linux-kernel - Re: [PATCH virt-pci] Fix application of sizeof to pointer

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Message-ID: <CA+E=9oto+8PptNNSzwkwrRd+_Ty4GpeyxE=xAggTa140pJxk9A@mail.gmail.com>
Date:   Tue, 12 Oct 2021 14:03:00 +0800
From:   David Yang <davidcomponentone@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     jdike@...toit.com, richard@....at, anton.ivanov@...bridgegreys.com,
        johannes.berg@...el.com, linux-um@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH virt-pci] Fix application of sizeof to pointer

I'm agree with you. Using the "buf->data" instead is better.


On Mon, Oct 11, 2021 at 08:48:27PM -0700, Joe Perches wrote:
> On Tue, 2021-10-12 at 11:23 +0800, davidcomponentone@...il.com wrote:
> > From: David Yang <davidcomponentone@...il.com>
> >
> > The coccinelle check report:
> > "./arch/um/drivers/virt-pci.c:192:20-26:
> > ERROR: application of sizeof to pointer"
> > Using the "sizeof(buf->data)" to fix it.
> []
> > diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
> []
> > @@ -189,7 +189,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
> >     buf = get_cpu_var(um_pci_msg_bufs);
> >     data = buf->data;
> >
> > -   memset(data, 0xff, sizeof(data));
> > +   memset(data, 0xff, sizeof(buf->data));
>
> Perhaps change this to:
>
>       memset(buf->data, 0xff, sizeof(buf->data));
>       data = buf->data;
>
> but honestly, the indirection to data doesn't make the code
> much more readable so maybe just remove data altogether.
> ---
>  arch/um/drivers/virt-pci.c | 13 ++++++-------
>  1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
> index c080666330234..75e05ead97b9a 100644
> --- a/arch/um/drivers/virt-pci.c
> +++ b/arch/um/drivers/virt-pci.c
> @@ -180,7 +180,6 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>       };
>       /* buf->data is maximum size - we may only use parts of it */
>       struct um_pci_message_buffer *buf;
> -     u8 *data;
>       unsigned long ret = ~0ULL;
>
>       if (!dev)
> @@ -189,7 +188,7 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>       buf = get_cpu_var(um_pci_msg_bufs);
>       data = buf->data;
>
> -     memset(data, 0xff, sizeof(data));
> +     memset(buf->data, 0xff, sizeof(buf->data));
>
>       switch (size) {
>       case 1:
> @@ -204,22 +203,22 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
>               goto out;
>       }
>
> -     if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, 8))
> +     if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, buf->data, 8))
>               goto out;
>
>       switch (size) {
>       case 1:
> -             ret = data[0];
> +             ret = buf->data[0];
>               break;
>       case 2:
> -             ret = le16_to_cpup((void *)data);
> +             ret = le16_to_cpup((void *)buf->data);
>               break;
>       case 4:
> -             ret = le32_to_cpup((void *)data);
> +             ret = le32_to_cpup((void *)buf->data);
>               break;
>  #ifdef CONFIG_64BIT
>       case 8:
> -             ret = le64_to_cpup((void *)data);
> +             ret = le64_to_cpup((void *)buf->data);
>               break;
>  #endif
>       default:
>
>