From: Arnd Bergmann <[email protected]>
clang warns about explicitly casting between incompatible function
pointers:
drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
1100 | priv->dev->release = (void (*)(struct device *)) kfree;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Add a separate function to handle this correctly.
Signed-off-by: Arnd Bergmann <[email protected]>
---
drivers/tty/hvc/hvc_iucv.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/hvc/hvc_iucv.c b/drivers/tty/hvc/hvc_iucv.c
index fdecc0d63731..b1149bc62ca1 100644
--- a/drivers/tty/hvc/hvc_iucv.c
+++ b/drivers/tty/hvc/hvc_iucv.c
@@ -1035,6 +1035,10 @@ static const struct attribute_group *hvc_iucv_dev_attr_groups[] = {
NULL,
};
+static void hvc_iucv_free(struct device *data)
+{
+ kfree(data);
+}
/**
* hvc_iucv_alloc() - Allocates a new struct hvc_iucv_private instance
@@ -1097,7 +1101,7 @@ static int __init hvc_iucv_alloc(int id, unsigned int is_console)
priv->dev->bus = &iucv_bus;
priv->dev->parent = iucv_root;
priv->dev->groups = hvc_iucv_dev_attr_groups;
- priv->dev->release = (void (*)(struct device *)) kfree;
+ priv->dev->release = hvc_iucv_free;
rc = device_register(priv->dev);
if (rc) {
put_device(priv->dev);
--
2.39.2
On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote:
> clang warns about explicitly casting between incompatible function
> pointers:
>
> drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> 1100 | priv->dev->release = (void (*)(struct device *)) kfree;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a
function using a non-compatible type is UB. This warning message is
quite misleading. Doubly so because of the -Werror, as always.
Your proposed new code of course is nice and simple (albeit a bit bigger
than it was before, both source and binary). Such is life ;-)
Segher
On 13. 02. 24, 11:17, Arnd Bergmann wrote:
> From: Arnd Bergmann <[email protected]>
>
> clang warns about explicitly casting between incompatible function
> pointers:
>
> drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> 1100 | priv->dev->release = (void (*)(struct device *)) kfree;
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Add a separate function to handle this correctly.
>
> Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Jiri Slaby <[email protected]>
> diff --git a/drivers/tty/hvc/hvc_iucv.c b/drivers/tty/hvc/hvc_iucv.c
> index fdecc0d63731..b1149bc62ca1 100644
> --- a/drivers/tty/hvc/hvc_iucv.c
> +++ b/drivers/tty/hvc/hvc_iucv.c
> @@ -1035,6 +1035,10 @@ static const struct attribute_group *hvc_iucv_dev_attr_groups[] = {
> NULL,
> };
>
> +static void hvc_iucv_free(struct device *data)
> +{
> + kfree(data);
> +}
>
> /**
> * hvc_iucv_alloc() - Allocates a new struct hvc_iucv_private instance
> @@ -1097,7 +1101,7 @@ static int __init hvc_iucv_alloc(int id, unsigned int is_console)
> priv->dev->bus = &iucv_bus;
> priv->dev->parent = iucv_root;
> priv->dev->groups = hvc_iucv_dev_attr_groups;
> - priv->dev->release = (void (*)(struct device *)) kfree;
> + priv->dev->release = hvc_iucv_free;
> rc = device_register(priv->dev);
> if (rc) {
> put_device(priv->dev);
--
js
suse labs
From: Segher Boessenkool
> Sent: 13 February 2024 19:13
>
> On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote:
> > clang warns about explicitly casting between incompatible function
> > pointers:
> >
> > drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct
> device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> > 1100 | priv->dev->release = (void (*)(struct device *)) kfree;
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a
> function using a non-compatible type is UB. This warning message is
> quite misleading. Doubly so because of the -Werror, as always.
But it will get called using the wrong type.
And (is it) fine-ibt will reject the incorrect call.
Has clang/gcc added an attribute to 'seed' the ibt hash yet?
So that functions that are void (*)(void) can be separated?
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
On Wed, Feb 14, 2024 at 09:46:33AM +0000, David Laight wrote:
> From: Segher Boessenkool
> > Sent: 13 February 2024 19:13
> >
> > On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote:
> > > clang warns about explicitly casting between incompatible function
> > > pointers:
> > >
> > > drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct
> > device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> > > 1100 | priv->dev->release = (void (*)(struct device *)) kfree;
> > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a
> > function using a non-compatible type is UB. This warning message is
> > quite misleading. Doubly so because of the -Werror, as always.
>
> But it will get called using the wrong type.
> And (is it) fine-ibt will reject the incorrect call.
And rightfully so, this type of casting abuse is just that, abuse.
Almost no one should be just calling kfree() on a device pointer, I'll
look at the surrounding code as odds are something odd is going on. But
for now, this patch is correct.
thanks,
greg k-h
On Wed, Feb 14, 2024 at 11:37:21AM +0100, Greg Kroah-Hartman wrote:
> On Wed, Feb 14, 2024 at 09:46:33AM +0000, David Laight wrote:
> > From: Segher Boessenkool
> > > Sent: 13 February 2024 19:13
> > >
> > > On Tue, Feb 13, 2024 at 11:17:49AM +0100, Arnd Bergmann wrote:
> > > > clang warns about explicitly casting between incompatible function
> > > > pointers:
> > > >
> > > > drivers/tty/hvc/hvc_iucv.c:1100:23: error: cast from 'void (*)(const void *)' to 'void (*)(struct
> > > device *)' converts to incompatible function type [-Werror,-Wcast-function-type-strict]
> > > > 1100 | priv->dev->release = (void (*)(struct device *)) kfree;
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > >
> > > Such a cast of course is explicitly allowed by 6.3.2.3/8, only calling a
> > > function using a non-compatible type is UB. This warning message is
> > > quite misleading. Doubly so because of the -Werror, as always.
> >
> > But it will get called using the wrong type.
> > And (is it) fine-ibt will reject the incorrect call.
>
> And rightfully so, this type of casting abuse is just that, abuse.
>
> Almost no one should be just calling kfree() on a device pointer, I'll
> look at the surrounding code as odds are something odd is going on. But
> for now, this patch is correct.
Yes, and I said so. My point is that the warning message pretends the
cast is bad or dangerous. It is not, similar casts are the only way in
C to do certain things (yes, you can always avoid it completely, by
writing completely different code, like the patch does, and that
sometimes is a better idea even).
But the warning message is misleading and does more damage than it helps
avoid.
Segher