rtl8139: do not assume TxStatus[] and TxAddr[] are adjacent

Commit afe0a595356192d5f79703cf6462fcc112df007c ("rtl8139: support byte
read to TxStatus registers") reused rtl8139_TxStatus_read() for reading
TxAddr registers.  It relies on the fact that TxStatus[] and TxAddr[]
are adjacent.

This causes a gcc warning because the compiler can detect that array
access is out-of-bounds:

  hw/rtl8139.c:2501:27: error: array subscript is above array bounds [-Werror=array-bounds]

This patch refactors the function so that we don't rely on out-of-bounds
accesses.

Cc: Jason Wang <jasonwang@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 hw/rtl8139.c |   26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

On 04/11/2012 06:01 AM, Stefan Hajnoczi wrote:
> Commit afe0a595356192d5f79703cf6462fcc112df007c ("rtl8139: support byte
> read to TxStatus registers") reused rtl8139_TxStatus_read() for reading
> TxAddr registers.  It relies on the fact that TxStatus[] and TxAddr[]
> are adjacent.
>
> This causes a gcc warning because the compiler can detect that array
> access is out-of-bounds:
>
>    hw/rtl8139.c:2501:27: error: array subscript is above array bounds [-Werror=array-bounds]
>
> This patch refactors the function so that we don't rely on out-of-bounds
> accesses.

Applied.  Thanks.

Regards,

Anthony Liguori

>
> Cc: Jason Wang<jasonwang@redhat.com>
> Signed-off-by: Stefan Hajnoczi<stefanha@linux.vnet.ibm.com>
> ---
>   hw/rtl8139.c |   26 +++++++++++++++-----------
>   1 file changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/hw/rtl8139.c b/hw/rtl8139.c
> index 4d553a8..4d0f5ba 100644
> --- a/hw/rtl8139.c
> +++ b/hw/rtl8139.c
> @@ -2482,15 +2482,17 @@ static void rtl8139_TxStatus_write(RTL8139State *s, uint32_t txRegOffset, uint32
>       rtl8139_transmit(s);
>   }
>
> -static uint32_t rtl8139_TxStatus_read(RTL8139State *s, uint8_t addr, int size)
> +static uint32_t rtl8139_TxStatus_TxAddr_read(RTL8139State *s, uint32_t regs[],
> +                                             uint32_t base, uint8_t addr,
> +                                             int size)
>   {
> -    uint32_t reg = (addr - TxStatus0) / 4;
> +    uint32_t reg = (addr - base) / 4;
>       uint32_t offset = addr&  0x3;
>       uint32_t ret = 0;
>
>       if (addr&  (size - 1)) {
> -        DPRINTF("not implemented read for TxStatus addr=0x%x size=0x%x\n", addr,
> -                size);
> +        DPRINTF("not implemented read for TxStatus/TxAddr "
> +                "addr=0x%x size=0x%x\n", addr, size);
>           return ret;
>       }
>
> @@ -2498,12 +2500,12 @@ static uint32_t rtl8139_TxStatus_read(RTL8139State *s, uint8_t addr, int size)
>       case 1: /* fall through */
>       case 2: /* fall through */
>       case 4:
> -        ret = (s->TxStatus[reg]>>  offset * 8)&  ((1<<  (size * 8)) - 1);
> -        DPRINTF("TxStatus[%d] read addr=0x%x size=0x%x val=0x%08x\n", reg, addr,
> -                size, ret);
> +        ret = (regs[reg]>>  offset * 8)&  ((1<<  (size * 8)) - 1);
> +        DPRINTF("TxStatus/TxAddr[%d] read addr=0x%x size=0x%x val=0x%08x\n",
> +                reg, addr, size, ret);
>           break;
>       default:
> -        DPRINTF("unsupported size 0x%x of TxStatus reading\n", size);
> +        DPRINTF("unsupported size 0x%x of TxStatus/TxAddr reading\n", size);
>           break;
>       }
>
> @@ -2977,7 +2979,8 @@ static uint32_t rtl8139_io_readb(void *opaque, uint8_t addr)
>               ret = s->mult[addr - MAR0];
>               break;
>           case TxStatus0 ... TxStatus0+4*4-1:
> -            ret = rtl8139_TxStatus_read(s, addr, 1);
> +            ret = rtl8139_TxStatus_TxAddr_read(s, s->TxStatus, TxStatus0,
> +                                               addr, 1);
>               break;
>           case ChipCmd:
>               ret = rtl8139_ChipCmd_read(s);
> @@ -3043,7 +3046,7 @@ static uint32_t rtl8139_io_readw(void *opaque, uint8_t addr)
>       switch (addr)
>       {
>           case TxAddr0 ... TxAddr0+4*4-1:
> -            ret = rtl8139_TxStatus_read(s, addr, 2);
> +            ret = rtl8139_TxStatus_TxAddr_read(s, s->TxAddr, TxAddr0, addr, 2);
>               break;
>           case IntrMask:
>               ret = rtl8139_IntrMask_read(s);
> @@ -3135,7 +3138,8 @@ static uint32_t rtl8139_io_readl(void *opaque, uint8_t addr)
>               break;
>
>           case TxStatus0 ... TxStatus0+4*4-1:
> -            ret = rtl8139_TxStatus_read(s, addr, 4);
> +            ret = rtl8139_TxStatus_TxAddr_read(s, s->TxStatus, TxStatus0,
> +                                               addr, 4);
>               break;
>
>           case TxAddr0 ... TxAddr0+4*4-1: