[PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[Su Yanjun]

When i debug mcp2518fd, some method to track registers is
needed. This easy debug interface will be ok.

For example,
read a register at 0xe00:
echo 0xe00 > can_get_reg
cat can_get_reg

write a register at 0xe00:
echo 0xe00,0x60 > can_set_reg

Signed-off-by: Su Yanjun <suyanjun218@gmail.com>
---
 .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 132 ++++++++++++++++++
 1 file changed, 132 insertions(+)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index ab8aad0a7594..d65abe5505d5 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -27,6 +27,131 @@
 
 #define DEVICE_NAME "mcp251xfd"
 
+/* Add sysfs debug interface for easy to debug
+ *
+ * For example,
+ *
+ * - read a register
+ * echo 0xe00 > can_get_reg
+ * cat can_get_reg
+ *
+ * - write a register
+ * echo 0xe00,0x1 > can_set_reg
+ *
+ */
+static int reg_offset;
+
+static int __get_param(const char *buf, char *off, char *val)
+{
+	int len;
+
+	if (!buf || !off || !val)
+		return -EINVAL;
+
+	len = 0;
+	while (*buf != ',') {
+		*off++ = *buf++;
+		len++;
+
+		if (len >= 16)
+			return -EINVAL;
+	}
+
+	buf++;
+
+	*off = '\0';
+
+	len = 0;
+	while (*buf) {
+		*val++ = *buf++;
+		len++;
+
+		if (len >= 16)
+			return -EINVAL;
+	}
+
+	*val = '\0';
+
+	return 0;
+}
+
+static ssize_t can_get_reg_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	int err;
+	u32 val;
+	struct mcp251xfd_priv *priv;
+
+	priv = dev_get_drvdata(dev);
+
+	err = regmap_read(priv->map_reg, reg_offset, &val);
+	if (err)
+		return 0;
+
+	return sprintf(buf, "reg = 0x%08x, val = 0x%08x\n", reg_offset, val);
+}
+
+static ssize_t can_get_reg_store(struct device *dev,
+				 struct device_attribute *attr, const char *buf, size_t len)
+{
+	u32 off;
+
+	reg_offset = 0;
+
+	if (kstrtouint(buf, 0, &off) || (off % 4))
+		return -EINVAL;
+
+	reg_offset = off;
+
+	return len;
+}
+
+static ssize_t can_set_reg_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return 0;
+}
+
+static ssize_t can_set_reg_store(struct device *dev,
+				 struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct mcp251xfd_priv *priv;
+	u32 off, val;
+	int err;
+
+	char s1[16];
+	char s2[16];
+
+	if (__get_param(buf, s1, s2))
+		return -EINVAL;
+
+	if (kstrtouint(s1, 0, &off) || (off % 4))
+		return -EINVAL;
+
+	if (kstrtouint(s2, 0, &val))
+		return -EINVAL;
+
+	err = regmap_write(priv->map_reg, off, val);
+	if (err)
+		return -EINVAL;
+
+	return len;
+}
+
+static DEVICE_ATTR_RW(can_get_reg);
+static DEVICE_ATTR_RW(can_set_reg);
+
+static struct attribute *can_attributes[] = {
+	&dev_attr_can_get_reg.attr,
+	&dev_attr_can_set_reg.attr,
+	NULL
+};
+
+static const struct attribute_group can_group = {
+	.attrs = can_attributes,
+	NULL
+};
+
 static const struct mcp251xfd_devtype_data mcp251xfd_devtype_data_mcp2517fd = {
 	.quirks = MCP251XFD_QUIRK_MAB_NO_WARN | MCP251XFD_QUIRK_CRC_REG |
 		MCP251XFD_QUIRK_CRC_RX | MCP251XFD_QUIRK_CRC_TX |
@@ -2944,6 +3069,12 @@ static int mcp251xfd_probe(struct spi_device *spi)
 	if (err)
 		goto out_free_candev;
 
+	err = sysfs_create_group(&spi->dev.kobj, &can_group);
+	if (err) {
+		netdev_err(priv->ndev, "Create can group fail.\n");
+		goto out_free_candev;
+	}
+
 	err = can_rx_offload_add_manual(ndev, &priv->offload,
 					MCP251XFD_NAPI_WEIGHT);
 	if (err)
@@ -2972,6 +3103,7 @@ static int mcp251xfd_remove(struct spi_device *spi)
 	mcp251xfd_unregister(priv);
 	spi->max_speed_hz = priv->spi_max_speed_hz_orig;
 	free_candev(ndev);
+	sysfs_remove_group(&spi->dev.kobj, &can_group);
 
 	return 0;
 }
-- 
2.25.1

Re: [PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[Marc Kleine-Budde]

[-- Attachment #1.1: Type: text/plain, Size: 888 bytes --]

On 1/22/21 7:22 AM, Su Yanjun wrote:
> When i debug mcp2518fd, some method to track registers is
> needed. This easy debug interface will be ok.

NACK

As the driver uses regmap, everything should be there already.

To read use:

| cat /sys/kernel/debug/regmap/spi0.0-crc/registers

Register write support for devices that are handles by proper kernel drivers is
a pure debugging tool, thus not enabled by default, not even with a Kconfig
switch. You have to enable it manually, have a look at commit:

09c6ecd39410 regmap: Add support for writing to regmap registers via debugfs

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

Re: [PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[Su]

在 2021/1/22 下午3:22, Marc Kleine-Budde 写道:
> On 1/22/21 7:22 AM, Su Yanjun wrote:
>> When i debug mcp2518fd, some method to track registers is
>> needed. This easy debug interface will be ok.
> NACK
>
> As the driver uses regmap, everything should be there already.
>
> To read use:
>
> | cat /sys/kernel/debug/regmap/spi0.0-crc/registers
>
> Register write support for devices that are handles by proper kernel drivers is
> a pure debugging tool, thus not enabled by default, not even with a Kconfig
> switch. You have to enable it manually, have a look at commit:
>
> 09c6ecd39410 regmap: Add support for writing to regmap registers via debugfs

You're right.

Thank you

>
> regards,
> Marc
>

Re: [PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[Vincent MAILHOL]

Hi,

In addition to Marc’s comment, I also have security concerns.

On Fri. 22 Jan 2021 at 15:22, Su Yanjun <suyanjun218@gmail.com> wrote:
> When i debug mcp2518fd, some method to track registers is
> needed. This easy debug interface will be ok.
>
> For example,
> read a register at 0xe00:
> echo 0xe00 > can_get_reg
> cat can_get_reg
>
> write a register at 0xe00:
> echo 0xe00,0x60 > can_set_reg

What about:
printf "A%0.s" {1..1000} > can_set_reg

Doesn’t it crash the kernel?

I see no checks of the buf len in your code and I suspect it to be
vulnerable to stack buffer overflow exploits.

> Signed-off-by: Su Yanjun <suyanjun218@gmail.com>
> ---
>  .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 132 ++++++++++++++++++
>  1 file changed, 132 insertions(+)
>
> diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> index ab8aad0a7594..d65abe5505d5 100644
> --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> @@ -27,6 +27,131 @@
>
>  #define DEVICE_NAME "mcp251xfd"
>
> +/* Add sysfs debug interface for easy to debug
> + *
> + * For example,
> + *
> + * - read a register
> + * echo 0xe00 > can_get_reg
> + * cat can_get_reg
> + *
> + * - write a register
> + * echo 0xe00,0x1 > can_set_reg
> + *
> + */
> +static int reg_offset;
> +
> +static int __get_param(const char *buf, char *off, char *val)
> +{
> +       int len;
> +
> +       if (!buf || !off || !val)
> +               return -EINVAL;
> +
> +       len = 0;
> +       while (*buf != ',') {
> +               *off++ = *buf++;
> +               len++;
> +
> +               if (len >= 16)
> +                       return -EINVAL;
> +       }
> +
> +       buf++;
> +
> +       *off = '\0';
> +
> +       len = 0;
> +       while (*buf) {
> +               *val++ = *buf++;
> +               len++;
> +
> +               if (len >= 16)
> +                       return -EINVAL;
> +       }
> +
> +       *val = '\0';
> +
> +       return 0;
> +}
> +
> +static ssize_t can_get_reg_show(struct device *dev,
> +                               struct device_attribute *attr, char *buf)
> +{
> +       int err;
> +       u32 val;
> +       struct mcp251xfd_priv *priv;
> +
> +       priv = dev_get_drvdata(dev);
> +
> +       err = regmap_read(priv->map_reg, reg_offset, &val);
> +       if (err)
> +               return 0;
> +
> +       return sprintf(buf, "reg = 0x%08x, val = 0x%08x\n", reg_offset, val);
> +}
> +
> +static ssize_t can_get_reg_store(struct device *dev,
> +                                struct device_attribute *attr, const char *buf, size_t len)
> +{
> +       u32 off;
> +
> +       reg_offset = 0;
> +
> +       if (kstrtouint(buf, 0, &off) || (off % 4))
> +               return -EINVAL;
> +
> +       reg_offset = off;
> +
> +       return len;
> +}
> +
> +static ssize_t can_set_reg_show(struct device *dev,
> +                               struct device_attribute *attr, char *buf)
> +{
> +       return 0;
> +}
> +
> +static ssize_t can_set_reg_store(struct device *dev,
> +                                struct device_attribute *attr, const char *buf, size_t len)
> +{
> +       struct mcp251xfd_priv *priv;
> +       u32 off, val;
> +       int err;
> +
> +       char s1[16];
> +       char s2[16];
> +
> +       if (__get_param(buf, s1, s2))
> +               return -EINVAL;
> +
> +       if (kstrtouint(s1, 0, &off) || (off % 4))
> +               return -EINVAL;
> +
> +       if (kstrtouint(s2, 0, &val))
> +               return -EINVAL;
> +
> +       err = regmap_write(priv->map_reg, off, val);
> +       if (err)
> +               return -EINVAL;
> +
> +       return len;
> +}
> +
> +static DEVICE_ATTR_RW(can_get_reg);
> +static DEVICE_ATTR_RW(can_set_reg);
> +
> +static struct attribute *can_attributes[] = {
> +       &dev_attr_can_get_reg.attr,
> +       &dev_attr_can_set_reg.attr,
> +       NULL
> +};
> +
> +static const struct attribute_group can_group = {
> +       .attrs = can_attributes,
> +       NULL
> +};
> +
>  static const struct mcp251xfd_devtype_data mcp251xfd_devtype_data_mcp2517fd = {
>         .quirks = MCP251XFD_QUIRK_MAB_NO_WARN | MCP251XFD_QUIRK_CRC_REG |
>                 MCP251XFD_QUIRK_CRC_RX | MCP251XFD_QUIRK_CRC_TX |
> @@ -2944,6 +3069,12 @@ static int mcp251xfd_probe(struct spi_device *spi)
>         if (err)
>                 goto out_free_candev;
>
> +       err = sysfs_create_group(&spi->dev.kobj, &can_group);
> +       if (err) {
> +               netdev_err(priv->ndev, "Create can group fail.\n");
> +               goto out_free_candev;
> +       }
> +
>         err = can_rx_offload_add_manual(ndev, &priv->offload,
>                                         MCP251XFD_NAPI_WEIGHT);
>         if (err)
> @@ -2972,6 +3103,7 @@ static int mcp251xfd_remove(struct spi_device *spi)
>         mcp251xfd_unregister(priv);
>         spi->max_speed_hz = priv->spi_max_speed_hz_orig;
>         free_candev(ndev);
> +       sysfs_remove_group(&spi->dev.kobj, &can_group);
>
>         return 0;
>  }
> --
> 2.25.1
>

Re: [PATCH v1] can: mcp251xfd: Add some sysfs debug interfaces for registers r/w

[knigh dark]

Vincent MAILHOL <mailhol.vincent@wanadoo.fr> 于2021年1月22日周五 下午4:51写道：
>
> Hi,
>
> In addition to Marc’s comment, I also have security concerns.
>
> On Fri. 22 Jan 2021 at 15:22, Su Yanjun <suyanjun218@gmail.com> wrote:
> > When i debug mcp2518fd, some method to track registers is
> > needed. This easy debug interface will be ok.
> >
> > For example,
> > read a register at 0xe00:
> > echo 0xe00 > can_get_reg
> > cat can_get_reg
> >
> > write a register at 0xe00:
> > echo 0xe00,0x60 > can_set_reg
>
> What about:
> printf "A%0.s" {1..1000} > can_set_reg
>
> Doesn’t it crash the kernel?
I check the input buffer in __get_param with 16 bytes limit.
Thanks for your review.
>
> I see no checks of the buf len in your code and I suspect it to be
> vulnerable to stack buffer overflow exploits.
>
> > Signed-off-by: Su Yanjun <suyanjun218@gmail.com>
> > ---
> >  .../net/can/spi/mcp251xfd/mcp251xfd-core.c    | 132 ++++++++++++++++++
> >  1 file changed, 132 insertions(+)
> >
> > diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > index ab8aad0a7594..d65abe5505d5 100644
> > --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
> > @@ -27,6 +27,131 @@
> >
> >  #define DEVICE_NAME "mcp251xfd"
> >
> > +/* Add sysfs debug interface for easy to debug
> > + *
> > + * For example,
> > + *
> > + * - read a register
> > + * echo 0xe00 > can_get_reg
> > + * cat can_get_reg
> > + *
> > + * - write a register
> > + * echo 0xe00,0x1 > can_set_reg
> > + *
> > + */
> > +static int reg_offset;
> > +
> > +static int __get_param(const char *buf, char *off, char *val)
> > +{
> > +       int len;
> > +
> > +       if (!buf || !off || !val)
> > +               return -EINVAL;
> > +
> > +       len = 0;
> > +       while (*buf != ',') {
> > +               *off++ = *buf++;
> > +               len++;
> > +
> > +               if (len >= 16)
> > +                       return -EINVAL;
> > +       }
> > +
> > +       buf++;
> > +
> > +       *off = '\0';
> > +
> > +       len = 0;
> > +       while (*buf) {
> > +               *val++ = *buf++;
> > +               len++;
> > +
> > +               if (len >= 16)
> > +                       return -EINVAL;
> > +       }
> > +
> > +       *val = '\0';
> > +
> > +       return 0;
> > +}
> > +
> > +static ssize_t can_get_reg_show(struct device *dev,
> > +                               struct device_attribute *attr, char *buf)
> > +{
> > +       int err;
> > +       u32 val;
> > +       struct mcp251xfd_priv *priv;
> > +
> > +       priv = dev_get_drvdata(dev);
> > +
> > +       err = regmap_read(priv->map_reg, reg_offset, &val);
> > +       if (err)
> > +               return 0;
> > +
> > +       return sprintf(buf, "reg = 0x%08x, val = 0x%08x\n", reg_offset, val);
> > +}
> > +
> > +static ssize_t can_get_reg_store(struct device *dev,
> > +                                struct device_attribute *attr, const char *buf, size_t len)
> > +{
> > +       u32 off;
> > +
> > +       reg_offset = 0;
> > +
> > +       if (kstrtouint(buf, 0, &off) || (off % 4))
> > +               return -EINVAL;
> > +
> > +       reg_offset = off;
> > +
> > +       return len;
> > +}
> > +
> > +static ssize_t can_set_reg_show(struct device *dev,
> > +                               struct device_attribute *attr, char *buf)
> > +{
> > +       return 0;
> > +}
> > +
> > +static ssize_t can_set_reg_store(struct device *dev,
> > +                                struct device_attribute *attr, const char *buf, size_t len)
> > +{
> > +       struct mcp251xfd_priv *priv;
> > +       u32 off, val;
> > +       int err;
> > +
> > +       char s1[16];
> > +       char s2[16];
> > +
> > +       if (__get_param(buf, s1, s2))
> > +               return -EINVAL;
> > +
> > +       if (kstrtouint(s1, 0, &off) || (off % 4))
> > +               return -EINVAL;
> > +
> > +       if (kstrtouint(s2, 0, &val))
> > +               return -EINVAL;
> > +
> > +       err = regmap_write(priv->map_reg, off, val);
> > +       if (err)
> > +               return -EINVAL;
> > +
> > +       return len;
> > +}
> > +
> > +static DEVICE_ATTR_RW(can_get_reg);
> > +static DEVICE_ATTR_RW(can_set_reg);
> > +
> > +static struct attribute *can_attributes[] = {
> > +       &dev_attr_can_get_reg.attr,
> > +       &dev_attr_can_set_reg.attr,
> > +       NULL
> > +};
> > +
> > +static const struct attribute_group can_group = {
> > +       .attrs = can_attributes,
> > +       NULL
> > +};
> > +
> >  static const struct mcp251xfd_devtype_data mcp251xfd_devtype_data_mcp2517fd = {
> >         .quirks = MCP251XFD_QUIRK_MAB_NO_WARN | MCP251XFD_QUIRK_CRC_REG |
> >                 MCP251XFD_QUIRK_CRC_RX | MCP251XFD_QUIRK_CRC_TX |
> > @@ -2944,6 +3069,12 @@ static int mcp251xfd_probe(struct spi_device *spi)
> >         if (err)
> >                 goto out_free_candev;
> >
> > +       err = sysfs_create_group(&spi->dev.kobj, &can_group);
> > +       if (err) {
> > +               netdev_err(priv->ndev, "Create can group fail.\n");
> > +               goto out_free_candev;
> > +       }
> > +
> >         err = can_rx_offload_add_manual(ndev, &priv->offload,
> >                                         MCP251XFD_NAPI_WEIGHT);
> >         if (err)
> > @@ -2972,6 +3103,7 @@ static int mcp251xfd_remove(struct spi_device *spi)
> >         mcp251xfd_unregister(priv);
> >         spi->max_speed_hz = priv->spi_max_speed_hz_orig;
> >         free_candev(ndev);
> > +       sysfs_remove_group(&spi->dev.kobj, &can_group);
> >
> >         return 0;
> >  }
> > --
> > 2.25.1
> >