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