LXR linux/fs/proc/self.c

   1#include <linux/sched.h>
   2#include <linux/namei.h>
   3#include <linux/slab.h>
   4#include <linux/pid_namespace.h>
   5#include "internal.h"
   6
   7/*
   8 * /proc/self:
   9 */
  10static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
  11                              int buflen)
  12{
  13        struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  14        pid_t tgid = task_tgid_nr_ns(current, ns);
  15        char tmp[PROC_NUMBUF];
  16        if (!tgid)
  17                return -ENOENT;
  18        sprintf(tmp, "%d", tgid);
  19        return vfs_readlink(dentry,buffer,buflen,tmp);
  20}
  21
  22static void *proc_self_follow_link(struct dentry *dentry, struct nameidata *nd)
  23{
  24        struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  25        pid_t tgid = task_tgid_nr_ns(current, ns);
  26        char *name = ERR_PTR(-ENOENT);
  27        if (tgid) {
  28                /* 11 for max length of signed int in decimal + NULL term */
  29                name = kmalloc(12, GFP_KERNEL);
  30                if (!name)
  31                        name = ERR_PTR(-ENOMEM);
  32                else
  33                        sprintf(name, "%d", tgid);
  34        }
  35        nd_set_link(nd, name);
  36        return NULL;
  37}
  38
  39static void proc_self_put_link(struct dentry *dentry, struct nameidata *nd,
  40                                void *cookie)
  41{
  42        char *s = nd_get_link(nd);
  43        if (!IS_ERR(s))
  44                kfree(s);
  45}
  46
  47static const struct inode_operations proc_self_inode_operations = {
  48        .readlink       = proc_self_readlink,
  49        .follow_link    = proc_self_follow_link,
  50        .put_link       = proc_self_put_link,
  51};
  52
  53static unsigned self_inum;
  54
  55int proc_setup_self(struct super_block *s)
  56{
  57        struct inode *root_inode = s->s_root->d_inode;
  58        struct pid_namespace *ns = s->s_fs_info;
  59        struct dentry *self;
  60        
  61        mutex_lock(&root_inode->i_mutex);
  62        self = d_alloc_name(s->s_root, "self");
  63        if (self) {
  64                struct inode *inode = new_inode_pseudo(s);
  65                if (inode) {
  66                        inode->i_ino = self_inum;
  67                        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  68                        inode->i_mode = S_IFLNK | S_IRWXUGO;
  69                        inode->i_uid = GLOBAL_ROOT_UID;
  70                        inode->i_gid = GLOBAL_ROOT_GID;
  71                        inode->i_op = &proc_self_inode_operations;
  72                        d_add(self, inode);
  73                } else {
  74                        dput(self);
  75                        self = ERR_PTR(-ENOMEM);
  76                }
  77        } else {
  78                self = ERR_PTR(-ENOMEM);
  79        }
  80        mutex_unlock(&root_inode->i_mutex);
  81        if (IS_ERR(self)) {
  82                pr_err("proc_fill_super: can't allocate /proc/self\n");
  83                return PTR_ERR(self);
  84        }
  85        ns->proc_self = self;
  86        return 0;
  87}
  88
  89void __init proc_self_init(void)
  90{
  91        proc_alloc_inum(&self_inum);
  92}
  93