sysctl: allow embedded targets to disable sysctl_check.c

Disable sysctl_check.c for embedded targets. This saves about about 11 kB
in .text and another 11 kB in .data on a PXA255 embedded platform.
Signed-off-by: Holger Schurig <hs4233@mail.mn-solutions.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/Kconfig

@@ -550,6 +550,17 @@ config SYSCTL_SYSCALL
 
 	  If unsure say Y here.
 
+config SYSCTL_SYSCALL_CHECK
+	bool "Sysctl checks" if EMBEDDED
+	depends on SYSCTL_SYSCALL
+	default y
+	---help---
+	  sys_sysctl uses binary paths that have been found challenging
+	  to properly maintain and use. This enables checks that help
+	  you to keep things correct.
+
+	  If unsure say Y here.
+
 config KALLSYMS
 	 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 	 default y

kernel/Makefile

@@ -11,7 +11,7 @@ obj-y     = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
 	    hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
 	    notifier.o ksysfs.o pm_qos_params.o
 
-obj-$(CONFIG_SYSCTL) += sysctl_check.o
+obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
 obj-y += time/
 obj-$(CONFIG_DEBUG_MUTEXES) += mutex-debug.o

kernel/sysctl.c

@@ -1592,9 +1592,13 @@ static void sysctl_set_parent(struct ctl_table *parent, struct ctl_table *table)
 
 static __init int sysctl_init(void)
 {
-	int err;
 	sysctl_set_parent(NULL, root_table);
+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+	{
+		int err;
 		err = sysctl_check_table(current->nsproxy, root_table);
+	}
+#endif
 	return 0;
 }
 
@@ -1721,10 +1725,12 @@ struct ctl_table_header *__register_sysctl_paths(
 	header->unregistering = NULL;
 	header->root = root;
 	sysctl_set_parent(NULL, header->ctl_table);
+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
 	if (sysctl_check_table(namespaces, header->ctl_table)) {
 		kfree(header);
 		return NULL;
 	}
+#endif
 	spin_lock(&sysctl_lock);
 	header_list = lookup_header_list(root, namespaces);
 	list_add_tail(&header->ctl_entry, header_list);