[SeaBIOS] [PATCH] pci: panic when out of bus numbers

[Marcel Apfelbaum]

On 01/04/2016 01:43 PM, Marcel Apfelbaum wrote:
> Currently the bios goes into an endless loop if more than
> 255 PCI buses are requested.
>

Hi,

This is the reproducing script:

cli="<qemu-bin> -M q35 <img>"

while [ ${i:=0} -lt ${1:-0} ]
do
     dstreamId=$((i))
     ustreamId=$((dstreamId/32))
     chassisId=$((dstreamId+1))
     blkDiskId=$((dstreamId))

     if [ $((dstreamId%32)) -eq 0 ]
     then
         cli="$cli -device ioh3420,bus=pcie.0,id=root.$ustreamId,slot=$ustreamId"
         cli="$cli -device x3130-upstream,bus=root.$ustreamId,id=upstream$ustreamId"
     fi

     cli="$cli -device xio3130-downstream,bus=upstream$ustreamId,id=downstream$dstreamId,chassis=$chassisId"
     i=$((i+1))
done

$cli


Run it with a numeric parameter > 240.


Thanks,
Marcel



> Change that to panic which is preferred in this case.
>
> Signed-off-by: Marcel Apfelbaum <marcel at redhat.com>
> ---
>
> Hi,
>
> I am well aware that this is not a common scenario, but the bug was found
> and maybe it deserves a little attention.
>
> I opted for using panic because I saw it used for other scenarios
> where the bios is out of resources.
>
> Another way to look at this would be to *stop* registering buses
> over 255 and loose some of the devices, but bring the system up.
>
> Thanks,
> Marcel
>
>   src/fw/pciinit.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/src/fw/pciinit.c b/src/fw/pciinit.c
> index c31c2fa..5da6cf6 100644
> --- a/src/fw/pciinit.c
> +++ b/src/fw/pciinit.c
> @@ -469,6 +469,9 @@ pci_bios_init_bus_rec(int bus, u8 *pci_bus)
>
>           u8 secbus = pci_config_readb(bdf, PCI_SECONDARY_BUS);
>           (*pci_bus)++;
> +        if (!(*pci_bus)) {
> +            panic("PCI: out of bus numbers!\n");
> +        }
>           if (*pci_bus != secbus) {
>               dprintf(1, "PCI: secondary bus = 0x%x -> 0x%x\n",
>                       secbus, *pci_bus);
>