Re: [PATCH v2] bluetooth: hci_qca: Fix QCA6390 memdump failure

From: Abhishek Pandit-Subedi
Date: Thu May 28 2020 - 14:26:58 EST

Hi,

On Wed, May 27, 2020 at 11:19 PM Zijun Hu <zijuhu@xxxxxxxxxxxxxx> wrote:
>
>
>
> On 5/28/2020 11:42 AM, Abhishek Pandit-Subedi wrote:
> > Hi Zijun,
> >
> > On Tue, May 26, 2020 at 8:37 PM Zijun Hu <zijuhu@xxxxxxxxxxxxxx> wrote:
> >>
> >> QCA6390 memdump VSE sometimes come to bluetooth driver
> >> with wrong sequence number as illustrated as follows:
> >> frame # in DEC: frame data in HEX
> >> 1396: ff fd 01 08 74 05 00 37 8f 14
> >> 1397: ff fd 01 08 75 05 00 ff bf 38
> >> 1414: ff fd 01 08 86 05 00 fb 5e 4b
> >> 1399: ff fd 01 08 77 05 00 f3 44 0a
> >> 1400: ff fd 01 08 78 05 00 ca f7 41
> >> it is mistook for controller missing packets, so results
> >> in page fault after overwriting memdump buffer allocated.
> >>
> >> it is fixed by ignoring QCA6390 sequence number error
> >> and checking buffer space before writing.
> >>
> >> Signed-off-by: Zijun Hu <zijuhu@xxxxxxxxxxxxxx>
> >> ---
> >> drivers/bluetooth/hci_qca.c | 45 ++++++++++++++++++++++++++++++++++++++-------
> >> 1 file changed, 38 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/bluetooth/hci_qca.c b/drivers/bluetooth/hci_qca.c
> >> index e4a6823..388fe01b 100644
> >> --- a/drivers/bluetooth/hci_qca.c
> >> +++ b/drivers/bluetooth/hci_qca.c
> >> @@ -114,6 +114,7 @@ struct qca_memdump_data {
> >> char *memdump_buf_tail;
> >> u32 current_seq_no;
> >> u32 received_dump;
> >> + u32 ram_dump_size;
> >> };
> >>
> >> struct qca_memdump_event_hdr {
> >> @@ -976,6 +977,8 @@ static void qca_controller_memdump(struct work_struct *work)
> >> char nullBuff[QCA_DUMP_PACKET_SIZE] = { 0 };
> >> u16 seq_no;
> >> u32 dump_size;
> >> + u32 rx_size;
> >> + enum qca_btsoc_type soc_type = qca_soc_type(hu);
> >>
> >> while ((skb = skb_dequeue(&qca->rx_memdump_q))) {
> >>
> >> @@ -1029,6 +1032,7 @@ static void qca_controller_memdump(struct work_struct *work)
> >>
> >> skb_pull(skb, sizeof(dump_size));
> >> memdump_buf = vmalloc(dump_size);
> >> + qca_memdump->ram_dump_size = dump_size;
> >> qca_memdump->memdump_buf_head = memdump_buf;
> >> qca_memdump->memdump_buf_tail = memdump_buf;
> >> }
> >> @@ -1052,25 +1056,52 @@ static void qca_controller_memdump(struct work_struct *work)
> >> * packets in the buffer.
> >> */
> >> while ((seq_no > qca_memdump->current_seq_no + 1) &&
> >> + (soc_type != QCA_QCA6390) &&
> >
> > This probably shouldn't be SOC specific.
> >
> make sense. but this logic block should be skipped for QCA6390
> the present logic to fix controller missing packets for the other products
> is not suitable for QCA6390. for QCA6390, it doesn't miss packet and sequence
> number field of the packet maybe have data error, but serdev driver doesn't propagate
> these error info detected by UART driver to bluetooth driver. so the sequence number
> extracted from packet received is not reliable.

Ok -- then I think it would be clearer to just set seq_no =
qca_memdump->current_seq_no for QCA6390 and leave a comment about it.

>
> >> seq_no != QCA_LAST_SEQUENCE_NUM) {
> >> bt_dev_err(hu->hdev, "QCA controller missed packet:%d",
> >> qca_memdump->current_seq_no);
> >> + rx_size = qca_memdump->received_dump;
> >> + rx_size += QCA_DUMP_PACKET_SIZE;
> >> + if (rx_size > qca_memdump->ram_dump_size) {
> >> + bt_dev_err(hu->hdev,
> >> + "QCA memdump received %d, no space for missed packet",
> >> + qca_memdump->received_dump);
> >> + break;
> >> + }
> >> memcpy(memdump_buf, nullBuff, QCA_DUMP_PACKET_SIZE);
> >> memdump_buf = memdump_buf + QCA_DUMP_PACKET_SIZE;
> >> qca_memdump->received_dump += QCA_DUMP_PACKET_SIZE;
> >> qca_memdump->current_seq_no++;
> >> }
> >
> > You can replace this loop with a memset(memdump_buf, 0, (seq_no -
> > qca_memdump->current_seq_no) * QCA_DUMP_PACKET_SIZE). This simplifies
> > the ram_dump_size check as well because it won't zero fill until the
> > end anymore (meaning a single bad seq_no doesn't make the rest of the
> > dump incorrect).
> >
> i don't think so
> as explained above, the sequence number is not reliable, so we can't memset buffer
> area calculated from seqence number. i just dump all the packets we received without
> any handling for QCA6390.

I suggest the following:

/* For QCA6390, ignore the seq_no and always assume packets are in order */
if (soc_type == QCA_QCA6390 && seq_no != QCA_LAST_SEQUENCE_NUM) {
seq_no = qca_memdump->current_seq_no;
} else if (seq_no > qca_memdump->current_seq_no &&
seq_no != QCA_LAST_SEQUENCE_NUM) {
/* For bounds checking, add the sizes of the current pkt + the
number of missing pkts.
* If the given seq_no exceeds the allocated size of the dump,
assume the seq_no is
* wrong.
*/
rx_size = (seq_no - qca_memdump->current_seq_no) * QCA_DUMP_PACKET_SIZE;
if (rx_size + skb->len <= (qca_memdump->ram_dump_size -
qca_memdump->received_dump)) {
memset(memdump_buf, 0, rx_size);
memdump_buf += rx_size;
qca_memdump->received_dump += rx_size;
qca_memdump->current_seq_no = seq_no;
} else {
seq_no = qca_memdump->current_seq_no;
}
}

> >>
> >> - memcpy(memdump_buf, (unsigned char *) skb->data, skb->len);
> >> - memdump_buf = memdump_buf + skb->len;
> >> - qca_memdump->memdump_buf_tail = memdump_buf;
> >> - qca_memdump->current_seq_no = seq_no + 1;
> >> - qca_memdump->received_dump += skb->len;
> >> + rx_size = qca_memdump->received_dump + skb->len;
> >> + if (rx_size <= qca_memdump->ram_dump_size) {
> >> + if ((seq_no != QCA_LAST_SEQUENCE_NUM) &&
> >> + (seq_no != qca_memdump->current_seq_no))
> >> + bt_dev_err(hu->hdev,
> >> + "QCA memdump unexpected packet %d",
> >> + seq_no);

This message doesn't make sense here anymore and should be removed.

> >> + bt_dev_dbg(hu->hdev,
> >> + "QCA memdump packet %d with length %d",
> >> + seq_no, skb->len);
> >> + memcpy(memdump_buf, (unsigned char *)skb->data,
> >> + skb->len);
> >> + memdump_buf = memdump_buf + skb->len;
> >> + qca_memdump->memdump_buf_tail = memdump_buf;
> >> + qca_memdump->current_seq_no = seq_no + 1;
> >> + qca_memdump->received_dump += skb->len;
> >> + } else {
> >> + bt_dev_err(hu->hdev,
> >> + "QCA memdump received %d, no space for packet %d",
> >> + qca_memdump->received_dump, seq_no);
> >> + }
> >> qca->qca_memdump = qca_memdump;
> >> kfree_skb(skb);
> >> if (seq_no == QCA_LAST_SEQUENCE_NUM) {
> >> - bt_dev_info(hu->hdev, "QCA writing crash dump of size %d bytes",
> >> - qca_memdump->received_dump);
> >> + bt_dev_info(hu->hdev,
> >> + "QCA memdump Done, received %d, total %d",
> >> + qca_memdump->received_dump,
> >> + qca_memdump->ram_dump_size);
> >> memdump_buf = qca_memdump->memdump_buf_head;
> >> dev_coredumpv(&hu->serdev->dev, memdump_buf,
> >> qca_memdump->received_dump, GFP_KERNEL);
> >> --
> >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
> >>
>
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project