Re: [PATCH v2 2/3] pci: sprinkle assert in PCI pin number

[Peter Maydell <peter.maydell@linaro.org>]

On Tue, 23 Mar 2021 at 17:26, Isaku Yamahata <isaku.yamahata@intel.com> wrote:
>
> If a device model
> (a) doesn't set the value to a correct interrupt number and then
> (b) triggers an interrupt for itself,
> it's device model bug. Add assert on interrupt pin number to catch
> this kind of bug more obviously.
>
> Suggested-by: Peter Maydell <Peter.maydel@linaro.org>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> ---
>  hw/pci/pci.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index ac9a24889c..cb6bab999b 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1450,6 +1450,8 @@ static void pci_irq_handler(void *opaque, int irq_num, int level)
>      PCIDevice *pci_dev = opaque;
>      int change;
>
> +    assert(0 <= irq_num && irq_num < PCI_NUM_PINS);
> +    assert(level == 0 || level == 1);

If you have these...

>      change = level - pci_irq_state(pci_dev, irq_num);
>      if (!change)
>          return;
> @@ -1463,7 +1465,13 @@ static void pci_irq_handler(void *opaque, int irq_num, int level)
>
>  static inline int pci_intx(PCIDevice *pci_dev)
>  {
> -    return pci_get_byte(pci_dev->config + PCI_INTERRUPT_PIN) - 1;
> +    int intx = pci_get_byte(pci_dev->config + PCI_INTERRUPT_PIN) - 1;
> +    /*
> +     * This function is used to setup/trigger irq.
> +     * So PIN = 0 (interrupt isn't used) doesn't make sense.
> +     */
> +    assert(0 <= intx && intx < PCI_NUM_PINS);

...you don't need this, because the assert in pci_irq_handler()
covers all the uses of pci_intx().

See also
https://patchew.org/QEMU/20210323164601.27200-1-peter.maydell@linaro.org/

thanks
-- PMM