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* [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy()
@ 2019-06-13 11:18 Yoshihiro Shimoda
  2019-06-17  8:40 ` Simon Horman
  2019-06-18  5:59 ` Greg KH
  0 siblings, 2 replies; 5+ messages in thread
From: Yoshihiro Shimoda @ 2019-06-13 11:18 UTC (permalink / raw)
  To: gregkh; +Cc: linux-usb, linux-renesas-soc, Yoshihiro Shimoda

To avoid the error-proneness of calls to sizeof() in the memcpy,
this patch uses struct assignment instead of memcpy.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
---
 This patch is based on Greg's linux-usb.git / usb-next branch.
 Note that mod_host.c also has memcpy but we cannot use struct assignment
 for it because the type of urb->setup_patcket is just "unsigned char *".

 drivers/usb/renesas_usbhs/common.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/renesas_usbhs/common.c b/drivers/usb/renesas_usbhs/common.c
index a501ea6..ebbe322 100644
--- a/drivers/usb/renesas_usbhs/common.c
+++ b/drivers/usb/renesas_usbhs/common.c
@@ -651,9 +651,8 @@ static struct renesas_usbhs_platform_info *usbhs_parse_dt(struct device *dev)
 		return NULL;
 
 	dparam = &info->driver_param;
-	memcpy(dparam, &data->param, sizeof(data->param));
-	memcpy(&info->platform_callback, data->platform_callback,
-	       sizeof(*data->platform_callback));
+	*dparam = data->param;
+	info->platform_callback = *data->platform_callback;
 
 	if (!of_property_read_u32(dev->of_node, "renesas,buswait", &tmp))
 		dparam->buswait_bwait = tmp;
@@ -714,17 +713,13 @@ static int usbhs_probe(struct platform_device *pdev)
 	 * care platform info
 	 */
 
-	memcpy(&priv->dparam,
-	       &info->driver_param,
-	       sizeof(struct renesas_usbhs_driver_param));
+	priv->dparam = info->driver_param;
 
 	if (!info->platform_callback.get_id) {
 		dev_err(&pdev->dev, "no platform callbacks");
 		return -EINVAL;
 	}
-	memcpy(&priv->pfunc,
-	       &info->platform_callback,
-	       sizeof(struct renesas_usbhs_platform_callback));
+	priv->pfunc = info->platform_callback;
 
 	/* set driver callback functions for platform */
 	dfunc			= &info->driver_callback;
-- 
2.7.4


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy()
  2019-06-13 11:18 [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy() Yoshihiro Shimoda
@ 2019-06-17  8:40 ` Simon Horman
  2019-06-18  5:59 ` Greg KH
  1 sibling, 0 replies; 5+ messages in thread
From: Simon Horman @ 2019-06-17  8:40 UTC (permalink / raw)
  To: Yoshihiro Shimoda; +Cc: gregkh, linux-usb, linux-renesas-soc

On Thu, Jun 13, 2019 at 08:18:48PM +0900, Yoshihiro Shimoda wrote:
> To avoid the error-proneness of calls to sizeof() in the memcpy,
> this patch uses struct assignment instead of memcpy.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>

Reviewed-by: Simon Horman <horms+renesas@verge.net.au>

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy()
  2019-06-13 11:18 [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy() Yoshihiro Shimoda
  2019-06-17  8:40 ` Simon Horman
@ 2019-06-18  5:59 ` Greg KH
  2019-06-18  7:26   ` Geert Uytterhoeven
  2019-06-18  8:42   ` Yoshihiro Shimoda
  1 sibling, 2 replies; 5+ messages in thread
From: Greg KH @ 2019-06-18  5:59 UTC (permalink / raw)
  To: Yoshihiro Shimoda; +Cc: linux-usb, linux-renesas-soc

On Thu, Jun 13, 2019 at 08:18:48PM +0900, Yoshihiro Shimoda wrote:
> To avoid the error-proneness of calls to sizeof() in the memcpy,
> this patch uses struct assignment instead of memcpy.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  This patch is based on Greg's linux-usb.git / usb-next branch.
>  Note that mod_host.c also has memcpy but we cannot use struct assignment
>  for it because the type of urb->setup_patcket is just "unsigned char *".
> 
>  drivers/usb/renesas_usbhs/common.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/usb/renesas_usbhs/common.c b/drivers/usb/renesas_usbhs/common.c
> index a501ea6..ebbe322 100644
> --- a/drivers/usb/renesas_usbhs/common.c
> +++ b/drivers/usb/renesas_usbhs/common.c
> @@ -651,9 +651,8 @@ static struct renesas_usbhs_platform_info *usbhs_parse_dt(struct device *dev)
>  		return NULL;
>  
>  	dparam = &info->driver_param;
> -	memcpy(dparam, &data->param, sizeof(data->param));
> -	memcpy(&info->platform_callback, data->platform_callback,
> -	       sizeof(*data->platform_callback));
> +	*dparam = data->param;
> +	info->platform_callback = *data->platform_callback;

How are the original calls here "error-prone"?  Yes, the compiler will
end up calling memcpy somehow with this change, but it feels "wrong" to
hide a memory copy like this.

So are you _sure_ you want this change?

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy()
  2019-06-18  5:59 ` Greg KH
@ 2019-06-18  7:26   ` Geert Uytterhoeven
  2019-06-18  8:42   ` Yoshihiro Shimoda
  1 sibling, 0 replies; 5+ messages in thread
From: Geert Uytterhoeven @ 2019-06-18  7:26 UTC (permalink / raw)
  To: Greg KH; +Cc: Yoshihiro Shimoda, USB list, Linux-Renesas

Hi Greg,

On Tue, Jun 18, 2019 at 9:17 AM Greg KH <gregkh@linuxfoundation.org> wrote:
> On Thu, Jun 13, 2019 at 08:18:48PM +0900, Yoshihiro Shimoda wrote:
> > To avoid the error-proneness of calls to sizeof() in the memcpy,
> > this patch uses struct assignment instead of memcpy.
> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> > ---
> >  This patch is based on Greg's linux-usb.git / usb-next branch.
> >  Note that mod_host.c also has memcpy but we cannot use struct assignment
> >  for it because the type of urb->setup_patcket is just "unsigned char *".
> >
> >  drivers/usb/renesas_usbhs/common.c | 13 ++++---------
> >  1 file changed, 4 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/usb/renesas_usbhs/common.c b/drivers/usb/renesas_usbhs/common.c
> > index a501ea6..ebbe322 100644
> > --- a/drivers/usb/renesas_usbhs/common.c
> > +++ b/drivers/usb/renesas_usbhs/common.c
> > @@ -651,9 +651,8 @@ static struct renesas_usbhs_platform_info *usbhs_parse_dt(struct device *dev)
> >               return NULL;
> >
> >       dparam = &info->driver_param;
> > -     memcpy(dparam, &data->param, sizeof(data->param));
> > -     memcpy(&info->platform_callback, data->platform_callback,
> > -            sizeof(*data->platform_callback));
> > +     *dparam = data->param;
> > +     info->platform_callback = *data->platform_callback;
>
> How are the original calls here "error-prone"?  Yes, the compiler will
> end up calling memcpy somehow with this change, but it feels "wrong" to
> hide a memory copy like this.

There are no checks that:
  - the source and destination pointers point to the same type,
  - the passed size matches the actual object size.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

^ permalink raw reply	[flat|nested] 5+ messages in thread

* RE: [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy()
  2019-06-18  5:59 ` Greg KH
  2019-06-18  7:26   ` Geert Uytterhoeven
@ 2019-06-18  8:42   ` Yoshihiro Shimoda
  1 sibling, 0 replies; 5+ messages in thread
From: Yoshihiro Shimoda @ 2019-06-18  8:42 UTC (permalink / raw)
  To: Greg KH; +Cc: linux-usb, linux-renesas-soc

Hi Greg,

> From: Greg KH, Sent: Tuesday, June 18, 2019 2:59 PM
> 
> On Thu, Jun 13, 2019 at 08:18:48PM +0900, Yoshihiro Shimoda wrote:
> > To avoid the error-proneness of calls to sizeof() in the memcpy,
> > this patch uses struct assignment instead of memcpy.
> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> > ---
> >  This patch is based on Greg's linux-usb.git / usb-next branch.
> >  Note that mod_host.c also has memcpy but we cannot use struct assignment
> >  for it because the type of urb->setup_patcket is just "unsigned char *".
> >
> >  drivers/usb/renesas_usbhs/common.c | 13 ++++---------
> >  1 file changed, 4 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/usb/renesas_usbhs/common.c b/drivers/usb/renesas_usbhs/common.c
> > index a501ea6..ebbe322 100644
> > --- a/drivers/usb/renesas_usbhs/common.c
> > +++ b/drivers/usb/renesas_usbhs/common.c
> > @@ -651,9 +651,8 @@ static struct renesas_usbhs_platform_info *usbhs_parse_dt(struct device *dev)
> >  		return NULL;
> >
> >  	dparam = &info->driver_param;
> > -	memcpy(dparam, &data->param, sizeof(data->param));
> > -	memcpy(&info->platform_callback, data->platform_callback,
> > -	       sizeof(*data->platform_callback));
> > +	*dparam = data->param;
> > +	info->platform_callback = *data->platform_callback;
> 
> How are the original calls here "error-prone"?

When I was developing the patch above [1], I had actually confused
about these arguments of memcpy...

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git/commit/drivers/usb/renesas_usbhs?h=usb-next&id=be21a02a5a5ec88b12ce535ead715d4bbb173a55

I think this is because object and pointer members are mixed in these structures.
So, as I mentioned on the following email [2], I should try to simplify the code
instead of this patch.

[2]
https://marc.info/?l=linux-usb&m=155748940717665&w=2

> So are you _sure_ you want this change?

I'm sorry, I would like to drop this patch.

Best regards,
Yoshihiro Shimoda

> thanks,
> 
> greg k-h

^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-06-13 11:18 [PATCH] usb: renesas_usbhs: Use struct assignment instead of memcpy() Yoshihiro Shimoda
2019-06-17  8:40 ` Simon Horman
2019-06-18  5:59 ` Greg KH
2019-06-18  7:26   ` Geert Uytterhoeven
2019-06-18  8:42   ` Yoshihiro Shimoda

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