Re: [PATCH -next 1/2] string.h: Introduce memset_range() for wiping members
flat view
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2021-12-08 04:28:38
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On Wed, 8 Dec 2021 11:04:50 +0800 Xiu Jianfeng [off-list ref] 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?
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...--- 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.
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+ * + * @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"?
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+ * + */ +#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'?