diff mbox series

[v2,09/11] gpiolib: provide a dedicated function for setting lineinfo

Message ID 20191204155912.17590-10-brgl@bgdev.pl
State New
Headers show
Series gpiolib: add an ioctl() for monitoring line status changes | expand

Commit Message

Bartosz Golaszewski Dec. 4, 2019, 3:59 p.m. UTC 
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

We'll soon be filling out the gpioline_info structure in multiple
places. Add a separate function that given a gpio_desc sets all relevant
fields.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
 drivers/gpio/gpiolib.c | 98 ++++++++++++++++++++++++------------------
 1 file changed, 55 insertions(+), 43 deletions(-)

Comments

Andy Shevchenko Dec. 4, 2019, 10:30 p.m. UTC | #1 
On Wed, Dec 4, 2019 at 6:02 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
>
> We'll soon be filling out the gpioline_info structure in multiple
> places. Add a separate function that given a gpio_desc sets all relevant
> fields.

> +       if (desc->name) {
> +               strncpy(info->name, desc->name, sizeof(info->name));
> +               info->name[sizeof(info->name) - 1] = '\0';
> +       } else {
> +               info->name[0] = '\0';
> +       }
> +
> +       if (desc->label) {
> +               strncpy(info->consumer, desc->label, sizeof(info->consumer));
> +               info->consumer[sizeof(info->consumer) - 1] = '\0';
> +       } else {
> +               info->consumer[0] = '\0';
> +       }

I think we have to fix GCC warnings first and then do whatever this patch does.
Bartosz Golaszewski Dec. 5, 2019, 9:28 a.m. UTC | #2 
śr., 4 gru 2019 o 23:30 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
>
> On Wed, Dec 4, 2019 at 6:02 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> >
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > We'll soon be filling out the gpioline_info structure in multiple
> > places. Add a separate function that given a gpio_desc sets all relevant
> > fields.
>
> > +       if (desc->name) {
> > +               strncpy(info->name, desc->name, sizeof(info->name));
> > +               info->name[sizeof(info->name) - 1] = '\0';
> > +       } else {
> > +               info->name[0] = '\0';
> > +       }
> > +
> > +       if (desc->label) {
> > +               strncpy(info->consumer, desc->label, sizeof(info->consumer));
> > +               info->consumer[sizeof(info->consumer) - 1] = '\0';
> > +       } else {
> > +               info->consumer[0] = '\0';
> > +       }
>
> I think we have to fix GCC warnings first and then do whatever this patch does.
>

What GCC warnings are you referring to exactly?

Bart

> --
> With Best Regards,
> Andy Shevchenko
Andy Shevchenko Dec. 5, 2019, 10:20 a.m. UTC | #3 
On Thu, Dec 5, 2019 at 11:28 AM Bartosz Golaszewski
<bgolaszewski@baylibre.com> wrote:
> śr., 4 gru 2019 o 23:30 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
> > On Wed, Dec 4, 2019 at 6:02 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> > > +       if (desc->name) {
> > > +               strncpy(info->name, desc->name, sizeof(info->name));
> > > +               info->name[sizeof(info->name) - 1] = '\0';
> > > +       } else {
> > > +               info->name[0] = '\0';
> > > +       }
> > > +
> > > +       if (desc->label) {
> > > +               strncpy(info->consumer, desc->label, sizeof(info->consumer));
> > > +               info->consumer[sizeof(info->consumer) - 1] = '\0';
> > > +       } else {
> > > +               info->consumer[0] = '\0';
> > > +       }
> >
> > I think we have to fix GCC warnings first and then do whatever this patch does.
> >
>
> What GCC warnings are you referring to exactly?

stncpy() against partial string without NUL-terminator.

So, if desc->label is longer than info->consumer, it will be copied
partially. I don't check if the modern GCC clever enough to see the
next operation which does the termination.
Bartosz Golaszewski Dec. 5, 2019, 1:45 p.m. UTC | #4 
czw., 5 gru 2019 o 11:21 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
>
> On Thu, Dec 5, 2019 at 11:28 AM Bartosz Golaszewski
> <bgolaszewski@baylibre.com> wrote:
> > śr., 4 gru 2019 o 23:30 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
> > > On Wed, Dec 4, 2019 at 6:02 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> > > > +       if (desc->name) {
> > > > +               strncpy(info->name, desc->name, sizeof(info->name));
> > > > +               info->name[sizeof(info->name) - 1] = '\0';
> > > > +       } else {
> > > > +               info->name[0] = '\0';
> > > > +       }
> > > > +
> > > > +       if (desc->label) {
> > > > +               strncpy(info->consumer, desc->label, sizeof(info->consumer));
> > > > +               info->consumer[sizeof(info->consumer) - 1] = '\0';
> > > > +       } else {
> > > > +               info->consumer[0] = '\0';
> > > > +       }
> > >
> > > I think we have to fix GCC warnings first and then do whatever this patch does.
> > >
> >
> > What GCC warnings are you referring to exactly?
>
> stncpy() against partial string without NUL-terminator.
>
> So, if desc->label is longer than info->consumer, it will be copied
> partially. I don't check if the modern GCC clever enough to see the
> next operation which does the termination.
>

I'm not sure I get it. What warnings does it produce and in what
environment? I don't see any.

If you want it simpler - we can do `snprintf(info->consumer,
sizeof(info->consumer), desc->label ?: "")`.

Bart
Andy Shevchenko Dec. 5, 2019, 4:47 p.m. UTC | #5 
On Thu, Dec 5, 2019 at 3:45 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> czw., 5 gru 2019 o 11:21 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
> > On Thu, Dec 5, 2019 at 11:28 AM Bartosz Golaszewski
> > <bgolaszewski@baylibre.com> wrote:
> > > śr., 4 gru 2019 o 23:30 Andy Shevchenko <andy.shevchenko@gmail.com> napisał(a):
> > > > On Wed, Dec 4, 2019 at 6:02 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> > > > > +       if (desc->name) {
> > > > > +               strncpy(info->name, desc->name, sizeof(info->name));
> > > > > +               info->name[sizeof(info->name) - 1] = '\0';
> > > > > +       } else {
> > > > > +               info->name[0] = '\0';
> > > > > +       }
> > > > > +
> > > > > +       if (desc->label) {
> > > > > +               strncpy(info->consumer, desc->label, sizeof(info->consumer));
> > > > > +               info->consumer[sizeof(info->consumer) - 1] = '\0';
> > > > > +       } else {
> > > > > +               info->consumer[0] = '\0';
> > > > > +       }
> > > >
> > > > I think we have to fix GCC warnings first and then do whatever this patch does.
> > > >
> > >
> > > What GCC warnings are you referring to exactly?
> >
> > stncpy() against partial string without NUL-terminator.
> >
> > So, if desc->label is longer than info->consumer, it will be copied
> > partially. I don't check if the modern GCC clever enough to see the
> > next operation which does the termination.
> >
>
> I'm not sure I get it. What warnings does it produce and in what
> environment?

Some kind of
warning: ‘strncpy’ specified bound 16 equals destination size
[-Wstringop-truncation]

> I don't see any.

Good, I just checked and see none as well. It means GCC understands
that strncpy() is followed by guaranteed NUL-termination.

> If you want it simpler - we can do `snprintf(info->consumer,
> sizeof(info->consumer), desc->label ?: "")`.

It makes sense only in above context.
diff mbox series

Patch

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index c89d297da270..711963aa9239 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1145,6 +1145,60 @@  static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	return ret;
 }
 
+static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
+				  struct gpioline_info *info)
+{
+	struct gpio_chip *chip = desc->gdev->chip;
+	unsigned long flags;
+
+	spin_lock_irqsave(&gpio_lock, flags);
+
+	if (desc->name) {
+		strncpy(info->name, desc->name, sizeof(info->name));
+		info->name[sizeof(info->name) - 1] = '\0';
+	} else {
+		info->name[0] = '\0';
+	}
+
+	if (desc->label) {
+		strncpy(info->consumer, desc->label, sizeof(info->consumer));
+		info->consumer[sizeof(info->consumer) - 1] = '\0';
+	} else {
+		info->consumer[0] = '\0';
+	}
+
+	/*
+	 * Userspace only need to know that the kernel is using this GPIO so
+	 * it can't use it.
+	 */
+	info->flags = 0;
+	if (test_bit(FLAG_REQUESTED, &desc->flags) ||
+	    test_bit(FLAG_IS_HOGGED, &desc->flags) ||
+	    test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
+	    test_bit(FLAG_EXPORT, &desc->flags) ||
+	    test_bit(FLAG_SYSFS, &desc->flags) ||
+	    !pinctrl_gpio_can_use_line(chip->base + info->line_offset))
+		info->flags |= GPIOLINE_FLAG_KERNEL;
+	if (test_bit(FLAG_IS_OUT, &desc->flags))
+		info->flags |= GPIOLINE_FLAG_IS_OUT;
+	if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+		info->flags |= GPIOLINE_FLAG_ACTIVE_LOW;
+	if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
+		info->flags |= (GPIOLINE_FLAG_OPEN_DRAIN |
+				GPIOLINE_FLAG_IS_OUT);
+	if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
+		info->flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
+				GPIOLINE_FLAG_IS_OUT);
+	if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
+		info->flags |= GPIOLINE_FLAG_BIAS_DISABLE;
+	if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+		info->flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
+	if (test_bit(FLAG_PULL_UP, &desc->flags))
+		info->flags |= GPIOLINE_FLAG_BIAS_PULL_UP;
+
+	spin_unlock_irqrestore(&gpio_lock, flags);
+}
+
 /*
  * gpio_ioctl() - ioctl handler for the GPIO chardev
  */
@@ -1185,49 +1239,7 @@  static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		if (IS_ERR(desc))
 			return PTR_ERR(desc);
 
-		if (desc->name) {
-			strncpy(lineinfo.name, desc->name,
-				sizeof(lineinfo.name));
-			lineinfo.name[sizeof(lineinfo.name)-1] = '\0';
-		} else {
-			lineinfo.name[0] = '\0';
-		}
-		if (desc->label) {
-			strncpy(lineinfo.consumer, desc->label,
-				sizeof(lineinfo.consumer));
-			lineinfo.consumer[sizeof(lineinfo.consumer)-1] = '\0';
-		} else {
-			lineinfo.consumer[0] = '\0';
-		}
-
-		/*
-		 * Userspace only need to know that the kernel is using
-		 * this GPIO so it can't use it.
-		 */
-		lineinfo.flags = 0;
-		if (test_bit(FLAG_REQUESTED, &desc->flags) ||
-		    test_bit(FLAG_IS_HOGGED, &desc->flags) ||
-		    test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
-		    test_bit(FLAG_EXPORT, &desc->flags) ||
-		    test_bit(FLAG_SYSFS, &desc->flags) ||
-		    !pinctrl_gpio_can_use_line(chip->base + lineinfo.line_offset))
-			lineinfo.flags |= GPIOLINE_FLAG_KERNEL;
-		if (test_bit(FLAG_IS_OUT, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_IS_OUT;
-		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_ACTIVE_LOW;
-		if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
-			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_DRAIN |
-					   GPIOLINE_FLAG_IS_OUT);
-		if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
-			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
-					   GPIOLINE_FLAG_IS_OUT);
-		if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_BIAS_DISABLE;
-		if (test_bit(FLAG_PULL_DOWN, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_DOWN;
-		if (test_bit(FLAG_PULL_UP, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_BIAS_PULL_UP;
+		gpio_desc_to_lineinfo(desc, &lineinfo);
 
 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;