* [PATCH] m68k/uaccess: Revive 64-bit get_user()
@ 2018-05-14 13:57 Geert Uytterhoeven
2018-05-14 21:34 ` Martijn Coenen
0 siblings, 1 reply; 2+ messages in thread
From: Geert Uytterhoeven @ 2018-05-14 13:57 UTC (permalink / raw)
To: linux-m68k
Cc: Martijn Coenen, Christoph Hellwig, linux-kernel, Geert Uytterhoeven
Revive support for 64-bit get_user(), which was disabled in commit
d94af931af42152e ("[PATCH] m68k: clean up uaccess.h") due to a "broken"
typeof in (then brand new) gcc-4.1.
- Keep on using u64 for the temporary, as __typeof__() doesn't drop
the const qualifier,
- Move it into a union (like mips32 does) to get rid of the cast, as
using get_user() to fetch a __user pointer would cause a "cast to
pointer from integer of different size" warning otherwise.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
arch/m68k/include/asm/uaccess_mm.h | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/m68k/include/asm/uaccess_mm.h b/arch/m68k/include/asm/uaccess_mm.h
index 75c172e909acdf18..c4cb889660aa0c35 100644
--- a/arch/m68k/include/asm/uaccess_mm.h
+++ b/arch/m68k/include/asm/uaccess_mm.h
@@ -141,10 +141,12 @@ asm volatile ("\n" \
case 4: \
__get_user_asm(__gu_err, x, ptr, u32, l, r, -EFAULT); \
break; \
-/* case 8: disabled because gcc-4.1 has a broken typeof \
- { \
- const void *__gu_ptr = (ptr); \
- u64 __gu_val; \
+ case 8: { \
+ const void *__gu_ptr = (ptr); \
+ union { \
+ u64 l; \
+ __typeof__(*(ptr)) t; \
+ } __gu_val; \
asm volatile ("\n" \
"1: "MOVES".l (%2)+,%1\n" \
"2: "MOVES".l (%2),%R1\n" \
@@ -162,13 +164,13 @@ asm volatile ("\n" \
" .long 1b,10b\n" \
" .long 2b,10b\n" \
" .previous" \
- : "+d" (__gu_err), "=&r" (__gu_val), \
+ : "+d" (__gu_err), "=&r" (__gu_val.l), \
"+a" (__gu_ptr) \
: "i" (-EFAULT) \
: "memory"); \
- (x) = (__force typeof(*(ptr)))__gu_val; \
+ (x) = __gu_val.t; \
break; \
- } */ \
+ } \
default: \
__gu_err = __get_user_bad(); \
break; \
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] m68k/uaccess: Revive 64-bit get_user()
2018-05-14 13:57 [PATCH] m68k/uaccess: Revive 64-bit get_user() Geert Uytterhoeven
@ 2018-05-14 21:34 ` Martijn Coenen
0 siblings, 0 replies; 2+ messages in thread
From: Martijn Coenen @ 2018-05-14 21:34 UTC (permalink / raw)
To: Geert Uytterhoeven; +Cc: linux-m68k, Christoph Hellwig, LKML
On Mon, May 14, 2018 at 3:57 PM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> Revive support for 64-bit get_user(), which was disabled in commit
> d94af931af42152e ("[PATCH] m68k: clean up uaccess.h") due to a "broken"
> typeof in (then brand new) gcc-4.1.
>
> - Keep on using u64 for the temporary, as __typeof__() doesn't drop
> the const qualifier,
> - Move it into a union (like mips32 does) to get rid of the cast, as
> using get_user() to fetch a __user pointer would cause a "cast to
> pointer from integer of different size" warning otherwise.
Can't vouch for the existing asm, but the changes to it look good to
me otherwise.
>
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Martijn Coenen <maco@android.com>
> ---
> arch/m68k/include/asm/uaccess_mm.h | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> diff --git a/arch/m68k/include/asm/uaccess_mm.h b/arch/m68k/include/asm/uaccess_mm.h
> index 75c172e909acdf18..c4cb889660aa0c35 100644
> --- a/arch/m68k/include/asm/uaccess_mm.h
> +++ b/arch/m68k/include/asm/uaccess_mm.h
> @@ -141,10 +141,12 @@ asm volatile ("\n" \
> case 4: \
> __get_user_asm(__gu_err, x, ptr, u32, l, r, -EFAULT); \
> break; \
> -/* case 8: disabled because gcc-4.1 has a broken typeof \
> - { \
> - const void *__gu_ptr = (ptr); \
> - u64 __gu_val; \
> + case 8: { \
> + const void *__gu_ptr = (ptr); \
> + union { \
> + u64 l; \
> + __typeof__(*(ptr)) t; \
> + } __gu_val; \
> asm volatile ("\n" \
> "1: "MOVES".l (%2)+,%1\n" \
> "2: "MOVES".l (%2),%R1\n" \
> @@ -162,13 +164,13 @@ asm volatile ("\n" \
> " .long 1b,10b\n" \
> " .long 2b,10b\n" \
> " .previous" \
> - : "+d" (__gu_err), "=&r" (__gu_val), \
> + : "+d" (__gu_err), "=&r" (__gu_val.l), \
> "+a" (__gu_ptr) \
> : "i" (-EFAULT) \
> : "memory"); \
> - (x) = (__force typeof(*(ptr)))__gu_val; \
> + (x) = __gu_val.t; \
> break; \
> - } */ \
> + } \
> default: \
> __gu_err = __get_user_bad(); \
> break; \
> --
> 2.7.4
>
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