Re: [PATCH] powerpc/uaccess: Don't use "m<>" constraint
On Thu, 2020-05-07 at 12:33:24 UTC, Michael Ellerman wrote:
> The "m<>" constraint breaks compilation with GCC 4.6.x era compilers.
>
> The use of the constraint allows the compiler to use update-form
> instructions, however in practice current compilers never generate
> those forms for any of the current uses of __put_user_asm_goto().
>
> We anticipate that GCC 4.6 will be declared unsupported for building
> the kernel in the not too distant future. So for now just switch to
> the "m" constraint.
>
> Fixes: 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm
> goto'")
> Signed-off-by: Michael Ellerman
Applied to powerpc topic/uaccess-ppc.
https://git.kernel.org/powerpc/c/e2a8b49e79553bd8ec48f73cead84e6146c09408
cheers
Re: [PATCH] powerpc/uaccess: Don't use "m<>" constraint
On Thu, May 07, 2020 at 10:33:24PM +1000, Michael Ellerman wrote:
> The "m<>" constraint breaks compilation with GCC 4.6.x era compilers.
>
> The use of the constraint allows the compiler to use update-form
> instructions, however in practice current compilers never generate
> those forms for any of the current uses of __put_user_asm_goto().
>
> We anticipate that GCC 4.6 will be declared unsupported for building
> the kernel in the not too distant future. So for now just switch to
> the "m" constraint.
>
> Fixes: 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm
> goto'")
> Signed-off-by: Michael Ellerman
Acked-by: Segher Boessenkool
Thanks! So much trouble for what looked like such a simple change, all
those years ago :-(
Segher
[PATCH] powerpc/uaccess: Don't use "m<>" constraint
The "m<>" constraint breaks compilation with GCC 4.6.x era compilers.
The use of the constraint allows the compiler to use update-form
instructions, however in practice current compilers never generate
those forms for any of the current uses of __put_user_asm_goto().
We anticipate that GCC 4.6 will be declared unsupported for building
the kernel in the not too distant future. So for now just switch to
the "m" constraint.
Fixes: 334710b1496a ("powerpc/uaccess: Implement unsafe_put_user() using 'asm
goto'")
Signed-off-by: Michael Ellerman
---
arch/powerpc/include/asm/uaccess.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/uaccess.h
b/arch/powerpc/include/asm/uaccess.h
index 62cc8d7640ec..164112007f54 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -210,7 +210,7 @@ do {
\
"1: " op "%U1%X1 %0,%1 # put_user\n" \
EX_TABLE(1b, %l2) \
: \
- : "r" (x), "m<>" (*addr)\
+ : "r" (x), "m" (*addr) \
: \
: label)
--
2.25.1
