Re: [PATCH 1/2] move offsetofend() from vfio.h to stddef.h
From: Denys Vlasenko
Date: Mon Mar 09 2015 - 11:16:23 EST
On Mon, Mar 9, 2015 at 3:58 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>> - * offsetofend(TYPE, MEMBER)
>> - *
>> - * @TYPE: The type of the structure
>> - * @MEMBER: The member within the structure to get the end offset of
>> - *
>> - * Simple helper macro for dealing with variable sized structures passed
>> - * from user space. This allows us to easily determine if the provided
>> - * structure is sized to include various fields.
>> - */
>> -#define offsetofend(TYPE, MEMBER) \
>> - (offsetof(TYPE, MEMBER) + sizeof(((TYPE *)0)->MEMBER))
> So I like it, and because it is not particularly trivial when to use
> this primitive it was explained nicely in a description in the vfio.h
> But you lost that nice description during the code move!!
That description was clearly specific to how that macro is used in
drivers/vfio/*.c, along the lines of
minsz = offsetofend(struct vfio_eeh_pe_op, op);
if (copy_from_user(&op, (void __user *)arg, minsz))
if (op.argsz < minsz || op.flags)
But the macro is generic, it has many other uses besides this one.
Nevertheless, I can resend a version where comment survives if you want...
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