在 2021/12/8 12:28, Andrew Morton 写道:
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?
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);
.
