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

[Herbert Poetzl <herbert@13thfloor.at>]

On Mon, May 22, 2006 at 05:24:25PM +1200, Sam Vilain wrote:
> 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.

hmm, IMHO what we want/need in the future is some
entries for the namespaces/nsproxies to make them
accessible from outside (kind of handle)

the processes could then use relative symlinks
to point to those entries, but I'm not sure they
really belong in /proc although that is probably
more approriate than the other 100 entries not
belonging to procfs :)

> ---
> 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 ?

I'm not very happy about the /sys and /proc/sys 
mixup, let's avoid further mixing there ...

best,
Herbert

>  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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