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