[PATCH 6.18 321/752] m68k: nommu: fix memmove() with differently aligned src and dest for 68000

Sasha Levin
2026-02-28T17:52:37Z

From: Daniel Palmer <daniel@thingy.jp>

[ Upstream commit 590fe2f46c8698bb758f9002cb247ca10ce95569 ]

68000 has different alignment needs to 68020+.
memcpy() checks if the destination is aligned and does a smaller copy
to fix the alignment and then critically for 68000 it checks if the
source is still unaligned and if it is reverts to smaller copies.

memmove() does not currently do the second part and malfunctions if
one of the pointers is aligned and the other isn't.

This is apparently getting triggered by printk. If I put breakpoints
into the new checks added by this commit the first hit looks like this:

memmove (n=205, src=0x2f3971 <printk_shared_pbufs+205>, dest=0x2f3980 <printk_shared_pbufs+220>) at arch/m68k/lib/memmove.c:82

Signed-off-by: Daniel Palmer <daniel@thingy.jp>
Signed-off-by: Greg Ungerer <gerg@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/m68k/lib/memmove.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/m68k/lib/memmove.c b/arch/m68k/lib/memmove.c
index 6519f7f349f66..e33f00b02e4c0 100644
--- a/arch/m68k/lib/memmove.c
+++ b/arch/m68k/lib/memmove.c
@@ -24,6 +24,15 @@ void *memmove(void *dest, const void *src, size_t n)
src = csrc;
n--;
}
+#if defined(CONFIG_M68000)
+ if ((long)src & 1) {
+ char *cdest = dest;
+ const char *csrc = src;
+ for (; n; n--)
+ *cdest++ = *csrc++;
+ return xdest;
+ }
+#endif
if (n > 2 && (long)dest & 2) {
short *sdest = dest;
const short *ssrc = src;
@@ -66,6 +75,15 @@ void *memmove(void *dest, const void *src, size_t n)
src = csrc;
n--;
}
+#if defined(CONFIG_M68000)
+ if ((long)src & 1) {
+ char *cdest = dest;
+ const char *csrc = src;
+ for (; n; n--)
+ *--cdest = *--csrc;
+ return xdest;
+ }
+#endif
if (n > 2 && (long)dest & 2) {
short *sdest = dest;
const short *ssrc = src;
--
2.51.0