fs/proc/self.c

   1 #include <linux/sched.h>
   2 #include <linux/slab.h>
   3 #include <linux/pid_namespace.h>
   4 #include "internal.h"
   5
   6 /*
   7  * /proc/self:
   8  */
   9 static const char *proc_self_get_link(struct dentry *dentry,
  10                                       struct inode *inode,
  11                                       struct delayed_call *done)
  12 {
  13         struct pid_namespace *ns = inode->i_sb->s_fs_info;
  14         pid_t tgid = task_tgid_nr_ns(current, ns);
  15         char *name;
  16
  17         if (!tgid)
  18                 return ERR_PTR(-ENOENT);
  19         /* 11 for max length of signed int in decimal + NULL term */
  20         name = kmalloc(12, dentry ? GFP_KERNEL : GFP_ATOMIC);
  21         if (unlikely(!name))
  22                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  23         sprintf(name, "%d", tgid);
  24         set_delayed_call(done, kfree_link, name);
  25         return name;
  26 }
  27
  28 static const struct inode_operations proc_self_inode_operations = {
  29         .get_link       = proc_self_get_link,
  30 };
  31
  32 static unsigned self_inum;
  33
  34 int proc_setup_self(struct super_block *s)
  35 {
  36         struct inode *root_inode = d_inode(s->s_root);
  37         struct pid_namespace *ns = s->s_fs_info;
  38         struct dentry *self;
  39
  40         inode_lock(root_inode);
  41         self = d_alloc_name(s->s_root, "self");
  42         if (self) {
  43                 struct inode *inode = new_inode_pseudo(s);
  44                 if (inode) {
  45                         inode->i_ino = self_inum;
  46                         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
  47                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  48                         inode->i_uid = GLOBAL_ROOT_UID;
  49                         inode->i_gid = GLOBAL_ROOT_GID;
  50                         inode->i_op = &proc_self_inode_operations;
  51                         d_add(self, inode);
  52                 } else {
  53                         dput(self);
  54                         self = ERR_PTR(-ENOMEM);
  55                 }
  56         } else {
  57                 self = ERR_PTR(-ENOMEM);
  58         }
  59         inode_unlock(root_inode);
  60         if (IS_ERR(self)) {
  61                 pr_err("proc_fill_super: can't allocate /proc/self\n");
  62                 return PTR_ERR(self);
  63         }
  64         ns->proc_self = self;
  65         return 0;
  66 }
  67
  68 void __init proc_self_init(void)
  69 {
  70         proc_alloc_inum(&self_inum);
  71 }