[Xen-devel] Re: [PATCH 3/6] trace: improve check_tbuf_size()

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

As long as we're being anal, we should be sure to use the actual types
from prod and cons to do the check.  Patch attached.

 -George

On Tue, Jun 29, 2010 at 4:34 PM, Jan Beulich <JBeulich@xxxxxxxxxx> wrote:
> It didn't consider the case of the incoming size not allowing for the
> 2*data_size range for t_buf->{prod,cons}
>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>
> --- 2010-06-15.orig/xen/common/trace.c  2010-06-28 11:58:37.000000000 +0200
> +++ 2010-06-15/xen/common/trace.c       2010-06-28 11:58:37.000000000 +0200
> @@ -77,11 +77,16 @@ static u32 tb_event_mask = TRC_ALL;
>
>  /**
>  * check_tbuf_size - check to make sure that the proposed size will fit
> - * in the currently sized struct t_info.
> + * in the currently sized struct t_info and allows prod and cons to
> + * reach double the value without overflow.
>  */
> -static inline int check_tbuf_size(int size)
> +static int check_tbuf_size(u32 pages)
>  {
> -    return (num_online_cpus() * size + T_INFO_FIRST_OFFSET) > (T_INFO_SIZE / 
> sizeof(uint32_t));
> +    u32 size = pages * PAGE_SIZE;
> +
> +    return (size / PAGE_SIZE != pages) || (size + size < size) ||
> +           (num_online_cpus() * pages + T_INFO_FIRST_OFFSET >
> +            T_INFO_SIZE / sizeof(uint32_t));
>  }
>
>  /**
>
>
>
>

Attachment: trace-check-size-v2.patch
Description: Text Data

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