */
- memcpy(buf->buf, in_buf, in_count);
- ret = 0; /* Emulate copy_from_user behaviour */
- }
- buf->len = in_count - ret;
-
- sg_init_one(sg, buf->buf, buf->len);
- ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, buf);
+ sg_init_one(sg, in_buf, in_count);
+ ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, in_buf);
/* Tell Host to go! */
out_vq->vq_ops->kick(out_vq);
if (ret < 0) {
- buf->len = 0;
+ len = 0;
goto fail;
}
@@ -444,13 +421,11 @@ static ssize_t send_buf(struct port *port, const char
*in_buf, size_t in_count,
* sent. Also ensure we return to userspace the number of
* bytes that were successfully consumed by the host.
*/
- while (!out_vq->vq_ops->get_buf(out_vq, &tmplen))
+ while (!out_vq->vq_ops->get_buf(out_vq, &len))
cpu_relax();
-
- buf->len = tmplen;
fail:
/* We're expected to return the amount of data we wrote */
- return buf->len;
+ return len;
}
/*
@@ -461,26 +436,25 @@ static ssize_t fill_readbuf(struct port *port, char
*out_buf, size_t out_count,
bool to_user)
{
struct port_buffer *buf;
- ssize_t ret;
unsigned long flags;
if (!out_count || !port_has_data(port))
return 0;
buf = port->inbuf;
- if (out_count > buf->len - buf->offset)
- out_count = buf->len - buf->offset;
+ out_count = min(out_count, buf->len - buf->offset);
if (to_user) {
+ ssize_t ret;
+
ret = copy_to_user(out_buf, buf->buf + buf->offset, out_count);
+ if (ret)
+ return -EFAULT;
} else {
memcpy(out_buf, buf->buf + buf->offset, out_count);
- ret = 0; /* Emulate copy_to_user behaviour */
}
- /* Return the number of bytes actually copied */
- ret = out_count - ret;
- buf->offset += ret;
+ buf->offset += out_count;
if (buf->offset == buf->len) {
/*
@@ -495,7 +469,8 @@ static ssize_t fill_readbuf(struct port *port, char
*out_buf, size_t out_count,
spin_unlock_irqrestore(&port->inbuf_lock, flags);
}
- return ret;
+ /* Return the number of bytes actually copied */
+ return out_count;
}
/* The condition that must be true for polling to end */
@@ -548,10 +523,27 @@ static ssize_t port_fops_write(struct file *filp, const
char __user *ubuf,
size_t count, loff_t *offp)
{
struct port *port;
+ char *buf;
+ ssize_t ret;
port = filp->private_data;
- return send_buf(port, ubuf, count, true);
+ count = min((size_t)(32 * 1024), count);
+
+ buf = kmalloc(count, GFP_KERNEL);
+ if (!buf)
+ return -ENOMEM;
+
+ ret = copy_from_user(buf, ubuf, count);
+ if (ret) {
+ ret = -EFAULT;
+ goto free_buf;
+ }
+
+ ret = send_buf(port, buf, count);
+free_buf:
+ kfree(buf);
+ return ret;
}
static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
@@ -657,7 +649,7 @@ static int put_chars(u32 vtermno, const char *buf, int
count)
if (unlikely(early_put_chars))
return early_put_chars(vtermno, buf, count);
- return send_buf(port, buf, count, false);
+ return send_buf(port, (void *)buf, count);
}
/*
@@ -874,7 +866,6 @@ static int remove_port(struct port *port)
cdev_del(&port->cdev);
discard_port_data(port);
- free_buf(port->outbuf);
kfree(port->name);
debugfs_remove(port->debugfs_file);
@@ -1143,11 +1134,6 @@ static int add_port(struct ports_device *portdev, u32 id)
err = -ENOMEM;
goto free_device;
}
- port->outbuf = alloc_buf(PAGE_SIZE);
- if (!port->outbuf) {
- err = -ENOMEM;
- goto free_inbuf;
- }
/* Register the input buffer the first time. */
add_inbuf(port->in_vq, inbuf);
@@ -1158,7 +1144,7 @@ static int add_port(struct ports_device *portdev, u32 id)
if (!use_multiport(port->portdev)) {
err = init_port_console(port);
if (err)
- goto free_outbuf;
+ goto free_inbuf;
}
spin_lock_irq(&portdev->ports_lock);
@@ -1186,8 +1172,6 @@ static int add_port(struct ports_device *portdev, u32 id)
}
return 0;
-free_outbuf:
- free_buf(port->outbuf);
free_inbuf:
free_buf(inbuf);
free_device:
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