Re: [PATCH v14 NEW ALT 1/3] safemath: Add ALIGN_UP_OVF() that checks for {over,under}flow

[Daniel Kiper]

On Sun, May 19, 2024 at 11:48:24AM +0800, Gao Xiang wrote:
> The following EROFS patch will use this helper to handle overflow
> ALIGN_UP() cases.
>
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

I think Vladimir is right.

Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Please post v15 an I will merge it this week.

Thank you for adding EROFS support!

Daniel

> ---
> Hi Daniel,
>
> I've also made another patch to conform Vladimir's and
> Boyang's comments as much as I can.
>
> Thanks,
> Gao Xiang
>
>  include/grub/safemath.h | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/include/grub/safemath.h b/include/grub/safemath.h
> index fbd9b5925..bb8a5b39c 100644
> --- a/include/grub/safemath.h
> +++ b/include/grub/safemath.h
> @@ -32,6 +32,22 @@
>
>  #define grub_cast(a, res)    grub_add ((a), 0, (res))
>
> +/*
> + * It's caller's responsibility that `align` should not equal to 0 and
> + * it must be a power of 2.
> + */
> +#define ALIGN_UP_OVF(v, align, res)                  \
> +({                                                   \
> +  bool __failed;                                     \
> +  typeof(v) __a = ((typeof(v))(align) - 1);          \
> +                                                     \
> +  __failed = grub_add (v, __a, res);                 \
> +  if (__failed == false)                             \
> +    {                                                        \
> +      *(res) &= ~__a;                                        \
> +    }                                                        \
> +__failed;})
> +
>  #else
>  #error gcc 5.1 or newer or clang 8.0 or newer is required
>  #endif