Re: [PATCH -next 1/2] string.h: Introduce memset_range() for wiping members
flat view
From: Alexey Dobriyan <hidden>
Date: 2021-12-08 17:12:34
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On Wed, Dec 08, 2021 at 11:04:50AM +0800, Xiu Jianfeng wrote:
quoted hunk ↗ jump to hunk
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. Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com> --- include/linux/string.h | 20 ++++++++++++++++++++ lib/memcpy_kunit.c | 12 ++++++++++++ 2 files changed, 32 insertions(+)diff --git a/include/linux/string.h b/include/linux/string.h index b6572aeca2f5..7f19863253f2 100644 --- 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. + * + * @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 + * + */ +#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)); \ +})
"u8*" should be "void*" as kernel legitimises pointer arithmetic on void* and there is no dereference. __val is redundant, just toss "v" into memset(), it will do the right thing. In fact, toss "__ptr" as well, it is simply unnecessary. All previous memsets are the same...