[RFC][PATCH 1/2] Virtualization of UTS

[Kirill Korotaev <dev@sw.ru>]

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This patch introduces utsname namespace in system, which allows to have 
different utsnames on the host.
Introduces config option CONFIG_UTS_NS and uts_namespace structure for this.

http://git.openvz.org/?p=linux-2.6-openvz-ms;a=commitdiff;h=216bb5e42c7eef7f1ed361244a60b1496e8bdf63

Signed-Off-By: Pavel Emelianov <xemul@openvz.org>
Signed-Off-By: Kirill Korotaev <dev@openvz.org>

Kirill

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--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -3,6 +3,7 @@
 
 #include <linux/file.h>
 #include <linux/rcupdate.h>
+#include <linux/utsname.h>
 
 #define INIT_FDTABLE \
 {							\
@@ -72,6 +73,12 @@
 
 extern struct group_info init_groups;
 
+#ifdef CONFIG_UTS_NS
+#define INIT_UTS_NS	.uts_ns = &init_uts_ns,
+#else
+#define INIT_UTS_NS
+#endif
+
 /*
  *  INIT_TASK is used to set up the first task table, touch at
  * your own risk!. Base=0, limit=0x1fffff (=2MB)
@@ -121,6 +128,7 @@ extern struct group_info init_groups;
 	.journal_info	= NULL,						\
 	.cpu_timers	= INIT_CPU_TIMERS(tsk.cpu_timers),		\
 	.fs_excl	= ATOMIC_INIT(0),				\
+	INIT_UTS_NS							\
 }
 
 
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -688,6 +688,7 @@ static inline void prefetch_stack(struct
 
 struct audit_context;		/* See audit.c */
 struct mempolicy;
+struct uts_namespace;
 
 struct task_struct {
 	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */
@@ -802,6 +803,9 @@ struct task_struct {
 	struct files_struct *files;
 /* namespace */
 	struct namespace *namespace;
+#ifdef CONFIG_UTS_NS
+	struct uts_namespace *uts_ns;
+#endif
 /* signal handlers */
 	struct signal_struct *signal;
 	struct sighand_struct *sighand;
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -30,7 +30,36 @@ struct new_utsname {
 	char domainname[65];
 };
 
+#ifdef CONFIG_UTS_NS
+#include <asm/atomic.h>
+
+struct uts_namespace {
+	atomic_t cnt;
+	struct new_utsname name;
+};
+
+extern struct uts_namespace *create_uts_ns(void);
+extern struct uts_namespace *clone_uts_ns(void);
+extern void free_uts_ns(struct uts_namespace *ns);
+
+static inline void get_uts_ns(struct uts_namespace *ns)
+{
+	atomic_inc(&ns->cnt);
+}
+
+static inline void put_uts_ns(struct uts_namespace *ns)
+{
+	if (atomic_dec_and_test(&ns->cnt))
+		free_uts_ns(ns);
+}
+
+#define system_utsname	(current->uts_ns->name)
+extern struct uts_namespace init_uts_ns;
+#else
+#define get_uts_ns(ns)	do { } while (0)
+#define put_uts_ns(ns)	do { } while (0)
 extern struct new_utsname system_utsname;
+#endif
 
 extern struct rw_semaphore uts_sem;
 #endif
--- a/init/version.c
+++ b/init/version.c
@@ -17,6 +17,51 @@
 
 int version_string(LINUX_VERSION_CODE);
 
+#ifdef CONFIG_UTS_NS
+struct uts_namespace init_uts_ns = {
+	.cnt = ATOMIC_INIT(1),
+	.name = {
+		.sysname	= UTS_SYSNAME,
+		.nodename	= UTS_NODENAME,
+		.release	= UTS_RELEASE,
+		.version	= UTS_VERSION,
+		.machine	= UTS_MACHINE,
+		.domainname	= UTS_DOMAINNAME,
+	},
+};
+
+struct uts_namespace *create_uts_ns(void)
+{
+	struct uts_namespace *ns;
+
+	ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
+	if (ns == NULL)
+		return NULL;
+
+	memset(&ns->name, 0, sizeof(ns->name));
+	atomic_set(&ns->cnt, 1);
+	return ns;
+}
+
+struct uts_namespace *clone_uts_ns(void)
+{
+	struct uts_namespace *ns, *cur;
+
+	ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL);
+	if (ns == NULL)
+		return NULL;
+
+	cur = current->uts_ns;
+	memcpy(&ns->name, &cur->name, sizeof(cur->name));
+	atomic_set(&ns->cnt, 1);
+	return ns;
+}
+
+void free_uts_ns(struct uts_namespace *ns)
+{
+	kfree(ns);
+}
+#else
 struct new_utsname system_utsname = {
 	.sysname	= UTS_SYSNAME,
 	.nodename	= UTS_NODENAME,
@@ -27,6 +72,7 @@ struct new_utsname system_utsname = {
 };
 
 EXPORT_SYMBOL(system_utsname);
+#endif
 
 const char linux_banner[] =
 	"Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -107,6 +107,7 @@ repeat: 
 	spin_unlock(&p->proc_lock);
 	proc_pid_flush(proc_dentry);
 	release_thread(p);
+	put_uts_ns(p->uts_ns);
 	put_task_struct(p);
 
 	p = leader;
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1192,6 +1192,7 @@ static task_t *copy_process(unsigned lon
 	}
 	attach_pid(p, PIDTYPE_TGID, p->tgid);
 	attach_pid(p, PIDTYPE_PID, p->pid);
+	get_uts_ns(p->uts_ns);
 
 	nr_threads++;
 	total_forks++;
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -229,12 +229,18 @@ static ctl_table root_table[] = {
 	{ .ctl_name = 0 }
 };
 
+#ifdef CONFIG_UTS_NS
+#define sysctl_system_utsname	(init_uts_ns.name)
+#else
+#define sysctl_system_utsname	(system_utsname)
+#endif
+
 static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_OSTYPE,
 		.procname	= "ostype",
-		.data		= system_utsname.sysname,
-		.maxlen		= sizeof(system_utsname.sysname),
+		.data		= sysctl_system_utsname.sysname,
+		.maxlen		= sizeof(sysctl_system_utsname.sysname),
 		.mode		= 0444,
 		.proc_handler	= &proc_doutsstring,
 		.strategy	= &sysctl_string,
@@ -242,8 +248,8 @@ static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_OSRELEASE,
 		.procname	= "osrelease",
-		.data		= system_utsname.release,
-		.maxlen		= sizeof(system_utsname.release),
+		.data		= sysctl_system_utsname.release,
+		.maxlen		= sizeof(sysctl_system_utsname.release),
 		.mode		= 0444,
 		.proc_handler	= &proc_doutsstring,
 		.strategy	= &sysctl_string,
@@ -251,8 +257,8 @@ static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_VERSION,
 		.procname	= "version",
-		.data		= system_utsname.version,
-		.maxlen		= sizeof(system_utsname.version),
+		.data		= sysctl_system_utsname.version,
+		.maxlen		= sizeof(sysctl_system_utsname.version),
 		.mode		= 0444,
 		.proc_handler	= &proc_doutsstring,
 		.strategy	= &sysctl_string,
@@ -260,8 +266,8 @@ static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_NODENAME,
 		.procname	= "hostname",
-		.data		= system_utsname.nodename,
-		.maxlen		= sizeof(system_utsname.nodename),
+		.data		= sysctl_system_utsname.nodename,
+		.maxlen		= sizeof(sysctl_system_utsname.nodename),
 		.mode		= 0644,
 		.proc_handler	= &proc_doutsstring,
 		.strategy	= &sysctl_string,
@@ -269,8 +275,8 @@ static ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_DOMAINNAME,
 		.procname	= "domainname",
-		.data		= system_utsname.domainname,
-		.maxlen		= sizeof(system_utsname.domainname),
+		.data		= sysctl_system_utsname.domainname,
+		.maxlen		= sizeof(sysctl_system_utsname.domainname),
 		.mode		= 0644,
 		.proc_handler	= &proc_doutsstring,
 		.strategy	= &sysctl_string,