On Wed, 8 Dec 2021 11:04:50 +0800 Xiu Jianfeng <xiujianfeng@xxxxxxxxxx> wrote:
> Motivated by memset_after() and memset_startat(), introduce a new helper,
> memset_range() that takes the target struct instance, the byte to write,
> and two member names where zeroing should start and end.
Is this likely to have more than a single call site?
> ...
>
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -291,6 +291,26 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
> sizeof(*(obj)) - offsetof(typeof(*(obj)), member)); \
> })
>
> +/**
> + * memset_range - Set a value ranging from member1 to member2, boundary included.
I'm not sure what "boundary included" means.
> + *
> + * @obj: Address of target struct instance
> + * @v: Byte value to repeatedly write
> + * @member1: struct member to start writing at
> + * @member2: struct member where writing should stop
Perhaps "struct member before which writing should stop"?
> + *
> + */
> +#define memset_range(obj, v, member_1, member_2) \
> +({ \
> + u8 *__ptr = (u8 *)(obj); \
> + typeof(v) __val = (v); \
> + BUILD_BUG_ON(offsetof(typeof(*(obj)), member_1) > \
> + offsetof(typeof(*(obj)), member_2)); \
> + memset(__ptr + offsetof(typeof(*(obj)), member_1), __val, \
> + offsetofend(typeof(*(obj)), member_2) - \
> + offsetof(typeof(*(obj)), member_1)); \
> +})
struct a {
int b;
int c;
int d;
};
How do I zero out `c' and `d'?
