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Subject[PATCH] namespaces: uts_ns: make information visible via /proc/PID/uts directory
Date
From: Sam Vilain <sam.vilain@catalyst.net.nz>

Export the UTS information to a per-process directory /proc/PID/uts,
that has individual nodes for hostname, ostype, etc - similar to
those in /proc/sys/kernel

This duplicates the approach used for /proc/PID/attr, which involves a
lot of duplication of similar functions. Much room for maintenance
optimisation of both implementations remains.
---
Sorry for the duplication of this to the list, stuffed up the stgit
command.

After doing this I noticed that the whole way this is done via sysctls
in /proc/sys is much, much nicer. I was going there to make
/proc/sys/kernel/osname -> /proc/self/uts/sysname (etc), but it seems
that symlinks from /proc/sys are not a done thing.

Is there an argument here perhaps for some integration between the way
this is done for /proc/sys and /proc/PID/xxx ?

fs/proc/base.c | 236 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 236 insertions(+), 0 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 2031913..76f5acb 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -73,6 +73,7 @@ #include <linux/cpuset.h>
#include <linux/audit.h>
#include <linux/poll.h>
#include <linux/nsproxy.h>
+#include <linux/utsname.h>
#include "internal.h"

/* NOTE:
@@ -179,6 +180,22 @@ #ifdef CONFIG_AUDITSYSCALL
#endif
PROC_TID_OOM_SCORE,
PROC_TID_OOM_ADJUST,
+#ifdef CONFIG_UTS_NS
+ PROC_TID_UTS,
+ PROC_TGID_UTS,
+ PROC_TGID_UTS_SYSNAME,
+ PROC_TGID_UTS_NODENAME,
+ PROC_TGID_UTS_RELEASE,
+ PROC_TGID_UTS_VERSION,
+ PROC_TGID_UTS_MACHINE,
+ PROC_TGID_UTS_DOMAINNAME,
+ PROC_TID_UTS_SYSNAME,
+ PROC_TID_UTS_NODENAME,
+ PROC_TID_UTS_RELEASE,
+ PROC_TID_UTS_VERSION,
+ PROC_TID_UTS_MACHINE,
+ PROC_TID_UTS_DOMAINNAME,
+#endif

/* Add new entries before this */
PROC_TID_FD_DIR = 0x8000, /* 0x8000-0xffff */
@@ -238,6 +255,9 @@ #endif
#ifdef CONFIG_AUDITSYSCALL
E(PROC_TGID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
#endif
+#ifdef CONFIG_UTS_NS
+ E(PROC_TGID_UTS, "uts", S_IFDIR|S_IRUGO|S_IXUGO),
+#endif
{0,0,NULL,0}
};
static struct pid_entry tid_base_stuff[] = {
@@ -280,6 +300,9 @@ #endif
#ifdef CONFIG_AUDITSYSCALL
E(PROC_TID_LOGINUID, "loginuid", S_IFREG|S_IWUSR|S_IRUGO),
#endif
+#ifdef CONFIG_UTS_NS
+ E(PROC_TID_UTS, "uts", S_IFDIR|S_IRUGO|S_IXUGO),
+#endif
{0,0,NULL,0}
};

@@ -300,6 +323,27 @@ static struct pid_entry tid_attr_stuff[]
};
#endif

+#ifdef CONFIG_UTS_NS
+static struct pid_entry tgid_uts_stuff[] = {
+ E(PROC_TGID_UTS_SYSNAME, "sysname", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TGID_UTS_NODENAME, "nodename", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TGID_UTS_RELEASE, "release", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TGID_UTS_VERSION, "version", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TGID_UTS_MACHINE, "machine", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TGID_UTS_DOMAINNAME, "domainname", S_IFREG|S_IRUGO|S_IWUGO),
+ {0,0,NULL,0}
+};
+static struct pid_entry tid_uts_stuff[] = {
+ E(PROC_TID_UTS_SYSNAME, "sysname", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TID_UTS_NODENAME, "nodename", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TID_UTS_RELEASE, "release", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TID_UTS_VERSION, "version", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TID_UTS_MACHINE, "machine", S_IFREG|S_IRUGO|S_IWUGO),
+ E(PROC_TID_UTS_DOMAINNAME, "domainname", S_IFREG|S_IRUGO|S_IWUGO),
+ {0,0,NULL,0}
+};
+#endif
+
#undef E

static int proc_fd_link(struct inode *inode, struct dentry **dentry, struct vfsmount **mnt)
@@ -1608,6 +1652,148 @@ static struct file_operations proc_tgid_
static struct inode_operations proc_tgid_attr_inode_operations;
#endif

+#ifdef CONFIG_UTS_NS
+static ssize_t proc_pid_uts_read(struct file * file, char __user * buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode * inode = file->f_dentry->d_inode;
+ ssize_t length;
+ loff_t __ppos = *ppos;
+ struct task_struct *task = get_proc_task(inode);
+ char __buf[__NEW_UTS_LEN+1];
+ char *which;
+
+ length = -ESRCH;
+ if (!task)
+ goto out_no_task;
+
+ switch (file->f_dentry->d_name.name[0]) {
+ case 's':
+ which = task->nsproxy->uts_ns->name.sysname;
+ break;
+ case 'n':
+ which = task->nsproxy->uts_ns->name.nodename;
+ break;
+ case 'r':
+ which = task->nsproxy->uts_ns->name.release;
+ break;
+ case 'v':
+ which = task->nsproxy->uts_ns->name.version;
+ break;
+ case 'm':
+ which = task->nsproxy->uts_ns->name.machine;
+ break;
+ case 'd':
+ which = task->nsproxy->uts_ns->name.domainname;
+ break;
+ default:
+ printk("procfs: impossible uts part '%s'",
+ (char*)file->f_dentry->d_name.name);
+ length = -EINVAL;
+ goto out;
+ }
+
+ length = strlen(which);
+ strcpy(__buf, which);
+ __buf[length++] = '\n';
+
+ if (__ppos >= length)
+ return 0;
+ if (count > length - __ppos)
+ count = length - __ppos;
+ if (copy_to_user(buf, __buf + __ppos, count))
+ return -EFAULT;
+
+out:
+ put_task_struct(task);
+out_no_task:
+ return length;
+}
+
+static ssize_t proc_pid_uts_write(struct file * file, const char __user * buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode * inode = file->f_dentry->d_inode;
+ ssize_t length;
+ struct task_struct *task = get_proc_task(inode);
+ char *which;
+ char __buf[__NEW_UTS_LEN+1];
+
+ length = -ESRCH;
+ if (!task)
+ goto out_no_task;
+ if (count > PAGE_SIZE)
+ count = PAGE_SIZE;
+
+ /* No partial writes. */
+ length = -EINVAL;
+ if (*ppos != 0)
+ goto out;
+ if (count > __NEW_UTS_LEN)
+ goto out;
+
+ length = -EPERM;
+ if (!capable(CAP_SYS_ADMIN))
+ goto out;
+
+ length = -EFAULT;
+ if (copy_from_user(__buf, buf, count))
+ goto out;
+
+ length = -EINVAL;
+ length = strnlen(__buf, count);
+ if (count != length)
+ goto out;
+
+ if (__buf[length-1] == '\n')
+ length = length - 1;
+ __buf[length] = '\0';
+
+ switch (file->f_dentry->d_name.name[0]) {
+ case 's':
+ which = task->nsproxy->uts_ns->name.sysname;
+ break;
+ case 'n':
+ which = task->nsproxy->uts_ns->name.nodename;
+ break;
+ case 'r':
+ which = task->nsproxy->uts_ns->name.release;
+ break;
+ case 'v':
+ which = task->nsproxy->uts_ns->name.version;
+ break;
+ case 'm':
+ which = task->nsproxy->uts_ns->name.machine;
+ break;
+ case 'd':
+ which = task->nsproxy->uts_ns->name.domainname;
+ break;
+ default:
+ printk("procfs: impossible uts part '%s'",
+ (char*)file->f_dentry->d_name.name);
+ length = -EINVAL;
+ goto out;
+ }
+
+ strcpy(which, __buf);
+
+out:
+ put_task_struct(task);
+out_no_task:
+ return length;
+}
+
+static struct file_operations proc_pid_uts_operations = {
+ .read = proc_pid_uts_read,
+ .write = proc_pid_uts_write,
+};
+
+static struct file_operations proc_tid_uts_operations;
+static struct inode_operations proc_tid_uts_inode_operations;
+static struct file_operations proc_tgid_uts_operations;
+static struct inode_operations proc_tgid_uts_inode_operations;
+#endif
+
/* SMP-safe */
static struct dentry *proc_pident_lookup(struct inode *dir,
struct dentry *dentry,
@@ -1760,6 +1946,30 @@ #ifdef CONFIG_SECURITY
case PROC_TGID_ATTR_FSCREATE:
inode->i_fop = &proc_pid_attr_operations;
break;
+ case PROC_TID_UTS:
+ inode->i_nlink = 2;
+ inode->i_op = &proc_tid_uts_inode_operations;
+ inode->i_fop = &proc_tid_uts_operations;
+ break;
+ case PROC_TGID_UTS:
+ inode->i_nlink = 2;
+ inode->i_op = &proc_tgid_uts_inode_operations;
+ inode->i_fop = &proc_tgid_uts_operations;
+ break;
+ case PROC_TGID_UTS_SYSNAME:
+ case PROC_TGID_UTS_NODENAME:
+ case PROC_TGID_UTS_RELEASE:
+ case PROC_TGID_UTS_VERSION:
+ case PROC_TGID_UTS_MACHINE:
+ case PROC_TGID_UTS_DOMAINNAME:
+ case PROC_TID_UTS_SYSNAME:
+ case PROC_TID_UTS_NODENAME:
+ case PROC_TID_UTS_RELEASE:
+ case PROC_TID_UTS_VERSION:
+ case PROC_TID_UTS_MACHINE:
+ case PROC_TID_UTS_DOMAINNAME:
+ inode->i_fop = &proc_pid_uts_operations;
+ break;
#endif
#ifdef CONFIG_KALLSYMS
case PROC_TID_WCHAN:
@@ -1889,6 +2099,32 @@ static struct inode_operations proc_tid_
};
#endif

+#ifdef CONFIG_UTS_NS
+static int proc_tgid_uts_readdir(struct file * filp,
+ void * dirent, filldir_t filldir)
+{
+ return proc_pident_readdir(filp,dirent,filldir,
+ tgid_uts_stuff,ARRAY_SIZE(tgid_uts_stuff));
+}
+
+static int proc_tid_uts_readdir(struct file * filp,
+ void * dirent, filldir_t filldir)
+{
+ return proc_pident_readdir(filp,dirent,filldir,
+ tid_uts_stuff,ARRAY_SIZE(tid_uts_stuff));
+}
+
+static struct file_operations proc_tgid_uts_operations = {
+ .read = generic_read_dir,
+ .readdir = proc_tgid_uts_readdir,
+};
+
+static struct file_operations proc_tid_uts_operations = {
+ .read = generic_read_dir,
+ .readdir = proc_tid_uts_readdir,
+};
+#endif
+
/*
* /proc/self:
*/
-
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