kernel/utsname.c

Source file repositories/reference/linux-study-clean/kernel/utsname.c

File Facts

System
Linux kernel
Corpus path
kernel/utsname.c
Extension
.c
Size
3622 bytes
Lines
165
Domain
Core OS
Bucket
Scheduler, Processes, Timers, Sync, And Syscalls
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  Copyright (C) 2004 IBM Corporation
 *
 *  Author: Serge Hallyn <serue@us.ibm.com>
 */

#include <linux/export.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
#include <linux/nstree.h>
#include <linux/sched/task.h>

static struct kmem_cache *uts_ns_cache __ro_after_init;

static struct ucounts *inc_uts_namespaces(struct user_namespace *ns)
{
	return inc_ucount(ns, current_euid(), UCOUNT_UTS_NAMESPACES);
}

static void dec_uts_namespaces(struct ucounts *ucounts)
{
	dec_ucount(ucounts, UCOUNT_UTS_NAMESPACES);
}

/*
 * Clone a new ns copying an original utsname, setting refcount to 1
 * @old_ns: namespace to clone
 * Return ERR_PTR(-ENOMEM) on error (failure to allocate), new ns otherwise
 */
static struct uts_namespace *clone_uts_ns(struct user_namespace *user_ns,
					  struct uts_namespace *old_ns)
{
	struct uts_namespace *ns;
	struct ucounts *ucounts;
	int err;

	err = -ENOSPC;
	ucounts = inc_uts_namespaces(user_ns);
	if (!ucounts)
		goto fail;

	err = -ENOMEM;
	ns = kmem_cache_zalloc(uts_ns_cache, GFP_KERNEL);
	if (!ns)
		goto fail_dec;

	err = ns_common_init(ns);
	if (err)
		goto fail_free;

	ns->ucounts = ucounts;
	down_read(&uts_sem);
	memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
	ns->user_ns = get_user_ns(user_ns);
	up_read(&uts_sem);
	ns_tree_add(ns);
	return ns;

fail_free:
	kmem_cache_free(uts_ns_cache, ns);
fail_dec:
	dec_uts_namespaces(ucounts);
fail:
	return ERR_PTR(err);
}

/*
 * 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.
 */
struct uts_namespace *copy_utsname(u64 flags,
	struct user_namespace *user_ns, struct uts_namespace *old_ns)
{
	struct uts_namespace *new_ns;

	BUG_ON(!old_ns);
	get_uts_ns(old_ns);

	if (!(flags & CLONE_NEWUTS))
		return old_ns;

	new_ns = clone_uts_ns(user_ns, old_ns);

Annotation

Implementation Notes