param: hand arguments after -- straight to init

The kernel passes any args it doesn't need through to init, except it
assumes anything containing '.' belongs to the kernel (for a module).
This change means all users can clearly distinguish which arguments
are for init.

For example, the kernel uses debug ("dee-bug") to mean log everything to
the console, where systemd uses the debug from the Scandinavian "day-boog"
meaning "fail to boot".  If a future versions uses argv[] instead of
reading /proc/cmdline, this confusion will be avoided.

eg: test 'FOO="this is --foo"' -- 'systemd.debug="true true true"'

Gives:
argv[0] = '/debug-init'
argv[1] = 'test'
argv[2] = 'systemd.debug=true true true'
envp[0] = 'HOME=/'
envp[1] = 'TERM=linux'
envp[2] = 'FOO=this is --foo'

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

include/linux/moduleparam.h

@@ -321,7 +321,7 @@ extern bool parameq(const char *name1, const char *name2);
 extern bool parameqn(const char *name1, const char *name2, size_t n);
 
 /* Called on module insert or kernel boot */
-extern int parse_args(const char *name,
+extern char *parse_args(const char *name,
 		      char *args,
 		      const struct kernel_param *params,
 		      unsigned num,

init/main.c

@@ -252,6 +252,27 @@ static int __init repair_env_string(char *param, char *val, const char *unused)
 	return 0;
 }
 
+/* Anything after -- gets handed straight to init. */
+static int __init set_init_arg(char *param, char *val, const char *unused)
+{
+	unsigned int i;
+
+	if (panic_later)
+		return 0;
+
+	repair_env_string(param, val, unused);
+
+	for (i = 0; argv_init[i]; i++) {
+		if (i == MAX_INIT_ARGS) {
+			panic_later = "init";
+			panic_param = param;
+			return 0;
+		}
+	}
+	argv_init[i] = param;
+	return 0;
+}
+
 /*
  * Unknown boot options get handed to init, unless they look like
  * unused parameters (modprobe will find them in /proc/cmdline).
@@ -478,7 +499,7 @@ static void __init mm_init(void)
 
 asmlinkage void __init start_kernel(void)
 {
-	char * command_line;
+	char * command_line, *after_dashes;
 	extern const struct kernel_param __start___param[], __stop___param[];
 
 	/*
@@ -519,9 +540,13 @@ asmlinkage void __init start_kernel(void)
 
 	pr_notice("Kernel command line: %s\n", boot_command_line);
 	parse_early_param();
-	parse_args("Booting kernel", static_command_line, __start___param,
+	after_dashes = parse_args("Booting kernel",
+				  static_command_line, __start___param,
 				  __stop___param - __start___param,
 				  -1, -1, &unknown_bootoption);
+	if (after_dashes)
+		parse_args("Setting init args", after_dashes, NULL, 0, -1, -1,
+			   set_init_arg);
 
 	jump_label_init();
 

kernel/module.c

@@ -3193,6 +3193,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 {
 	struct module *mod;
 	long err;
+	char *after_dashes;
 
 	err = module_sig_check(info);
 	if (err)
@@ -3277,10 +3278,15 @@ static int load_module(struct load_info *info, const char __user *uargs,
 		goto ddebug_cleanup;
 
 	/* Module is ready to execute: parsing args may do that. */
-	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
+	after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
 				  -32768, 32767, unknown_module_param_cb);
-	if (err < 0)
+	if (IS_ERR(after_dashes)) {
+		err = PTR_ERR(after_dashes);
 		goto bug_cleanup;
+	} else if (after_dashes) {
+		pr_warn("%s: parameters '%s' after `--' ignored\n",
+		       mod->name, after_dashes);
+	}
 
 	/* Link in to syfs. */
 	err = mod_sysfs_setup(mod, info, mod->kp, mod->num_kp);

kernel/params.c

@@ -177,7 +177,7 @@ static char *next_arg(char *args, char **param, char **val)
 }
 
 /* Args looks like "foo=bar,bar2 baz=fuz wiz". */
-int parse_args(const char *doing,
+char *parse_args(const char *doing,
 		 char *args,
 		 const struct kernel_param *params,
 		 unsigned num,
@@ -198,6 +198,9 @@ int parse_args(const char *doing,
 		int irq_was_disabled;
 
 		args = next_arg(args, &param, &val);
+		/* Stop at -- */
+		if (!val && strcmp(param, "--") == 0)
+			return args;
 		irq_was_disabled = irqs_disabled();
 		ret = parse_one(param, val, doing, params, num,
 				min_level, max_level, unknown);
@@ -208,22 +211,22 @@ int parse_args(const char *doing,
 		switch (ret) {
 		case -ENOENT:
 			pr_err("%s: Unknown parameter `%s'\n", doing, param);
-			return ret;
+			return ERR_PTR(ret);
 		case -ENOSPC:
 			pr_err("%s: `%s' too large for parameter `%s'\n",
 			       doing, val ?: "", param);
-			return ret;
+			return ERR_PTR(ret);
 		case 0:
 			break;
 		default:
 			pr_err("%s: `%s' invalid for parameter `%s'\n",
 			       doing, val ?: "", param);
-			return ret;
+			return ERR_PTR(ret);
 		}
 	}
 
 	/* All parsed OK. */
-	return 0;
+	return NULL;
 }
 
 /* Lazy bastard, eh? */