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@xxxxxxxxxx>
---
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)); \
+})
+
/**
* str_has_prefix - Test if a string has a given prefix
* @str: The string to test
diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c
index 62f8ffcbbaa3..0dd800412455 100644
--- a/lib/memcpy_kunit.c
+++ b/lib/memcpy_kunit.c
@@ -229,6 +229,13 @@ static void memset_test(struct kunit *test)
0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79, 0x79,
},
};
+ struct some_bytes range = {
+ .data = { 0x30, 0x30, 0x30, 0x30, 0x81, 0x81, 0x81, 0x30,
+ 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+ 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+ 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30,
+ },
+ };
struct some_bytes dest = { };
int count, value;
u8 *ptr;
@@ -269,6 +276,11 @@ static void memset_test(struct kunit *test)
dest = control;
memset_startat(&dest, 0x79, four);
compare("memset_startat()", dest, startat);
+
+ /* Verify memset_range() */
+ dest = control;
+ memset_range(&dest, 0x81, two, three);
+ compare("memset_range()", dest, range);
#undef TEST_OP
}
--
2.17.1
