On Mon, Jun 22, 2020 at 07:56:21PM +0530, Sumit Garg wrote:
> From: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
>
> Add a generic NMI fallback to support kgdb NMI console feature which can
> be overridden by arch specific implementation.
arch_kgdb_ops.enable_nmi should probably be killed off. Given we now
have request_nmi() I'm dubious there are any good reasons to use this
API.
Daniel.
> This common fallback mechanism utilizes kgdb IO based interrupt in order
> to support entry into kgdb if a user types in kgdb_nmi_magic sequence. So
> during NMI console init, NMI handler is installed corresponding to kgdb
> IO based NMI which is invoked when a character is pending and that can be
> cleared by calling @read_char until it returns NO_POLL_CHAR.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
> Co-developed-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
> ---
> drivers/tty/serial/kgdb_nmi.c | 47 ++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 40 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
> index b32c6b1..2580f39 100644
> --- a/drivers/tty/serial/kgdb_nmi.c
> +++ b/drivers/tty/serial/kgdb_nmi.c
> @@ -42,9 +42,46 @@ MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)");
> static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0);
> static struct console *orig_dbg_cons;
>
> +static int kgdb_nmi_poll_one_knock(void);
> +
> +static irqreturn_t kgdb_handle_nmi(int irq, void *dev_id)
> +{
> + int ret;
> +
> + if (kgdb_nmi_knock < 0) {
> + kgdb_breakpoint();
> + return IRQ_HANDLED;
> + }
> +
> + ret = kgdb_nmi_poll_one_knock();
> + if (ret == NO_POLL_CHAR)
> + return IRQ_NONE;
> +
> + while (ret != 1) {
> + ret = kgdb_nmi_poll_one_knock();
> + if (ret == NO_POLL_CHAR)
> + return IRQ_HANDLED;
> + }
> +
> + kgdb_breakpoint();
> + return IRQ_HANDLED;
> +}
> +
> static int kgdb_nmi_console_setup(struct console *co, char *options)
> {
> - arch_kgdb_ops.enable_nmi(1);
> + int res;
> +
> + if (arch_kgdb_ops.enable_nmi) {
> + arch_kgdb_ops.enable_nmi(1);
> + } else if (dbg_io_ops->request_nmi) {
> + res = dbg_io_ops->request_nmi(kgdb_handle_nmi, co);
> + if (res) {
> + pr_err("ttyNMI0: Cannot request nmi/irq\n");
> + return res;
> + }
> + } else {
> + return -ENODEV;
> + }
>
> /* The NMI console uses the dbg_io_ops to issue console messages. To
> * avoid duplicate messages during kdb sessions we must inform kdb's
> @@ -328,9 +365,6 @@ int kgdb_register_nmi_console(void)
> {
> int ret;
>
> - if (!arch_kgdb_ops.enable_nmi)
> - return 0;
> -
> kgdb_nmi_tty_driver = alloc_tty_driver(1);
> if (!kgdb_nmi_tty_driver) {
> pr_err("%s: cannot allocate tty\n", __func__);
> @@ -380,9 +414,8 @@ int kgdb_unregister_nmi_console(void)
> {
> int ret;
>
> - if (!arch_kgdb_ops.enable_nmi)
> - return 0;
> - arch_kgdb_ops.enable_nmi(0);
> + if (arch_kgdb_ops.enable_nmi)
> + arch_kgdb_ops.enable_nmi(0);
>
> ret = unregister_console(&kgdb_nmi_console);
> if (ret)
> --
> 2.7.4
>
