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 int proc_thread_self_readlink(struct dentry *dentry, char __user *buffer,
  10                               int buflen)
  11 {
  12         struct pid_namespace *ns = dentry->d_sb->s_fs_info;
  13         pid_t tgid = task_tgid_nr_ns(current, ns);
  14         pid_t pid = task_pid_nr_ns(current, ns);
  15         char tmp[PROC_NUMBUF + 6 + PROC_NUMBUF];
  16         if (!pid)
  17                 return -ENOENT;
  18         sprintf(tmp, "%d/task/%d", tgid, pid);
  19         return readlink_copy(buffer, buflen, tmp);
  20 }
  21
  22 static const char *proc_thread_self_get_link(struct dentry *dentry,
  23                                              struct inode *inode,
  24                                              struct delayed_call *done)
  25 {
  26         struct pid_namespace *ns = inode->i_sb->s_fs_info;
  27         pid_t tgid = task_tgid_nr_ns(current, ns);
  28         pid_t pid = task_pid_nr_ns(current, ns);
  29         char *name;
  30
  31         if (!pid)
  32                 return ERR_PTR(-ENOENT);
  33         name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF,
  34                                 dentry ? GFP_KERNEL : GFP_ATOMIC);
  35         if (unlikely(!name))
  36                 return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
  37         sprintf(name, "%d/task/%d", tgid, pid);
  38         set_delayed_call(done, kfree_link, name);
  39         return name;
  40 }
  41
  42 static const struct inode_operations proc_thread_self_inode_operations = {
  43         .readlink       = proc_thread_self_readlink,
  44         .get_link       = proc_thread_self_get_link,
  45 };
  46
  47 static unsigned thread_self_inum;
  48
  49 int proc_setup_thread_self(struct super_block *s)
  50 {
  51         struct inode *root_inode = d_inode(s->s_root);
  52         struct pid_namespace *ns = s->s_fs_info;
  53         struct dentry *thread_self;
  54
  55         inode_lock(root_inode);
  56         thread_self = d_alloc_name(s->s_root, "thread-self");
  57         if (thread_self) {
  58                 struct inode *inode = new_inode_pseudo(s);
  59                 if (inode) {
  60                         inode->i_ino = thread_self_inum;
  61                         inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  62                         inode->i_mode = S_IFLNK | S_IRWXUGO;
  63                         inode->i_uid = GLOBAL_ROOT_UID;
  64                         inode->i_gid = GLOBAL_ROOT_GID;
  65                         inode->i_op = &proc_thread_self_inode_operations;
  66                         d_add(thread_self, inode);
  67                 } else {
  68                         dput(thread_self);
  69                         thread_self = ERR_PTR(-ENOMEM);
  70                 }
  71         } else {
  72                 thread_self = ERR_PTR(-ENOMEM);
  73         }
  74         inode_unlock(root_inode);
  75         if (IS_ERR(thread_self)) {
  76                 pr_err("proc_fill_super: can't allocate /proc/thread_self\n");
  77                 return PTR_ERR(thread_self);
  78         }
  79         ns->proc_thread_self = thread_self;
  80         return 0;
  81 }
  82
  83 void __init proc_thread_self_init(void)
  84 {
  85         proc_alloc_inum(&thread_self_inum);
  86 }