On Fri, Jun 15, 2018 at 12:26 AM, Johannes Berg
<[email protected]> wrote:
> There's a bug in *_encode_bits() in using ~field_multiplier() for
> the check whether or not the constant value fits into the field,
> this is wrong and clearly ~field_mask() was intended. This was
> triggering for me for both constant and non-constant values.
>
> Additionally, make this case actually into an compile error.
> Declaring the extern function that will never exist with just a
> warning is pointless as then later we'll just get a link error.
>
> While at it, also fix the indentation in those lines I'm touching.
I'm just wondering if we have test cases for that API.
If not, perhaps it's a good time to start (perhaps extend test_bitmap.c)?
Otherwise, the fix looks good!
>
> Fixes: 00b0c9b82663 ("Add primitives for manipulating bitfields both in host-
> and fixed-endian.")
> Signed-off-by: Johannes Berg <[email protected]>
> ---
> v2: replace stray tab by space
>
> If you don't mind, I'd like to take this through the networking
> tree(s) as a fix since I have some pending code that depends on
> it.
> ---
> include/linux/bitfield.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h
> index cf2588d81148..147a7bb341dd 100644
> --- a/include/linux/bitfield.h
> +++ b/include/linux/bitfield.h
> @@ -104,7 +104,7 @@
> (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
> })
>
> -extern void __compiletime_warning("value doesn't fit into mask")
> +extern void __compiletime_error("value doesn't fit into mask")
> __field_overflow(void);
> extern void __compiletime_error("bad bitfield mask")
> __bad_mask(void);
> @@ -121,8 +121,8 @@ static __always_inline u64 field_mask(u64 field)
> #define ____MAKE_OP(type,base,to,from) \
> static __always_inline __##type type##_encode_bits(base v, base field) \
> { \
> - if (__builtin_constant_p(v) && (v & ~field_multiplier(field))) \
> - __field_overflow(); \
> + if (__builtin_constant_p(v) && (v & ~field_mask(field))) \
> + __field_overflow(); \
> return to((v & field_mask(field)) * field_multiplier(field)); \
> } \
> static __always_inline __##type type##_replace_bits(__##type old, \
> --
> 2.14.4
>
--
With Best Regards,
Andy Shevchenko
