linux-kernel - RE: [PATCH v2] virt: vbox: use %pap format for printing resource_size

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Date:   Thu, 21 Dec 2017 17:02:45 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arnd Bergmann' <arnd@...db.de>,
        Hans de Goede <hdegoede@...hat.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
CC:     Joe Perches <joe@...ches.com>,
        Larry Finger <Larry.Finger@...inger.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] virt: vbox: use %pap format for printing
 resource_size_t

From: Arnd Bergmann
> Sent: 21 December 2017 16:15
> 
> resource_size_t may be larger than pointers depending on configuration,
> so we can run into this build warning:
> 
> drivers/virt/vboxguest/vboxguest_linux.c: In function 'vbg_pci_probe':
> drivers/virt/vboxguest/vboxguest_linux.c:295:4: error: cast to pointer from integer of different size
> [-Werror=int-to-pointer-cast]
> drivers/virt/vboxguest/vboxguest_linux.c:367:4: error: cast to pointer from integer of different size
> [-Werror=int-to-pointer-cast]
> 
> This uses the special %pap to print the address by reference.
> 
> Fixes: 0ba002bc4393 ("virt: Add vboxguest driver for Virtual Box Guest integration")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2: Use %pap instead of the %rR that was just as incorrect, as
>     pointed out by Joe Perches.
> ---
>  drivers/virt/vboxguest/vboxguest_linux.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virt/vboxguest/vboxguest_linux.c b/drivers/virt/vboxguest/vboxguest_linux.c
> index d045aa51ce03..82e280d38cc2 100644
> --- a/drivers/virt/vboxguest/vboxguest_linux.c
> +++ b/drivers/virt/vboxguest/vboxguest_linux.c
> @@ -291,8 +291,8 @@ static int vbg_pci_probe(struct pci_dev *pci, const struct pci_device_id *id)
> 
>  	vmmdev = devm_ioremap(dev, mmio, mmio_len);
>  	if (!vmmdev) {
> -		vbg_err("vboxguest: Error ioremap failed; MMIO addr=%p size=%d\n",
> -			(void *)mmio, (int)mmio_len);
> +		vbg_err("vboxguest: Error ioremap failed; MMIO addr=%pap size=%pap\n",
> +			&mmio, &mmio_len);

Are you sure about the type of mmio_len?
While the argument to devm_ioremap() is of type resource_size_t it seems
extremely unlikely that the actual value will exceed 2^32.
Using a 64bit type for the length on 32bit systems will generate horrid code.

I can't see the code in my tree to check.

	David