Messages in this thread | | | Date | Tue, 7 Dec 2021 20:28:29 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH -next 1/2] string.h: Introduce memset_range() for wiping members |
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On Wed, 8 Dec 2021 11:04:50 +0800 Xiu Jianfeng <xiujianfeng@huawei.com> 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'?
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