[PATCH] kgdboc: Disable all the early code when kgdboc is a module

From: Douglas Anderson
Date: Tue May 19 2020 - 11:48:49 EST


When kgdboc is compiled as a module all of the "ekgdboc" and
"kgdb_earlycon" code isn't useful and, in fact, breaks compilation.
This is because early_param() isn't defined for modules and that's how
this code gets configured.

It turns out that this was broken by commit eae3e19ca930 ("kgdboc:
Remove useless #ifdef CONFIG_KGDB_SERIAL_CONSOLE in kgdboc") and then
made worse by commit 220995622da5 ("kgdboc: Add kgdboc_earlycon to
support early kgdb using boot consoles"). I guess the #ifdef wasn't
so useless, even if it wasn't obvious why it was useful. When kgdboc
was compiled as a module only "CONFIG_KGDB_SERIAL_CONSOLE_MODULE" was
defined, not "CONFIG_KGDB_SERIAL_CONSOLE". That meant that the old
module.

Let's basically do the same thing that the old code (pre-removal of
the #ifdef) did but use "IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)" to
make it more obvious what the point of the check is. We'll fix
kgdboc_earlycon in a similar way.

Fixes: 220995622da5 ("kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles")
Fixes: eae3e19ca930 ("kgdboc: Remove useless #ifdef CONFIG_KGDB_SERIAL_CONSOLE in kgdboc")
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---

drivers/tty/serial/kgdboc.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 34b5e91dd245..fa6f7a3e73b9 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -43,9 +43,11 @@ static int kgdb_tty_line;

static struct platform_device *kgdboc_pdev;

+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static struct kgdb_io kgdboc_earlycon_io_ops;
static struct console *earlycon;
static int (*earlycon_orig_exit)(struct console *con);
+#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */

#ifdef CONFIG_KDB_KEYBOARD
static int kgdboc_reset_connect(struct input_handler *handler,
@@ -140,10 +142,19 @@ static void kgdboc_unregister_kbd(void)
#define kgdboc_restore_input()
#endif /* ! CONFIG_KDB_KEYBOARD */

-static void cleanup_kgdboc(void)
+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
+static void cleanup_earlycon(void)
{
if (earlycon)
kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
+}
+#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+static inline void cleanup_earlycon(void) { }
+#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+
+static void cleanup_kgdboc(void)
+{
+ cleanup_earlycon();

if (configured != 1)
return;
@@ -388,6 +399,7 @@ static struct kgdb_io kgdboc_io_ops = {
.post_exception = kgdboc_post_exp_handler,
};

+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static int kgdboc_option_setup(char *opt)
{
if (!opt) {
@@ -544,6 +556,7 @@ static int __init kgdboc_earlycon_init(char *opt)
}

early_param("kgdboc_earlycon", kgdboc_earlycon_init);
+#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */

module_init(init_kgdboc);
module_exit(exit_kgdboc);
--
2.26.2.761.g0e0b3e54be-goog