[PATCH] m68k/uaccess: Fix asm constraints for userspace access

[PATCH] m68k/uaccess: Fix asm constraints for userspace access

[Geert Uytterhoeven]

When compiling a MMU kernel with CPU_HAS_ADDRESS_SPACES=n (e.g. "MMU=y
allnoconfig": "echo CONFIG_MMU=y > allno.config && make KCONFIG_ALLCONFIG=1
allnoconfig"), we use plain "move" instead of "moves", and I got:

  CC      arch/m68k/lib/uaccess.o
{standard input}: Assembler messages:
{standard input}:47: Error: operands mismatch -- statement `move.b %a0,(%a1)' ignored

This happens because plain "move" doesn't support byte transfers between
memory and address registers, while "moves" does.

Fix the asm constraints for __generic_copy_from_user(),
__generic_copy_to_user(), and __clear_user() to only use data registers
when accessing userspace.

Also, relax the asm constraints for 16-bit userspace accesses in
__put_user() and __get_user(), as both "move" and "moves" do support
such transfers between memory and address registers.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
 arch/m68k/include/asm/uaccess_mm.h |    4 ++--
 arch/m68k/lib/uaccess.c            |    6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/m68k/include/asm/uaccess_mm.h b/arch/m68k/include/asm/uaccess_mm.h
index 472c891..7aa681b 100644
--- a/arch/m68k/include/asm/uaccess_mm.h
+++ b/arch/m68k/include/asm/uaccess_mm.h
@@ -90,7 +90,7 @@ asm volatile ("\n"					\
 		__put_user_asm(__pu_err, __pu_val, ptr, b, d, -EFAULT);	\
 		break;							\
 	case 2:								\
-		__put_user_asm(__pu_err, __pu_val, ptr, w, d, -EFAULT);	\
+		__put_user_asm(__pu_err, __pu_val, ptr, w, r, -EFAULT);	\
 		break;							\
 	case 4:								\
 		__put_user_asm(__pu_err, __pu_val, ptr, l, r, -EFAULT);	\
@@ -158,7 +158,7 @@ asm volatile ("\n"					\
 		__get_user_asm(__gu_err, x, ptr, u8, b, d, -EFAULT);	\
 		break;							\
 	case 2:								\
-		__get_user_asm(__gu_err, x, ptr, u16, w, d, -EFAULT);	\
+		__get_user_asm(__gu_err, x, ptr, u16, w, r, -EFAULT);	\
 		break;							\
 	case 4:								\
 		__get_user_asm(__gu_err, x, ptr, u32, l, r, -EFAULT);	\
diff --git a/arch/m68k/lib/uaccess.c b/arch/m68k/lib/uaccess.c
index 5e97f2e..35d1442 100644
--- a/arch/m68k/lib/uaccess.c
+++ b/arch/m68k/lib/uaccess.c
@@ -52,7 +52,7 @@ unsigned long __generic_copy_from_user(void *to, const void __user *from,
 		"	.long	3b,30b\n"
 		"	.long	5b,50b\n"
 		"	.previous"
-		: "=d" (res), "+a" (from), "+a" (to), "=&r" (tmp)
+		: "=d" (res), "+a" (from), "+a" (to), "=&d" (tmp)
 		: "0" (n / 4), "d" (n & 3));
 
 	return res;
@@ -96,7 +96,7 @@ unsigned long __generic_copy_to_user(void __user *to, const void *from,
 		"	.long	7b,50b\n"
 		"	.long	8b,50b\n"
 		"	.previous"
-		: "=d" (res), "+a" (from), "+a" (to), "=&r" (tmp)
+		: "=d" (res), "+a" (from), "+a" (to), "=&d" (tmp)
 		: "0" (n / 4), "d" (n & 3));
 
 	return res;
@@ -141,7 +141,7 @@ unsigned long __clear_user(void __user *to, unsigned long n)
 		"	.long	7b,40b\n"
 		"	.previous"
 		: "=d" (res), "+a" (to)
-		: "r" (0), "0" (n / 4), "d" (n & 3));
+		: "d" (0), "0" (n / 4), "d" (n & 3));
 
     return res;
 }
-- 
1.7.0.4

Re: [PATCH] m68k/uaccess: Fix asm constraints for userspace access

[Andreas Schwab]

Geert Uytterhoeven <geert@linux-m68k.org> writes:

> Also, relax the asm constraints for 16-bit userspace accesses in
> __put_user() and __get_user(), as both "move" and "moves" do support
> such transfers between memory and address registers.

There's another occurrence in __constant_copy_from_user and
__constant_copy_to_user.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH] m68k/uaccess: Fix asm constraints for userspace access

[Geert Uytterhoeven]

On Thu, Jun 13, 2013 at 2:25 PM, Andreas Schwab <schwab@linux-m68k.org> wrote:
> Geert Uytterhoeven <geert@linux-m68k.org> writes:
>
>> Also, relax the asm constraints for 16-bit userspace accesses in
>> __put_user() and __get_user(), as both "move" and "moves" do support
>> such transfers between memory and address registers.
>
> There's another occurrence in __constant_copy_from_user and
> __constant_copy_to_user.

Thanks! I will fix those, too.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds