On Mon, 22 Jun 2020 at 22:06, Daniel Thompson
<daniel.thompson@xxxxxxxxxx> wrote:
>
> 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.
>
Sounds reasonable. Along with this, kgdb_nmi_poll_knock() seems to be
unused and can be removed as well.
-Sumit
>
> 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
> >
