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[Qemu-devel] [PATCH v4 1/7] hw/net/stellaris_enet: Restructure tx_fifo c
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH v4 1/7] hw/net/stellaris_enet: Restructure tx_fifo code to avoid buffer overrun |
Date: |
Thu, 8 May 2014 12:53:01 +0100 |
The current tx_fifo code has a corner case where the guest can overrun
the fifo buffer: if automatic CRCs are disabled we allow the guest to write
the CRC word even if there isn't actually space for it in the FIFO.
The datasheet is unclear about exactly how the hardware deals with this
situation; the most plausible answer seems to be that the CRC word is
just lost.
Implement this fix by separating the "can we stuff another word in the
FIFO" logic from the "should we transmit the packet now" check. This
also moves us closer to the real hardware, which has a number of ways
it can be configured to trigger sending the packet, some of which we
don't implement.
Signed-off-by: Peter Maydell <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
Cc: address@hidden
---
hw/net/stellaris_enet.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
index d04e6a4..bd844cd 100644
--- a/hw/net/stellaris_enet.c
+++ b/hw/net/stellaris_enet.c
@@ -253,10 +253,12 @@ static void stellaris_enet_write(void *opaque, hwaddr
offset,
s->tx_fifo[s->tx_fifo_len++] = value >> 24;
}
} else {
- s->tx_fifo[s->tx_fifo_len++] = value;
- s->tx_fifo[s->tx_fifo_len++] = value >> 8;
- s->tx_fifo[s->tx_fifo_len++] = value >> 16;
- s->tx_fifo[s->tx_fifo_len++] = value >> 24;
+ if (s->tx_fifo_len + 4 <= ARRAY_SIZE(s->tx_fifo)) {
+ s->tx_fifo[s->tx_fifo_len++] = value;
+ s->tx_fifo[s->tx_fifo_len++] = value >> 8;
+ s->tx_fifo[s->tx_fifo_len++] = value >> 16;
+ s->tx_fifo[s->tx_fifo_len++] = value >> 24;
+ }
if (s->tx_fifo_len >= s->tx_frame_len) {
/* We don't implement explicit CRC, so just chop it off. */
if ((s->tctl & SE_TCTL_CRC) == 0)
--
1.9.2
- [Qemu-devel] [PATCH v4 0/7] stellaris_enet: overhaul tx/rx, convert to vmstate, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 4/7] hw/net/stellaris_enet: Correctly implement the TR and THR registers, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 1/7] hw/net/stellaris_enet: Restructure tx_fifo code to avoid buffer overrun,
Peter Maydell <=
- [Qemu-devel] [PATCH v4 7/7] hw/net/stellaris_enet: Convert to vmstate, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 5/7] hw/net/stellaris_enet: Fix debug format strings, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 2/7] hw/net/stellaris_enet: Correct handling of packet padding, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 6/7] hw/net/stellaris_enet: Get rid of rx_fifo pointer, Peter Maydell, 2014/05/08
- [Qemu-devel] [PATCH v4 3/7] hw/net/stellaris_enet: Rewrite tx fifo handling code, Peter Maydell, 2014/05/08