Re: Bug in memcpy() for m68k

Hi Corinna,

Thank you for the advice.
I have attached the patch to this email.

Best regards,
Yuichi Nakamura


On 2026/03/30 17:47, Corinna Vinschen wrote:
> Hi Yuichi,
> 
> unfortunately your patch doesn't apply cleanly due to whitespace issues.
> 
> Can you please create a patch with `git format-patch' and send it via
> `git send-email' to this list?  Alternatively, append the patch created
> with git format-patch as attachment to your mail.  This should avoid
> whitespace issue entirely.
> 
> 
> Thanks,
> Corinna
> 
> 
> On Mar 28 10:35, Yuichi Nakamura via Newlib wrote:
>> Hi all,
>>
>> I found the following issues in the m68k version of memcpy(). In particular,
>> issue #1 is critical because it causes incorrect behavior on the 68000.
>>
>> 1. On CPUs that do not support misaligned access (MISALIGNED_OK=0), such as
>> the 68000, memcpy() does not correctly copy regions larger than 64 KB when
>> the destination is not long-word aligned.
>> 2. The 68020 supports misaligned access, but this is not currently
>> implemented.
>> 3. The 68000 can access long-word data at even addresses, but alignment is
>> checked as if the address must be a multiple of 4.
>> 4. Because the loop count is checked using signed comparison, memcpy() fails
>> for data sizes larger than 2 GB.
>>
>> The following patch fixes these issues.
>>
>> Best regards,
>> Yuichi Nakamura
>>
>>
>> diff --git a/newlib/libc/machine/m68k/memcpy.S
>> b/newlib/libc/machine/m68k/memcpy.S
>> index 464da95ef..ecf1da611 100644
>> --- a/newlib/libc/machine/m68k/memcpy.S
>> +++ b/newlib/libc/machine/m68k/memcpy.S
>> @@ -15,7 +15,7 @@
>>
>>   #include "m68kasm.h"
>>
>> -#if defined (__mcoldfire__) || defined (__mc68030__) || defined
>> (__mc68040__) || defined (__mc68060__)
>> +#if defined (__mcoldfire__) || defined (__mc68020__) || defined
>> (__mc68030__) || defined (__mc68040__) || defined (__mc68060__)
>>   # define MISALIGNED_OK 1
>>   #else
>>   # define MISALIGNED_OK 0
>> @@ -49,10 +49,10 @@ SYM(memcpy):
>>   #if !MISALIGNED_OK
>>          /* Goto .Lresidue if either dest or src is not 4-byte aligned */
>>          move.l  a0,d0
>> -       and.l   #3,d0
>> +       and.l   #1,d0
>>          bne     .Lresidue
>>          move.l  a1,d0
>> -       and.l   #3,d0
>> +       and.l   #1,d0
>>          bne     .Lresidue
>>   #else /* MISALIGNED_OK */
>>          /* align dest */
>> @@ -95,7 +95,7 @@ SYM(memcpy):
>>   #else
>>          subq.l  #1,d0
>>   #endif
>> -       bpl     1b
>> +       bcc     1b
>>          bra     .Lresidue
>>
>>   1:
>> @@ -104,9 +104,13 @@ SYM(memcpy):
>>   .Lresidue:
>>   #if !defined (__mcoldfire__)
>>          dbra    d1,1b           | loop until done
>> +#if !MISALIGNED_OK
>> +       sub.l   #0x10000,d1
>> +       bcc     1b
>> +#endif /* !MISALIGNED_OK */
>>   #else
>>          subq.l  #1,d1
>> -       bpl     1b
>> +       bcc     1b
>>   #endif
>>          move.l  4(sp),d0        | return value
>>          rts

From 1bb0e3e1e05fe97974f8e967814c7ff70046dfbf Mon Sep 17 00:00:00 2001
From: Yuichi Nakamura <[email protected]>
Date: Mon, 30 Mar 2026 22:55:33 +0900
Subject: [PATCH] Fix memcpy alignment problems for m68k architecture

---
 newlib/libc/machine/m68k/memcpy.S | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/newlib/libc/machine/m68k/memcpy.S b/newlib/libc/machine/m68k/memcpy.S
index 464da95ef..ecf1da611 100644
--- a/newlib/libc/machine/m68k/memcpy.S
+++ b/newlib/libc/machine/m68k/memcpy.S
@@ -15,7 +15,7 @@
 
 #include "m68kasm.h"
 
-#if defined (__mcoldfire__) || defined (__mc68030__) || defined (__mc68040__) || defined (__mc68060__)
+#if defined (__mcoldfire__) || defined (__mc68020__) || defined (__mc68030__) || defined (__mc68040__) || defined (__mc68060__)
 # define MISALIGNED_OK 1
 #else
 # define MISALIGNED_OK 0
@@ -49,10 +49,10 @@ SYM(memcpy):
 #if !MISALIGNED_OK
 	/* Goto .Lresidue if either dest or src is not 4-byte aligned */
 	move.l	a0,d0
-	and.l	#3,d0
+	and.l	#1,d0
 	bne	.Lresidue
 	move.l	a1,d0
-	and.l	#3,d0
+	and.l	#1,d0
 	bne	.Lresidue
 #else /* MISALIGNED_OK */
 	/* align dest */
@@ -95,7 +95,7 @@ SYM(memcpy):
 #else
 	subq.l	#1,d0
 #endif
-	bpl	1b
+	bcc	1b
 	bra	.Lresidue
 
 1:
@@ -104,9 +104,13 @@ SYM(memcpy):
 .Lresidue:
 #if !defined (__mcoldfire__)
 	dbra	d1,1b		| loop until done
+#if !MISALIGNED_OK
+	sub.l	#0x10000,d1
+	bcc	1b
+#endif /* !MISALIGNED_OK */
 #else
 	subq.l	#1,d1
-	bpl	1b
+	bcc	1b
 #endif
 	move.l	4(sp),d0	| return value
 	rts
-- 
2.43.0