1 /* 2 * Copyright (C) 2004 IBM Corporation 3 * 4 * Author: Serge Hallyn <serue@us.ibm.com> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation, version 2 of the 9 * License. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/uts.h> 14 #include <linux/utsname.h> 15 #include <linux/version.h> 16 #include <linux/err.h> 17 #include <linux/slab.h> 18 19 /* 20 * Clone a new ns copying an original utsname, setting refcount to 1 21 * @old_ns: namespace to clone 22 * Return NULL on error (failure to kmalloc), new ns otherwise 23 */ 24 static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns) 25 { 26 struct uts_namespace *ns; 27 28 ns = kmalloc(sizeof(struct uts_namespace), GFP_KERNEL); 29 if (!ns) 30 return ERR_PTR(-ENOMEM); 31 32 down_read(&uts_sem); 33 memcpy(&ns->name, &old_ns->name, sizeof(ns->name)); 34 up_read(&uts_sem); 35 kref_init(&ns->kref); 36 return ns; 37 } 38 39 /* 40 * Copy task tsk's utsname namespace, or clone it if flags 41 * specifies CLONE_NEWUTS. In latter case, changes to the 42 * utsname of this process won't be seen by parent, and vice 43 * versa. 44 */ 45 struct uts_namespace *copy_utsname(unsigned long flags, struct uts_namespace *old_ns) 46 { 47 struct uts_namespace *new_ns; 48 49 BUG_ON(!old_ns); 50 get_uts_ns(old_ns); 51 52 if (!(flags & CLONE_NEWUTS)) 53 return old_ns; 54 55 new_ns = clone_uts_ns(old_ns); 56 57 put_uts_ns(old_ns); 58 return new_ns; 59 } 60 61 void free_uts_ns(struct kref *kref) 62 { 63 struct uts_namespace *ns; 64 65 ns = container_of(kref, struct uts_namespace, kref); 66 kfree(ns); 67 } 68