Re: [Xen-devel] [PATCH 2/4] hvm/dmop: Implement copy_{to, from}_guest_buf() in terms of raw accessors

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.04.17 at 10:02, <Paul.Durrant@xxxxxxxxxx> wrote:
>> From: jennifer.herbert@xxxxxxxxxx [mailto:jennifer.herbert@xxxxxxxxxx]
>> Sent: 20 April 2017 19:00
>> +#define copy_from_guest_buf(dst, args, buf_idx) \
>> +    _raw_copy_from_guest_buf(dst, args, buf_idx, sizeof(*(dst)))
>> +
>> +#define copy_to_guest_buf(args, buf_idx, src) \
>> +    _raw_copy_to_guest_buf(args, buf_idx, src, sizeof(*(src)))
>> +
> 
> Not sure I like the use of sizeof(*<thing>) in a macro. If someone was to use 
> these macros and pass a pointer to allocated memory rather than 
> &<thing-on-stack> 
> then they would not have the desired effect. Clearly such use would be very 
> naïve but I wonder whether having something like:
> 
> #define copy_to_guest_buf(args, buf_idx, src) \
>     _raw_copy_to_guest_buf(args, buf_idx, &src, sizeof(src))
> 
> would be safer.

You mean in the case the allocated memory was an array? If it's a
pointer to a singular object, I don't think there would be anything
wrong.

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel