[PATCH 6/9] uts namespaces: implement utsname namespaces

From: Serge E. Hallyn
Date: Tue May 09 2006 - 22:13:50 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 Hallyn <serue@xxxxxxxxxx>

---

include/linux/init_task.h | 2 ++
include/linux/nsproxy.h | 1 +
include/linux/sched.h | 1 +
include/linux/utsname.h | 55 ++++++++++++++++++++++++++++++++++++++++++---
init/Kconfig | 8 +++++++
init/version.c | 22 +++++++++++-------
kernel/Makefile | 1 +
kernel/exit.c | 7 +++++-
kernel/fork.c | 7 +++++-
kernel/utsname.c | 43 +++++++++++++++++++++++++++++++++++
10 files changed, 132 insertions(+), 15 deletions(-)
create mode 100644 kernel/utsname.c

d7e342120496af2cd8520bc89f7b1e54b7ab2749
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 672dc04..ceb68b7 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 \
{ \
@@ -70,6 +71,7 @@ extern struct nsproxy init_nsproxy;
#define INIT_NSPROXY(nsproxy) { \
.count = ATOMIC_INIT(1), \
.nslock = SPIN_LOCK_UNLOCKED, \
+ .uts_ns = &init_uts_ns, \
.namespace = NULL, \
}

diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 64e9075..18fcd8f 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -9,6 +9,7 @@ struct namespace;
struct nsproxy {
atomic_t count;
spinlock_t nslock;
+ struct uts_namespace *uts_ns;
struct namespace *namespace;
};
extern struct nsproxy init_nsproxy;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f2c945b..3332d5e 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,
diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 8f0decf..b6b9801 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -1,6 +1,11 @@
#ifndef _LINUX_UTSNAME_H
#define _LINUX_UTSNAME_H

+#include <linux/sched.h>
+#include <linux/kref.h>
+#include <linux/nsproxy.h>
+#include <asm/atomic.h>
+
#define __OLD_UTS_LEN 8

struct oldold_utsname {
@@ -30,15 +35,57 @@ 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;
+
+static inline void get_uts_ns(struct uts_namespace *ns)
+{
+ kref_get(&ns->kref);
+}
+
+#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 struct new_utsname *utsname(void) {
- return &system_utsname;
+static inline void exit_utsname(struct task_struct *p)
+{
+ struct uts_namespace *uts_ns = p->nsproxy->uts_ns;
+ if (uts_ns) {
+ put_uts_ns(uts_ns);
+ }
+}
+
+#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->nsproxy->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 215fb33..ab7426c 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 1862d36..921a4b7 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -14,7 +14,7 @@ #include <linux/capability.h>
#include <linux/completion.h>
#include <linux/personality.h>
#include <linux/tty.h>
-#include <linux/nsproxy.h>
+#include <linux/utsname.h>
#include <linux/namespace.h>
#include <linux/key.h>
#include <linux/security.h>
@@ -415,11 +415,15 @@ void daemonize(const char *name, ...)
fs = init_task.fs;
current->fs = fs;
atomic_inc(&fs->count);
+
+ exit_utsname(current);
exit_namespace(current);
exit_nsproxy(current);
current->nsproxy = init_task.nsproxy;
get_nsproxy(current->nsproxy);
get_namespace(current->nsproxy->namespace);
+ get_uts_ns(current->nsproxy->uts_ns);
+
exit_files(current);
current->files = init_task.files;
atomic_inc(&current->files->count);
@@ -922,6 +926,7 @@ #endif
exit_sem(tsk);
__exit_files(tsk);
__exit_fs(tsk);
+ exit_utsname(current);
exit_namespace(current);
exit_nsproxy(current);
exit_thread();
diff --git a/kernel/fork.c b/kernel/fork.c
index 06cc87a..4d7cbae 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -45,6 +45,7 @@ #include <linux/rmap.h>
#include <linux/acct.h>
#include <linux/cn_proc.h>
#include <linux/nsproxy.h>
+#include <linux/utsname.h>

#include <asm/pgtable.h>
#include <asm/pgalloc.h>
@@ -1063,8 +1064,10 @@ #endif
goto bad_fork_cleanup_mm;
if ((retval = copy_nsproxy(clone_flags, p)))
goto bad_fork_cleanup_keys;
- if ((retval = copy_namespace(clone_flags, p)))
+ if ((retval = copy_utsname(clone_flags, p)))
goto bad_fork_cleanup_nsproxy;
+ if ((retval = copy_namespace(clone_flags, p)))
+ goto bad_fork_cleanup_utsname;
retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs);
if (retval)
goto bad_fork_cleanup_namespace;
@@ -1221,6 +1224,8 @@ #endif

bad_fork_cleanup_namespace:
exit_namespace(p);
+bad_fork_cleanup_utsname:
+ exit_utsname(p);
bad_fork_cleanup_nsproxy:
exit_nsproxy(p);
bad_fork_cleanup_keys:
diff --git a/kernel/utsname.c b/kernel/utsname.c
new file mode 100644
index 0000000..2818c9b
--- /dev/null
+++ b/kernel/utsname.c
@@ -0,0 +1,43 @@
+/*
+ * 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>
+
+/*
+ * 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->nsproxy->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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