fs/proc/thread_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/thread_self:
   8  */
   9 static const char *proc_thread_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         pid_t pid = task_pid_nr_ns(current, ns);
  16         char *name;
  17
  18         if (!pid)
  19                 return ERR_PTR(-ENOENT);
  20         name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF,
  21                                 dentry ? GFP_KERNEL : GFP_ATOMIC);
  22         if (unlikely(!name))
  23                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  24         sprintf(name, "%d/task/%d", tgid, pid);
  25         set_delayed_call(done, kfree_link, name);
  26         return name;
  27 }
  28
  29 static const struct inode_operations proc_thread_self_inode_operations = {
  30         .get_link       = proc_thread_self_get_link,
  31 };
  32
  33 static unsigned thread_self_inum;
  34
  35 int proc_setup_thread_self(struct super_block *s)
  36 {
  37         struct inode *root_inode = d_inode(s->s_root);
  38         struct pid_namespace *ns = s->s_fs_info;
  39         struct dentry *thread_self;
  40
  41         inode_lock(root_inode);
  42         thread_self = d_alloc_name(s->s_root, "thread-self");
  43         if (thread_self) {
  44                 struct inode *inode = new_inode_pseudo(s);
  45                 if (inode) {
  46                         inode->i_ino = thread_self_inum;
  47                         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
  48                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  49                         inode->i_uid = GLOBAL_ROOT_UID;
  50                         inode->i_gid = GLOBAL_ROOT_GID;
  51                         inode->i_op = &proc_thread_self_inode_operations;
  52                         d_add(thread_self, inode);
  53                 } else {
  54                         dput(thread_self);
  55                         thread_self = ERR_PTR(-ENOMEM);
  56                 }
  57         } else {
  58                 thread_self = ERR_PTR(-ENOMEM);
  59         }
  60         inode_unlock(root_inode);
  61         if (IS_ERR(thread_self)) {
  62                 pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
  63                 return PTR_ERR(thread_self);
  64         }
  65         ns->proc_thread_self = thread_self;
  66         return 0;
  67 }
  68
  69 void __init proc_thread_self_init(void)
  70 {
  71         proc_alloc_inum(&thread_self_inum);
  72 }