[PATCH v2] kgdboc: fix return value of __setup handler

[Randy Dunlap]

__setup() handlers should return 1 to obsolete_checksetup() in
init/main.c to indicate that the boot option has been handled.
A return of 0 causes the boot option/value to be listed as an Unknown
kernel parameter and added to init's (limited) environment strings.
So return 1 from kgdboc_option_setup().

Unknown kernel command line parameters "BOOT_IMAGE=/boot/bzImage-517rc7
  kgdboc=kbd kgdbts=", will be passed to user space.

 Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc7
     kgdboc=kbd
     kgdbts=

Fixes: 1bd54d851f50 ("kgdboc: Passing ekgdboc to command line causes panic")
Fixes: f2d937f3bf00 ("consoles: polling support, kgdboc")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Reported-by: Igor Zhbanov <i.zhbanov@xxxxxxxxxxxx>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@xxxxxxxxxxxx
Cc: He Zhe <zhe.he@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
Cc: kgdb-bugreport@xxxxxxxxxxxxxxxxxxxxx
Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Cc: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Cc: Douglas Anderson <dianders@xxxxxxxxxxxx>
Cc: linux-serial@xxxxxxxxxxxxxxx
---
v2- correct Fixes: tag(s) (thanks Doug)
  - drop Cc: Laura Abbott <labbott@xxxxxxxxxx> (bouncing)
  - add a reference to init/main.c::obsolete_checksetup()

 drivers/tty/serial/kgdboc.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- lnx-517-rc7.orig/drivers/tty/serial/kgdboc.c
+++ lnx-517-rc7/drivers/tty/serial/kgdboc.c
@@ -403,16 +403,16 @@ static int kgdboc_option_setup(char *opt
 {
 	if (!opt) {
 		pr_err("config string not provided\n");
-		return -EINVAL;
+		return 1;
 	}
 
 	if (strlen(opt) >= MAX_CONFIG_LEN) {
 		pr_err("config string too long\n");
-		return -ENOSPC;
+		return 1;
 	}
 	strcpy(config, opt);
 
-	return 0;
+	return 1;
 }
 
 __setup("kgdboc=", kgdboc_option_setup);