On Fri, Mar 10, 2006 at 04:22:41PM +0100, Blaisorblade wrote:
> 686: if (get_user(c, buf))
> where "buf" is a "const char __user *".
>
> It's complaining because "const" was lost.
>
> Ultimately, I think we should remove all this copying of pointers and do like
> i386 in this regard - there is only one cast to do, in put_user, as I
> mentioned in last mail.
OK, my first patch was insane, try this one:
Index: linux-2.6.15/include/asm-um/uaccess.h
===================================================================
--- linux-2.6.15.orig/include/asm-um/uaccess.h 2006-03-23 15:41:15.000000000
-0500
+++ linux-2.6.15/include/asm-um/uaccess.h 2006-03-23 15:48:52.000000000
-0500
@@ -42,10 +42,10 @@
#define __get_user(x, ptr) \
({ \
const __typeof__(ptr) __private_ptr = ptr; \
- __typeof__(*(__private_ptr)) __private_val; \
+ __typeof__(x) __private_val; \
int __private_ret = -EFAULT; \
(x) = (__typeof__(*(__private_ptr)))0; \
- if (__copy_from_user(&__private_val, (__private_ptr), \
+ if (__copy_from_user((void *) &__private_val, (__private_ptr), \
sizeof(*(__private_ptr))) == 0) {\
(x) = (__typeof__(*(__private_ptr))) __private_val; \
__private_ret = 0; \
The (void *) fixes the warnings all by itself, but I changed the
typeof because that's more correct and fixes some of the warnings by
itself.
What it can't fix is things like (from include/linux/pagemap.h):
volatile char c;
ret = __get_user(c, uaddr);
We unavoidably lose the volatile because we can't know it was there,
so the (void *) cast seems necessary in this case.
Looking at this some more, it seems like most of the complexity could
go away. I think I was avoiding any assignment to the target variable
until I knew that the copy_from_user had succeeded. I think that was
being too paranoid, and just copy_from_user straight into x should be
fine.
Jeff
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