[PATCH 4/7] uts namespaces: implement utsname namespaces

From: Serge E. Hallyn
Date: Mon May 01 2006 - 15:55:24 EST

This patch defines the uts namespace and some manipulators.
Adds the uts namespace to task_struct, and initializes a
system-wide init namespace.

It leaves a #define for system_utsname so sysctl will compile.
This define will be removed in a separate patch.

Changes:
Moved code from init/version.c to kernel/utsname.c.
Modified the clone/unshare functions to better fit
unsharing at clone and sys_unshare, vs allowing
other parts of the kernel to unshare.

Signed-off-by: Serge E. Hallyn <serue@xxxxxxxxxx>

---

include/linux/init_task.h | 2 ++
include/linux/sched.h | 2 ++
include/linux/utsname.h | 51 +++++++++++++++++++++++++++++++++++++++++----
init/Kconfig | 8 +++++++
init/version.c | 22 +++++++++++--------
kernel/Makefile | 1 +
kernel/exit.c | 2 ++
kernel/fork.c | 11 +++++++---
kernel/utsname.c | 48 ++++++++++++++++++++++++++++++++++++++++++
9 files changed, 131 insertions(+), 16 deletions(-)
create mode 100644 kernel/utsname.c

73a1721f20bb13cb49bc29b7553768fc788d4d22
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 41ecbb8..21b1751 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -3,6 +3,7 @@ #define _LINUX__INIT_TASK_H

#include <linux/file.h>
#include <linux/rcupdate.h>
+#include <linux/utsname.h>

#define INIT_FDTABLE \
{ \
@@ -123,6 +124,7 @@ #define INIT_TASK(tsk) \
.journal_info = NULL, \
.cpu_timers = INIT_CPU_TIMERS(tsk.cpu_timers), \
.fs_excl = ATOMIC_INIT(0), \
+ .uts_ns = &init_uts_ns, \
}


diff --git a/include/linux/sched.h b/include/linux/sched.h
index 29b7d4f..3d74d77 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -685,6 +685,7 @@ #endif
struct audit_context; /* See audit.c */
struct mempolicy;
struct pipe_inode_info;
+struct uts_namespace;

enum sleep_type {
SLEEP_NORMAL,
@@ -808,6 +809,7 @@ #endif
struct files_struct *files;
/* namespace */
struct namespace *namespace;
+ struct uts_namespace *uts_ns;
/* signal handlers */
struct signal_struct *signal;
struct sighand_struct *sighand;
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 8f0decf..a28e956 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -1,5 +1,8 @@
#ifndef _LINUX_UTSNAME_H
#define _LINUX_UTSNAME_H
+#include <linux/sched.h>
+#include <linux/kref.h>
+#include <asm/atomic.h>

#define __OLD_UTS_LEN 8

@@ -30,15 +33,55 @@ struct new_utsname {
char domainname[65];
};

-extern struct new_utsname system_utsname;
+struct uts_namespace {
+ struct kref kref;
+ struct new_utsname name;
+};
+extern struct uts_namespace init_uts_ns;
+
+#ifdef CONFIG_UTS_NS
+extern int copy_utsname(int flags, struct task_struct *tsk);
+extern void free_uts_ns(struct kref *kref);
+
+static inline void put_uts_ns(struct uts_namespace *ns)
+{
+ kref_put(&ns->kref, free_uts_ns);
+}
+
+static inline void exit_utsname(struct task_struct *p)
+{
+ struct uts_namespace *uts_ns = p->uts_ns;
+ if (uts_ns) {
+ task_lock(p);
+ p->uts_ns = NULL;
+ task_unlock(p);
+ put_uts_ns(uts_ns);
+ }
+}

-static inline struct new_utsname *utsname(void) {
- return &system_utsname;
+#else
+static inline int copy_utsname(int flags, struct task_struct *tsk)
+{
+ return 0;
+}
+static inline void put_uts_ns(struct uts_namespace *ns)
+{
+}
+static inline void exit_utsname(struct task_struct *p)
+{
+}
+#endif
+
+static inline struct new_utsname *utsname(void)
+{
+ return &current->uts_ns->name;
}

static inline struct new_utsname *init_utsname(void) {
- return &system_utsname;
+ return &init_uts_ns.name;
}

+#define system_utsname init_uts_ns.name
+
extern struct rw_semaphore uts_sem;
#endif
diff --git a/init/Kconfig b/init/Kconfig
index 3b36a1d..8460e5a 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -166,6 +166,14 @@ config SYSCTL
building a kernel for install/rescue disks or your system is very
limited in memory.

+config UTS_NS
+ bool "UTS Namespaces"
+ default n
+ help
+ Support uts namespaces. This allows containers, i.e.
+ vservers, to use uts namespaces to provide different
+ uts info for different servers. If unsure, say N.
+
config AUDIT
bool "Auditing support"
depends on NET
diff --git a/init/version.c b/init/version.c
index 3ddc3ce..78cef48 100644
--- a/init/version.c
+++ b/init/version.c
@@ -11,23 +11,27 @@ #include <linux/module.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/version.h>
+#include <linux/sched.h>

#define version(a) Version_ ## a
#define version_string(a) version(a)

int version_string(LINUX_VERSION_CODE);

-struct new_utsname system_utsname = {
- .sysname = UTS_SYSNAME,
- .nodename = UTS_NODENAME,
- .release = UTS_RELEASE,
- .version = UTS_VERSION,
- .machine = UTS_MACHINE,
- .domainname = UTS_DOMAINNAME,
+struct uts_namespace init_uts_ns = {
+ .kref = {
+ .refcount = ATOMIC_INIT(2),
+ },
+ .name = {
+ .sysname = UTS_SYSNAME,
+ .nodename = UTS_NODENAME,
+ .release = UTS_RELEASE,
+ .version = UTS_VERSION,
+ .machine = UTS_MACHINE,
+ .domainname = UTS_DOMAINNAME,
+ },
};

-EXPORT_SYMBOL(system_utsname);
-
const char linux_banner[] =
"Linux version " UTS_RELEASE " (" LINUX_COMPILE_BY "@"
LINUX_COMPILE_HOST ") (" LINUX_COMPILER ") " UTS_VERSION "\n";
diff --git a/kernel/Makefile b/kernel/Makefile
index 58908f9..70a69bc 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_RELAY) += relay.o
+obj-$(CONFIG_UTS_NS) += utsname.o

ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
# According to Alan Modra <alan@xxxxxxxxxxxxxxxx>, the -fno-omit-frame-pointer is
diff --git a/kernel/exit.c b/kernel/exit.c
index f86434d..6a46059 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -35,6 +35,7 @@ #include <linux/mutex.h>
#include <linux/futex.h>
#include <linux/compat.h>
#include <linux/pipe_fs_i.h>
+#include <linux/utsname.h>

#include <asm/uaccess.h>
#include <asm/unistd.h>
@@ -174,6 +175,7 @@ repeat:
spin_unlock(&p->proc_lock);
proc_pid_flush(proc_dentry);
release_thread(p);
+ put_uts_ns(p->uts_ns);
call_rcu(&p->rcu, delayed_put_task_struct);

p = leader;
diff --git a/kernel/fork.c b/kernel/fork.c
index d2fa57d..cedfd86 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -44,6 +44,7 @@ #include <linux/profile.h>
#include <linux/rmap.h>
#include <linux/acct.h>
#include <linux/cn_proc.h>
+#include <linux/utsname.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1064,9 +1065,11 @@ #endif
goto bad_fork_cleanup_mm;
if ((retval = copy_namespace(clone_flags, p)))
goto bad_fork_cleanup_keys;
+ if ((retval = copy_utsname(clone_flags, p)))
+ goto bad_fork_cleanup_namespace;
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
- goto bad_fork_cleanup_namespace;
+ goto bad_fork_cleanup_utsns;

p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL;
/*
@@ -1153,7 +1156,7 @@ #endif
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -ERESTARTNOINTR;
- goto bad_fork_cleanup_namespace;
+ goto bad_fork_cleanup_utsns;
}

if (clone_flags & CLONE_THREAD) {
@@ -1166,7 +1169,7 @@ #endif
spin_unlock(&current->sighand->siglock);
write_unlock_irq(&tasklist_lock);
retval = -EAGAIN;
- goto bad_fork_cleanup_namespace;
+ goto bad_fork_cleanup_utsns;
}

p->group_leader = current->group_leader;
@@ -1218,6 +1221,8 @@ #endif
proc_fork_connector(p);
return p;

+bad_fork_cleanup_utsns:
+ exit_utsname(p);
bad_fork_cleanup_namespace:
exit_namespace(p);
bad_fork_cleanup_keys:
diff --git a/kernel/utsname.c b/kernel/utsname.c
new file mode 100644
index 0000000..f9e8f86
--- /dev/null
+++ b/kernel/utsname.c
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2004 IBM Corporation
+ *
+ * Author: Serge Hallyn <serue@xxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation, version 2 of the
+ * License.
+ */
+
+#include <linux/compile.h>
+#include <linux/module.h>
+#include <linux/uts.h>
+#include <linux/utsname.h>
+#include <linux/version.h>
+
+static inline void get_uts_ns(struct uts_namespace *ns)
+{
+ kref_get(&ns->kref);
+}
+
+/*
+ * Copy task tsk's utsname namespace, or clone it if flags
+ * specifies CLONE_NEWUTS. In latter case, changes to the
+ * utsname of this process won't be seen by parent, and vice
+ * versa.
+ */
+int copy_utsname(int flags, struct task_struct *tsk)
+{
+ struct uts_namespace *old_ns = tsk->uts_ns;
+ int err = 0;
+
+ if (!old_ns)
+ return 0;
+
+ get_uts_ns(old_ns);
+
+ return err;
+}
+
+void free_uts_ns(struct kref *kref)
+{
+ struct uts_namespace *ns;
+
+ ns = container_of(kref, struct uts_namespace, kref);
+ kfree(ns);
+}
--
1.3.0


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