Messages in this thread | | | Subject | Re: [PATCH -next 1/2] string.h: Introduce memset_range() for wiping members | From | xiujianfeng <> | Date | Wed, 8 Dec 2021 18:30:26 +0800 |
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在 2021/12/8 12:28, Andrew Morton 写道: > 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? There maybe more call site for this function, but I just use bpf as an example. > >> ... >> >> --- 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. I mean zeroing from member1 to member2(including position indicated by member1 and member2) > >> + * >> + * @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"? memset_range should include position indicated by member2 as well > >> + * >> + */ >> +#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'? if you want to zero out 'c' and 'd', you can use it like memset_range(a_ptr, c, d); > > > .
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