| Date | Tue, 6 Jan 2015 17:44:43 +0200 | From | "Michael S. Tsirkin" <> | Subject | [PATCH v2 22/40] tile: fix put_user sparse errors |
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virtio wants to write bitwise types to userspace using put_user. At the moment this triggers sparse errors, since the value is passed through an integer.
For example:
__le32 __user *p; __le32 x; put_user(x, p);
is safe, but currently triggers a sparse warning on tile.
The reason has to do with this code: __typeof((x)-(x)) which seems to be a way to force check for an integer type.
Since this is part of __put_user_8 which is only ever used for unsigned and signed char types, this seems unnecessary - I also note that no other architecture has such protections.
Fix that up using __force u64 cast.
Note: this does not suppress any useful sparse checks since the original merely casted x to typeof(x-x).
Tile currently does not trigger sparse warnings when get_user causes an illegal assignment across bitwise types. This patch does not attempt to fix this.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- arch/tile/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/tile/include/asm/uaccess.h b/arch/tile/include/asm/uaccess.h index b6cde32..22cffa1 100644 --- a/arch/tile/include/asm/uaccess.h +++ b/arch/tile/include/asm/uaccess.h @@ -246,7 +246,7 @@ extern int __get_user_bad(void) #define __put_user_4(x, ptr, ret) __put_user_asm(sw, x, ptr, ret) #define __put_user_8(x, ptr, ret) \ ({ \ - u64 __x = (__typeof((x)-(x)))(x); \ + u64 __x = (__force u64)(x); \ int __lo = (int) __x, __hi = (int) (__x >> 32); \ asm volatile("1: { sw %1, %2; addi %0, %1, 4 }\n" \ "2: { sw %0, %3; movei %0, 0 }\n" \ -- MST
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