[PATCH 04/20] libchip/serial/ns16550* and z8530*: Assert on baud number to avoid divide by 0

[Gedare Bloom]

On Tue, Nov 25, 2014 at 6:02 PM, Joel Sherrill
<joel.sherrill at oarcorp.com> wrote:
> From: Josh Oguin <josh.oguin at oarcorp.com>
>
> This was flagged by CodeSonar. It should be impossible to get an
> incorrect baud number back but ensure this in debug mode. The _Assert()
> keeps their scanner from evaluating for divide by 0 past this point.
> ---
>  c/src/libchip/serial/ns16550-context.c | 4 ++++
>  c/src/libchip/serial/ns16550.c         | 3 +++
>  c/src/libchip/serial/z85c30.c          | 8 +++++++-
>  3 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/c/src/libchip/serial/ns16550-context.c b/c/src/libchip/serial/ns16550-context.c
> index 00ad89c..087627a 100644
> --- a/c/src/libchip/serial/ns16550-context.c
> +++ b/c/src/libchip/serial/ns16550-context.c
> @@ -592,9 +592,13 @@ static bool ns16550_set_attributes(
>
>    /*
>     *  Calculate the baud rate divisor
> +   *
> +   *  Assert ensures there is no division by 0.
Try not to add obvious comments.

>     */
>
>    baud_requested = rtems_termios_baud_to_number(t->c_cflag);
> +  _Assert( baud_requested != 0 );
> +
>    ulBaudDivisor = NS16550_GetBaudDivisor(ctx, baud_requested);
>
>    ucLineControl = 0;
> diff --git a/c/src/libchip/serial/ns16550.c b/c/src/libchip/serial/ns16550.c
> index 2c3bc94..801533b 100644
> --- a/c/src/libchip/serial/ns16550.c
> +++ b/c/src/libchip/serial/ns16550.c
> @@ -532,9 +532,12 @@ int ns16550_set_attributes(
>
>    /*
>     *  Calculate the baud rate divisor
> +   *
> +   *  Assert ensures there is no division by 0.
>     */
>
>    baud_requested = rtems_termios_baud_to_number(t->c_cflag);
> +  _Assert( baud_requested != 0 );
>    ulBaudDivisor = NS16550_GetBaudDivisor(c, baud_requested);
>
>    ucLineControl = 0;
> diff --git a/c/src/libchip/serial/z85c30.c b/c/src/libchip/serial/z85c30.c
> index 4b1b422..1f43271 100644
> --- a/c/src/libchip/serial/z85c30.c
> +++ b/c/src/libchip/serial/z85c30.c
> @@ -437,6 +437,7 @@ Z85C30_STATIC int z85c30_set_attributes(
>    uint32_t               wr4;
>    uint32_t               wr5;
>    int                    baud_requested;
> +  uint32_t               baud_number;
>    setRegister_f          setReg;
>    rtems_interrupt_level  Irql;
>
> @@ -445,15 +446,20 @@ Z85C30_STATIC int z85c30_set_attributes(
>
>    /*
>     *  Calculate the baud rate divisor
> +   *
> +   *  Assert ensures there is no division by 0.
>     */
>
>    baud_requested = t->c_cflag & CBAUD;
>    if (!baud_requested)
>      baud_requested = B9600;              /* default to 9600 baud */
>
> +  baud_number = (uint32_t) rtems_termios_baud_to_number( baud_requested );
> +  _Assert( baud_number != 0 );
> +
>    ulBaudDivisor = Z85C30_Baud(
>      (uint32_t) Console_Port_Tbl[minor]->ulClock,
> -    (uint32_t) rtems_termios_baud_to_number( baud_requested )
> +    baud_number
>    );
>
>    wr3 = SCC_WR3_RX_EN;
> --
> 1.9.3
>
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