linux/kernel/utsname_sysctl.c

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/*
* Copyright (C) 2007
*
* Author: Eric Biederman <ebiederm@xmision.com>
*
* 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/export.h>
#include <linux/uts.h>
#include <linux/utsname.h>
#include <linux/sysctl.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#ifdef CONFIG_PROC_SYSCTL
static void *get_uts(struct ctl_table *table)
{
char *which = table->data;
struct uts_namespace *uts_ns;
uts_ns = current->nsproxy->uts_ns;
which = (which - (char *)&init_uts_ns) + (char *)uts_ns;
return which;
}
/*
* Special case of dostring for the UTS structure. This has locks
* to observe. Should this be in kernel/sys.c ????
*/
static int proc_do_uts_string(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table uts_table;
int r;
char tmp_data[__NEW_UTS_LEN + 1];
memcpy(&uts_table, table, sizeof(uts_table));
uts_table.data = tmp_data;
/*
* Buffer the value in tmp_data so that proc_dostring() can be called
* without holding any locks.
* We also need to read the original value in the write==1 case to
* support partial writes.
*/
down_read(&uts_sem);
memcpy(tmp_data, get_uts(table), sizeof(tmp_data));
up_read(&uts_sem);
r = proc_dostring(&uts_table, write, buffer, lenp, ppos);
if (write) {
/*
* Write back the new value.
* Note that, since we dropped uts_sem, the result can
* theoretically be incorrect if there are two parallel writes
* at non-zero offsets to the same sysctl.
*/
down_write(&uts_sem);
memcpy(get_uts(table), tmp_data, sizeof(tmp_data));
up_write(&uts_sem);
proc_sys_poll_notify(table->poll);
}
return r;
}
#else
#define proc_do_uts_string NULL
#endif
static DEFINE_CTL_TABLE_POLL(hostname_poll);
static DEFINE_CTL_TABLE_POLL(domainname_poll);
static struct ctl_table uts_kern_table[] = {
{
.procname = "ostype",
.data = init_uts_ns.name.sysname,
.maxlen = sizeof(init_uts_ns.name.sysname),
.mode = 0444,
.proc_handler = proc_do_uts_string,
},
{
.procname = "osrelease",
.data = init_uts_ns.name.release,
.maxlen = sizeof(init_uts_ns.name.release),
.mode = 0444,
.proc_handler = proc_do_uts_string,
},
{
.procname = "version",
.data = init_uts_ns.name.version,
.maxlen = sizeof(init_uts_ns.name.version),
.mode = 0444,
.proc_handler = proc_do_uts_string,
},
{
.procname = "hostname",
.data = init_uts_ns.name.nodename,
.maxlen = sizeof(init_uts_ns.name.nodename),
.mode = 0644,
.proc_handler = proc_do_uts_string,
.poll = &hostname_poll,
},
{
.procname = "domainname",
.data = init_uts_ns.name.domainname,
.maxlen = sizeof(init_uts_ns.name.domainname),
.mode = 0644,
.proc_handler = proc_do_uts_string,
.poll = &domainname_poll,
},
{}
};
static struct ctl_table uts_root_table[] = {
{
.procname = "kernel",
.mode = 0555,
.child = uts_kern_table,
},
{}
};
#ifdef CONFIG_PROC_SYSCTL
/*
* Notify userspace about a change in a certain entry of uts_kern_table,
* identified by the parameter proc.
*/
void uts_proc_notify(enum uts_proc proc)
{
struct ctl_table *table = &uts_kern_table[proc];
proc_sys_poll_notify(table->poll);
}
#endif
static int __init utsname_sysctl_init(void)
{
[PATCH] sysctl: remove insert_at_head from register_sysctl The semantic effect of insert_at_head is that it would allow new registered sysctl entries to override existing sysctl entries of the same name. Which is pain for caching and the proc interface never implemented. I have done an audit and discovered that none of the current users of register_sysctl care as (excpet for directories) they do not register duplicate sysctl entries. So this patch simply removes the support for overriding existing entries in the sys_sysctl interface since no one uses it or cares and it makes future enhancments harder. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Acked-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: David Howells <dhowells@redhat.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Andi Kleen <ak@muc.de> Cc: Jens Axboe <axboe@kernel.dk> Cc: Corey Minyard <minyard@acm.org> Cc: Neil Brown <neilb@suse.de> Cc: "John W. Linville" <linville@tuxdriver.com> Cc: James Bottomley <James.Bottomley@steeleye.com> Cc: Jan Kara <jack@ucw.cz> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Mark Fasheh <mark.fasheh@oracle.com> Cc: David Chinner <dgc@sgi.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Patrick McHardy <kaber@trash.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-14 08:34:09 +00:00
register_sysctl_table(uts_root_table);
return 0;
}
device_initcall(utsname_sysctl_init);