[PATCH] namespaces: uts_ns: make information visible via /proc/PID/uts directory

[Sam Vilain]

From: Sam Vilain <sam.vilain@xxxxxxxxxxxxxxx>

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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