[PATCH v2 2/3] lib/string: optimized memmove
From: Matteo Croce <hidden>
Date: 2021-07-02 12:32:25
Also in:
linux-riscv, lkml
Subsystem:
generic string library, library code, the rest · Maintainers:
Kees Cook, Andrew Morton, Linus Torvalds
From: Matteo Croce <redacted> When the destination buffer is before the source one, or when the buffers doesn't overlap, it's safe to use memcpy() instead, which is optimized to use a bigger data size possible. This "optimization" only covers a common case. In future, proper code which does the same thing as memcpy() does but backwards can be done. Signed-off-by: Matteo Croce <redacted> --- lib/string.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-)
diff --git a/lib/string.c b/lib/string.c
index caeef4264c43..108b83c34cec 100644
--- a/lib/string.c
+++ b/lib/string.c@@ -975,19 +975,13 @@ EXPORT_SYMBOL(memcpy); */ void *memmove(void *dest, const void *src, size_t count) { - char *tmp; - const char *s; + if (dest < src || src + count <= dest) + return memcpy(dest, src, count); + + if (dest > src) { + const char *s = src + count; + char *tmp = dest + count; - if (dest <= src) { - tmp = dest; - s = src; - while (count--) - *tmp++ = *s++; - } else { - tmp = dest; - tmp += count; - s = src; - s += count; while (count--) *--tmp = *--s; }
--
2.31.1