Re: [PATCH net-next v2 02/10] net: dsa: debugfs: add tree

Vivien Didelot
2017-09-08T15:00:56Z

Hi Greg,

You wrote:

> > Can I ask for a quick review of this patch as well? It's the one adding
> > the boilerplate for a single debugfs file, and I'm pretty sure it can be
> > reduced somehow.
>
> I don't see a patch here :(

Oops, you weren't originally in Cc. Please find the patch below.

> > Also more important, you will notice what seems to be a bug to me:
> > I can read or write a file even if I didn't mask the corresponding mode
> > hence the double check in dsa_debugfs_show and dsa_debugfs_write.
>
> The mode can be changed by userspace, you shouldn't ever need to check
> it in any debugfs calls, right?

Correct. But this happens even if the file mode isn't changed by
userspace in the meantime, which seemed weird to me. e.g. echo
redirected to a -r--r--r-- debugfs entry will call dsa_debugfs_write.

Thanks,

Vivien

------ Beginning of the patch ------

This commit adds the boiler plate to create a DSA related debug
filesystem entry as well as a "tree" file, containing the tree index.

# cat switch1/tree
0

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
net/dsa/debugfs.c | 107 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 107 insertions(+)

diff --git a/net/dsa/debugfs.c b/net/dsa/debugfs.c
index b6b5e5c97389..54e97e05a9d7 100644
--- a/net/dsa/debugfs.c
+++ b/net/dsa/debugfs.c
@@ -10,6 +10,7 @@
*/

#include <linux/debugfs.h>
+#include <linux/seq_file.h>

#include "dsa_priv.h"

@@ -19,6 +20,107 @@
/* DSA module debugfs directory */
static struct dentry *dsa_debugfs_dir;

+struct dsa_debugfs_ops {
+ int (*read)(struct dsa_switch *ds, int id, struct seq_file *seq);
+ int (*write)(struct dsa_switch *ds, int id, char *buf);
+};
+
+struct dsa_debugfs_priv {
+ const struct dsa_debugfs_ops *ops;
+ struct dsa_switch *ds;
+ int id;
+};
+
+static int dsa_debugfs_show(struct seq_file *seq, void *p)
+{
+ struct dsa_debugfs_priv *priv = seq->private;
+ struct dsa_switch *ds = priv->ds;
+
+ /* Somehow file mode is bypassed... Double check here */
+ if (!priv->ops->read)
+ return -EOPNOTSUPP;
+
+ return priv->ops->read(ds, priv->id, seq);
+}
+
+static ssize_t dsa_debugfs_write(struct file *file, const char __user *user_buf,
+ size_t count, loff_t *ppos)
+{
+ struct seq_file *seq = file->private_data;
+ struct dsa_debugfs_priv *priv = seq->private;
+ struct dsa_switch *ds = priv->ds;
+ char buf[count + 1];
+ int err;
+
+ /* Somehow file mode is bypassed... Double check here */
+ if (!priv->ops->write)
+ return -EOPNOTSUPP;
+
+ if (copy_from_user(buf, user_buf, count))
+ return -EFAULT;
+
+ buf[count] = '\0';
+
+ err = priv->ops->write(ds, priv->id, buf);
+
+ return err ? err : count;
+}
+
+static int dsa_debugfs_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, dsa_debugfs_show, inode->i_private);
+}
+
+static const struct file_operations dsa_debugfs_fops = {
+ .open = dsa_debugfs_open,
+ .read = seq_read,
+ .write = dsa_debugfs_write,
+ .llseek = no_llseek,
+ .release = single_release,
+ .owner = THIS_MODULE,
+};
+
+static int dsa_debugfs_create_file(struct dsa_switch *ds, struct dentry *dir,
+ char *name, int id,
+ const struct dsa_debugfs_ops *ops)
+{
+ struct dsa_debugfs_priv *priv;
+ struct dentry *entry;
+ umode_t mode;
+
+ priv = devm_kzalloc(ds->dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->ops = ops;
+ priv->ds = ds;
+ priv->id = id;
+
+ mode = 0;
+ if (ops->read)
+ mode |= 0444;
+ if (ops->write)
+ mode |= 0200;
+
+ entry = debugfs_create_file(name, mode, dir, priv, &dsa_debugfs_fops);
+ if (IS_ERR_OR_NULL(entry))
+ return -EFAULT;
+
+ return 0;
+}
+
+static int dsa_debugfs_tree_read(struct dsa_switch *ds, int id,
+ struct seq_file *seq)
+{
+ seq_printf(seq, "%d\n", ds->dst->tree);
+
+ return 0;
+}
+
+static const struct dsa_debugfs_ops dsa_debugfs_tree_ops = {
+ .read = dsa_debugfs_tree_read,
+};
+
static int dsa_debugfs_create_port(struct dsa_switch *ds, int port)
{
struct dentry *dir;
@@ -48,6 +150,11 @@ static int dsa_debugfs_create_switch(struct dsa_switch *ds)
if (IS_ERR_OR_NULL(ds->debugfs_dir))
return -EFAULT;

+ err = dsa_debugfs_create_file(ds, ds->debugfs_dir, "tree", -1,
+ &dsa_debugfs_tree_ops);
+ if (err)
+ return err;
+
for (i = 0; i < ds->num_ports; i++) {
if (ds->enabled_port_mask & BIT(i)) {
err = dsa_debugfs_create_port(ds, i);
--
2.14.1