[PATCH] defer panic for too many items in boot parameter line

From: Werner Almesberger <werner@almesberger.net>

When passing too many unrecognized boot command line options (which become
arguments or environment variables), the 2.6 kernel panics (unlike 2.4,
which just ignores the extra items).  Unfortunately, this happens before
the console is initialized, so all you get is a kernel that dies quickly,
for no apparent reason.

This is particularly irritating if using UML with
init=something wi th a lot of ar gu men t s

The patch below delays the panic until after console_init.

(akpm: I mainly added this in because we have other places where the
panic-later-on machinery is needed).

init/main.c

@@ -141,6 +141,7 @@ __setup("maxcpus=", maxcpus);
 
 static char * argv_init[MAX_INIT_ARGS+2] = { "init", NULL, };
 char * envp_init[MAX_INIT_ENVS+2] = { "HOME=/", "TERM=linux", NULL, };
+static const char *panic_later, *panic_param;
 
 __setup("profile=", profile_setup);
 
@@ -253,20 +254,27 @@ static int __init unknown_bootoption(char *param, char *val)
 		return 0;
 	}
 
+	if (panic_later)
+		return 0;
+
 	if (val) {
 		/* Environment option */
 		unsigned int i;
 		for (i = 0; envp_init[i]; i++) {
-			if (i == MAX_INIT_ENVS)
-				panic("Too many boot env vars at `%s'", param);
+			if (i == MAX_INIT_ENVS) {
+				panic_later = "Too many boot env vars at `%s'";
+				panic_param = param;
+			}
 		}
 		envp_init[i] = param;
 	} else {
 		/* Command line option */
 		unsigned int i;
 		for (i = 0; argv_init[i]; i++) {
-			if (i == MAX_INIT_ARGS)
-				panic("Too many boot init vars at `%s'",param);
+			if (i == MAX_INIT_ARGS) {
+				panic_later = "Too many boot init vars at `%s'";
+				panic_param = param;
+			}
 		}
 		argv_init[i] = param;
 	}
@@ -424,6 +432,8 @@ asmlinkage void __init start_kernel(void)
 	 * this. But we do want output early, in case something goes wrong.
 	 */
 	console_init();
+	if (panic_later)
+		panic(panic_later, panic_param);
 	profile_init();
 	local_irq_enable();
 #ifdef CONFIG_BLK_DEV_INITRD